Applied Thermal Engineering

• Theoretical and experimental study of bringing the compression process to isothermal. • Designed two-stage piston hybrid power machine with liquid piston. • The kinematics of liquid piston motion has three zones: two isothermal (hyperisothermic) and one non-isothermal compression. • With a decrease in the temperature of the surface of the working chamber and its diameter, the average velocities of the liquid piston of the real and isothermal compression process converge. • According to the obtained results, new highly efficient designs of hybrid power machines are proposed. The implementation of the isothermal process of gas compression in the compressor increases the indicator efficiency up to 20%, which is a determining increase in their operation and saves a significant amount of energy and financial resources, as compressor units consume up to 10% of the energy consumed by production sector. Its implementation is possible in many ways: by changing the heat exchange surface (injection of coolant during compression), changing the heat transfer coefficient, changing the speed of gas compression, etc. The article considers a scheme for gas compression in a cylinder with a liquid piston having a variable speed to ensure an isothermal compression process, and a design of piston hybrid power machine, which brings the gas compression process closer to isothermal. According to theoretical studies, we determine the speed of the liquid piston for the implementation of the isothermal compression process, the amount of liquid required to supplied to the cylinder and the amount of liquid to be be drained from the pump into the gas cap. Using the method of mathematical modeling, according to the fundamental laws of conservation of energy, mass and motion, a mathematical model of a two-stage piston hybrid power machine with a liquid piston and a gas cap has been developed. The performance of the machine is verified by the created prototype, a test stand for its research and a series of experimental studies. As a result of ...

Approximation of the compression process to isothermal in a reciprocating compressor with a liquid piston