Compensation of Intake Induced Flow Non-Uniformities With Compressor Blade Lean Angle Changes

The compression system has traditionally drawn most of the attention concerning the gas turbine engine performance assessment and design procedure. It is the most vulnerable component to flow fluctuations within a gas turbine engine. In particular this study focuses on performance deviations, between an installed and an uninstalled compressor. Test results acquired from a test bed installation will differ from these recorded when the compressor operates as an integral part of the engine. The upstream duct, whether an intake or an interstage duct, will affect the flow field pattern ingested into the compressor. The case studies presented into this work aim to mostly qualify the effect of boundary layer growth along the upstream duct walls, upon compressor performance. Additionally, compressor performance response on blade lean angle variation is being addressed, with the aim of acquiring an understanding as to how compressor blade lean angle changes interact with intake induced flow non uniformities. Such studies are usually conducted during the preliminary design stage, before the compressor is built. Consequently, experimental performance investigation is excluded at this stage of development. Computer aided simulation techniques are between the few if not the only option for compressor performance prediction. Given the fact that many such design parameters need to be assessed under the time pressure exerted by the tight compressor development program, the compressor flow simulation technique used needs to provide reliable results while consuming the least possible computational time. Such a low computational time compressor flow simulation method, among others, is the two dimensional (2D) streamline curvature (SLC) method, being applied within the frame of reference of the current study. The paper is introduced by a brief discussion on SLC method that was proposed more than 50 years ago. Then a reference is made to the Radial Equilibrium Equation (REE) which is the mathematical basis of the code, commenting on the assumptions that were undertaken. Subsequently the influence of the intake presence on the compressor inlet radial flow distribution is being addressed, with the aim of adjusting compressor blade inlet lean angle, in order to minimize compressor performance deterioration. Finally the paper is concluded with a discussion of the results.