High Pressure Turbine Low Radius Radial TOBI Discharge Coefficient Validation Process

Abstract

A TOBI (tangential on board injection), or preswirl, system is a critical component of a high pressure turbine cooling delivery system. Its efficient performance and characterization are critical because the blade and disk life depend on the accuracy of delivering the required flow at the correct temperature and pressure. This paper presents a TOBI flow discharge coefficient validation process applied to a low radius radial configuration starting from a 1dimensional (1D) network flow analysis to a 3 dimensional (3D) frozen rotor computational fluid dynamics (CFD) analysis of the rotor cooling air delivery system. The analysis domain commences in the combustor plenum stationary reference frame, includes the TOBI, transitions to the rotating reference frame as the flow travels through the rotating cover plate orifice, continues up the turbine disk into the slot bottom blade feed cavity, and terminates in the turbine blade. The present effort includes matching a 1D network model with 3D CFD results using simultaneous goalmatching of the pressure predictions throughout the circuit, defining test rig pressure measurements at critical “nondisturbingâ€‌ locations for quanification of pressure ratio across the TOBI, and finally comparing the TOBI flow coefficient resulting from stationary cold flow tests with what was obtained from the 3D CFD results. An analysis of the results indicates that the discharge coefficient varies with the pressure ratio and that the traditional method of using a constant discharge coefficient extracted from a cold flow test run under choked conditions leads to overpredicting turbine cooling flows. The TOBI flow coefficient prediction for the present study compares well with the stationary data published by otherresearchers for the configuration under investigation and the process described in this paper is general for any TOBI configuration.