Turbine Stator Well Cooling: Improved Geometry Benefits

Abstract

Nowadays, it is common practice to expose engine components to air temperatures exceeding the thermal material limit in order to increase the overall engine performance and to minimise the engine specific fuel consumption (SFC). To avoid the overheating of the materials and thus the reduction of the component life, an internal flow system is designed to cool the critical engine parts and to protect them. As the coolant flow is bled from the compressor and not used for the combustion the amount of coolant is aimed to be minimised as much as possible to preserve the overall engine performance. Experiments as well as numerical simulations have shown that with the use of a deflector plate, the cooling flow is fed more directly into the disc boundary layer, allowing more effective use of less cooling air, leading to an improved engine efficiency. In this paper, the benefits of the use of a stationary deflector plate inside a turbine stator well (TSW) are presented. So far unpublished experimental data obtained from tests carried out in a two-stage turbine rig are presented. The main objective of this research has been to produce reliable methods for predicting the effects of geometry changes in this type of engine cavity, with a view to optimising the cooling flows required to maintain component integrity and life. Therefore, a numerical methodology is presented and validated against the experimental data. Steady and unsteady computational fluid dynamics (CFD) calculations of a sector model are used to determine whether fluid side flow distributions and heat transfer can be adequately represented, as well as to expose the limits of these approaches. The main annulus geometry is meshed with a multi-block structured mesh using the in-house code PADRAM. The cavity geometry is meshed once with a multi-block structured mesh using the commercial tool ANSYS ICEM and once with an unstructured mesh using the in-house code PADRAM. The CFD calculations are carried out with the commercial code FLUENT from ANSYS as well as the in-house code HYDRA. Finally, for the cavity with the deflector plate and no net ingestion, the steady state solution of the CFD is coupled to a finite element analysis (FEA) model created in the in-house code SC03 in order to take the conjugate effects into account. With this method the final non-adiabatic flow field inside the cavity as well as the final metal temperatures are obtained, which again are compared against thermocouple measured data in order to evaluate the accuracy of the numerical prediction method.