Time Averaged and Time Accurate Aerodynamic Effects of Forward Rotor Cavity Purge Flow for a High Pressure Turbine—Part I: Analytical and Experimental Comparisons

Abstract

The effect of rotor purge flow on the unsteady aerodynamics of a highpressure turbine stage operating at design corrected conditions has been investigated, both experimentally and computationally. The experimental configuration consisted of a singlestage highpressure turbine with a modern filmcooling configuration on the vane airfoil and the inner and outer end wall surfaces. Purge flow was introduced into the cavity located between the highpressure vane and the highpressure disk. The highpressure blades and the downstream lowpressure turbine nozzle row were not cooled. All of the hardware featured an aerodynamic design typical of a commercial highpressure ratio turbine and the flow path geometry was representative of the actual engine hardware. In addition to instrumentation in the main flow path, the stationary and rotating seals of the purge flow cavity were instrumented with high frequency response flushmounted pressure transducers and miniature thermocouples in order to measure the flow field parameters above and below the angel wing.Predictions of the timedependent flow field in the turbine flow path were obtained using FINE/Turbo, a threedimensional Reynoldsaveraged Navier–Stokes computational fluid dynamics CFD code that had the capability to perform both a steady and unsteady analysis. The steady and unsteady flow fields throughout the turbine were predicted using a three bladerow computational model that incorporated the purge flow cavity between the highpressure vane and disk. The predictions were performed in an effort to mimic the design process with no adjustment of boundary conditions to better match the experimental data. The timeaccurate predictions were generated using the harmonic method. Part I of this paper concentrates on the comparison of the timeaveraged and timeaccurate predictions with measurements in and around the purge flow cavity. The degree of agreement between the measured and predicted parameters is described in detail, providing confidence in the predictions for the flow field analysis that will be provided in Part II.