Ideal mathematical model of shock compression and shock expansion

Abstract

Shock compression and expansion are phenomena which occur mainly in screw or vane compressors. They occur when there is an imbalance in the built-in and total pressure ratio. These are phenomena that have a negative impact on the operation of these machines and, in general, cause instability in operation, an increase in energy consumption and an overall worsening of the operational economy. The aim of this article is to present newly discovered information regarding making work processes of said compressors more effective, as in many cases, shock phenomena are subconsciously underestimated. The set aim was reached by creating an ideal simulation of isothermal compression of an ideal gas with the implementation of shock phenomena, which were performed on a screw compressor with the operating pressure 7 bar and a flow performance of 3 440 l min−1. Based on the simulations performed, the hypotheses which set forth that the impact of shock phenomena ultimately leads to a sudden increase in compressor power consumption were confirmed. E.g. at 6 bar, the instantaneous power consumption increases by about 5.74% during shock compression and by about 55.95% during shock expansion. This paper deals with new insights and at the same time presents the follow-up research.

Keywords

• screw compressor
• built-in pressure ratio
• shock compression
• shock expansion
• mathematical model