Mathematical modelling of a reciprocating compressor with coolant injection and valve control

Abstract

Compressed air is used throughout industry in various forms, ranging from small pneumatic tools to long pipelines at mines, and it accounts for 9%–10% of total energy consumption. Many energy providers utilise fossil fuels for electricity production, which has prompted the need to invest in renewable energy solutions. The cost of a compressed air system depends on multiple components, the largest being energy cost, which accounts for 75%–80% of the total life-cycle cost of the system. Thus, with increased efficiency, the cost and energy consumption of compressed air will decrease. The aim of this research is to further investigate the effects of timed coolant injection in a reciprocating compressor to create a quasi-isobaric process followed by a quasi-isothermal process with the aim to increase compressor efficiency. A mathematical model and numerical simulation, utilising the first law of thermodynamics, was created to simulate the effects of timed coolant injection at the commencement of the compression stroke. The mathematical model and numerical simulation were validated against experimental results and exhibited being in good agreement. The application of the mathematical model beyond its tested operating range was also presented.