化工学报 ›› 2022, Vol. 73 ›› Issue (7): 2912-2923.DOI: 10.11949/0438-1157.20220076
收稿日期:
2022-01-14
修回日期:
2022-05-19
出版日期:
2022-07-05
发布日期:
2022-08-01
通讯作者:
邓建强
作者简介:
李亚飞(1994—),男,博士研究生,基金资助:
Yafei LI1,2(),Jianqiang DENG1,2(),Yang HE1,2
Received:
2022-01-14
Revised:
2022-05-19
Online:
2022-07-05
Published:
2022-08-01
Contact:
Jianqiang DENG
摘要:
跨临界CO2在高速膨胀时,压力和温度剧烈下降,会发生非平衡相变。其中在天然气超声速分离设备和超临界CO2离心压缩机中CO2会发生非平衡冷凝相变;在引射膨胀制冷系统中,跨临界CO2在引射器主动喷嘴中发生非平衡闪蒸相变。为解决跨临界CO2在膨胀过程中物性变化剧烈,非平衡相变模拟困难的问题,构建了新型非平衡相变CFD模型,以研究跨临界CO2在超声速缩放喷嘴中的非平衡冷凝和非平衡闪蒸的相变过程和膨胀机理,模型耦合了温度驱动的蒸发-冷凝相变机制和压力驱动的空化-冷凝相变机制,并用文献中的试验结果验证了模型的准确性。研究结果表明,在冷凝相变过程中,由压力驱动的冷凝传质具有主要影响,压力驱动的冷凝传质主要存在于喷嘴喉部与内流区域,温度驱动的冷凝传质主要存在于喷嘴渐扩段壁面。冷凝传质速率随着进口压力的增加和进口温度的降低而增加,从而使冷凝的非平衡程度和喷嘴内的干度降低,喷嘴渐扩段内达到声速的位置也相应延后。在闪蒸相变过程中,由温度驱动的蒸发传质占据主导,蒸发相变主要发生在喷嘴喉部附近,空化相变主要发生在喷嘴渐扩段,两相CO2在喷嘴的渐扩段达到声速。随着喷嘴进口压力的增加和进口温度的降低,闪蒸的非平衡程度增加,使喷嘴内的干度减小。本研究有助于厘清跨临界CO2快速膨胀中的非平衡闪蒸和冷凝相变机理,并为跨临界CO2膨胀设备的分析和优化设计提供参考。
中图分类号:
李亚飞, 邓建强, 何阳. 跨临界CO2快速膨胀过程中非平衡冷凝和闪蒸机理的数值研究[J]. 化工学报, 2022, 73(7): 2912-2923.
Yafei LI, Jianqiang DENG, Yang HE. Numerical study on non-equilibrium condensation and flashing mechanisms in rapid expansion process of transcritical CO2[J]. CIESC Journal, 2022, 73(7): 2912-2923.
进口压力pin/MPa | 进口温度Tin/K | 出口压力pout/MPa |
---|---|---|
9.5 | 323.55 | 4.06 |
表1 喷嘴进出口条件
Table 1 Inlet and outlet conditions of nozzle
进口压力pin/MPa | 进口温度Tin/K | 出口压力pout/MPa |
---|---|---|
9.5 | 323.55 | 4.06 |
几何参数 | 数值 | 几何参数 | 数值 |
---|---|---|---|
γ1 | 29.59o | Lmix | 38.00 mm |
γ2 | 71.47o | Wmix | 2.82 mm |
γ3 | 88.19o | Ld1 | 30.50 mm |
γnc | 23.73o | Ld2 | 24.00 mm |
Wn | 8.00 mm | Wd | 10.00 mm |
Ws | 8.00 mm | γd | 13.43o |
Ls | 26.55 mm | Hn | 0.78 mm |
NXP | 8.40 mm | Hmix | 1.78 mm |
NDA | 2.00o |
表2 CO2引射器的几何参数
Table 2 Geometric parameters of CO2 ejector
几何参数 | 数值 | 几何参数 | 数值 |
---|---|---|---|
γ1 | 29.59o | Lmix | 38.00 mm |
γ2 | 71.47o | Wmix | 2.82 mm |
γ3 | 88.19o | Ld1 | 30.50 mm |
γnc | 23.73o | Ld2 | 24.00 mm |
Wn | 8.00 mm | Wd | 10.00 mm |
Ws | 8.00 mm | γd | 13.43o |
Ls | 26.55 mm | Hn | 0.78 mm |
NXP | 8.40 mm | Hmix | 1.78 mm |
NDA | 2.00o |
算例编号 | 主动流压力 pp/MPa | 主动流温度 Tp/K | 引射流压力 ps/MPa | 引射流温度 Ts/K | 引射器出口压力 peo/MPa |
---|---|---|---|---|---|
A1 | 9.50 | 306.59 | 3.73 | 297.17 | 3.80 |
A2 | 9.00 | 304.92 | 2.99 | 299.53 | 3.10 |
A3 | 8.49 | 303.17 | 3.04 | 299.47 | 3.13 |
表3 CO2引射器的进出口操作条件
Table 3 Inlet and outlet operating conditions of CO2 ejector
算例编号 | 主动流压力 pp/MPa | 主动流温度 Tp/K | 引射流压力 ps/MPa | 引射流温度 Ts/K | 引射器出口压力 peo/MPa |
---|---|---|---|---|---|
A1 | 9.50 | 306.59 | 3.73 | 297.17 | 3.80 |
A2 | 9.00 | 304.92 | 2.99 | 299.53 | 3.10 |
A3 | 8.49 | 303.17 | 3.04 | 299.47 | 3.13 |
算例编号 | 主动流流量试验值mp,exp/(g/s) | 引射流流量试验值ms,exp/(g/s) | 主动流流量模拟值mp,num/(g/s) | 引射流流量模拟值ms,num/(g/s) | 主动流流量 误差/% | 引射流流量 误差/% |
---|---|---|---|---|---|---|
A1 | 19.25 | 10.70 | 17.05 | 10.96 | -11.43 | 2.43 |
A2 | 15.55 | 6.60 | 16.03 | 6.92 | 3.09 | 4.85 |
A3 | 14.67 | 6.21 | 15.06 | 6.75 | 2.66 | 8.70 |
表4 CFD模拟得到的质量流量和试验结果的比较
Table 4 Comparison of mass flow rates obtained by CFD simulation and experimental results
算例编号 | 主动流流量试验值mp,exp/(g/s) | 引射流流量试验值ms,exp/(g/s) | 主动流流量模拟值mp,num/(g/s) | 引射流流量模拟值ms,num/(g/s) | 主动流流量 误差/% | 引射流流量 误差/% |
---|---|---|---|---|---|---|
A1 | 19.25 | 10.70 | 17.05 | 10.96 | -11.43 | 2.43 |
A2 | 15.55 | 6.60 | 16.03 | 6.92 | 3.09 | 4.85 |
A3 | 14.67 | 6.21 | 15.06 | 6.75 | 2.66 | 8.70 |
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