Direct contact condensation of the steam jet in the subcooled water flow inside the pipe can induce severe pipe vibrations. In this paper, a high-speed camera and an acceleration sensor were used to capture the evolution of the jet interface and the induced pipeline vibration. The characteristics of grayscale centroid oscillation considering steam jet plume morphology and pipeline vibration are quantitatively described. The oscillation amplitude of the grayscale centroid of the plume is the highest in the Oscil-I condensation regime, the lower in the chugging regime, and the lowest in the stable regime. The intensities of the centroid oscillation and pipeline vibration decline with increasing steam mass flux and a strong correlation is revealed. On this basis, the distribution diagram of pipeline vibration intensity with steam mass flux and subcooled water temperature is drawn, and the vibration intensity increases with the increase of subcooled water temperature. Correlation analysis quantitatively confirmed that the axial oscillation of the plume grayscale centroid is the dominant factor of the pipeline vibration along the steam injection direction.

The liquid film serves as the primary medium directly involved in the spray cooling process and capturing its flow characteristics are crucial. However, accurately capturing these characteristics is extremely challenging due to strong interference from the interaction between droplets, liquid film, and heated wall. As a result, the spray cooling and high-efficiency heat exchange mechanism has not yet been essentially clarified. In this study, we investigated the imaging quality of HFE-7000 and HFE-7100 liquid films to establish an appropriate testing and diagnostic approach for the liquid film dynamics, including the coupled factors such as built-in sensitivity parameters of cameras, shutter speed and aperture combinations, and sampling strategies. The method yielded favorable results for various surfaces. The ADD-type error analyses based on standard liquid films was proposed to determine the bias and random errors associated with relevant parameters. The morphologies, wetted area, and contact line length of HFE-7100 spray under different heat fluxes, pressures, and nozzle heights were obtained to explore the mechanisms governing spray cooling. It was observed that the isolated wetted areas decreased with the increasing surface temperature while the contact lines exhibited either a decreasing or occasionally an increasing trend under certain operating conditions. Furthermore, the connection between liquid film dynamics and heat transfer characteristics was discussed and verified.

The gas-liquid spiral annular flow in the tube can be formed by setting a cyclone with fixed blades. The structure of the cyclone greatly affects the stability of the spiral annular flow. To investigate this, four typical swirler structures were selected for experimental research under three typical inflow conditions. The stability of the formed spiral annular flow was analyzed by using image processing combined with the probability density function (PDF) fitting method. Additionally, the fluctuation characteristics of the liquid film and the internal action process of the swirler were analyzed. It was found that the liquid film generated by flat plate swirlers with central cylinder cyclone under different inflow conditions is more stable than that of the spiral blade A/B cyclone, and the instability distance under the same working conditions is also longer. However, the stability of the spiral annular flow generated by spiral vane type A/B swirlers is poorer, with instability occurring over a shorter distance. The increase in the equivalent liquid phase velocity under different conditions contributes to improving the stability of the liquid film and the instability distance of the spiral annular flow, thus forming a more stable spiral annular flow. The pressure gradient and the radial velocity within the fluid under the action of the vanes are highly correlated, where the pressure gradient and the radial velocity are the main factors in the formation of spiral annular flow, and their magnitudes determine to some extent the stability of the gas-liquid interface of the spiral annular flow.

Application of an electric field to control the movement of charged particles is widely used in industrial processes. The behavior of a collection of dielectric particles in electric fields is still insufficiently studied. Therefore, we conduct numerical simulations to investigate the full dynamics of dielectric particle layers in an external electric field. Based on the results, the phase diagram for patterns of particle behaviors in an electric field is constructed, and boundaries between adjacent regions are derived. Then, the structure of particle layers is characterized to explore the influence of external field and interparticle electrostatic interactions on the structural reconstruction. Finally, the levitation process of particle layers is analyzed.

During the solid-liquid phase change process, the external force can cause relative motion of the solid phase change material within the liquid phase change material, which can seriously affect the flow and heat transfer. An Euler-Lagrange iterative solid-liquid phase change algorithm is proposed to numerically solve the above problem. The Lagrange iteration for predicting the solid relative motion is externally coupled to the Euler iteration for calculating the phase change flow and heat transfer, which can stably and accurately simulate the flow and heat transfer of the solid-liquid phase change and the relative motion of the solid phase change material. Based on the present algorithm, the close-contact melting processes in the square cavity are investigated under gravity. Furthermore, the influence of different mushy zone coefficients and gravity accelerations on this algorithm is explored. The results show that the average error of the algorithm in predicting the liquid phase volume fraction is 4.93%, and the numerical oscillation of the solid relative motion prediction is reduced by 51.42%. For paraffin materials, the mushy zone coefficient of 10¹⁰ is recommended for this algorithm. The increase of the gravity acceleration can improve the melting rate and accelerate the relative downward motion, yet has less impact on the overall trends of liquid phase fraction and solid phase relative motion. The results can be used as the theoretical guideline for the design and optimization of the efficient solid-liquid phase change energy storage devices.

The hollow nozzle with a spiral flow guide structure on the top of the swirl chamber was studied experimentally. A spray test bench capable of accommodating 1—4 nozzles is set up, and a visual spiral nozzle is manufactured for spray characteristic experiments. High-speed cameras are employed for visualizing the internal flow field characteristics, and the distribution of external flow field spray density is collected through measurement devices. The variations of internal flow field air columns and turbulent flow under different operating conditions, as well as the characteristics of external flow field spray density, are analyzed. The results show that under the influence of internal and external pressure differences, an air column forms inside the nozzle, and due to the effects of the single-side tangential inlet and the spiral guiding structure, the centerline of the air column is offset from the centerline of the swirl chamber. The circumferential effective spray density of the external flow field presents a double-peak distribution, with the peak areas located near 120° and 280° respectively.

The wet granulation process in the spray fluidized bed is widely used in various industrial sectors, such as energy, pharmaceutical, food, and chemical industries. However, the granular growth process in the fluidized bed involves the interaction of complex gas-liquid-solids, and it is difficult to achieve precise control of the granular process. Therefore, based on the discrete element model, the influence of the draft plate structure in the spray fluidized bed on the flow and growth characteristics of particles in the bed was studied by adding the liquid bridge force model and the particle growth model. The influence of the particle fluidization state on the uniformity of particle growth was analyzed. The results indicate that increasing the lengths of the draft plates in the fluidized bed or decreasing the gaps and heights of the draft plates enhances the fluidization state of the particles, extends the particle growth area, lengthens the particle cycle times, inhibits the growth of a single particle coating, and improves the uniformity of particle growth.

Steam direct contact condensation has high efficiency in heat and mass transfer and is widely used in nuclear energy safety and other fields. Compared with the stable condition on land, the swing movement under the marine conditions may exacerbate the oscillation of the auto liquid interface and further affect the safe operation of the equipment. Therefore, the condensation process of low flow rate steam under rolling conditions was studied by numerical simulation, and the changes of pressure, heat transfer characteristics and bubble forces under rolling conditions were analyzed. The results showed that the sharp fluctuations of pressure and heat transfer coefficient mainly concentrated in the phase of bubble shrinkage and separation, when the bubble forces also reached the maximum, and the bubble was mainly affected by the inertia force and condensation force. In addition, it is found that the inertia force partially increases due to the change of bubble velocity under the rolling condition, and the additional rolling velocity brought by the rolling motion strengthens the heat transfer performance of the vapor-liquid interface, and the average heat transfer coefficient is much higher than that under the stationary condition.

During the operation of automotive fuel cells, dynamic loads may drastic changes in local physical quantities of the fuel cell, which in turn leads to a sharp decline in fuel cell performance and service life. To prevent the occurrence of the issues above, a thorough analysis of the local dynamic characteristics of the fuel cell under dynamic operating conditions is necessary. This study considers the 7-layer structural features of the membrane electrode assembly, and the energy transport facilitated by gas component diffusion and gas-liquid two-phase macroscopic convection, while also taking into account the localized energy changes resulting from phase transitions between gas-liquid-membrane phases. Building upon these considerations, a two-phase, non-isothermal, three-dimensional dynamic physical model of the fuel cell has been established. This model reveals the internal features of the fuel cell under dynamic loads, particularly focusing on the heat and mass transport, as well as the dynamic response characteristics of electrochemical reactions, in the catalytic layer region beneath the channel and rib of the bipolar plate along the flow channel. Furthermore, it elucidates the mechanisms underlying the formation of dynamic behaviors. The research findings indicate the presence of significant spatial-temporal thermal-mass response non-uniformities within the membrane electrode during the step change in current load, resulting in a decrease of approximately 20 mV in fuel cell output voltage, triggering additional power losses and heat generation, thereby causing further increasing in local temperature.

Boundary layer integration method is applied to variable property turbulent flow in tube, and the shear stress distribution equation is derived. Based on this equation, a reasonable qualitative explanation can be made for the convective heat transfer behavior of supercritical pressure fluid. For the heat-transfer cases under heating conditions, and a thermal resistance coefficient of buoyancy is proposed to indicate the buoyancy effect due to the fluid density variation in radial direction, a thermal resistance coefficient of acceleration is proposed to indicate the acceleration effect due to the fluid density variation in axial direction. According to the boundary layer theory and the analogy between momentum and heat transfer, a new correlation equation has been developed to unify the calculation of turbulent convection heat transfer in tubes for incompressible and thermally compressible fluids. The proposed correlation is applied to predict the turbulent convective heat transfer coefficients in tubes for different supercritical fluids. The comparison between the calculated results and the experimental data shows that the correlation formula can accurately and reasonably predict the enhanced heat transfer and deteriorated heat transfer behavior under most heat transfer conditions, and its prediction accuracy is related to the calculation of friction resistance coefficient.

Accurate measurement of the boundary heat transfer characteristics of supercritical CO₂ flow-through a channel is crucial for the safe design and operation of advanced supercritical CO₂ cycle systems. The research is based on an improved non-contact phase-shifting laser interference system to explore the evolution trend of the boundary thermal flow field of supercritical CO₂ in a rectangular cross-section channel under turbulent conditions. A phase-shift technique is utilized to analyze the transient variations in density and temperature fields following the sudden localized heat addition applied in the bottom boundary. These quantitative data are used to estimate the local criterion numbers for supercritical boundary heat transfer under different heat flux (q = 14057, 5500, 2014 W/m²). The results indicate that the rapid density reduction (1.8 kg/m³) occurs in a localized boundary transfer process. The buoyancy force induces the turbulent mixing from the boundary to the bulk flow region, eventually reaching equilibrium. Relatively dramatic and rapid shifts in temperature and density gradients occurs under high heat flux conditions, emphasizing the fast generation and transport of thermal boundary layers.

Heat exchangers with parallel microchannels, sparse micropillar arrays, and dense micropillar cluster arrays were designed and manufactured to enhance flow boiling heat transfer capabilities in silicon-based microchannels. Flow boiling experiments were conducted with acetone as the working fluid at heat fluxes from 200 to 650 kW·m^-2. The results indicated that both sparse and dense micropillar cluster microchannels had superior heat transfer performance compared to parallel microchannels; at a mass flux of 43 kg·m^-2·s^-1, the average heat transfer coefficients for sparse and dense micropillar cluster microchannels reached 18.6 and 17.8 kW·m^-2·K^-1, respectively. The sparse micropillar cluster microchannel's performance evaluation criteria (PEC) reached 1.49. The micropillar cluster arrays exhibited three distinct flow patterns as heat flux increased. Visualization investigation showed that the vapor phase in sparse micropillar clusters arrays was prone to flow around the micropillars. It is more inclined to wrap the micro-pillar clusters, which makes the former show stronger two-phase heat transfer performance.

Based on the numerical simulation results of transcritical methane flow in a Zigzag-channel printed circuit plate heat exchanger, machine learning models were used to predict the local convection heat transfer coefficient and pressure drop in the channel. The local multiple physical parameters along the channel were obtained by the microsegment method to create a database. The input parameters are screened by Mutual Information method, and the optimal network structure and hyper parameters are determined according to the predicting effect of validation set. The predicting results show that the artificial neural network model performs best, with a mean absolute percentage error of 2.228% for predicting heat transfer coefficient and 5.009% for predicting pressure drop. Using machine learning to predict flow heat transfer parameters, a one-dimensional simulation method for Zigzag-shaped channel printed circuit board heat exchangers was developed to achieve rapid and accurate prediction of fluid temperature, wall temperature, convective heat transfer coefficient and pressure drop in the channel, providing a new method for heat exchanger design.

Chemical looping hydrogen generation technology has the advantages of low energy consumption, high purity of hydrogen production, cleanness and efficiency, etc., and is receiving more and more attention in the field of hydrogen energy. However, the complex flow and mass transfer mechanisms inherent in the system pose significant challenges to its technological development. Therefore, conducting comprehensive research aimed at elucidating the operational characteristics of the chemical looping hydrogen generation reactor is of significant importance. This study performs a three-dimensional numerical simulation of a dual fluidized bed reactor for chemical looping hydrogen generation utilizing the two-fluid model (TFM) to examine the impacts of various operating conditions and oxygen carrier properties on system performance. The particle quantity and pressure drop in the riser obtained from the simulation agree well with experimental results, which suggests that the current model is capable for the simulation. The numerical results show that increasing the bed material reduces the pressure fluctuation amplitudes in the riser, leading to enhanced operational stability. The distribution of the solid phase in the radial direction of the riser is non-uniform, attributed to the arrangement of the inlet. And non-uniformity distribution of solid becomes more pronounced at higher gas velocities and results in severe operating conditions. Under the current operating conditions, the reactor operates most steadily when the inlet gas velocity of the riser is 7 m/s, and an increase in fluidization gas velocity leads to a significant fluctuation in solid circulation. The flow characteristics of reactor, derived from numerical simulation, provide insights into the operation and optimization of the dual fluidized bed in chemical looping hydrogen generation.

In order to achieve the efficient separation of gas-liquid two-phase flow in a wide flow range, a new volute type multi-channel cyclone separator was designed based on the spiral theory, and its structure was optimized. A numerical simulation method was used to compare its performance with that of a traditional single-inlet gas-liquid cyclone separator. The results showed that the new volute type multi-channel cyclone separator can effectively solve the problem of air core eccentricity and oscillation caused by a single inlet. The flow field in the separator has distinct axial symmetry and higher stability under different inlet gas content conditions, and the amount of liquid in the overflow zone decreases significantly. Although the overall pressure loss is greater, the secondary flow can be effectively inhibited, and the suppression effect is more pronounced when the inlet gas content is higher.

The coal-supercritical water hydrogen production technology utilizes high-temperature and high-pressure conditions to gasify coal in supercritical water, enabling efficient and low-emission coal conversion and hydrogen production process. To alleviate the time-consuming simulation process caused by the complex multiphase flow behavior within the reactor, as well as the issues such as short prediction time and rapid prediction deterioration when constructing conventional data-driven surrogate models, this paper proposed a deep learning model called POD-Koopman based on the proper orthogonal decomposition (POD) and the Koopman theory, which can capture and learn the long-term spatiotemporal evolution characteristics of the complex flow, thus facilitating the long-term rolling prediction. The test results show that it can accurately predict the time-varying behavior of the multiphase flow field in the reactor on a rolling basis with a small computational overhead, and assist in the industrial design and optimization tasks of downstream hydrogen production reactors.

The motion process of a single droplet on a cylindrical wall under gravity is simulated by using the pseudo-potential lattice Boltzmann method with a large density ratio multiphase flow model based on the real fluid state equation. The results indicate that as the hydrophobicity of the cylindrical surface progressively increases along the direction of gravity, the motion of droplet can be split into two stages: spreading and sliding. The wall wettability distribution and its change rate will affect the droplet motion process. When the droplet moves to the lower half of the cylinder, its average velocity, maximum velocity, attachment length and droplet height begin to differentiate with time. In addition, the horizontal and vertical components of the adhesion force acting on the droplet reached a maximum when it started and fully moved to the lower half of the cylinder, respectively. These findings provide important theoretical support for a deeper understanding of the droplet motion characteristics on the circular cylinder.

Natural gas hydrate (also known as flammable ice) is a common unconventional shallow gas reservoir in seabed reservoirs. It has the characteristics of mud and low permeability. Its safe and efficient development is of great practical significance. During the hydrate exploitation process, both gas seepage and hydrate dissociation behavior change dynamically, and the complex coupling of the two determines the gas production efficiency of hydrate reservoirs, but there is a lack of research on their dynamic coupling prediction models. Therefore, it is necessary to further analyze the gas seepage and hydrate dissociation behaviors during the depressurization production process of gas hydrate reservoirs. The muddy, low-permeability hydrate reservoir using South China Sea soil was remolded within a core holder. The exploitation characteristics during depressurization and the influence of reservoir pressure on gas production were explored. In addition, a prediction model for depressurization extraction that included key indexes of reservoir pressure, hydrate decomposition, and gas production flow rate was innovatively proposed. The spatial and temporal correlation between seepage and dissociation of a muddy, low-permeability hydrate reservoir was predicted with high precision. Correlation coefficients (R²) between measured and predicted values were all distributed above 99%. The results can provide theoretical guidance for the optimization and control of hydrate exploitation in the field.

Based on the background of development in regenerative cooling technology, the flow heat transfer characteristics and thermal cracking coking characteristics of high-density endothermic hydrocarbon fuel JP-10 were experimentally studied in a Φ4 mm×1 mm high-temperature alloy steel round tube under the conditions of heat flux density of 100—2000 kW/m² and normal pressure to 6 MPa. The results of the experiments indicate that under 2 MPa pressure, 1204.6 kW/m² is the critical heat flux density for the deterioration of kerosene heat transfer. The experiments have delineated the heat transfer regions of kerosene under subcritical/supercritical pressures: entrance region, forced convection heat transfer region, (pseudo) subcooling boiling region, (pseudo) saturated boiling region, etc. It was observed that fluid temperature primarily governs fuel coking, with the onset of coking occurring at 679℃, 652℃, and 643℃ under pressures of 2,4, and 6 MPa, respectively. The wall temperature synchronously affects coking quantity after high coking reactions occur. The main reason is that the coking in the fuel pipe intensifies with the increase in pressure, and the residence time of the high-temperature fuel in the pipeline increases.

During the assembly process of proton exchange membrane fuel cell (PEMFC) stacks, the gas diffusion layer (GDL) will deform due to the assembly pressure and invade the flow channel. Utilizing the volume of fluid (VOF) method, numerical models were established for flow channel with rectangular, trapezoidal, and square cross-sections to investigate the two-phase gas-liquid flow behavior under varying degrees of GDL intrusion. The insights into liquid retention, drainage effectiveness, and GDL surface mass transfer area were analyzed. In instances of GDL intrusion into flow channel, the fragmentation of liquid during the discharge process decreases, facilitating the accumulation of liquid into larger droplets or film formation. The intrusion of GDL into the flow channel affects the liquid retention during the internal drainage process, with rectangular cross-section channel exhibiting longer drainage time, and trapezoidal and square cross-section channel experiencing delayed liquid discharge moments. In the presence of GDL intrusion into flow channel, the reduction in channel cross-sectional area results in an increased inlet gas velocity, maintaining a stable discharge velocity for relatively clustered liquid droplets without a substantial decrease. For cases of substantial GDL intrusion, the rectangular cross-section channel shows a higher incidence of liquid droplets adhering to the channel sidewalls and GDL surface, resulting in a larger GDL surface coverage. Additionally, in channels with significant GDL intrusion, the trapezoidal cross-section channel exhibits the formation of a stable film flow at the top, with higher drainage velocity and smaller GDL surface coverage.

The salt ion components in seawater hinder the hydrate nucleation process, making the hydrate method for marine carbon sequestration take a long time and have a low sequestration rate. Considering the non-homogeneous nucleation characteristics of hydrates, it is feasible to implement a storage method that achieves preferential hydrate nucleation in local areas, leading to the extended generation of hydrates across large sea areas. Therefore, fundamental research on the enhanced generation of seawater hydrate is essential for promoting the application of the hydrate method for ocean carbon sequestration. Based on this premise, laboratory-scale investigations were conducted to study the effects of high subcooling, additives (TBAB), and variable temperature rates on the seawater hydrate generation characteristics, aiming for efficient and high conversion rate hydrate generation. The results indicated that the natural generation of hydrates in seawater at a depth of 400 m is extremely difficult due to the inhibitory effects of salt ions. However, increasing the supercooling degree of the generation process can enhance the driving force for hydrate formation. Although the thermodynamic additive TBAB did not significantly improve the conditions for seawater hydrate generation in the present experiments, it did increase the rate of generation. Furthermore, the study found that the hydrate conversion rate at a cooling rate of 0.3 K/min was enhanced by 1.28 and 1.19 times compared to the effects of subcooling degree and additives, respectively. In conclusion, future studies should consider the coupling effects of various enhanced generation methods to develop technical means that can better mitigate the challenges of seawater hydrate generation.

This paper presents a comprehensive computational particle fluid dynamics (CPFD) simulation of a self-designed 10 MW_th chemical looping combustion (CLC) reactor, providing detailed gas-solid two-phase flow hydrodynamic information within the system. First, the reliability of various drag models was validated based on classical experiments. Subsequently, utilizing the preferred EMMS-Yang drag model, the system was simulated comprehensively to analyze pressure balance within the system. Furthermore, the key parameters such as solid circulation rate, solid concentration distribution within the reactor, and pressure distribution were analyzed. The detailed results which are difficult to measure in operation can guide the development of operational conditions optimization and reactor control strategies. The simulation results show that the reactor system realizes good pressure balance, the solid circulation rate at the outlet of the air reactor reaches 103.80 kg/s, the solid circulation rate at the outlet of the fuel reactor reaches 40.10 kg/s, and the lower loop seal returns the material smoothly, which makes the system reach the stable operation state quickly.

Water-gas shift reaction (WGSR) is a key homogeneous reaction in the supercritical water gasification (SCWG) of coal, but the impact of the WGSR on the heterogeneous reaction of coal in the particle pores remains unclear. The mechanism of intrapore water-gas shift reaction on the SCWG of irregular-shaped coal particles was investigated through three-dimensional numerical simulation. It is revealed that the intrapore WGSR consumed a significant amount of supercritical water intended for the heterogeneous reaction of coal, inhibiting the gasification rate. Additionally, a large amount of CO₂ was generated and accumulated in the particle pores, reducing the diffusion coefficient of the supercritical water. An effective gasification factor was introduced to quantitatively characterize the inhibition by the intrapore WGSR, showing that the inhibition effect increased with the particle size. The increased gasification time of the coal particle due to the inhibition was found to have a simple logarithmic relationship with the effective gasification factor.

Decoupling of temperature and pressure in hydrothermal process was achieved via external nitrogen gas pressurization. Effects of organic matters and initial pressure on the phosphorus transformation during subcritical hydrothermal conversion of sewage sludge were investigated, and the feasibility of vivianite formation was verified simultaneously. The results show that initial pressure can enhance the enrichment of phosphorus in hydrochar. It promotes the decomposition and conversion of glucose and protein into reducing substances, which favors the formation of vivianite confirming by its strong intensity of diffraction peaks. Phosphorus is preferred to enrich in hydrochar and further enhanced by increasing initial pressure. The increase of total phosphorus (TP) content from 31.45 mg/g (0.1 MPa) to 39.68 mg/g (1.0 MPa) is observed. At hydrothermal temperature of 110℃, increasing the initial pressure promotes the conversion of Fe(Ⅲ)-P to Fe(Ⅱ)-P. The Fe(Ⅱ)-P content in the hydrochar (1.0 MPa) is 6.31 times that of raw sludge. Increasing the initial pressure promotes the decomposition of organic compounds such as carbohydrates and proteins in sludge. The organic acids in the process water lower its value of pH, while the increasing \mathrm{N}{\mathrm{H}}_{\mathrm{4}}^{+}-\mathrm{N} concentration is observed due to the degradation of proteins. The increase in redox potential of process water indicates that reducing substances such as organic acids are consumed, which promotes the reduction of trivalent iron with the increase of Fe(Ⅱ)-P content in hydrochar. The characteristic diffraction peaks of vivianite are observed in the XRD patterns of hydrochar samples under the pressurized conditions, indicating that it is feasible for the formation of vivianite during the decoupling temperature-pressure hydrothermal conversion of sewage sludge. This study provides a new way for the phosphorus recovery from sewage sludge.

Droplet combustion in an electric field is the research basis of electrostatic spray combustion. An experimental setup of fuel droplet combustion in the electric field is constructed. The combustion behavior of the biodiesel droplet is investigated by using the visualization method. The effects of electric field strength on flame and droplet morphologies as well as the droplet combustion law are discussed. The results show that the competition between the electric field force and natural buoyancy determines the flame morphology. As the electric field intensity increases, upward flames, quasi-spherical flames and downward flames appear one after another. It manifests that the upper flame height decreases, the lower flame height increases, the flame width first increases and then decreases, the flame front area first decreases and then increases, and their maximum change amplitudes are 69.9%, 243.1%, 17.0% and 10.9% respectively. As the flame front is the reaction area between fuel vapor and oxygen, increasing the electric field strength leads to a successive increase and decrease in the combustion duration of the droplet with a maximum variation of 18.1%.

In order to further improve the electrochemical performance of microbial fuel cell (MFC), a central pulse gas-liquid-solid circulating fluidized bed microbial fuel cell reactor (CPCFB-MFC) was designed and constructed. The effects of pulse liquid flow frequency, amplitude, particle circulation rate, and gas flow rate on the power generation and sewage treatment characteristics of CPCFB-MFC were studied by designing multiple experimental conditions. Under the conditions of central liquid flow pulse frequency of 0.25 Hz, pulse amplitude of 0.08 m/s, particle circulation rate of 3.3 kg/(m²·s) and gas flow of 2 L/min, the output voltage of CPCFB-MFC reached the highest, which was 649.2 mV, and the sewage treatment time was the shortest, which was 77 h. By comparing the sewage treatment efficiency and comprehensive energy consumption under different operating conditions, it can be proven that the adoption of pulse liquid flow and gas-liquid-solid multiphase operation can further improve the comprehensive performance of MFC reactors. This work is of great significance for promoting the industrialization of microbial fuel cell technology.

The porous structure of the catalyst layer of the proton exchange membrane fuel cell (PEMFC) was reconstructed, and the water capillary condensation process in the catalyst layer is simulated by a lattice Boltzmann Shan-Chen model. The effects of operating humidity on proton conduction, electrochemical surface area, and gas transport are analyzed. Based on the developed pore-scale model that couples cathode oxygen transport, proton conductivity, and electrochemical reaction, the distributions of physical quantities in the catalyst layer under different operating conditions are resolved, and the polarization curves of the catalyst layer are obtained. The optimal relative humidity for catalyst layer operation is determined to be 95%—98%.