Fundamental Optimal Design Guideline for Reciprocating Compressors to Maximize Mechanical Efficiency

Abstract

There are many combinations of the piston stroke and the cylinder bore that yield a given suction volume in the reciprocating compressors. This study presents a fundamental optimal design concept to determine the combination of the piston stroke and the cylinder bore, which maximizes the mechanical efficiency of a compact single-cylinder reciprocating refrigerant compressor with a given ratio of the crank arm rotating radius to the connecting rod length. First, theoretical development of the equation of motion of the rotating crankshaft is briefly presented. Secondly, computer calculations are carried out to identify the mechanical efficiency for a variety of combinations of the major parameters, thereby permitting identification of the optimal combination for maximum mechanical efficiency. Finally, the identified optimal combination is subjected to a parametric study with a variety of friction coefficients, thus resulting in no effect of the values of friction coefficients upon the optimal combination.