Research On Key Technologies Of Ejector Refrigeration System Driven By Automobile Exhaust Heat

Automobile exhaust is one of the important causes of smog weather,the use of automobile waste heat to drive ejector refrigeration is a new research direction of automobile energy saving and emission reduction.The ejector refrigeration system uses primary refrigerant to absorb the waste heat of the automobile exhaust gases and engine heat dissipation to entrain secondary flow which completes heat transfer through phase change and then provides comfortable air-conditioned driving environment.At the same time,due to the use of vehicle waste heat to drive the ejector refrigeration system without additional fuel consumption,it opens up a new way for energy recycling,which is of great significance for emission reduction and environmental protection.The main research work is as follows:A waste heat recovery device based on heat pipe is designed,which is used as an ejector refrigerant generator,and then a model is proposed for waste heat recovery process by considering variable engine conditions and heat pipe arrangements.The state of automobile waste heat is systemly investigated in an established experimental platform under different working loads.By analyzing the experimental data,a heat recovery device based on heat pipe is designed,and a hybrid modeling method for recovery process is put forward.The prediction model accuracy was validated by sufficient experimental results under different engine speeds,heat pipe numbers and heat pipe arrangements,respectively.Based on the results of this section,the trend of recoverable heat with the change of waste heat are obtained,which provides the database for the design of the ejector refrigeration platform and system generator.The influence of the internal roughness on the ejector performance is studied,the loss coefficient parameter is determined for the calibration of one-dimensional model.Owing to the fact that ejector is sensitive to friction and isentropic efficiency value of one-dimensional model,a serie of CFD simulations are carried out to explore the relationship between the roughness height of each component efficiency and the performance of the ejector.The component efficiencies were obtained by the simulations mentioned above,this improves the precision of present one-dimensional theoretical model and provides the basis for the design and control of the ejector refrigeration system.An ejector performance testing platform is built for ejector model validation.The influence of friction on ejector performance is verified by using different roughness nozzles and then the accuracy of the model and the friction loss coefficient is determined by the experimental data.The influence of the different key geometric parameters of the ejector on the performance is analyzed by CFD simulations under different working conditions.Based on the simulation data,the relationship between ejector geometry parameters and its working conditions is obtained and the optimal geometric parameter range is calculated by the above relations.An ejector-compressor hybrid refrigeration system is proposed for the complex working conditions of automobile waste heat.The hybrid refrigeration system is designed by considering the insufficient recoverable waste heat when the automobile is on starting stage and at low speed.When the waste heat is insufficient,the automobile air conditioner operates at the compressor mode.With the gradual increase of waste heat,the ejector and the compressor begin to run at the same time for the sake of saving energy.And then,the system works at the ejector refrigeration mode when the waste heat is enough to reduce energy cost.Meanwhile,a control-oriented model is proposed for the hybrid refrigeration system,which provides the basis for the deeper research of the hybrid system.The experimental platform driven by waste heat for the ejector-compressor refrigeration system is built.It mainly includes three subsystems:the waste heat simulation system,the compression refrigeration system and the ejector refrigeration system.The ejector refrigeration system consists of a geometric parameter variable ejector,a circulating pump,a condenser and an evaporator,etc.The performance of the hybrid system with different roughness heights,different geometric dimensions XII and different working conditions is tested in depth.At the same time,the accuracy of the ejector model,the optimal geometry size determination method and the control-oriented system model is verified,which provides a reference for the establishment of the control strategy.