Research On Optimal Design And Control Strategy Of Electronic Expansion Valve Of Variable Frequency Air Conditioner

The study topic of air conditioning system energy saving and improving air conditioning APF(annual energy consumption efficiency)focuses on improving the efficiency of heat exchanger and compressor performance,while the electronic expansion valve(EEV)has received relatively little attention.The application of electronic expansion valve can not only greatly improve the efficiency of air conditioning operation and enhance the comfort of air conditioning operation.Currently,the application of 5G communication technology,artificial intelligence,deep learning,image processing and other cutting-edge technologies in the field of refrigeration requires EEV,which can realize the flow control components of refrigerant medium.This paper describes the current development status and market application prospect of electronic expansion valve at home and abroad,and studies the working characteristics,model structure,fluid characteristics and control strategy of electronic expansion valve.(1)Introduce the basic principles of the variable frequency air conditioning system and the electronic expansion valve,describe the characteristics of the internal mechanical structure of the electronic expansion valve and its important role in the variable frequency air conditioning system,and determine the selection and application characteristics of the EEV used in this study.The refrigerant material used in this study is R410 A,and the different characteristics between R407 C and R410 A are briefly analyzed.The physical and mathematical model of EEV is analyzed,and the flow characteristics of electronic expansion valve are studied under different conditions such as pressure difference,valve structure parameters and refrigerant types.(2)Construct the 3D model of the electronic expansion valve,clearly display the detailed mechanical structure inside the electronic expansion valve,and construct the fluid domain structure during EEV simulation.On the basis of fluid mechanics,the influence of EEV fluid pressure,velocity and other related physical properties on the internal mechanism of the valve and the influence on the control strategy was simulated,and the EEV fluid flow field was deeply simulated.In the study,the phase transformation process and energy loss in the refrigerant flow were considered,and the single-phase flow and two-phase flow under different cooling and heating conditions were analyzed respectively.(3)Steady-state response analysis is carried out on the compound control strategy of the variable-frequency compressor and electronic expansion valve with the traditional PID control method,the transfer function of each control module of the electronic expansion valve is determined,the PID control parameters are analyzed and set by the program,and the steady-state response curve is obtained and analyzed.(4)Fuzzy theory is introduced to design the flow control system and optimize the traditional PID control mode.On the basis of the traditional PID,the fuzzy PID control system is designed and analyzed.The response curve shows that the fuzzy PID has better control effect than the traditional PID,which is more suitable for the control system,and the control strategy of this study is optimized.