On the Prediction of Rotating Stall in an Industrial Gas Turbine Compressor

An investigation is presented into the computation of rotating stall in an industrial gas turbine compressor using a hybrid whole annulus and single passage computational domain. The objective of this investigation is to demonstrate the use of large-scale unsteady computations with quicker turn-around times in the design cycle to develop and evaluate a number of variable guide vane schedules. This means that subsequent engine test campaign could be carried out with significantly lower test matrix size in terms of the number of variable guide vane schedules and/or the handling bleed settings thus reducing the overall development time and cost. Rotating stall that was measured and characterised during a previous compressor rig test (subject matter of an accompanying paper “Quick Start of an Industrial Gas Turbine Engine Through the Development of “Silent Start” VGV Schedule”) for a variable guide vane setting viz., ‘initial schedule’ and its absence for other settings namely the ‘Silent Start’ variable guide vane schedule were successfully predicted by large-scale unsteady computations using TurboStream, a commercial solver. The predicted number of stall cells and their speed agreed closely with the test data. The methodology thus validated was applied to predict the rotating stall characteristics during the development of a compressor for a new gas turbine engine. These predictions helped in deciding the speed at which handling bleed is opened/shut. The engine tests eventually carried out agreed closely with the predictions further validating the process.