Numerical analysis of gas leakage in the piston-cylinder clearance of reciprocating compressors considering compressibility effects

10th International Conference on Compressors and their Systems

Braga, V.M.^1 ; Deschamps, C.J.^1

POLO Research Labs for Emerging Technologies in Cooling and Thermophysics, Federal University of Santa Catarina, Florianopolis

SC

88040-900, Brazil^1

关键词: Compressibility effects;    Compressible fluid flow;    Compression chambers;    Compressor efficiency;    Domestic refrigeration;    Isentropic efficiency;    Oil-free compressors;    Volumetric efficiency;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/232/1/012006/pdf
DOI  :  10.1088/1757-899X/232/1/012006

来源: IOP

【 摘 要 】

Leakage is a major source of inefficiency in low-capacity reciprocating compressors. Not only does it lower the mass flow rate provided by the compressor, reducing its volumetric efficiency, but also gives rise to outflux of energy that decreases the isentropic efficiency. Leakage in the piston-cylinder clearance of reciprocating compressors is driven by the piston motion and pressure difference between the compression chamber and the shell internal environment. In compressors adopted for domestic refrigeration, such a clearance is usually filled by a mixture of refrigerant and lubricating oil. Besides its lubricating function, the oil also acts as sealing element for the piston-cylinder clearance, and hence leakage is expected to be more detrimental to oil-free compressors. This paper presents a model based on the Reynolds equation for compressible fluid flow to predict leakage in oil-free reciprocating compressors. The model is solved throughout the compression cycle so as to assess the effect of the clearance geometry and piston velocity on leakage and compressor efficiency. The results show that compressible fluid flow formulation must be considered for predictions of gas leakage in the cylinder-piston clearance.