电子膨胀阀对电动汽车空调系统的调节特性研究

电子膨胀阀是电动汽车空调系统的主要调控部件，探究其调节特性对于制定系统控制策略具有重要意义.本文搭建了以R134a为制冷剂的电动汽车空调系统实验台，研究了电子膨胀阀调节过程中，空调系统内制冷剂流量和压力的动态变化规律，分析了不同压缩机转速下，阀开度对系统制冷量、空调箱出风温度、压缩机功耗和系统COP等性能参数的影响.结果表明：阀前制冷剂相态是影响电子膨胀阀调节时系统压力变化强弱的重要因素.在阀前制冷剂为过冷液态时，调节阀开度对系统压力影响更大，并且在阀前制冷剂具有较大过冷度(大于10℃)时，下调阀开度会导致短时间的过节流造成系统压力大幅波动；系统中制冷剂循环流量与阀开度呈线性变化趋势，不受阀前制冷剂相态的影响.在实验工况下，100%阀开度对应的制冷剂循环流量为97.2～115.5 kg/h,阀开度每下调10%,系统中制冷剂循环流量下降6%～9%.

Study on Regulating Characteristics of Electronic Expansion Valve for Electric Vehicle Air Conditioning System

Electronic expansion valve is the main regulating component of electric vehicle air conditioning system. It is of great significance to explore its regulating characteristics for formulating system control strategy.In this work,an experimental bench for electric vehicle air conditioning system with R134a as refrigerant was built,and the dynamic variation of refrigerant flow rate and pressure in the air conditioning system during the electronic expansion valve regulation was studied.The effects of valve opening on system cooling capacity,air outlet temperature of air conditioning box,compressor power consumption and COP were analyzed under different compressor speed.The results show that the phase state of refrigerant in front of valve is an important factor affecting the system pressure variation during electronic expansion valve adjustment.When the refrigerant in front of the valve is supercooled liquid,regulating the valve opening has a greater impact on the system pressure,and when the refrigerant in front of the valve has a large undercooling degree (greater than 10 C),reducing the valve opening will lead to a short time of over-throttling,resulting in large fluctuation of system pressure.The refrigerant circulating flow rate in the system changes linearly with the valve opening,and is not affected by the phase state of the refrigerant before the valve.Under the experimental condition,the refrigerant circulating flow corresponding to 100%valve opening is 97.2~115.5 kg/h.When the valve opening is reduced by 10%,the circulating refrigerant flow decreases by 6%~9%.