Factors affecting reciprocating compressor performance

A reciprocating compressor is a positive displacement machine and, in principal, its capacity and horsepower can be calculated very easily. In practice, however, several loss mechanisms act to decrease capacity and increase horsepower from the ideal predicted values. Many of these effects are quite difficult to predict accurately and the only effective way of developing reciprocating compressor performance prediction methods is to run a large number of tests on different compressors under different operating conditions. Combined with an understanding of the physics controlling the losses, experimental results allow good empirical models of losses to be developed. However, without the benefit of a good understanding of the physics of the loss mechanisms, it is impossible to interpret test results. Some factors affecting the magnitude of losses are compressor design, compressor speed, suction and discharge pressure and temperature, gas composition, suction and discharge piping design, and valve design. Losses that are important in some applications may be negligible in others so it is essential that a wide range of compressor designs, valve designs, gas molecular weight and operating conditions be tested when developing a performance prediction model. The paper discusses the effects of clearance and pressure ratio; the primary losses affecting capacitymore » and power, including valve and port pressure loss, valve springing, valve inertia, piston ring leakage, packing leakage, discharge valve leakage, suction valve leakage, pulsations, heat transfer in the suction passage, and heat transfer in the cylinder; heat transfer in compressor cylinders; performance prediction methods; and compressor diagnosis.« less