Reciprocating compressor, piston-cylinder clearance, leakage
Leakage can significantly affect the performance of low-capacity reciprocating compressors, reducing the mass flow rate and increasing energy consumption. In reciprocating compressors, leakage takes place mainly in the piston-cylinder clearance and is brought about by the piston motion and pressure difference between the compression chamber and the shell internal environment. This paper reports a numerical analysis of leakage in the piston-cylinder clearance of a low-capacity reciprocating compressors based on the Reynolds equation for compressible fluid flow. A simulation model is developed and applied throughout the compression cycle to assess the effect of the clearance geometry, piston velocity and piston secondary motion on the leakage and compressor performance. A simplified version of the model considering the piston concentric in the cylinder is also adopted to assess the effect of the piston secondary motion on leakage. The results show that the compressibility effects are significant and have to be considered in the analysis and that the piston secondary motion can increase gas leakage by 90%.