Theoretical analysis and realization of stepless capacity regulation for reciprocating compressors

Abstract

The present article focuses on a stepless capacity regulation system for reciprocating compressors in the capacity range between 0 and 100 per cent. This system is based on the so-called reverse flow regulation principle. The principle works by reversing part of the total gas that has been taken into the cylinder by conveying it back to the suction chamber by holding the suction valve open for a controlled and variable proportion of the compression stroke. Therefore the discharge capacity and power reduction are virtually proportional. In this study, the thermal cycle of reciprocating compressors in the case of stepless capacity regulation is analysed. The theoretical model of the thermodynamics cycle is first established. The relationship between the variation of the capacity and the opening time of the suction valve in a compression stroke can be obtained. Based on this approach, a new stepless capacity regulation system is designed, which consists of a hydraulic unit, a distributor, an unloader, and a control system. The resulting system is applied to a type 3L-10/8 reciprocating compressor to demonstrate its effectiveness. The experimental results show that the capacity of the compressor can be regulated steplessly, and the energy consumption is reduced proportionally with respect to the reduction in the capacity.