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选择目前已得到大量应用的、采用等螺距螺杆转子的无油螺杆真空泵作为研究对象,针对其内部的气体输运过程开展热力学研究。基于等螺距螺杆真空泵的结构特点和抽气原理,论文将被抽气体在泵内所经历的输运过程,分解为膨胀吸气、等容输送、绝热压缩和等压排气四个阶段,并详细讨论了各阶段的内在机制。依据气体热力学基本原理,分别对每一个阶段进行了定量分析,推导出每一阶段内气体质量、体积、温度、压力、内能、焓、熵等热力学参数随时间的变化规律公式。以某一指定抽速真空泵为例,计算给出了泵内气体的各个热力学参数随时间变化的数据图表,并讨论了等螺距螺杆泵排气功耗和排气温度随入口压力变化的规律。
Choosing the oil-free screw vacuum pump which has been widely used at present and adopts the screw rotor with equal pitch screw as the research object, the thermodynamics research is carried out for the internal gas transport process. Based on the structural characteristics and suction principle of the screw pump with constant pitch, the paper decomposes the transport process of the pump in the pump into four phases: expansion suction, isotropic transmission, adiabatic compression and isobaric pressure discharge Discussed in detail the internal mechanism of each stage. Based on the basic principles of gas thermodynamics, the quantitative analysis of each stage was carried out, and the formula of the variation of the thermodynamic parameters with time in each stage of gas quality, volume, temperature, pressure, internal energy, enthalpy and entropy was deduced. Taking a certain pumping speed vacuum pump as an example, a data chart of the thermodynamic parameters of the gas in the pump as a function of time is given, and the law of discharge power consumption and exhaust temperature of the screw pump with constant pressure changes with the inlet pressure is discussed.