Development of a Simulation Method of Surge Transient Flow Phenomena in a Multistage Axial Flow Compressor and Duct System

Abstract

Abstract A practical method of surge simulation in a system of a high-pressure-ratio multistage axial flow compressor and ducts, named SRGTRAN, is described about the principal procedures and the details. The code is constructed on the basis of one-dimensional stage-by-stage modeling and application of fundamental equations of mass, momentum, and energy. An example of analytical result on surge behaviors is included as an experimental verification. It will enable to examine the transient flow phenomena caused by possible compressor surges and their influences on the system components in plant systems including high-pressure-ratio axial compressors or gas turbines. Keywords: Fluid Machine, Axial Flow Compressor, Surge, Fluid Dynamics, Analytical Simulation, Transient Flow 1. Introduction High-pressure-ratio axial flow compressors have been employed in many applications of high power output, such as jet engines, gas turbines, industrial air sources, etc. With the advent of the environmental ages, they will be utilized further in various types of advanced combined-cycle plants using gas turbines as high-temperature core components. If a surging happens to occur in spite of various surge-preventive measures, violent waves and oscillations of flow could propagate both upstream and downstream in the system, having possibly adverse influences on the structural and operational safety of the system and structures. The waves could include various multi-scale phenomena, such as surge waves, sudden stop and possible reversal of the air flow, possible back-fire of burning gases accompanying very high temperature, abrupt positive and negative pressure changes resulting from surge hammer-shocks, rotating stalls, and local waves, etc. Stall stagnation phenomena could occur depending on the situations. They could occur nearly simultaneously over the whole ducts and compressor passages. Thus surge and post-stall behaviors of the flows in compressors and flow-paths have been and should be paid attention to. In this context, it is required to make clear and evaluate quantitatively the phenomena accompanied by the surging. For the purpose, it is necessary to treat the large-amplitude transient phenomena distributed over the whole flow-path and related components. Furthermore, it should be reasonably taken into consideration that significant mismatching of stage operating points in the off-design conditions caused by the flow compressibility effects could complicate the surge phenomena particularly in the high-pressure-ratio multi-stage compressor environments. The principle of the surge phenomena in pump systems was clarified as early as 1947 by Fujii