Thermodynamic performance analysis of reciprocating compressor based on suction valve independent operation model under capacity control conditions

With the application of stepless capacity control systems, an increasing number of reciprocating compressor suction valves have shifted from automatic to controlled operation. Inconsistencies in the modification of suction valves, along with various fault states during operation, have reduced the adaptability of traditional integrated valve operation models, making it difficult to meet the analysis requirements for the transient thermodynamic processes of compressors. This study introduces a new independent operation model for the suction valves of a reciprocating compressor. The flow channel structure, flow performance parameters of different suction valves, and the structure and motion parameters of the unloaders were designed as independent variables to perform numerical simulations of compressor operation under complex working conditions. To address the nonlinear relationship between the mechanical structure of the suction valve and the forward and reverse flow performance of the capacity control, a three-dimensional simulation model was constructed to calculate the flow coefficient. Using experimental data, the accuracy of the theoretical model was validated, and the flow coefficients under various states were integrated into the new independent operation model for the suction valves. A detailed thermodynamic performance analysis of the compressor was conducted under abnormal conditions, such as inconsistent suction valve lift, unloader fork wear, and unloader retraction delay. Variations in thermodynamic parameters, including dynamic pressure, exhaust volume, and indicated work, were analysed, providing technical guidance for suction valve design, fault monitoring, and the optimisation control of reciprocating compressors.