Performance analysis and optimization of reciprocating compressor with stepless capacity control system under variable load conditions

Abstract

The stepless capacity control system uses mechanical unloaders to press off suction valves during a partial stroke, so that the quantity of gas that is compressed matches the cooling load of the refrigeration and air-conditioning systems. In this paper, an improved numerical model is developed for a reciprocating compressor under stepless capacity regulation to analyze the influence of critical parameters, including hydraulic force, displacement, and velocity of the unloader. The dynamic pressure of the gas in the cylinder is investigated under the influence of different parameters. The results show that the lowest power requirement for the same performance is achieved with a 360 N force of the unloader, indicating that it is the optimal force. Moreover, the displacement of 1.75 mm is preferable than that of 2 mm, and the withdrawal velocity of the unloader must be limited below 1.1 m s−1 to avoid large impact stress of valve plate.