变容量双级压缩系统压缩机动态耦合模型

Dynamic Coupled Model of Compressors in Two-stage Compression System with Variable Capacity

以低压端为变频双转子、高压端为定频单转子的两台压缩机构成的双级压缩系统为研究对象,基于转子压缩机几何模型,依据质量与能量守恒方程,建立变容量双级压缩系统压缩机动态耦合模型,并利用试验对模型进行校核。基于模拟和试验结果,分析中间压力、中间气体温度和高压压缩机排气温度等参数随时间和低压压缩机频率的变化规律。结果表明,系统的中间压力、中间气体温度和高压压缩机排气温度具有脉动特性;在蒸发温度0℃,冷凝温度40℃,低高压压缩机理论输气量比为2.82时,中间压力已接近冷凝压力,系统将失去中间补气增焓效果;通过增大低压压缩机频率可有效提高系统制热量,但系统制热性能系数(Coefficient of Performance for heating,COPh)改善较小,且COPh最优值所对应的低压压缩机频率随蒸发温度的降低将逐渐增大。

A two-stage compression heat pump system with variable capacity has been studied,which consists of two compressors including a double-rotor compressor with variable capacity for the low compression,and a single-rotor compressor for the high compression.A compressor dynamic coupled model of a two-stage compression system with variable capacity is established,based on the compressor geometry,the mass and energy conservation equations.The model is finally verified by the experiment.The variations of the intermediate gas pressure and temperature,and the high compressor discharge temperature with time and low compressor frequency are analyzed.The results show that the intermediate gas pressure and temperature,and the high compressor discharge temperature of the system are pulsatile.And when the evaporation and condensation temperatures equal 0 ℃ and 40 ℃ respectively,and the ratio of theoretical displacement of the low compressor to that of the high one is 2.82,it is shown that the intermediate gas pressure will draw close to the condensation pressure and the enthalpy-increasing effect of the vapor injection will disappear.In addition,increasing the low compressor frequency can improve the heating capacity significantly,but the coefficient of performance for heating（COPh） improves a little.However,the low compressor frequency corresponding to the optimal COPh increases with the decrease of the evaporation temperature.