Archive | 2021
A Pragmatic Method for Matching Conjugate Heat Transfer Predictions of High-Pressure Turbine Blades with Thermal Paint Tests
Abstract
The development of novel high-pressure turbine blades necessitates a numerical validation of the cooling design. It has to be ensured that, on the one hand, the thermal loading capacity of the blade material is not exceeded and, on the other hand, that there are no penalties on the thermal efficiency due to the waste of cooling air. Since conventional methods for determining the heat transfer at the blade walls are solely based on fluid simulations, the thermal back coupling between the solid and the fluid is neglected. That is why conjugate heat transfer (CHT) calculations are being employed which couple the fluid side thermal prediction with the thermal conduction of the solid structure. \nIn this work, the numerical prediction of turbine blades by means of CHT simulations is explored with regard to aero-thermal and numerical uncertainties. Two simple test cases are investigated which involve a solely internally cooled cascade vane and a leading edge model featuring a showerhead film cooling configuration. For both test cases, the uncertainties of the conjugate thermal predictions are evaluated with regard to measurement data. The gained knowledge is, then, transferred to a high-pressure turbine blade of a jet engine in the medium thrust segment. For the real engine blade, the numerical predictions are compared with thermal paint test results because the poor accessibility and the high temperatures make the use of conventional measurement techniques almost impossible. \nBased on the deviations between experiment and numerical simulations, a tool is introduced that uses an additional thermal contact resistance (TCR) to adjust the numerical prediction in order to achieve a match between conjugate heat transfer analysis and experimentally determined temperature values. In this way, the CHT models are made consistent with the measurement data. This helps to generate trustworthy temperature distributions in the material that can be used for life estimations of engine blades. \nIn order to allow a practical application of the developed tool in the design process of blade cooling configurations, it is shown how the presented method can be transferred with regard to a change of the operating point or even regarding the relocation of film cooling holes.