A Numerical Method for the Study of Surge and Flow Instabilities in Gas Compression Systems

Abstract

Abstract A numerical method is developed to study the effect of various geometrical and operational parameters on the stability of flow in gas compression systems. It is hoped that this and similar type of studies will help us to understand the effect of coupling of the flow characteristics of a compressor with that of a pipeline. In this study, the gas compression system is assumed to be comprised of a compressor, a throttling valve, and a long pipe. A nonlinear lumped parameter model is used to represent the compressor. The gas flow inside the pipeline is modeled by discrete elements in which the flow is assumed to be one dimensional, viscous, and compressible. The throttling valve is modeled by a single element where the pressure drop across it is predicted through an empirical relation. The governing set of equations for the comprehensive model are linearized using explicit finite difference techniques and then solved for the unknowns of the problem. The results indicate that the amplitude and frequency of the flow oscillations experienced by the coupled system depend on the length of the pipe. The frictional losses seem to dampen the amplitude of the flow oscillations experienced in the compressor and the pipeline.