Development Of An Auto-Tuning Nozzle Exit Position Ejector For Refrigeration Applications

Energy shortages are one of the serious challenges facing humanity.Ejector refrigeration system can recycle waste heat from automobiles for refrigeration to replace traditional car air conditioners,which can save a lot of energy.However,the development of ejector refrigeration system is limited due to the poor cooling effect,which is led by the fluctuant waste heat of automobiles.This paper presents an ejector that can automatically adjust the nozzle exit position,which is beneficial for the application of ejector refrigeration system to the vehicle.The research has important theoretical and practical values for energy conservation and emission reduction of automobiles.In this paper,a design method of auto-tuning nozzle exit position ejector is proposed for the characteristics of generator pressure instability in ejector refrigeration system driven by waste heat.Designing an auto-tuning nozzle position injector requires establishing a relationship between primary flow pressure and NXP(nozzle exit position).This paper selects the ejector designed for refrigeration conditions as a prototype,and conducts a comprehensive study of the prototype ejector through numerical simulation and experimental research methods.Based on the results,we draw the following conclusions.1.Under the condition that the secondary flow pressure and back pressure are constant and the primary flow pressure gradually increases,the primary flow mass flow rate of the ejector gradually increases,the secondary flow mass flow rate rises first and then decreases,and the ejector ratio rises first and then decreases.2.When designing ejectors for high back pressure conditions,the NXP can be appropriately increased to increase the critical back pressure of the ejector.3.When the pressure of the primary flow changes,there is an optimal NXP interval to optimize the ejector performance.4.Compared with conventional ejectors,the entrainment ratio of auto-tuning nozzle exit position ejector can be increased by at least 3.6%,and it can always maintain a relatively high entrainment ratio when the primary flow pressure fluctuates.5.In this paper,the experimental data of the ejector test system is compared with the experimental data of the ejector refrigeration system.The relative error is only 8.7%.Therefore,the experimental data of this platform can be used to further study the ejector.The relational equation is validated by the ejector test platform.The results show that this relation can be used to predict the optimal NXP of the ejector used in this paper under each primary flow pressure.The innovation of this paper is that we propose an auto-tuning nozzle exit position ejector that can automatically adjust the ejector nozzle exit position according to the primary flow pressure to optimize its performance under current operating conditions and we demonstrate its feasibility.Another innovation is the design of the ejector test experimental platform.The platform can test ejector performance under any operating conditions and is easy to operate.The experimental data can be mutually verified with traditional experimental data and CFD simulation data,which has certain value for promoting the research of ejectors.