An Analysis of the Influence of some External Disturbances on the Aerodynamic Stability of Turbine Engine Axial Flow Fans and Compressors.

摘要

The overall objective of the work described herein was to develop an improved method for the computation of the influence of external disturbances on turbine engine compressor stability,and,in so doing,to gain added physical insight into the destabilizing processes. The objectives were accomplished through the development of a one-dimensional,time-dependent mathematical compressor model for analysis of planar disturbances and an extension of the model to a three-dimensional form for analysis of distorted inflows. The models satisfy mass,momentum and energy equations on a time-dependent basis. Compressor stage force and shaft work were determined from empirical stage characteristics with corrections made for unsteady cascade airfoil aerodynamics. The system of equations comprising the model is solved using a digital computer. Example problems with comparisons to experiments are presented for three different compressors. Example problems solved using the one-dimensional analysis include:determination of the steady-state stability limit (surge line) with undisturbed flow,instability caused by oscillating planar inflow,dynamic response of a compressor to oscillating entry pressure,dynamic response to oscillating discharge pressure,and compressor instability caused by rapid upward ramps of entry temperature. Example problems solved using the distortion model include:stability limit (surge) line reduction caused by a combined radial and circumferential pressure distortion,time-variant distortion effects,pure radial pressure distortion effects,and pure pressure and temperature circumferential distortion effects.