Study the Effect of Unstable Air Flow in the Suction and Discharge System on the Performance of Reciprocating Air Compressor

Abstract

This research aims at studying the effect of unstable air flow in the suction and discharge system on the performance of reciprocating air compressor. The study was conducted on a reciprocating air compressor with two cylinders diagonally, which operates in three stages to generate the required pressure and cooling between the two cylinders by the air. To clarify the flow, three different pipes in length and diameter were used. A mathematical model was prepared to calculate the one-dimensional unstable flow in the pipes by using the characteristics method and the flow relationships that include effect of friction losses, change of entropy and heat transfer; as well as, the compressive waves formed in the pipes with their effect on the flowing mass inside the cylinder and the dynamic behavior of the compressor valves were predicted. In addition, the pressure, temperature, volume, mass and efficiency were calculated, and an optimal method was adopted to solve the differential equations system through numerical analysis and by using Rung-Kutta method. The results manifested that the use of multi-stage reciprocating air compressor gives a high efficiency due to the air cooling, and the length and diameter of the suction pipe and the speed of compressor have an effect on the capacity of compressive waves which affect the final pressure generated by the compressor that causes an increase in volumetric efficiency.