Working processes and dynamics of the liquid piston motion in an ideal piston compressor with a liquid active piston during isothermal compression of gas

Based on a previously developed conceptual model of a reciprocating compressor with a liquid-actuated piston and utilizing the fundamental laws of conservation of energy, mass, and motion, as well as the equation of state, a mathematical model of the compressor’s operating processes has been developed. This model allows for determining changes in the thermodynamic parameters of the compressed gas and coolant, as well as the dynamics (displacement and velocity) of the liquid-actuated piston. A numerical experiment using the developed mathematical model revealed that the entire compression process can be divided into three parts: the first section, which organizes the process for isothermal compression, accounts for approximately 7.2% of the total compression process; the second section, the isothermal compression process, accounts for 75%; and the third section, the non-isothermal compression process, since the height of the liquid piston remains constant and equal to the dead space. The compression process proceeds at a speed equal to the speed of the mechanical piston and a constant height of the liquid piston, allowing for the complete displacement of the compressed gas from the working chamber. During the suction process, the height of the liquid piston decreases from the dead space to 0, allowing the entire volume of the working chamber to be filled by the end of the suction process. To supply liquid to the working chamber, it is necessary to use a sub-piston space, in which the pressure must change according to the appropriate law to ensure the dynamics of the liquid piston. The change in coolant temperature in the working chamber is negligible and can be ignored for practical calculations.
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