Development Of A Pure Electric Vehicle Air Conditioning System Based On Reverse Stirling Cycle

At present,the share of domestic pure electric vehicles in the market is increasing year by year.The power consumption of pure electric vehicles decreases sharply after opening air conditioning,especially in winter,air conditioning and heating will consume about 1/3 of the vehicle’s power.Therefore,the development of new efficient and environmentally friendly air conditioning for pure electric vehicles is one of the important topics to overcome the short battery life of pure electric vehicles.In this paper,an air conditioning system based on the principle of inverse Stirling cycle is proposed.In order to verify the feasibility and stability of the system,the following research is carried out.A free piston Stirling prototype was designed and processed,and the structural parameters and initial operating conditions were obtained on the basis of meeting the design requirements.The overall structure and key components of the prototype are described,and the feasibility of heating and cooling on the same Stirling prototype is analyzed theoretically.A set of air conditioning system is built on Stirling prototype by using a pump-driven heat transfer mode,which can realize the switching between refrigeration and heating.The CFD method was used to simulate the operation of Stirling prototype,and the feasibility of Stirling prototype for refrigeration and heating under different working environments was verified.Based on the prototype structure,the model is simplified and the motion of piston is defined by dynamic mesh technology.Through transient analysis,the variation characteristics of temperature,pressure and velocity inside the prototype under heating and cooling conditions are obtained.The working temperature of the Stirling prototype can maintain stability in different environments,and the pressure change also has certain regularity.The internal disturbance points obtained from the speed change provide theoretical support for the subsequent structural improvement.The force conditions of the valve piston and the power piston were analyzed,and the dynamic equation of the piston vibration system was established.Based on the rotation vector method,the vector relationship between various forces is obtained,and the basic conditions such as electromagnetic driving force,gas force,back pressure chamber pressure,and the number of plate springs required for the stable operation of the piston system are derived,so that the power piston and the valve piston maintain a constant phase change and achieve dynamic balance.Several important losses in the existing regenerators are compared,and the design of a new type of regenerator suitable for air conditioning temperature zones is completed.The internal heat transfer characteristics were analyzed by establishing a three-dimensional local model,and the relationship between velocity and pressure drop was obtained.The overall analysis of the regenerator was carried out on the porous medium model.By comparing the temperature distribution and heat transfer of the regenerator with different aspect ratios under unidirectional flow,the appropriate aspect ratio was selected.The regenerator is analyzed under oscillation conditions,and it is concluded that the regenerator can reach a stable state after a period of time.A one-way flow experiment system was built to conduct hot and cold blowing experiments on the new regenerator.The correctness of the simulation is verified by comparing the experimental and simulation data under the same inlet conditions.The free piston Stirling prototype was assembled and debugged,and the external circulation system of air conditioning was constructed based on the prototype.To sum up,based on the principle of inverse Stirling cycle,this paper proposes a pure electric vehicle air conditioning scheme that can realize cold and hot switching.The simulation analysis of Stirling prototype under refrigeration and heating conditions is carried out respectively,and it is concluded that both conditions have certain effects under approximate working conditions.It is concluded that the stable phase change between the valve piston and the power piston is needed for Stirling prototype to achieve heating and refrigeration,and the basic conditions for piston system to achieve dynamic balance are calculated and deduced.The structural improvement of the regenerator is completed,and the simulation and experiment verify that the regenerator has certain advantages,which provides theoretical support for the regenerator applied in the air conditioning temperature zone.It has certain guiding significance for the application of reverse Stirling cycle in pure electric vehicle air conditioning.