The effect of upstream duct boundary layer growth and compressor blade leanangle variation on an axial compressor performance

摘要

The compressor of a gas turbine engine is extremely vulnerable on upstream duct-induced flow non-uniformities whether the duct is an engine intake or aninterconnecting duct. This is justified by its position being literally anextension of the duct flow path, coupled to the fact that it operates underadverse pressure gradients. In particular, this study focuses on performancedeviations between installed and uninstalled compressors. Test results acquiredfrom a test bed installation will differ from those recorded when the compressoroperates as an integral part of an engine. The upstream duct, whether an engineintake or an inter-stage duct, will affect the flow-field pattern ingested intothe compressor. The case study presented here aims mostly at qualifying theeffect of boundary layer growth along the upstream duct wall on compressorperformance. Additionally, the compressor performance response on blade leanangle variation is also addressed, with the aim of acquiring an understanding asto how compressor blade lean angle changes interact with intake-induced flownon-uniformities. Such studies are usually conducted as part of the preliminarydesign phase. Consequently, experimental performance investigation is excludedat this stage of development, and therefore, computer-aided simulationtechniques are used if not the only option for compressor performanceprediction. Given the fact that many such design parameters need to be assessedunder the time pressure exerted by the tight compressor development programme,the compressor flow simulation technique needs to provide reliable results whileconsuming the least possible computational time. Such a low computational timecompressor flow simulation method, among others, is the two-dimensionalstreamline curvature (SLC) method, being also applied within the frame ofreference of the current study. The paper is introduced by a brief discussion onSLC method. Then, a reference is made to the radial equilibrium equation, whichis the mathematical basis of SOCRATES, a turbomachinery flow simulation toolthat was used in this study. Subsequently, the influence of the upstream duct onthe compressor inlet radial flow distribution is being addressed, with the aimof adjusting the compressor blade inlet lean angle, in order to minimizecompressor performance deterioration. The paper concludes with a discussion ofthe results.