The Study On Auto-cascade Refrigeration System Supercharged By Gas Wave

The wave rotor is an unsteady-flow device which can realize energy exchange through direct contact between high-and low-pressure fluids.And the wave rotor has the several advantages,such as high isentropic efficiency,slow speed of revolution,compact structure,etc.After consulting related literature,it is found that the wave rotor is widely used in the field of gas turbine engine.For the field of refrigeration,wave rotor is mostly used in expansion refrigeration.There are few research results on using the supercharging characteristics of wave rotor to improve refrigeration cycle performance.The performance of refrigeration cycle can be improved,and the pressure ratio of compressor can be decreased by embedding refrigerant wave rotor in the auto-cascade refrigeration system because of the supercharging and entrainment characteristics of wave rotor.So this research has great value.This article studies the supercharging characteristics of wave rotor with different mixing ratio of refrigerants based on the numerical simulation of refrigerant wave rotor.Combined with the thermodynamic model of the wave rotor auto-cascade refrigeration with double evaporators.Then the structure design and equipment processing of the wave rotor are carried out.The specific research contents are as follows:(1)To simulate the refrigerant wave rotor,the numerical calculation model of mixed refrigerant real gas wave rotor and the thermodynamic model of the wave rotor auto-cascade refrigeration with double evaporators are built.The thermodynamic calculation results of refrigeration cycle are used as the boundary conditions of the numerical simulation of wave rotor.By the diagrams of pressure and temperature contour can be achieved by the simulation.The size and relative position of the wave rotor’s ports can be designed based on the movement rules of the pressure and temperature waves.Completing the design of the main structure of the wave rotor,as the basis for subsequent drawing of the wave rotor machining drawings.(2)During the numerical simulation of mixing-refrigerant wave rotor,keeping the pressure and temperature boundary conditions constant,changing the mixture ratio of refrigerants to study the influence on the supercharging characteristics of shock tube and wave rotor.The structure and the effect of gas wave supercharging and heating of wave rotor are influenced by the mixture ratio of refrigerants as well.The results show that as the mole fraction of highboiling-point refrigerant in mixture decreases,the propagation speed of the pressure wave in the wave rotor increases,and the width of the wave rotor port becomes narrower.(3)Based on the results of numerical simulation,the thermodynamic model of wave rotor auto-cascade refrigeration cycle is built considering the restriction of the entrainment ratio and supercharging ratio.The influence of the isentropic efficiency of wave rotor,the evaporating temperature of the major evaporator,the vapor phase fraction of the condenser outlet,the fraction of low-boiling-point refrigerant in mixture,the driving pressure of wave rotor on the energy efficiency of the cycle and the pressure ratio of the compressor are studied.And the comparison between the auto-cascade refrigeration cycle with or without wave rotor is conducted.The results show that the refrigeration cycle with wave rotor has lower pressure ratio of the compressor and better performance because of the supercharging characteristic of wave rotor.