A New Simplified Model of Post Stall Transients inAxial Compression Systems

INTRODUCTIONItiswellknown,thattheusefuloperatingrangeofturbomachinerycompressionsystemsislimitedbytheonsetofoneofthetwokindsoffluiddynamicinstabilities:rotatingstallandsurgetandbothofthemwilldegradecompressionsystemperformanceanddurability1].Thesetw...

A new simplified model of post stall transients in axial compression systems

Based on the theory developed by Moors and Greitzer, a new simplifying approximation, which takesinto account the influence of higher harmonics of rotating waves, is proposed in this paper to get a simplified model of post stall transients in axial compression systems. This approximation leads to a set ofthree simultaneous nonlinear first order partial differential equations. The further investigation of poststall behavior for different response modes of instabilities (rotating stall and/or surge), recoverability,prestall period during stall inception, and the effect of compression system parameters on them canbe carried out by this model and has been discussed in detail in the present paper. It has been foundthat stall inception exhibits a large prestall period in the region with small slope of compressor characteristic, and in this region, final throttle setting, compressor characteristic and time-lag parametershave a strong influence on the period. The inertia parameters of blade rows have a strong influenceon the recoverability of compression systems and the blockage of stall cell at recovery point. Somequalitative comparisons with available experimental results and experience are made, and it shows thatthe proposed model is very simple and reliable.