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Table of Content
05 April 2018, Volume 69 Issue 4
    Highlights of international forward osmosis technology symposium (IFOS2016): is forward osmosis feasible?
    ZHAO Shuwei, HE Tao, LI Xuemei, GAO Congjie, HO Kyong Shon, NGHIEM Long D, ELIMELECH Menachem
    2018, 69(4):  1255-1260.  doi:10.11949/j.issn.0438-1157.20170836
    Abstract ( 492 )   PDF (376KB) ( 382 )  
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    The research highlights on forward osmosis (FO) technology at the International Forward Osmosis Symposium (IFOS2016) in Sydney by the end of 2016 are summarized. For FO membrane materials, reduction in the structure parameter of the support layer, rather than the increase of the permeability of the active separation layer, is the key to improve the FO flux. Overall, the improvement in the rejection and antifouling properties is the key factor for high performance membrane. For draw solutes, inorganic salts appear to be the most promising candidates. Osmotic dilution and hybrid processes with other separation technologies for treating high salinity wastewater remain the main potential application. Unfortunately, in a short term, FO based salinity power generation is not competitive to other new energy alternatives.

    Vanadium phosphorous oxide and its catalytic application
    LIU Ruixia, HE Bin, LUO Chen, DAI Fei, LI Zihang, ZHANG Ruirui
    2018, 69(4):  1261-1275.  doi:10.11949/j.issn.0438-1157.20170997
    Abstract ( 604 )   PDF (1211KB) ( 512 )  
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    Vanadium phosphorous oxide (VPO) is an important complex oxide with excellent catalytic performances in many reactions such as selective oxidization of light alkanes and ammonium oxidation. Because VPO has quite complicated structures, its phase composition, surface morphology, and acidity are closely related to preparation methods, which affect VPO catalytic performance. Various VPO preparation methods were reviewed to systematically analyze structure, characteristics, and transformation of VPO crystals. Techniques to improve catalytic performance and recent progress were assessed especially. Major application, challenges, and future development of VPO catalysts were further discussed. Advanced in-situ characterization and theoretical simulation were used to explore structure-property relationship and novel synthesis methods of VPO catalyst. With facilitation of modern nanomaterial theory, high performance nanomicro-structured VPO catalyst could be developed.

    Analyses on dynamical process of high pressure combustible gas leakage and thermal hazard of jet fire
    ZHOU Kuibin, LIU Jiaoyan, JIANG Juncheng
    2018, 69(4):  1276-1287.  doi:10.11949/j.issn.0438-1157.20170707
    Abstract ( 536 )   PDF (774KB) ( 718 )  
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    This paper reviews the jet fire due to the leakage of combustible gas in high pressure vessels. The physical models are given and analyzed for the state physical parameters of steady-state gas flow at the leakage orifice, the flame geometry and size of jet fire after the ignition of the leakage gas, and jet flame radiant heat flux, respectively. The high pressure gas leakage models are extensively introduced respectively based on the ideal gas and Abel-Noble state gas equations, then the flame length model, flame width model and lift-off height model are presented to predict the jet flame geometry and size, finally the point source radiation model, multipoint source radiation model, solid flame radiation model and line source radiation model are given and compared. The three kinds of physical models are linked and coupled to analyze the thermal hazard of jet fire at different leakage conditions. Analysis shows the considerable application of the linked physical model.

    Research progress on mechanisms of acid-catalyzed cellulose and chitin liquefaction to small molecular chemicals under atmospheric pressure
    XU Wenrong, ZHANG Jie, ZHENG Fengyi, ZHANG Yucang
    2018, 69(4):  1288-1298.  doi:10.11949/j.issn.0438-1157.20171187
    Abstract ( 449 )   PDF (842KB) ( 447 )  
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    In the past two decades, the studies on converting lignocellulosic biomass, especially cellulose to small molecular chemicals through atmospheric pressure catalytic liquefaction technology have achieved certain success. This technology began to be applied to transform chitin biomass to small molecular chemicals in recent years. The expansion of biomass resource is beneficial to enrich the types of liquefied products, in particular, nitrogen-containing chemicals. This review summarizes the small molecular chemicals produced by acid-catalyzed liquefaction of cellulose and chitin, respectively, in different solvents under atmospheric pressure. Moreover, the research progress of their liquefaction mechanisms is emphatically described. Some problems were pointed out in the research of cellulose and chitin liquefaction to small molecular chemicals and proposed the solution. The research on the liquefaction of chitin is prospected.

    Experimental determination,thermodynamic modeling and process simulation of methyl isopropyl ketone-phenol-hydroquinone-water quaternary systems
    CHEN Yun, LÜ Ran, XIONG Kangning, ZHANG Tao, LI Libo
    2018, 69(4):  1299-1306.  doi:10.11949/j.issn.0438-1157.20170067
    Abstract ( 498 )   PDF (486KB) ( 466 )  
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    Experimental determination of the liquid-liquid equilibrium system provides basic data for accurate simulation, design and process development of solvent extraction and recovery. In this work, methyl isopropyl ketone (MIPK) was chosen as the extraction agent and the liquid-liquid equilibrium of methyl isopropyl ketone-phenol-hydroquinone-water was studied since phenol and hydroquinone are typical monophenols and polyphenols in the coal chemical industry wastewater. The liquid-liquid equilibrium data were determined at 40℃ under atmospherics pressure. The experimental data were correlated with the NRTL and UNIQUAC models. The binary interaction parameters of the quaternary systems were obtained. The LLE results calculated by the NRTL and UNIQUAC models agreed quite well with the experimental data with root mean square deviations below 0.190% and 0.266% for these two models. Furthermore, the extraction process was simulated with binary interaction parameters calculated from the UNIQUAC model. According to these simulations, the total phenols and total polyphenols in the phenolic wastewater could respectively decrease from 12700 mg×L-1 to 300 mg×L-1 and from 4250 mg×L-1 to 299 mg×L-1 under the operation condition of extraction temperature 40℃, extraction stages 5 and solvent to wastewater ratio 1:7.72.

    Measurement and correlation of solubility of diphenyl sulfoxide in several solvents
    OUYANG Bo, KONG Ming, QIAN Chao, CHEN Xinzhi
    2018, 69(4):  1307-1314.  doi:10.11949/j.issn.0438-1157.20170799
    Abstract ( 560 )   PDF (455KB) ( 587 )  
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    The measurement of solubility of diphenyl sulfoxide in ethanol, ethyl acetate, toluene, acetone, chloroform and a series of different concentrations of ethanol-water binary solvent mixtures was conducted experimentally from 288.30-334.32 K under atmospheric pressure with the synthetic method. The data showed that the solubility in the above five pure solvents is in the order:chloroform > acetone > toluene > ethyl acetate > ethanol at the desired temperatures. The solubility in ethanol-water binary solvent mixtures increased rapidly with the increase of ethanol concentration. Further, the dissolution process was an endothermic entropy-increasing process and the enthalpy change played a major influence to the Gibbs energy change. Moreover, the solubility of diphenyl sulfoxide in the selected solvent decreased with the increase of the Gibbs energy change. The data was correlated by the modified Apelblat equation and van't Hoff equation. Besides, the values of solubility in ethanol-water binary solvent mixtures were fitted by Jouban-Acree equation. The fitting results agreed well with the data. The solid-liquid equilibrium data provides suitable solvents for the synthesis and purification of diphenyl sulfoxide.

    Helmholtz equation of state for n-pentene
    YANG Jian, MENG Xianyang, GAO Kehui, WU Jiangtao
    2018, 69(4):  1315-1323.  doi:10.11949/j.issn.0438-1157.20170972
    Abstract ( 440 )   PDF (600KB) ( 672 )  
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    To popularize the application of n-pentene in industry, such as chemical simulation, process optimization, and properties research, the equation of state for n-pentene was developed based on a body of experimental data that has been critically assessed for internal consistency and for agreement with theory in this work. The Helmholtz energy as the fundamental property with independent variables of density and temperature was used for the equation of state. The equation of state is valid from the triple-point temperature to 500 K, with pressures up to 100 MPa and densities up to 15 mol×dm-3. Overall,the uncertainties in density range of the equation of state are 0.2% in the liquid region and 0.5% in the critical and vapor region. The uncertainty is 0.3% for the vapor pressure and 0.2% for the saturated liquid density. The uncertainties in the properties related to energy (such as heat capacity, sound speed, enthalpy and so on) are estimated to be 1%. The behavior of the equation of state is reasonable within the region of validity and at higher and lower temperatures and pressures.

    Effects of feed position and inlet gas velocity on particle classification in cyclonic classifier
    SUN Zhanpeng, SUN Guogang, DU Yan
    2018, 69(4):  1324-1331.  doi:10.11949/j.issn.0438-1157.20170916
    Abstract ( 339 )   PDF (1103KB) ( 375 )  
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    Feed areas of cyclonic classifier was divided according to air velocity distribution characteristics. The effects of three representative feed positions on particle trajectory and classifying accuracy was investigated and force on 1 μm and 10 μm particles in different areas was analyzed by unsteady discrete particle model and classification experiments. Near-wall feeding mingled fine particle into coarse powder and impaired classification accuracy. Near-center feeding exerted strong centrifuge force on coarse particles and high axial shear force on fine particles by high flow field intensity which reduced particle residence time in classification zone and achieved rapid classification with improved classification efficiency. Center feeding extended classification move distance of coarse particles and increased possibility of coarse particles going into fine fraction, which simulation showed that 11.7% of 15 μm coarse particle by mass was mixed with fine powder. Experimental results showed that near-center feeding at inlet air velocity in a range of 10 m·s-1 to 22 m·s-1 minimized overlap between distribution curves of coarse and fine particles and increased average ratio of classified particle diameter by 25.3%. Those results could provide guidance to design feed position of air cyclonic classifiers.

    Characteristics of dynamic ice-making via Al2O3-H2O nanofluid's vacuum flash
    ZHANG Xuelai, WANG Zhangfei, LI Yue, JIA Xiaoya
    2018, 69(4):  1332-1340.  doi:10.11949/j.issn.0438-1157.20170612
    Abstract ( 466 )   PDF (844KB) ( 254 )  
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    Al2O3 nano particles were added into the water with xanthan and ultrasonic wave to prepare the well-distributed Al2O3-H2O nanofluid. Based on the theory of flash evaporation, an experimental apparatus of dynamic ice-making under vacuum was designed. In the same flash pressure (300 Pa), it is investigated the vacuum flash experimental characteristics in different conditions,like solid adsorption,nanofluid concentration, particle size and diaphragm metering pump flow. The results shown that the adsorption action had obvious effect on keeping the stability of the pressure and it was useful to capture the water vapor in the system. When the temperature of the cooling medium is lower than the initial temperature of the adsorbent, the adsorbent had better adsorption capacity, but the cooling temperature should not be too low. The larger the concentraction of the nanofluid is, the smaller the particle size is,the better for getting the high ice packing factor of ice slurry. For the same concentration of nanofluid, ice packing factor of ice slurry can be gotten by reasonable to control the diaphragm metering pump flow. In 2%(mass) NaCl, the nanofluid concentration in different particle size should not exceed 0.05%(mass).

    CaSO4 fouling characteristics on dimple tube
    XU Zhiming, GUO Yuanjie, HAN Zhimin, ZHAO Yu
    2018, 69(4):  1341-1348.  doi:10.11949/j.issn.0438-1157.20170944
    Abstract ( 520 )   PDF (1305KB) ( 356 )  
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    A physical model of dimple tube was established. The effects of structure and working conditions on CaSO4 fouling characteristics were simulated based on standard k-ε equation and SIMPLE algorithm. The results show that dimple arrangement has little effect on the fouling resistance asymptotic value. For the high Reynolds number, the fouling resistance of dimple tube is always smaller than that of smooth tube. For the low Reynolds number, the fouling resistance of the dimple tube with a low height is slightly higher than that of the smooth tube. The height and density of dimple have a remarkable effect on the fouling resistance. The anti-fouling rate of the dimple tube is 1.150 and 0.730, when the dimple height is 0.8 and the dimple density is 5.30, respectively. Furthermore, the anti-fouling rate increases with the increase of the inlet flow rate, and decreases with the increase of the working fluid concentration and the wall temperature.

    Experimental investigation of convective heat transfer coefficient using Fe3O4/water nanofluids under different magnetic field in laminar flow
    SHA Lili, JU Yonglin, ZHANG Hua
    2018, 69(4):  1349-1356.  doi:10.11949/j.issn.0438-1157.20170820
    Abstract ( 335 )   PDF (659KB) ( 597 )  
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    The convective heat transfer coefficients of 3%(vol) Fe3O4/water nanofluids were investigated at different inlet temperatures, under the perpendicular, uniform and gradient magnetic field and parallel magnetic field. Based on the non-dimensional analysis of the energy equation for the Fe3O4/water nanofluids, the effect of the magnetic field instead of the thermal motion of magnetic nanoparticles dominated the thermal transfer performance of Fe3O4/water nanofluids. The maximum increase of the convective heat transfer of Fe3O4/water nanofluids were 5.2% and 9.2%, respectively, under perpendicular, uniform and gradient magnetic fields. The maximum decrease of 4.8% for the convective heat transfer was observed under parallel and uniform magnetic field. In addition, the convective heat transfer coefficient increased with the temperature of Fe3O4/water nanofluids. The experimental results agreed well with the non-dimensional analysis.

    A capacitance sensor with hydrocyclone phase separator for measuring water volume fraction in gas-liquid two-phase flow
    XU Ying, XIE Fei, LI Jian, ZHANG Tao, LI Tao, MI Baotong
    2018, 69(4):  1357-1364.  doi:10.11949/j.issn.0438-1157.20170510
    Abstract ( 321 )   PDF (1037KB) ( 516 )  
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    In order to improve capability of electric capacitor for liquid volume fraction measurement, a capacitive liquid volume fraction sensor with a hydrocyclone phase separator was designed for measurement of water fraction in gas-liquid two phase flow. The hydrocyclone phase separator, which was added to the measuring section of a capacitance sensor, was optimized in structure according to kinetic theory of gas liquid two-phase flow and was determined for the number of separation cycles by actual application conditions to ensure efficiency of gas liquid phase separation. The hydrocyclone phase separation could overcome influence of various flow patterns of gas liquid two-phase flow, and convert water volume fraction information into liquid film thickness cross-section water fraction information measurement. The experimental results show that cross-section gas fraction measured by the capacitance sensor is in good agreement with the Lockhart-Martinelli cross section gas fraction model. The gas liquid two-phase flow with water volume fraction below 20% can be effectively measured with less than ±2% absolute error.

    Effects of tube bundle structure on heat transfer and resistance characteristics of slit finned elliptical tube heat exchangers
    YANG Tao, YUAN Yichao
    2018, 69(4):  1365-1373.  doi:10.11949/j.issn.0438-1157.20170877
    Abstract ( 373 )   PDF (658KB) ( 454 )  
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    Numerical simulation on slit finned elliptical tube heat exchangers with different transverse tube pitch S1, longitudinal tube pitch S2 and the ratio a/b of major and minor axis of the elliptical tube, was verified by model experiment. The effect of tube bundle structure on the heat transfer and resistance characteristics of slit finned elliptical tube heat exchangers was analyzed. The results indicate that as S1 decreases from 70.55 mm to 60.55 mm, Nu and Eu at air-side increase, with optimized comprehensive flow and heat transfer performance of the heat exchangers when S1 equals to 60.55 mm. As S2 decreases from 75 mm to 65 mm, Nu at air-side increases, but Eu at air-side has no significant changes, with optimized comprehensive flow and heat transfer performance of the heat exchangers when S2 equals to 65 mm. The heat transfer and resistance characteristics of slit finned elliptical tube heat exchangers are significantly influenced by the transverse tube pitch. When the elliptical tube circumference is equal and a/b is between 1.5 and 2.5, the optimized comprehensive flow and heat transfer performance of the heat exchangers was the best when a/b was 1.8. The findings of this paper provide proofs of the application and further optimization of such heat exchangers in engineering practice.

    Numerical study on flow and heat transfer characteristics in corrugated tube with loose-fit twisted tape insert
    HAN Huaizhi, CHEN Xin, HU Yiran, WANG Kunfang, CUI Yunlei, YU Ruitian
    2018, 69(4):  1374-1384.  doi:10.11949/j.issn.0438-1157.20170376
    Abstract ( 385 )   PDF (756KB) ( 737 )  
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    The flow and heat transfer characteristics of a novel kind of loose-fit twisted insert (CLT) are studied by RNG k-ε numerical method. The verification has been conducted to compare the numerical and the experimental results of Manglik and Bergles. The difference of flow and heat transfer characteristic is investigated by comparing between CLT and corrugated tube with loose-fit twisted tape insert (SLT). Finally, the effect of twisted ratio and clearance ratio for the flow and heat transfer characteristics is investigated in CLT. The results show that compared with the traditional SLT, the heat transfer performance in CLT increases by 1.17 times and the maximum increasing of absolute value for overall heat transfer performance is 0.15. The overall heat transfer performance in CLT increases with the increasing twisted ratio, but the increasing slope decreases gradually, meanwhile, the decreasing extent is more obvious in high Reynolds number. Meanwhile, the overall heat transfer performance in CLT decreases with the increasing clearance ratio, and the decreasing slope also decreases gradually. The decreasing extent is very obvious at the range of low Reynolds number, however, the values of overall heat transfer performance decrease slightly at the range of high Reynolds number. Take into consideration for various factors, low clearance ratio of twisted tape should be selected at the range of low Reynolds number, the high one is suitable for high Reynolds number.

    Analysis of influence of key parameters on ablative heat transfer of resin based thermal protection material
    WANG Xiaomin, CHENG Wenlong, ZHANG Lisong, LIU Na
    2018, 69(4):  1385-1390.  doi:10.11949/j.issn.0438-1157.20170635
    Abstract ( 391 )   PDF (542KB) ( 255 )  
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    To analysis the key parameters of ablation heat transfer resin based thermal protection materials, a charring layer-pyrolysis layer-original material layer one-dimensional model is applied, heat transfer process is analyzed, and the uncertain parameters sensitivity of ablative heat response of thermal protection material is obtained. The results show that the thermal conductivity is the greatest impact on the heat transfer characteristics of resin based thermal protection material ablation, the density, specific heat capacity and material thickness are secondary, and the influence of other parameters can be ignored. Meanwhile, the dimensionless correlation between the temperature and the uncertain parameters is established, which provides a reference for the selection, design and parameters correction of the thermal protection materials.

    Experimental study on heat transfer capability of Ti64ELI capillary wick in loop heat pipe
    SUN Qi, CHEN Xi, XIE Rongjian, ZHANG Chang, WU Yinong
    2018, 69(4):  1391-1397.  doi:10.11949/j.issn.0438-1157.20170652
    Abstract ( 344 )   PDF (957KB) ( 379 )  
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    In the loop heat pipe (LHP), the structure of the evaporation section is the most complex, and the capillary wick is a part that directly affects its working performance, so it has a great research value. To simulate the real operation of the capillary wick in LHP, an experimental device was designed to measure the surface temperature during the operation at room temperature. The heat transfer capacity of the capillary wick in the evaporative section of LHP was studied independently. The experimental study consisted of measuring the effective thermal conductivity using ethanol and water as working fluid at different heating power. It was found that the effective thermal conductivity of the ethanol-containing capillary wick is higher than that of the water-containing capillary wick at low heating power, while the results were reversed at high heating power. The conclusion of this experiment has a certain reference value for the evaluation of the heat transfer performance of the capillary wick, and it can also provide some experimental data for the simulation of the LHP evaporator.

    Flow resistance characteristics in rod bundle channel under natural circulation condition
    ZHU Zhiqiang, YAN Changqi, WANG Jianjun, TIAN Chunping
    2018, 69(4):  1398-1404.  doi:10.11949/j.issn.0438-1157.20170747
    Abstract ( 360 )   PDF (519KB) ( 237 )  
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    Rod bundle channel is widely applied as reactor core coolant passage, in which the flow characteristic is of great significance for safe operation of the reactor, it is necessary to do some experimental investigations on it. The flow resistance characteristics experiments were performed under natural circulation condition. It was found that the friction factor is less than predicted value by Cheng & Todreas correlation and has no obvious rise when the flow transition happens, which is different from the results in regular channel. A correlation to calculate the friction factor in laminar regime was proposed and it also has the same form with the correlation in regular channel. In addition, there is still a large transition region for friction factor in rod bundle channel under natural circulation condition. Based on the experimental results with different heat flux, it was found that the friction factor decreased with the rise of heat flux and viscosity revision was considered. As for local resistance at the spacer grid, no obvious flow transition occurred and correlations for local resistance calculation were fitted in different range of Reynolds number.

    Effects of supersonic and subsonic nozzles on performance of adjustable ejectors
    JIN Xu, YU Yue, CHEN Zuozhou, DANG Chaobin, LIU Zhongyan
    2018, 69(4):  1405-1411.  doi:10.11949/j.issn.0438-1157.20170270
    Abstract ( 571 )   PDF (816KB) ( 417 )  
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    An adjustable ejector with axial moving probe was taken as the object, the effects of ejector with supersonic and subsonic nozzles were investigated by experiment and simulation. The results showed that the flow characteristics of nozzles exit driving flow has close relationship with performance of the ejector, and was the main reason for the differences of the performance on the ejectors of two configurations of nozzles. For supersonic nozzles, the state of the nozzle exit's driving flow varies with the position of the probe, while the subsonic nozzle has no such variation characteristic. In the process of adjusting the performance of the ejector through the probe, when the supersonic nozzle exit's driving flow was ideally-expanded, the system was at an optimal operating condition. While the driving flow was over-expanded, the compression shock waves would be generated, the system performance would be reduced and its performance was inferior to the performance of subsonic nozzle. Furthermore, alternatives for two nozzle configurations were proposed.

    Characteristic and prediction of thermo-acoustic oscillation of aviation kerosene under supercritical pressures
    WANG Yanhong, LI Sufen
    2018, 69(4):  1412-1418.  doi:10.11949/j.issn.0438-1157.20170956
    Abstract ( 390 )   PDF (667KB) ( 159 )  
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    The flow instability with a type of thermo-acoustic oscillation of aviation kerosene at supercritical pressures in a vertical upward circular tube was investigated. The formation mechanism and development process of thermo-acoustic oscillation were revealed based on the boundary layer theory. The effect mechanisms of operational parameters on thermo-acoustic oscillation border were analyzed. The prediction criterion for thermo-acoustic oscillation border was established by the sub-pseudo-critical number and trans-pseudo-critical number. The prediction problem for final state heat transfer of thermo-acoustic oscillation was solved. Results indicate that the stable flow and thermal boundary layers are destroyed owing to the drastic thermo-properties fluctuations. They lead to the thermo-acoustic oscillation flow instability phenomenon with enhanced heat transfer capability. The critical heat flux of thermo-acoustic oscillation increases with the increasing mass flow rate and inlet temperature. The thermo-properties variations tend to gentle as the pressure increases, hence the flow stability is enhanced and the thermo-acoustic oscillation does not appear easily. The critical trans-pseudo-critical number for thermo-acoustic oscillation approximately linear decreases with the increasing sub-pseudo-critical number. It consequently provides a discriminating criterion to avoid the flow instability phenomenon.

    Experimental study on bubble departure diameter of ethane saturated nucleate pool boiling
    CHEN Hanzhi, YAO Yuan, GONG Maoqiong, CHEN Gaofei, ZOU Xin, DONG Xueqiang, SHEN Jun
    2018, 69(4):  1419-1427.  doi:10.11949/j.issn.0438-1157.20170802
    Abstract ( 365 )   PDF (630KB) ( 575 )  
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    Nucleate pool boiling in ethane was studied at 0.15, 0.2 and 0.3 MPa at heat flux between 14.27 and 81.22 kW·m-2 by visualization technique. Images of departure ethane bubbles at upper smooth surface of the vertical 20 mm-diameter heating copper rod were recorded at a frame rate of 2619 fps and a full resolution of 960×720 pixels by Phantom high-speed digital camera. The departure bubble diameters were got by image processing and analyzed relationship with Jacob number(Ja). With the increase in Ja, bubble departure diameter tended to increase but not monotonically. Compared experimental diameter data with predictions of six most used correlations, it was found that Kim and Kim(2006) model had the best prediction with absolute average deviation (AAD) below 30% at all three pressures and 50% of the predicted values within 30%-40% deviations at 0.15 MPa. Finally, a new correlation was proposed on a basis of fitting bubble departure data and Kim and Kim (2006) power law model, which has within ±30% difference between prediction and experimental data. The prediction for methane departure diameters at four different pressures were within ±30% (only one over ±30%) of the literature data. The new correlation works well for both methane and ethane at various operating conditions, however, its application range is limited because the correlation is obtained from data under low Ja.

    Flow boiling heat transfer characteristics of CO2 in horizontal micro-tube
    JIANG Linlin, LIU Jianhua, ZHANG Liang, ZHAO Yue
    2018, 69(4):  1428-1436.  doi:10.11949/j.issn.0438-1157.20170693
    Abstract ( 360 )   PDF (559KB) ( 200 )  
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    The characteristics of heat transfer for CO2 flow boiling in horizontal micro-tube were studied. Experimental conditions:saturated temperature -40-0℃, heat flux 5-35 kW·m-2, mass flow rate 200-1500 kg·m-2·s-1, and inner diameter 1.5 mm. Experimental results show that:the increase of heat flux has significant effect on enhancing nucleate boiling heat transfer, meanwhile speeds up the dryout process and decreases the starting vapor quality of dryout; the effect of mass flow rate on heat transfer coefficient is slight, but as mass flow rate increasing, the starting vapor quality of dryout decreases, and the heat transfer coefficient increases after the dryout happens; the effect of saturation temperature on the physical properties of CO2 is the main cause of the different heat transfer characteristics in different experimental conditions.With the increasing of saturation temperature, the starting vapor quality of dryout has a decline tendency and the heat transfer coefficient has a steeper fall after dryout happens. Compared with the prediction model, the Cheng's model has a higher prediction accuracy, it is presented with 77.1% of predicted points within ±30% and 20.5% mean absolute deviation before dryout phenomenon happened, while it has only 22.9% and 57.8% after dryout phenomenon happened.

    Performance analysis on direct contact condensation refrigeration cycle of high temperature gas with super-cooled liquid
    NING Jinghong, LIU Shengchun
    2018, 69(4):  1437-1444.  doi:10.11949/j.issn.0438-1157.20170122
    Abstract ( 380 )   PDF (449KB) ( 624 )  
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    The direct contact condensation refrigeration cycle of high temperature gas discharged by compressor with super-cooled liquid is designed. Combined with the thermodynamic properties of natural refrigerant ammonia, the thermal performances of direct contact condensation refrigeration cycle are analyzed and compared with that of convention two stage compression refrigeration cycle and one stage compression refrigeration cycle. The following conclusions are obtained. With the increasing of saturated liquid temperature of main cycle, the coefficient of performance (COP) of direct contact condensation refrigeration cycle first increases, then decreases and has the maximum, the condenser heat load first decreases, then increases and has the minimum. The refrigerant mass flow rate in evaporator is gradually increasing. At the same evaporating and condensation temperature, when the super cooling degree of supercooled liquid is 20℃, compared with that of conventional two stage compression refrigeration cycle, the COP of direct contact condensation refrigeration cycle increases 4.92%, the condenser heat load reduces 6.65%, and the refrigerant mass flow rate in evaporator reduces 7.2%-7.9%. As well as when the super cooling degree of supercooled liquid is 5℃, compared with that of conventional one stage compression refrigeration cycle, the COP of direct contact condensation refrigeration cycle increases 6.52%, the condenser heat load reduces 3.32%, and refrigerant mass flow rate in the evaporator reduces 8.58%-8.91%. The results show that the ammonia direct contact condensation refrigeration cycle has obvious advantages over the conventional refrigeration cycle.

    Influence of temperature-pressure coupling characteristics on desorption performance of adsorption refrigeration unit
    DU Wenping, LI Ming, WANG Yunfeng, HE Jinghong, FENG Zhikang, ZHANG Xiaodie
    2018, 69(4):  1445-1453.  doi:10.11949/j.issn.0438-1157.20170858
    Abstract ( 341 )   PDF (790KB) ( 143 )  
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    The mass transfer performance is limited by the unstable heat source temperature during the desorption process of a solar energy adsorption refrigeration cycle. However, the pressure regulation can be used as an effective compensation method for mass transfer enhancement. The expressions of desorption ratio(l) and desorption rate are given by building a theoretical model of constant temperature desorption. The effect of mass transfer enhancement through pressure swing was calculated. The theoretical results revealed the regularities that the desorption ratio(l) would increase with the decrease of the system pressure at different desorption temperatures. The results showed that there were the same effects on the improvement of desorption rate through reducing the pressure of the system of 10 kPa or increasing the heat source temperature of 6-8℃. In addition, a solar adsorption unit tube adsorption refrigeration platform with activated carbon-methanol as working pair was constructed. Experiments were carried out under different desorption temperatures and system pressures, and the theoretical results were verified by experiments. The results showed that when the system pressure decreased by 14 kPa, at the desorption temperature of 90℃, 100℃ and 110℃, the desorption ratio(l) increased by 20.5%, 15.1% and 12.1%, and the average desorption rate increased by 49.3%, 44.6% and 37.1%, respectively. The experimental results are in good agreement with the theoretical calculation. The coupling relationship between the temperature and pressure on desorption performance was obtained. Finally, the method of lowering pressure for enhanced desorption is proposed in a practical application of solar adsorption refrigeration system.

    Visualization of particle movement in flow path of flue gas turbine
    WANG Jianjun, GUO Ying, CHEN Shuaifu, JIN Youhai, DING Jian, HAN Zhaoyu
    2018, 69(4):  1454-1460.  doi:10.11949/j.issn.0438-1157.20171082
    Abstract ( 404 )   PDF (1251KB) ( 275 )  
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    Flue gas turbine is a key equipment in energy recovery system of catalytic cracking unit. But easy deposition of catalyst particles in flue gas on inner wall caused erosion and wear on turbine blades and affected normal system operation. In order to study complex two-phase movement in flue gas turbine, a model flue gas turbine was designed based on actual system. Particle movement in flow path of flue gas turbine was photographed by high speed camera to capture interaction process between particles and wall surface. The results show that the leading edge of turbine moving blade is high collision frequency region where velocity direction is largely changed after particle collision. The trailing edge of moving blade pressure surface is a place where particles have multiple collisions. Small size particles easily move close to the moving blade pressure surface. The experimental results provide important bases for further exploring catalyst particle deposition mechanism in flue gas turbine.

    Deposition behavior of barium sulfate in microchannel reactors
    ZHANG Baodan, YANG Bei, YANG Suohe, SU Mingyue, HE Guangxiang, GUO Xiaoyan, JIN Haibo
    2018, 69(4):  1461-1468.  doi:10.11949/j.issn.0438-1157.20171257
    Abstract ( 418 )   PDF (804KB) ( 486 )  
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    Fouling of barium sulfate is often observed and difficult to clean up in the process of petroleum production. Barium sulfate deposition of simulated oilfield water in the microchannel reactor was studied by varying tube length, flow rate, concentration and temperature. Barium concentration and pressure drop in each microchannel section were obtained by flame atomic absorption and differential pressure method, respectively. The results show that the rate and amount of barium sulfate deposition in the microchannel increased with increase of tube length, flow rate, and concentration, which deposition rate was increased nonlinearly. With temperature increase, ion diffusion in the microchannel accelerated and deposition rate of barium sulfate increased. However, a slight rise of temperature did not change concentration of barium sulfate significantly and hence deposition amount of barium sulfate was increased very little. SEM morphology of barium sulfate in both inlet and outlet verified impacts of different factors on deposition and crystallization in the microchannel. Deposition of barium sulfate in pipeline is not just a simple homogeneous sedimentary process, as a result of influence of crystal nucleation. The barium sulfate crystal formation has two regular stages of nucleation and crystal growth.

    Flow characteristics of granule discharged from eccentric wedge-shaped feed hopper
    LIU Yilun, LIU Siqi, ZHAO Xianqiong, LIU Chi, ZHANG Zhe
    2018, 69(4):  1469-1475.  doi:10.11949/j.issn.0438-1157.20170852
    Abstract ( 377 )   PDF (1793KB) ( 474 )  
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    Flow field distributions of discharging various sized granular materials from wedge-shaped feed hopper was numerically simulated using three-dimensional discrete element method. A mathematical model of mass flow index (MFI) was proposed for the wedge-shaped feed hopper. The discharge flow pattern and its relationship with discharge mass flow rate was analyzed, and model reliability was verified experimentally. The results show that granular flow field in the hopper has a high velocity region near feed pipe outlet and is radially attenuated towards low velocity region at the upper hopper which is away from vertical wall and feed pipe. The flow direction of particles in high velocity region was well consistent, whereas granular flow in low velocity region exhibited local vortices. With the increase of particle size, overall flowability of particles in the hopper decreased, which high velocity region shrinked, low velocity region enlarged, and transition region became obscure, hence both MFI and discharge mass flow rate were decreased. When particle size was no more than 10 mm, MFI was negatively linearly related to particle size, but was positively linearly to discharge mass flow rate.

    Mechanisms of selective hydrogenation of crotonaldehyde on In/Au (111) and Ir/Au (111) surfaces
    XIA Shengjie, LUO Wei, XUE Jilong, MENG Yue, JIANG Junhui, NI Zheming
    2018, 69(4):  1476-1483.  doi:10.11949/j.issn.0438-1157.20170871
    Abstract ( 337 )   PDF (1246KB) ( 177 )  
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    From stable structures of vertical crotonaldehyde (CAL) adsorption on alloy surfaces of M/Au (111) (M=In, Ir), reaction mechanisms of incomplete hydrogenation (C=O addition, C=C addition, and 1,4-conjugate addition) of CAL on the M/Au (111) surface were studied by density functional theory (DFT) in combination with periodic slab model. Calculation of activation energy and heat of elementary step reactions and analysis of conformation change at various hydrogenation mechanisms showed that CAL on the In/Au (111) and Ir/Au (111) planes first hydrogenated near-surface C=O by A2 mechanism, which an H atom was first added to active C on generation of MS1 and then another H atom was added to intermediate MS1. Both elementary reactions were exothermic but the first one was the rate-determining step due to higher activation energy. The maximum energy barrier of elementary reactions of CAL hydrogenation by the optimal hydrogenation mechanism on In/Au (111) surface was 0.969 eV, which was much lower than that of 1.332 eV on the Ir/Au (111) surface. Hence, In/Au (111) had better catalytic activity than Ir/Au (111) surface for incomplete hydrogenation of CAL. Adsorption of reactant and products on M/Au (111) surface indicated that formation of strong chemical adsorption between crotonaldehyde O atom and alloy doping element M improved selectivity of M/Au (111) to C=O hydrogenation.

    Effect of MnOx on Pt/CeZrO2 catalyzed CO oxidation under water vapor and CO2 conditions
    ZHU Li, DENG Yun, SONG Yupeng, WANG Yuejuan, LU Jiqing, LUO Mengfei
    2018, 69(4):  1484-1492.  doi:10.11949/j.issn.0438-1157.20170942
    Abstract ( 255 )   PDF (814KB) ( 393 )  
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    Adding MnOx to CeZrO2 solid solution carrier could effectively enhance Pt/CeZrO2 catalyst activity for CO oxidation. The effect of the amount of MnOx on catalytic activity and resistance of H2O and CO2 was studied. The results showed that the activity of Pt/MnOx/CeZrO2 catalyst was first increased and then decreased as MnOx content was increased with a maximum activity at 0.5% (mass) MnOx content. The addition of MnOx improved catalyst activity by reducing Pt particle size and changing catalyst reducibility. The presence of H2O vapor and CO2 in feed gas suppressed activity of Pt/CeZrO2 catalyst, which was effectively alleviated by MnOx in the catalyst. Kinetic study revealed that CO reaction order was considerably increased with presence of H2O and CO2for the Pt/CeZrO2 catalyst. Such a decline of catalyst activity might be due to competitive adsorption of H2O and CO2 over CO on catalyst surface. In contrast, the CO reaction order was slightly increased with presence of H2O and CO2 for Pt/0.5MnOx/CeZrO2 catalyst, implying that addition of MnOx could suppress competitive adsorption of H2O and CO2 over CO on catalyst surface and hence improve resistance to H2O and CO2.

    Preparation of monodispersed core-shell Co3O4@SiO2 catalyst and its application in N2O catalytic decomposition
    QIU Yuan, WANG Changzhen, LI Haitao, HU Xiaobo, WANG Yongzhao, ZHAO Yongxiang
    2018, 69(4):  1493-1499.  doi:10.11949/j.issn.0438-1157.20170998
    Abstract ( 336 )   PDF (773KB) ( 714 )  
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    N2O is an important greenhouse gas with significant destructive effect on ozone layer. Direct catalytic decomposition is one of the most cost-effective ways to remove N2O. In recent years, plenty of researches on direct catalytic decomposition of N2O have been focusing on supported cobalt oxide catalysts due to their excellent low-temperature catalytic performance. An encapsulated cobalt-based core-shell material was first introduced into the N2O direct catalytic decomposition reaction. The dimension-limited core structure and mesoporous shell structure could effectively improve the metal dispersion, reduce particle size, and increase contact interface between active metal oxide and reactants, so that low temperature catalytic activity was significantly enhanced in N2O catalytic decomposition. Furthermore, a series of Co3O4@SiO2 spherical core-shell catalysts with different metal content were prepared to investigate the effect of encapsulation structure on catalytic performance. Characterizations on catalysts with techniques such as X-ray fluorescence spectroscopy (XRF), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), N2 adsorption-desorption and hydrogen temperature-programmed reduction (H2-TPR) indicated that catalysts with more active Co sites have better activity under premise of stable monodisperse core-shell structure.

    Adsorption isotherms and selectivity of CH4/C2H6/C3H8 on MOF-505@5GO
    WU Houxiao, CHEN Yongwei, LIANG Junjie, SHI Renfeng, XIA Qibin, LI Zhong
    2018, 69(4):  1500-1507.  doi:10.11949/j.issn.0438-1157.20170670
    Abstract ( 338 )   PDF (727KB) ( 280 )  
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    MOF-505@GO composites with different ratios of MOF-505 to graphite oxide were synthesized by solvothermal method. They were characterized by powder X-ray diffractions(PXRD), scanning electron microscopy (SEM), Raman and porosity measurement through nitrogen adsorption. The isotherms of CH4, C2H6 and C3H8 on the MOF-505@GO and MOF-505 were measured separately. Results showed that MOF-505@5GO had the largest pore volumes and BET surface area. The pore volumes and BET surface areas of MOF-505@GO increased as the GO content increased, when GO contents increased to 8%(mass) and 10%(mass), the opposite trend was observed in which the pore volumes and BET surface areas decreased. Accordingly, MOF-505@5GO exhibited the highest CH4, C2H6 and C3H8 uptake of 0.88, 4.81 and 5.17 mmol·g-1 at 298 K and 0.1 MPa, having an increase of 14.9%, 30.7% and 13.1%, respectively. Moreover, IAST-predicted C2H6/CH4 selectivity of MOF-505@5GO was about 40.1 and C3H8/CH4 selectivity was about 3056.1. It suggests that MOF-505@5GO is a promising candidate for the separation of C2H6/CH4 and C3H8/CH4.

    Facile synthesis of carbon nanotubes-graphene aerogels and its adsorption property for emulsified oil in water
    MA Yanbing, LIU Hui'e, CHEN Shuang, DING Chuanqin
    2018, 69(4):  1508-1517.  doi:10.11949/j.issn.0438-1157.20170895
    Abstract ( 450 )   PDF (1230KB) ( 435 )  
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    Graphene oxide (GO) was prepared by an improved Hummers-Offeman's method. The GO and carboxylated multi-walled carbon nanotubes (CNTs-COOH) was used as raw materials, polyvinyl pyrrolidone (PVP) as crosslinking agent and ethylenediamine (EDA) as the reducing agent. Hydro-thermal method was adopted in the preparation of carbon nanotubes-graphene aerogel (CGA). The density was between 8.40 mg·cm-3 and 14.42 mg·cm-3 for CGAs under different mass ratios of GO to CNTs-COOH. The mechanical strength of the composite aerogel under the mass ratio of GO:CNTs-COOH=3:1 is optimal. The characterized results by scanning electron microscopy (SEM), X ray diffraction (XRD), X ray photoelectron spectroscopy (XPS) showed that GO and CNTs-COOH have been successfully assembled into reducing porous aerogel structure. The study on CGA sample adsorption characteristics of emulsified diesel oil in water at different temperatures showed that the adsorption capacity of CGA increased rapidly in the first 6 min. The adsorption equilibrium was achieved in about 30 min. With the increase of temperature, the equilibrium adsorption capacity increased gradually. The adsorption process follows pseudo-second order kinetics model. The apparent activation energy is 7.10 kJ·mol-1. Through the particle diffusion model analysis, it is found that the adsorption process of CGA is divided into an outer surface adsorption and pore adsorption processes, which include large inner pore adsorption, mesopore adsorption and small-size pore adsorption.

    Interaction effect of optimized value of geometric parameters of spiral groove of dry gas seal
    JIANG Jinbo, CHEN Yuan, ZHAO Wenjing, LI Jiyun, PENG Xudong
    2018, 69(4):  1518-1527.  doi:10.11949/j.issn.0438-1157.20170857
    Abstract ( 334 )   PDF (795KB) ( 181 )  
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    The interaction effects of other geometric parameters on the optimized value of a certain geometric parameters of spiral groove dry gas seal (DGS) in low pressure are analyzed for the purpose of solving the problem of the interaction effect of geometric parameters of hydrodynamic groove on objective function that have been ignored in optimization design of hydrodynamic groove of DGS which leads to the inaccuracy of optimized value of geometric parameters. Geometrical and mathematical model of spiral groove DGS are set up according to the theory of gas lubrication. The pressure distribution and steady performance are obtained by solving the Reynolds equations by using finite difference method, and several characterized parameters of spiral groove are defined. The change rules of optimized values for the maximum film stiffness of a certain geometric parameter of spiral groove with other geometric parameters in different operation velocity are presented. The results show that complicated interaction effect relationship existed between the geometric parameters of spiral groove DGS, of which suit for the three comprehensive design criteria, including decrease the amplitude changes of real flow area of groove, groove length-width ratio and groove length-depth ratio. The maximum film stiffness obtained by the optimization method of considering the interaction effect of geometric parameters is about 11.4% which is larger than that obtained by the single factor optimization method in the given example.

    Analysis on leakage mechanism for contacting mechanical seal interface
    SUN Jianjun, CHEN Guoqi, JI Zhengbo, MA Chenbo
    2018, 69(4):  1528-1536.  doi:10.11949/j.issn.0438-1157.20170908
    Abstract ( 446 )   PDF (869KB) ( 410 )  
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    The sealing performance of rotating mechanical equipment has an important impact on the energy consumption, efficiency and environmental protection during the production process. Based on the percolation theory, the variation law of the porosity distribution of the contacting mechanical seal interface with fractal parameters concerning the surface topography of rotary and stationary rings as well as the normal contact pressure was also discussed. A single-layer lattice leakage channel structure model of sealing interface was also established. A single-layer lattice leakage model referring to the channel structure of sealing interface was established, and three different states (percolating state, critical percolating state and non-percolating state) can be acquired under different contact pressure. According to the liquid capillary force and gas Knudsen number, the fluid flow criterion in the micro-channel was proposed, and flow resistance and leakage flow through sealing interface were analyzed, moreover, leakage mechanism of contacting mechanical seal interface was also illustrated. The research results provide a theoretical basis for the optimal design and leakage control of contacting mechanical seals in the next work.

    Parameters analysis of steady micro-scale flow of cylindrical spiral groove dry gas seal
    DING Xuexing, HE Zhenhong, ZHANG Weizheng, LU Junjie, MIAO Chunhao
    2018, 69(4):  1537-1546.  doi:10.11949/j.issn.0438-1157.20170873
    Abstract ( 389 )   PDF (685KB) ( 451 )  
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    A new-type of cylindrical spiral dry gas seal was employed in gas turbine with large vibration. In order to investigate the performance of the cylindrical gas seal, the approximate analytic solution of the gas pressure was obtained by the methods of PH linearization and iteration, which was deduced from the steady micro-scale cylindrical Reynolds equation with the slip boundary conditions. According to the related formulas, the dimensionless buoyancy, leakage and friction torque of cylindrical spiral gas film were analyzed with the different operation conditions and groove structural parameters. Furthermore, part of the optimized structural parameters of spiral groove was proposed based on the comparison of the steady characteristics. It is indicated that the influence of pressure difference on the steady characteristic is more significant than the eccentricity ratio. The influence of the groove number(n) on the buoyancy is not obvious. The friction torque increases with the increase of the groove number but the leakage decreases to a stable value when n=12. The buoyancy decreases with the increase of the groove depth, which is opposite to the friction torque and leakage. With the increase of the seal width(L), the leakage get stable at L=0.035 m. The increase of the spiral angle leads to the decrease of the buoyancy but the increase of the friction torque and leakage. The friction torque increases with the structural parameters under the pressure difference. The increase of the groove number leads to the decrease of the buoyancy, which is opposite to the influence of groove depth. The buoyancy decreases at L=0.04 m then increases with the increase of the seal width, which is opposite to the influence of spiral angle. The increase of the groove number and seal width lead to the robust decrease of the leakage. Optimized structural parameters are obtained: n=12-18, L=0.03-0.045 m, a=40°-50°.

    Transient characteristics of liquid film seals under unsteady conditions
    XU Lushuai, HAO Muming, LI Yongfan, YANG Wenjing, WANG Yunlei, CAO Hengchao
    2018, 69(4):  1547-1557.  doi:10.11949/j.issn.0438-1157.20170817
    Abstract ( 284 )   PDF (973KB) ( 225 )  
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    Transient change of the operating parameters has a serious influence on the stability of liquid film seals. Three-dimensional model of sealing clearance was established based on Matlab. Reynolds equation considering JFO cavitation boundary was discretized by finite difference method. SOR iteration was used to solve fluid film pressure distribution. By further solved coupled Reynolds equation and transient dynamic equations, the influence of continuous change of working conditions and pressure disturbance on transient characteristics were analyzed. The results show that squeeze effect of liquid film during transient change of pressure has more significant influence on sealing performance than speed change. The faster approach speed of seal face, the higher carrying capacity of liquid film extrusion and the greater the velocity of the discharge of the end face fluid. Instantaneous change of pressure easily leads to the axial velocity oscillation of stator ring. The greater the pressure difference, the greater shock amplitude. Leakage rate and cavitation ratio has a large disturbance tends to be stable after abrupt mutation in the case of differential pressure disturbance. Pressure rise compared to pressure drop is more easily to restore stable state. Friction torque varies smoothly during the condition changing without significant fluctuation.

    Cavitation effect and leakage control mechanism of reverse spiral grooves mechanical end face seals
    MA Xuezhong, MENG Xiangkai, WANG Yuming, ZHAO Wenjing, SHEN Mingxue, PENG Xudong
    2018, 69(4):  1558-1568.  doi:10.11949/j.issn.0438-1157.20170726
    Abstract ( 547 )   PDF (1652KB) ( 526 )  
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    The Reynolds equation of a reverse spiral groove mechanical end face seals was solved based on the JFO cavitation boundary condition by the Stream-Upwind/Petrov-Galerkin (SUPG) finite element method. The cavitation effect of the reverse spiral grooves was investigated. A novel reverse-spiral-grooved seal end face combined with forward-spiral grooves was proposed. The sealing performance under the different operating conditions was analyzed. The results show that the liquid film in grooved zones is prone to cavitation for the reverse spiral groove end face seal. The cavitation zones significantly affect the flow field distribution of the fluid film. The fluid at the inner side can be absorbed into the cavitation zones due to the pressure difference between the cavitation zones and the inner side. The novel seal end face combines the leakage control effect of the reverse spiral grooves and the hydrodynamic effect of the forward spiral grooves, and shows good upstream pumping capacity and load carrying capacity.

    Chaos analysis of electrochemical noise and its application in localized corrosion detection
    XIA Dahai, SONG Shizhe, WANG Jihui
    2018, 69(4):  1569-1577.  doi:10.11949/j.issn.0438-1157.20170816
    Abstract ( 377 )   PDF (1301KB) ( 928 )  
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    The chaos theory was used to analyze electrochemical noise (EN) data for corrosion detection during coating degradation and stress corrosion cracking (SCC) process and insightful results were achieved by correlation dimensional characterization of localized corrosion. Analysis of electrochemical potential noise (EPN) during corrosion degradation of novolac epoxy coated on tinplate indicated that number of correlation dimensions corresponding to EPN tended to increase as localized corrosion accelerated. In addition, chaos phase space reconstruction was employed to analyze stress corrosion EN of 304 stainless steel (SS) and to characterize SCC process via correlation dimensions. The results showed that phase space trajectory resembled spherical shape in the initial SCC stage and then changed to elliptical shape in the later SCC stage. The increase of correlation dimension during crack initiation and propagation revealed increment in uncertainty and complexity of EN signals.

    Distribution of sulfur in chemical looping combustion of anthracite based on Fe-based oxygen carrier
    ZHANG Zhifeng, WANG Yifei, ZHU Longchu, LI Jilin, WANG Fuchen, YU Guangsuo
    2018, 69(4):  1578-1585.  doi:10.11949/j.issn.0438-1157.20170838
    Abstract ( 303 )   PDF (1068KB) ( 260 )  
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    In a batch fixed bed reactor, distribution of sulfur was studied during chemical looping combustion of anthracite based Fe2O3/Al2O3 oxygen carrier(OC). Reduction temperature and content of Fe2O3 were tested as variables. The work showed that the carbonaceous gas quantity increased with increasing temperature, while it increased first and then decreased with content of Fe2O3 improved. The proportion of CO2 reached the highest value 37.6% at 850℃ and there were no SO2 detected at experiments. At 2 h, the occupation of sulfur in OC increased with improvement of both temperature and the content of Fe2O3. At 5.5 h, the occupation of sulfur in OC decreased obviously with improvement of temperature. Surface microstructure of reacted OC was also evaluated using a scanning electron microscope. The results showed that OC sintered gradually with increase of content of Fe2O3.

    Effect of SO2 on CO2 sorption characteristics using solid amine CO2 sorbent
    ZHANG Wenjing, WU Ye, CAI Tianyi, LIU Daoyin, MA Jiliang, LIANG Cai, CHEN Xiaoping
    2018, 69(4):  1586-1594.  doi:10.11949/j.issn.0438-1157.20170957
    Abstract ( 327 )   PDF (854KB) ( 461 )  
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    The presence of trace SO2 in the flue gas of the power plant will affect the CO2 sorption performance and cyclic characteristics of the solid amine sorbent. A solid amine-based CO2 sorbent was prepared by a one-pot sol-gel process followed by supercritical drying (SCD) and the CO2 sorption performance. Deactivation mechanism of the sorbent were studied by using fixed-bed reactor combined with infrared spectroscopy, BET and other test methods. The results show that the solid amine-based CO2 sorbent has excellent CO2 sorption performance and cyclic characteristics when the reaction temperature was 50℃. However, when the reaction atmosphere contains SO2,the non-renewable sulphite or sulfate byproducts reduces the utilization rate of active amine sites, thus significantly decreasing the CO2 adsorption capacity, and consequently, the cyclic characteristics were seriously affected. Besides, the pore distribution of sorbent also tends to small pore volume. Increasing the sorption temperature will enhance the CO2 sorption competivity of the amine based sorbent.

    Effects of surface properties of activated carbon on its adsorption and oxidation of hydroquinone
    LIU Yuzhi, WANG Chen, GAO Yu, SUI Zhenying, ZOU Donglei
    2018, 69(4):  1595-1601.  doi:10.11949/j.issn.0438-1157.20170864
    Abstract ( 322 )   PDF (738KB) ( 540 )  
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    The oxygen-containing functional groups and pore structures of activated carbon in adsorption and oxidation mechanism of hydroquinone were studied. Effects of initial pH value, the dosage of activated carbon, on the adsorption and oxidation efficiency of hydroquinone were studied. Then the relationship between adsorption rate, apparent conversion rate of hydroquinone and the materials of activated carbon, the dosage of activated carbon was discussed. The results showed that the oxygen-containing functional groups of activated carbon could adsorb and oxidate hydroquinone, wood-chip activated carbon was better than the other two types of activated carbon on the adsorption and oxidation efficiency of hydroquinone. Under the condition of not to adjust the initial pH, reaction time 3 h, and reaction temperature 25℃, if wood-chip activated carbon dosage was 0.5 g·L-1 quality its base adsorption was 95.5% and if dosage was 0.1 g·L-1 the conversion of hydroquinone was 32.1%. The microporous surface area of sawdust activated carbon was larger than the other two activated carbon's, and the phenol hydroxyl group, carboxyl group, and carbonyl group were more abundant. Therefore, the adsorption and oxidation efficiency of hydroquinone using sawdust activated carbon was better. On the basis of this, the mechanism of activated carbon adsorption and oxidation of hydroquinone were proposed. It provided the theoretical basis for the treatment of wastewater containing phenolic organic pollutants by activated carbon as adsorbent and catalyst carrier.

    Effects of negative DC electric fields on CH4/airpremixed flame at different initial pressures
    HOU Juncai, LI Chao, JIA Weidong, WEI Xuxing, LI Yiming, MENG Hao, ZHANG Qing'ang, WU Xiaomin
    2018, 69(4):  1602-1610.  doi:10.11949/j.issn.0438-1157.20170658
    Abstract ( 297 )   PDF (1732KB) ( 508 )  
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    The effect of DC electric field on methane/air premixed flame was studied under the room temperature (298 K) and initial pressure Pinitial of 0.1-0.5 MPa. The results are as follows. The flame is mainly stretched in the horizontal direction with the applied voltage under different initial pressures. The change of the flame deformation increases with the voltage amplitude. The flame instability increases with the initial pressure. Compared to without the applied voltage, the flame propagation speed is improved obviously with the applied voltage, and the enhancement in flame propagation speed increases with the voltage amplitude and initial pressure, so the effect of the electric fields on the flame increases with the initial pressure. When λ=1.4,U=-10 kV,and Pinitial=0.1-0.5 MPa, the average flame propagation speed increases by 35.67%-52.71%. The enhancement in the mass burning rate increases with the voltage amplitude and the initial pressure with the applied voltage. The initial burning period and the main combustion period are shortened with the applied voltage, and the decrease in them increase with the initial pressure, and the change of the initial burning period is more obvious.

    Numerical simulation of effect of phase change material on temperature distribution in power battery pack of vehicle
    WANG Jian, GUO Hang, YE Fang, MA Chongfang
    2018, 69(4):  1611-1619.  doi:10.11949/j.issn.0438-1157.20170803
    Abstract ( 339 )   PDF (2699KB) ( 226 )  
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    The temperature has a significant effect on electric vehicle lithium-ion battery, i.e., higher temperature will reduce the battery discharge efficiency to accelerate the decay of battery life, while lower temperature will reduce the charging efficiency of battery to shorten the electric vehicle mileage. In order to keep the temperature of the battery in the appropriate temperature range, this paper designed a phase change material management system. The phase change material was wrapped on the outside of the battery, and the influence of phase change material on the temperature field of the battery was studied. The results showed that the latent heat of the phase change material was the most important physical parameter, which directly determined the maximum temperature of the battery pack. The bigger the thermal conductivity of the phase change material, the more uniform the temperature distribution of the battery pack. Compared with pure paraffin, the maximum temperature of the battery pack could be reduced by 2℃ by the phase change material with graphite content of about 25%. In winter, a phase change material heat preservation system made the average temperature of the battery pack 8℃ higher than that without the phase change material.

    Effect of alternating electromagnetic field and ultrasonic on hard water solution and its crystallization
    ZHANG Chuanxin, HAN Yong, ZHU Lin, ZHAO Ruikuan, WU Huifan
    2018, 69(4):  1620-1630.  doi:10.11949/j.issn.0438-1157.20170856
    Abstract ( 515 )   PDF (1274KB) ( 317 )  
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    The pH and conductivity, which can reflect the physicochemical properties of hard water directly, were studied. The pH and conductivity were measured under alternating electromagnetic field, ultrasonic and their combination respectively. The variations of pH and conductivity caused by the three physical forces were discussed. In addition, the effects on the surface morphology and composition of calcium carbonate crystals caused by alternating electromagnetic field, ultrasonic and their combination were investigated by scanning electron microscope(SEM). The results show that the alternating electromagnetic field can enhance the rate of collision of positive and negative ions, promote small crystal particles forming and inhibit its volume increasing. Ultrasonic can promote the calcium carbonate precipitation forming, increase the ion migration rate in the solution, destroy the order of CO32- in CaCO3 crystals and induce the crystal surface to grow defectively. The combination of alternating electromagnetic field and ultrasonic can increase the number of small crystals, inhibit its volume growing, and increase the proportion of aragonite in the scale.

    Effect of solubility between R32 and new PVE oil on performance of air conditioning system
    JIN Wufeng, YU Bin, GAO Pan, XU Lei
    2018, 69(4):  1631-1637.  doi:10.11949/j.issn.0438-1157.20170091
    Abstract ( 504 )   PDF (698KB) ( 1097 )  
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    The oil soluble test system was built to get the two phase separation temperature curve of new PVE oil and R32. The mutual solubility of new PVE oil and R32 was analyzed. Then the air conditioning performance of a heat pump split air conditioner was tested at two conditions, one is charging R32 combined with POE oil and the other is charging R32 combined with PVE oil. The results showed that the mutual solubility of R32 and POE oil was not ideal in the test range of oil content. The two phase separation temperature at condition of charging R32 combined with POE oil was higher than that of R410A and POE. The mutual solubility of PVE oil and R32 was better. The minimum separation temperature was 8.4℃ which is lower than that of R410A and POE. In the aspect of the effect on air conditioner performance, the exhaust temperature in case of using PVE oil was 2.6℃ which is lower than that of using POE oil. It also had improvement on cooling capacity and COP by using PVE oil.

    Influence of active phase compressor on performance of pulse tube cryocoolers
    ZENG Yangping, CHEN Xi, JIANG Zhenhua, WU Yinong, ZHU Haifeng, ZHOU Zhipo
    2018, 69(4):  1638-1645.  doi:10.11949/j.issn.0438-1157.20170628
    Abstract ( 321 )   PDF (724KB) ( 340 )  
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    The experimental performance of a pulse tube cryocooler (PTC) with an active phase compressor (APC) is presented. In order to investigate the phase shifting ability of APC, phase locked loop (PLL) was adopted to control APC's voltage amplitude and phase between APC and main compressor (MC). When the voltage phase (APC lags MC) are 210° and 240°, performances of the cryocooler are tested under the displacement phase angle of 90°-130°. The results show that PTC with APC performs differently when the cryocooler working at different voltage phases, though displacement phase angle is the same. Comparing with PTC with inertance tube (IT), performance of PTC with APC is better. Specifically, if cooling power is 30W, input power of PTC with APC decreased 8.1%. At last, from the perspective of phase shifting and matching with compressor, the reason why PTC performs differently under different phase-shifting method is demonstrated, which indicates APC could replace IT to shift PTC's phase.

    Effect of polyoctadecyl acrylate pour point depressant on characteristics of wax deposits of synthetic waxy oil
    LI Chuanxian, CHENG Liang, YANG Fei, LIU Hongye, CAI Jinyang
    2018, 69(4):  1646-1655.  doi:10.11949/j.issn.0438-1157.20170720
    Abstract ( 351 )   PDF (975KB) ( 183 )  
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    Based on an in-house Couette wax deposition device, the effect of polyoctadecyl acrylate (POA) pour point depressant upon wax deposition formed by synthetic waxy oils was investigated. The macroscopic morphology, DSC test, HTGC and wax crystal microscopic observation of the outer deposit (away from the wax deposition barrel) and inner deposit (close to the wax deposition barrel) were analyzed. It was found that the addition of POA reduces the wax deposition rate, accelerates the aging rate of the wax deposit, and leads to the formation of heterogeneous wax deposition structure (wax content gradually increased from outer deposit to inner deposit) in a certain concentration range (50-200 μg·g-1), while the structure of wax deposit became homogeneous when adding 400 μg·g-1 of POA. The critical carbon number (CCN) of the wax deposit of pure waxy oil is C24, but the CCN of the wax deposit formed by additive treated waxy oil rises to C25. In comparison with the outer-layer wax deposit, the contents of the n-alkanes with carbon number ≤ C24 in the inner-wax deposit are lower and the contents of the n-alkanes with carbon number ≥ C25 are higher. With the increase of POA content, the waxy morphology of the wax deposit is gradually changed from small needle-like wax crystals to big sheet-like wax crystals, and the structure becomes more compact.

    Test and analysis of fluidized ice machine with dual evaporator
    WANG Zepu, WANG Feibo, LI Minxia, MA Yitai
    2018, 69(4):  1656-1662.  doi:10.11949/j.issn.0438-1157.20170949
    Abstract ( 370 )   PDF (512KB) ( 347 )  
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    The theoretical cycle of the fluidized ice making machine under the chilling mode and ice making mode was analyzed. It is found that the traditional single evaporator (ice slurry generator) based on the ice making mode couldn't match the performance of the compressor, resulting in lower efficiency of chilling mode, the dual evaporators were proposed to optimize the fluidized ice making machine. The performance of the ice making machine with single and dual evaporators was tested under different ice making solution flow rate. The results showed that the ice cooling rate increased by 34% and 56%, and the coefficient of performance increased by 9% and 54% with dual evaporators under 2000 L·h-1 and 2500 L·h-1 respectively when compared with the single evaporator fluidized ice making machine. The efficiency of ice making machine was enhanced during the process from a normal temperature to a rated concentration of fluidized ice. The cooling rate and coefficient of performance were improved much more, especially in the case of larger flow rate of the ice making solution. It is proved that the fluidized ice making machine got optimized and the efficiency of ice making process was enhanced with dual evaporators.

    Performance and mechanism of Pb2+ removal by phosphorus removal granular sludge
    LI Xiaojia, WANG Randeng, RONG Hongwei, CAO Yongfeng, LI Cuicui
    2018, 69(4):  1663-1669.  doi:10.11949/j.issn.0438-1157.20170805
    Abstract ( 324 )   PDF (537KB) ( 461 )  
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    In this study, based on the adsorption of aerobic granular sludge and the chelating action of phosphate on heavy metals, phosphate containing biological phosphorus removal granular sludge was used as adsorbent to treat Pb2+ containing wastewater, and the removal efficiency of Pb2+ by granular sludge under different adsorption conditions was investigated. The results showed that the highest removal efficiency of Pb2+ (up to 99.9%) was achieved under the optimal adsorption conditions (pH=4 and the initial concentration of Pb2+ 150 mg·L-1), and the adsorption equilibrium reached in 20 min. The adsorption of Pb2+ by biological phosphorus removal granular sludge can be described by Langmuir model. The correlation coefficient R2 was 0.993, and the maximum adsorption quantity was about 49.5 mg·g-1. Ion exchange and chelation of phosphate with Pb2+ played a significant role in the removal of Pb2+ by using the phosphorus removal granular sludge. The results of Fourier transform infrared spectroscopy (FTIR) indicated that a variety of functional groups such as -COOH,-OH and phosphoryl were involved in the removal of Pb2+ by phosphorus removal granular sludge.

    Volatilization characteristics and mode of occurrence of arsenic during coal combustion
    ZOU Chan, WANG Chunbo, GUO Hui, WANG Hefei
    2018, 69(4):  1670-1677.  doi:10.11949/j.issn.0438-1157.20170855
    Abstract ( 487 )   PDF (546KB) ( 426 )  
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    The volatilization characteristics and mode of occurrence of arsenic for three coals were studied by a customized isothermal thermogravimetric experimental system. Limited by online monitoring of gaseous arsenic, the volatilization characteristics of arsenic were determined by measuring the arsenic concentration of ash at the specified residence time in this paper. The volatilization ratio of arsenic at the various residence time was obtained and the volatilization characteristics of arsenic were fitted through B-spline curve. Mode of occurrence of arsenic in the coals and corresponding ashes at the specified residence time was measured by sequential chemical extraction method. The results showed that the volatilization ratio of arsenic increased gradually with temperature, while most arsenic volatilized in 700-1000℃ period. The volatilization rate of arsenic was correlated to the combustion rate of coal. The volatilization rate of arsenic was relative high due to the release of volatile matter, and it began to slow down with the increase of burning time. After coal combustion, the final volatilization ratios of arsenic for coals (WL, HY, and MH) were 49.5%, 80.7% and 65.0%, respectively. The residue and sulfide arsenic would be partly migrated to be exchangeable state.

    Detoxification of chromium ore processing residue from roasting chromite without calcium by SO2 reduction
    WU Jun, QUAN Xuejun, LI Gang, LU Cunfang, LUO Huazheng
    2018, 69(4):  1678-1686.  doi:10.11949/j.issn.0438-1157.20170863
    Abstract ( 291 )   PDF (672KB) ( 385 )  
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    Chromium ore processing residue (COPR) from roasting chromite without calcium is characterized systematically.The detoxification of COPR by SO2 reduction is investigated. The detoxification process combining mechanical activation with SO2 reduction is proposed. The results show that the main phases of the COPR are (Fe, Mg) (Cr,Fe) 2O4 and MgAlFeO4. The content of Cr2O3 in the CPR is 12.23%. The smaller the particle size of COPR, the lower the content of the total Cr(Ⅵ), water-soluble Cr(Ⅵ) and insoluble Cr(Ⅵ). In the detoxification process of COPR by SO2 reduction, stirring can promote the process of external diffusion effectively and increasing liquid solid ratio is beneficial to the leaching of Cr(Ⅵ) in the COPR. With the increase of temperature, the leaching of Cr(Ⅵ) in COPR increases first, then decreases sharply. The pressure of reaction system has little influence on the detoxification of the COPR. Under the optimized experimental conditions:the pressure 0.1 MPa, the temperature 60℃, the stirring speed 500 r·min-1, and the reaction time 60 min, the removal rate of Cr(Ⅵ) in COPR was 90%, while the removal rate of Cr(Ⅵ) in COPR was 98.1%, and Cr(Ⅵ) content falls below 25 mg·kg-1, meeting the national discharge standard after 90 min of mechanical activation to the COPR.

    Degradation of tetracycline hydrochloride using dielectric barrier discharge plasma reactor
    WANG Baowei, WANG Chao, XU Yan, PENG Yeping, YAO Shumei
    2018, 69(4):  1687-1694.  doi:10.11949/j.issn.0438-1157.20170878
    Abstract ( 303 )   PDF (602KB) ( 551 )  
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    A dielectric barrier discharge plasma reactor was applied to the degradation of tetracycline hydrochloride in the aqueous solution. A series of parameters including input power, air-gap distance, initial concentration and air flow rate were investigated for their effects on the degradation efficiency. The results showed that the degradation efficiency was as high as 92% at the optimum degradation parameters:input power 1.3 W, air-gap distance 2.5 mm, air flow rate 150 ml·min-1, tetracycline hydrochloride initial concentration 100 mg·L-1 and treatment time 30 min. The kinetic studies indicated that the degradation of tetracycline hydrochloride followed the pseudo-second-order kinetics. Based on the intermediate products identified by LC-MS, a possible degradation pathway of tetracycline hydrochloride was proposed.

    Start-up of high-performance CANON reactor by alternating continuous flow and sequencing batch operation modes
    CHEN Xi, WANG Jianfang, QIAN Feiyue, GAO Junjun, SHEN Yaoliang, ZHOU Feng
    2018, 69(4):  1695-1702.  doi:10.11949/j.issn.0438-1157.20170894
    Abstract ( 298 )   PDF (1426KB) ( 185 )  
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    In order to start up a completely autotrophic nitrogen removal over nitrite (CANON) process, the continuous flow and sequencing batch modes were used in stages to operate the completely mixed flow reactor inoculated with nitrosation granular sludges. The variations of reactor performance, sludge morphology and activity, and the microbial community structure were investigated in details. Results showed that sequencing batch operation could promote the increases in both sludge concentration and reaction activity at high influent ammonium loading rate and high dissolved oxygen level, on basis of an appropriate nitrogen substrate ratio obtained in the initial continuous flow stage. Then a superior total nitrogen removal rate of 1.75 kg·(m3·d)-1 was achieved in the subsequent continuous flow mode. During the operation period, the compactness and settling property of granules were improved obviously. And Miseq high-throughput pyrosequencing analysis revealed that CANON granular sludge showed a relative higher microbial diversity. Corresponding to the specific nitrogen removal rate of 0.24 g·(g VSS·d)-1, the abundance ratio between aerobic and anaerobic ammonium oxidation bacteria was around 3 to 1, in terms of gene Nitrosomonas and Candidatus Kuenenia, respectively. In addition, few oligotrophic nitrite oxidation bacteria in the granules would not affect the efficiency of CANON process significantly.

    Simulation of NOx formation in novel dual circulating fluidized-bed boiler
    ZHANG Yi, LI Jianbo, WANG Quanhai, LU Xiaofeng
    2018, 69(4):  1703-1713.  doi:10.11949/j.issn.0438-1157.20170919
    Abstract ( 358 )   PDF (779KB) ( 169 )  
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    The NOx formation of a novel dual circulating fluidized-bed (DCFB) boiler were numerically studied based on the detailed chemical reaction mechanism in a one dimensional chemical reaction network (1D-CRN). The sensitivity of NOx formation and the effect of reaction temperature, excess air ratio and primary air ratio were investigated. The results indicated that the NOx emission of traditional CFB was calculated to be 224.48 mg·m-3, while the value of DCFB was 97.29 mg·m-3, indicating that DCFB would reduce the NOx formation. In addition, the sensitivity analysis showed that the reactions such as R398, R1-N-1, R569 and R17 promoted NOx formation, while those including R411, R412, R570, R571, R5 and R6 inhibited NOx formation. Moreover, it was revealed that oxygen in the reaction zone was one contributing factor to NOx formation by the fact that less oxygen in the reaction zone would inhibit NOx formation. Likewise, NOx formation decreased with increasing reaction temperature but increased with increasing excess air ratio and primary air ratio.

    Relationship between fine particle emission and droplets during limestone-gypsum WFGD process
    HOU Dawei, PAN Danping, ZHOU Xincheng, HUANG Rongting, SHEN Kai, YANG Linjun
    2018, 69(4):  1714-1722.  doi:10.11949/j.issn.0438-1157.20171000
    Abstract ( 410 )   PDF (761KB) ( 532 )  
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    Slurry droplets containing fine particles are entrained out of the scrubber in the process of the limestone-gypsum desulphurization, leading to significant impacts on the fine particle emission characteristics. The slurry atomization, entrainment characteristics of desulfurization slurry, and the relationship between fine particle emission and desulfurization slurry characteristics were on-line measured with the Phase Doppler Analyzer (PDA) system and the electrical low pressure impactor (ELPI+). The results show that large numbers of fine droplets and submicron solid particles exist in the flue gas after desulfurization, which attributes to the slurry entrainment during the desulfurization process. The emitted droplet sizes are related to the slurry atomization characteristics. They are mainly less than 20 μm and the solid content ratio of the emitted droplets and the slurry ranges from 20% to 40%. The operating parameters have significant effects on the amount of entrained slurry droplets such as the superficial gas velocity, the liquid gas ratio and the slurry concentration. With the decrease of these operating parameters and the spray optimization such as the increase of spray layers and the proper arrangement of the nozzles, the slurry entrainment is inhibited, resulting in the reduction of fine particle emissions.

    Structure optimization simulation of slit burner with low NOx
    LIU Hui, ZHANG Lin, YANG Xiaoxi, LI Donggang
    2018, 69(4):  1723-1730.  doi:10.11949/j.issn.0438-1157.20170934
    Abstract ( 382 )   PDF (1484KB) ( 278 )  
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    Natural gas has the characteristics of high heat value, high efficiency, low cost and low emission when used as fuel. However, when natural gas is burned, the local high temperature region can easily appear, and NOx is generated. Therefore, the optimized design of natural gas burner has a very important role for cleanly and effectively use of natural gas. The structure of the existing new type of slit burner with low NOx is optimized. There are two ways to improve the structure:the oblique air holes are opened on natural gas pipeline, the diversion baffles are added next to the small slit. The software Fluent is used for numerical simulation, and the experiment on the optimized burner is carried out. The simulation results are well verified by the data measured in the experiment. The results on the optimized structure are obtained as following:round holes are oblique opened on the natural gas pipeline, compared with the original burner, the temperature distribution is more uniform and NOx emission is reduced. Round opening at the same direction with slit is better. When round holes are opened the same direction with slit in the natural gas pipeline, the average concentration of NOx in the flue gas outlet dropped a lot, and the average concentration of NOx decreases gradually with the increase of the opening angle. The effect of diversion baffles added on the right side of slits is not as good as the original structure. When the diversion baffles are added on the left side of the slits, the average NOx emissions in the flue gas outlet is reduced, and the NOx emissions decreases first and then increases with the increase of the angle of the flap. Holes at the same direction with slit angle of 50° on natural gas pipeline are the best choice in all cases.

    Study on formation of polymeric TiO2-ZrO2 sols by small angle X-ray scattering
    DU Qianqian, GU Jinghua, MO Guang, WEI Yanru, YIN Wenjie, LI Jia
    2018, 69(4):  1731-1740.  doi:10.11949/j.issn.0438-1157.20170730
    Abstract ( 285 )   PDF (585KB) ( 273 )  
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    Metal oxide sols can be prepared from metal alkoxides M(OR)4 by hydrolyzation, which has been widely used in synthesis of nano-porous ceramic membranes by sol-gel method. Polymeric TiO2-ZrO2 sols were prepared by controlled hydrolyzation of the mixture of titanium isopropoxide and zirconium n-propoxide in isopropanol. The formation of TiO2-ZrO2 sols from the initial reactant mixtures with a molar ratio of Ti(i-OC3H7)4:Zr(n-OC3H7)4:H2O:i-C3H7OH=0.9:0.1:m:30 (m=1.8, 2.0, 2.2) was investigated by small angle X-ray scattering (SAXS). The effects of the molar ratio of water to metal alkoxides H2O/M(OR)4 (M=Ti+Zr) in the initial reactant mixture, reaction temperature and Zr(n-OC3H7)4 on formation of TiO2-ZrO2 sols were discussed. When the molar ratio of H2O/M(OR)4=1.8, a few colloidal particles form. When the molar ratio of H2O/M(OR)4 is in the range of 2.0-2.2, the colloidal particles in TiO2-ZrO2 sols have a mass fractal structure with a fractal dimension of 1.2 ≤ Dm < 1.4. As the molar ratio of H2O/M(OR)4 increases from 2.0 to 2.2, the duration of colloidal particle formation becomes shorter, the size and fractal dimension of colloidal particles increase, and the stability of TiO2-ZrO2 sol decreases. Furthermore, the mixture of[Ti(i-OC3H7)4+Zr(n-OC3H7)4] hydrolyzes faster than Ti(i-OC3H7)4. TiO2-ZrO2 sol has lower stability than TiO2 sol from the initial reactant mixtures with the same molar ratio of H2O/M(OR)4.

    Synthesis and electrochemical performance of Ag-doped VO2(B) as cathode materials
    HAN Shichang, ZOU Zhengguang, LÜ Tingting, WU Xingyu, YANG Qian
    2018, 69(4):  1741-1748.  doi:10.11949/j.issn.0438-1157.20170812
    Abstract ( 409 )   PDF (1443KB) ( 186 )  
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    Ag-doped VO2(B) cathode material was fabricated by hydrothermal reaction. Vanadium pentoxide (V2O5), maltose (C12H22O11) and silver nitrate (AgNO3) were used as starting materials. The physical properties of samples were characterized by X-ray diffraction, XPS, FESEM and EDS. Meanwhile, the electrochemical performance of material were observed with means of galvanostatic charge-discharge, cyclic voltammetry(CV) and electrochemical impedance spectroscopy (EIS). The results showed that the specific discharge capacity of the sample of Ag1[0.43%(atom)] was 340.5 mA·h·g-1 at 0.1C rate over the voltage range of 1.5-4.0 V, which was increased by 80.5% than the pure sample. The sample of Ag3[1.28%(atom)] exhibited the optimal electrochemical performance. The initial discharge capacity maintained 213.6 mA·h·g-1 after 100 cycles. The retention rate of capacity was 58.3%.

    Preparation and properties of paraffin/water phase change emulsion
    HUANG Li
    2018, 69(4):  1749-1757.  doi:10.11949/j.issn.0438-1157.20170818
    Abstract ( 513 )   PDF (847KB) ( 650 )  
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    A paraffin/water emulsion is a phase change slurry (PCS), which uses both the sensible heat capacity of the carrier fluid and the latent heat capacity of the phase change material (PCM), is pumpable and has a high energy storage density. The energy consumption of central cold supply networks could be reduced when applying low-temperature paraffin phase change emulsion as a heat transfer fluid. Based on the application requirements, different components have been selected to prepare emulsions, inclusive paraffins, surfactants and nucleating agents. The impact of their fractions on the emulsion properties has been studied, namely on the droplet size distribution, thermal properties and rheological behaviors. Finally, the emulsion components and their suitable fractions have been determined for preparing a stable paraffin/water emulsion with a energy storage density 2-6 times water and a subcooling degree lower than 2 K.

    Synthesis and photocatalytic activity of RGO-BiOCl/Bi2WO6 heterojunction photocatalyst by microwave etching method
    CHEN Ying, HAN Xingyue, LIANG Hongbao, LIANG Yuning, GAO Yanhua
    2018, 69(4):  1758-1764.  doi:10.11949/j.issn.0438-1157.20170765
    Abstract ( 604 )   PDF (943KB) ( 566 )  
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    The oxidized graphite was prepared by modified Hummers method for oxidation treatment of natural graphite. BiOCl/Bi2WO6 catalyst was loaded on RGO by microwave and chemical etching with Bi(NO3)3·5H2O, KCl and Na2WO4. The morphology and structure of as-synthesized products were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET), UV-visible diffuse reflectance spectra (UV-Vis DRS) and transmission electron microscope(TEM). Rhodamine B solution was used as target degradation to investigate the photocatalytic performance of catalyst. The results illustrated that RGO:RGO-BiOCl(mass ratio) was 2%, Bi2WO6:RGO-BiOCl/Bi2WO6 (molar ratio) was 50%, and the degradation rate reached as high as 94.6%, compared to pure BiOCl.

    Gelatinization modification of calcium alginate fibers nonwoven fabrics and mechanism research
    LEI Mingyue, YAN Chao, CUI Li, ZHANG Chuanjie, LIU Yun, WANG Huaifang, ZHU Ping
    2018, 69(4):  1765-1773.  doi:10.11949/j.issn.0438-1157.20170889
    Abstract ( 385 )   PDF (896KB) ( 386 )  
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    Calcium alginate fibers nonwoven fabrics which could absorb plenty of water and then transformed into gels were prepared by using two-step chemical modification methods. Calcium alginate fibers nonwoven fabrics were dipped into hydrochloric acid aqueous solution and sodium hydroxide solution using ethanol as the solvent. The comprehensive properties of gels derived from calcium alginate fibers nonwoven fabrics were the best, when concentration of hydrochloric acid solution was 0.05%-0.1%(mass) and concentration of sodium hydroxide solution was 0.008%-0.016%(mass). Under this condition, absorbing water capacity of calcium alginate nonwoven fabrics increased by 1.45 times after being modified chemically, and the ratio of preserving water capacity to absorbing water capacity of calcium alginate nonwoven fabrics increased by 10.67 times after modification. Thickness, mass of per unit area, air permeability and breaking strength of modified calcium alginate nonwoven fabrics changed a little before absorbing water, but the size of modified calcium alginate nonwoven fabrics after absorbing water adequately improved about 3 times. It indicated that the reason for formation of gel was related to structure and properties of calcium alginate fibers but not to fabric texture. At the stage of treatment with hydrochloric acid solution, the formed “egg-box” structure in calcium alginate fibers, and the crystal structure of these fibers were damaged partially and the degree of crystallinity and Ca2+ content of these fibers were decreased, but ester bond formed in these fibers. At the stage of treatment with sodium hydroxide solution, the formed ester groups changed into carboxyl groups and hydroxyl groups and intermolecular forces of fibers weakened for this change. Crosslinking degree and intermolecular forces of modified calcium alginate fibers were adjusted to appropriate states, so plenty of water molecules were absorbed by modified calcium alginate fibers and the absorbed water molecules could interact with fibers molecules in the form of hydrogen bond. For these reasons, modified calcium alginate fibers nonwoven fabrics changed into gels as soon as they were put in water.

    Preparation of superhydrophobic CA/SiNPs-FAS electrospun nanofibrous membranes for direct contact membrane distillation
    DING Chunli, LIN Dichu, WANG Dewu, HOU Deyin, WANG Jun
    2018, 69(4):  1774-1782.  doi:10.11949/j.issn.0438-1157.20170865
    Abstract ( 433 )   PDF (1312KB) ( 573 )  
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    In this study, cellulose acetate/silica nanoparticles (CA/SiNPs) composite membranes were prepared by electrospinning and PET nonwoven were used as a support layer. Then the fiber mats were modified by immerged into fluoroalkyl silane (FAS) solution. In polymer dope, the mixture of 1-methyl-2-pyrrolidone (NMP) and acetone[80/20,%(mass)] was selected as a mixture solvent and the content of CA was 10%(mass). The morphology, pore size distribution and wettability of the composite membranes properties were investigated. The CA and CA/silica fibers were found to be randomly oriented as nonwoven mats with fiber diameters around 0.8 μm. With the addition of SiNPs in the polymer dope, the SEM surface morphology images of flat-sheet composite membranes exhibited a microscale (SiO2 aggregation node) to nanoscale (SiO2 nanoparticles) hierarchical stratum structure. After the FAS modification, the surface wettability of the CA/silica mats was converted from hydrophilic to superhydrophobic. Compared with commercial PVDF membrane, the fluorinated mats with the metastable structure showed the highest water contact angle (WCA) of 156° and exhibited an excellent property of anti-surfactant wettability[4.0 μl 5%(mass), SDS solution, the contact angle is 125°]. The composite membrane salt rejection rate could reach more than 99.99%; the CA/SiNPs-FAS membrane flux could be stabilized at 11.2 kg·(m2·h)-1 with the feed solution at 60℃ and the cold distillate water at 20℃ during the desalination process of 35 g·L-1 sodium chloride solution through direct contact membrane distillation.

    Preparation and properties of fluorescent waterborne polyurethane as paper sizing agent
    ZHAO Yanna, ZHAO Yao, ZHAO Chunyan, BAI Zhe, SHI Jianyu, KE Meidong
    2018, 69(4):  1783-1789.  doi:10.11949/j.issn.0438-1157.20170723
    Abstract ( 348 )   PDF (777KB) ( 264 )  
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    A series of fluorescent waterborne polyurethane (FWPU) dispersion had been successfully prepared by importing the fluorescent whitening modifier 5,7-dihydroxy-4-methylcoumarin (DHMC). The structure and properties of FWPU were characterized by FTIR, 1H NMR, DLS, fluorescence spectra, the degree of sizing, whiteness and SEM. The surface sizing properties of FWPU emulsion were studied. FTIR and 1H NMR analysis showed that DHMC had been introduced into the molecular chain of FWPU. When w (DHMC)=0.6%, the particle size of FWPU emulsion was 86.17 nm, the fluorescence effect was 40220.44 a.u.(1a.u.=27.2114 eV). The results showed that the FWPU emulsion had an excellent paper sizing property. Paper sizing value could reach 51.92 s, the whiteness was 77.93%.

    Preparation and reaction kinetics of epoxy resin microcapsules
    NI Zhuo, LIN Yuhao, HUANG Weiying, LIN Lirong
    2018, 69(4):  1790-1798.  doi:10.11949/j.issn.0438-1157.20170619
    Abstract ( 492 )   PDF (1008KB) ( 602 )  
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    A series of microcapsules were prepared by interfacial polymerization, epoxy resin E-51 as core materials and the condensation of triethylenetetramine and epoxy resin E-51 to wall materials. The kind of epoxy microcapsules provide an investigation model for scientific research and engineering applications of the epoxy resin self-healing composites with no different interfaces. The microcapsule formation process, particle size and size distribution, morphology and chemical structure were analyzed by optical microscopy (OM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), etc. Optimum synthetic conditions are obtained as the following:emulsifier (Tween 80) dosage is 1%, dosage of triethylenetetramine is 2.5%, reaction temperature is 90℃, and agitation rate is 600-1000 r·min-1. The reaction kinetic parameters such as reaction rate constant and activation energy of primary and secondary amines in triethylenetetramine curing agent were studied in details. Quantitative analysis was conducted for the reactive difference of primary and secondary amine groups between these amines in the chemical condesation of epoxy resin and triethylene tetramine.

    Thermal decomposition characteristics of HANFO by using C80 calorimeter
    LI Hongwei, XU Feiyang, XIA Manman, CHENG Yangfan, GONG Yue
    2018, 69(4):  1799-1805.  doi:10.11949/j.issn.0438-1157.20170667
    Abstract ( 376 )   PDF (603KB) ( 431 )  
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    A CALVET calorimeter C80 was used to analyze the thermal behavior of porous granular ANFO explosive, three commonly used heavy ANFO explosives and emulsion explosive. The mass ratios of emulsion explosive/porous granular ammonium oil blasting agent of the heavy ANFO explosives are 25/75, 50/50, and 75/25. The thermal kinetic parameters of apparent activation energy (Ea), pre-exponential factor (lnA), and thermodynamic parameter of reaction heat (ΔH) of the five explosive samples were calculated based on the heat flux data in C80 curve with the heating rate of 0.2 K·min-1. The results show that emulsion explosive has an apparent inhibitory effect on the thermal decomposition reaction of porous granular ANFO explosive, which makes the thermal decomposition onset temperature of porous granular ANFO explosive obviously increased. The calculated values of the apparent activation energy and the onset temperature of the heavy ANFO explosives are higher than that of porous granular ANFO and emulsion explosive. It could be concluded that the thermal stability of heavy ANFO explosives is higher than that of porous granular ANFO explosive and emulsion explosive.