活塞式压缩机变工况热力学分析

Thermodynamical analysis on unsteady stage conditions of piston compressor.

建立了活塞式压缩机变工况下的绝热吸气和等温排气模型 ,讨论了模型的瞬时压力、瞬时压力比、排气量、质量流量、抽气时间、充气时间、最低抽气压力、最高充气压力及指示功率等工作参数 ,并推导了相应的计算公式。通过分析计算 ,指出变工况操作时 ,活塞式压缩机的功率将在某一时刻达到最大值。因工作介质假设为理想气体 ,导致理论与实际出现偏差。在工程实践中 ,可根据实际气体的临界状态参数 ,查取其压缩性系数 ,计入实际气体的状态方程中 ,并将过程指数换成实际气体的容积绝热指数 ,这样就可把结论用于实践以解决工程问题。

A model for piston compressors under unsteady stage working conditions, the adiabatic suction and isothermal discharge model, is established. Some parameters of this model, such as the instant pressure and instant pressure ratio, discharge volume, mass discharge, suction and discharge time, minimum suction pressure and maximum discharge pressure, and nominal power, are analyzed, and relevant calculating equations are derived. Relying on the analysis, it is pointed out that under unsteady stage working conditions, the power of the piston compressor would reach a maximum value at a certain time. Besides, two particular working conditions, filling a vessel with gas and sucking gas out of a vessel, are discussed in detail, and the equations for calculating the time for gas filling and suction are presented.