Study On The Performance Of Two-Phase Ejector And Two-Phase Ejector With Bypass

Two-phase ejector is the key device to recover throttling loss in the bi-evaporative compression/ejection refrigeration cycle(BCERC).The performance of two-phase ejector seriously restricts the improvement of the system efficiency.How to improve the efficiency of two-phase ejector under actual operating conditions is an important research content for practical application of the cycle.In this article,the two-phase ejector used in the BCERC is investigated.The pressure of the system pipeline connected to the two-phase ejector under the standard test conditions specified in the national standard is determined.Then the internal flow field and influencing factors of the two-phase ejector under the corresponding pressure boundary conditions were analyzed,and the optimal structure size parameter matching was explored.Finally,to further improve the performance of two-phase ejector,a new two-phase bypass ejector with high pressure fluid as bypass medium was proposed.Analysis of its performance and influencing factors,explore the best structural matching parameters of bypass.The main research contents and results are as follows:(1)The effects of operating parameters on the performance of refrigeration system was studied by using the BCERC test bench.The inlet and outlet pressure parameters of the two-phase ejector are determined under the standard test conditions specified in the national standard.The results show that under the same conditions and refrigerating capacity,compared with the traditional vapor compression refrigeration cycle,the COP of the BCERC is increased by 21.1 %～39.8 %.Under the standard test conditions specified in the national standard,with the increase of compressor frequency,the cooling capacity and compressor power consumption of the BCERC increase,and the COP decreases.The entrainment ratio of the two-phase ejector decreases and the pressure rise ratio increases.(2)Using ANSYS Fluent software,under the experimental parameters,the flow of the internal flow field of the two-phase ejector was simulated and analyzed,and the influence of structural parameters on the performance of the two-phase ejector was studied.The results show that when the nozzle throat diameter is 1.9 mm,the outlet diameter is 4.6 mm,the expanding angle of the expanding section is 5°,the mixing chamber diameter is 10 mm,and the expansion angle of the diffuser is in the range of5°～11°,the performance of the two-phase ejector is better.The length of the mixing chamber has little effect on the performance of the two-phase ejector.(3)A new bypass ejector was proposed.The effects of structural parameters and working conditions on the performance of the new ejector was simulated and analyzed.Explore the best structural matching parameters of bypass.The results show that: when the main structural parameters and working parameters of the two-phase ejector are fixed,there is an optimal bypass inlet angle of 15°,an inlet width of 3 mm,an inlet position of 0 mm(the inlet of diffuser)and an inlet pressure of 618.5 k Pa,which optimizes the performance of the two-phase bypass ejector.There is an optimal matching relationship between the bypass inlet angle and the diffuser angle of the diffuser,and the relationship is: y=-x+20.Compared with the traditional two-phase ejector,the entrainment ratio of the two-phase bypass ejector is increased by 45.5 %.