Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System

Abstract

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.

Heat Transfer Coefficient Determination on 3D Geometries from Transient Thermochromic Liquid Crystal Experiments

“…In studies which produce spatially resolved maps of HTC, (e.g. [9,10]) ribs have generally been excluded from transient TLC experiments due to 3D conduction effects. Some authors present information for the average HTC over ribbed surface (e.g.…”

Investigations on Nusselt Number Enhancement in Ribbed Rectangular Turbine Blade Cooling Channels of Different Aspect Ratios and Rotation Numbers

“…As indicated by Iacovides and Raisee [5] simple turbulence models are inappropriate to predict flow separation at the ribs. The computational simulations are getting better to predict experimental values with high accuracy, see Jackson [11], but there is still a discrepancy and some fine-tuning (turbulence model settings) is needed.…”

Local Heat Transfer Coefficient Measurements on an Engine-Representative Internal Cooling Passage

“…A direct recommendation from the authors was for further work to obtain locally resolved HTC. Jackson et al [13] presented a comparison of numerical and experimental studies on a highly representative model of a multipass internal cooling passage. Although this was a highly complex study, only qualitative judgments can be made due to the results being normalized using an unknown method.…”