Effect of Combustor Swirl on Transonic High Pressure Turbine Efficiency

Abstract

This paper presents an experimental and computational study of the effect of inlet swirl on the efficiency of a transonic turbine stage. The efficiency penalty is approximately 1%, but it is argued that this could be recovered by correct design. There are attendant changes in capacity, work function, and stage totaltototal pressure ratio, which are discussed in detail. Experiments were performed using the unshrouded MT1 highpressure turbine installed in the Oxford Turbine Research Facility (OTRF) (formerly at QinetiQ Farnborough): an engine scale, short duration, rotating transonic facility, in which M, Re, Tgas/Twall, and N/T01 are matched to engine conditions. The research was conducted under the EU Turbine AeroThermal External Flows (TATEF II) program. Turbine efficiency was experimentally determined to within bias and precision uncertainties of approximately آ±1.4% and آ±0.2%, respectively, to 95% confidence. The stage mass flow rate was metered upstream of the turbine nozzle, and the turbine power was measured directly using an accurate straingauge based torque measurement system. The turbine efficiency was measured experimentally for a condition with uniform inlet flow and a condition with pronounced inlet swirl. Full stage computational fluid dynamics (CFD) was performed using the RollsRoyce Hydra solver. Steady and unsteady solutions were conducted for both the uniform inlet baseline case and a case with inlet swirl. The simulations are largely in agreement with the experimental results. A discussion of discrepancies is given.