Gas Turbine Temperature Prediction Using Unsteady CFD and Realistic Non-Uniform 2D Combustor Exit Properties

Typical Computational Fluid Dynamics (CFD) studies performed on High Pressure Turbines (HPT) do not include the combustor domain in their analyses. Boundary conditions from the combustor exit have to be prescribed at the inlet of the computational domain for the first HPT nozzle. It is desirable to include the effect of combustor non-uniformities and flow gradients in order to enhance the accuracy of the aerodynamics and heat transfer predictions on the nozzle guide vanes and downstream turbine blades. The present work is the continuation of steady and quasi-unsteady studies performed previously by the authors. A fully unsteady nonlinear approach, also referred to as sliding mesh, is now used to investigate a first HPT stage and the impact of realistic non-uniformities and flow gradients found along the exit plane of a gas turbine combustor. Two Turbine Inlet Boundary Conditions (TIBC) are investigated. Simulations using a two-dimensional TIBC dependant on both the radial and circumferential directions are performed and compared to baseline analyses, where the previous two-dimensional TIBC is circumferentially averaged in order to generate inlet boundary conditions dependant only on the radial direction. The two elements included in the present work, combustor pitchwise non-uniformities and full unsteady blade row interactions are shown to: (1) alter the gas temperature profile predictions up to ±5%; (2) modify the surface temperature predictions by ±8% near the trailing edge of the vane suction side; (3) increase the overall pressure losses by roughly 1%, and (4) modified the ingestion behavior of the purge cavity flow. In addition, keeping in mind the tradeoff between improved predictions and computational cost, the use of an unsteady sliding mesh formulation, instead of a quasiunsteady frozen gust, reveals the importance of the two-way unsteady coupling between adjacent blade rows for temperature and pressure predictions.Copyright © 2008 by ASME