Study of Film Cooling in the Trailing Edge Region of a Turbine Rotor Blade in High Speed Flow Using Pressure Sensitive Paint

Abstract

This research focuses on film cooling of the trailing edge of a scaled up turbine rotor blade with engine-representative Mach number distribution. Pressure sensitive paint was used to obtain high-resolution adiabatic film cooling effectiveness measurements in the trailing edge region of the scaled turbine blade. The large scale, high-speed experimental set-up consists of a Perspex test section for maximum visibility of the PSP coated blade. The test section was designed to recreate a single blade passage of a gas turbine with inlet Mach and Reynolds numbers matching the corresponding values in an engine. The test blade has a constant cross section, representative of the mid-span profile of the high pressure turbine rotor blade. It was manufactured from aluminium to minimize temperature gradients over the surface of the test blade. In the current research, pressure surface cooling slots at the trailing edge were examined and the effect of cutback surface protuberance, or ‘land’, shapes on trailing edge film cooling was studied. Nitrogen and air were used as coolant gases giving a coolant to mainstream density ratio close to 1. Two land geometries-straight and tapered-were studied for a set of 6 blowing ratios from 0.4 to 1.4 in steps of 0.2. Land taper has a benefit for film cooling near the slot exit but its advantage reduces close to the trailing edge. For both geometries, film effectiveness falls with blowing ratio from 0.4 to 0.8 and increases with blowing ratio in the 0.8 to 1.4 range. Crossflow causes the coolant film to be biased towards one side of the lands. Film effectiveness results are compared with data from a scaled up low speed flat plat model of the trailing edge to explain the effect of acceleration on film cooling.

Film Cooling Effectiveness Downstream of Trailing Edge Slots Including Cutback Surface Protuberances

“…This was later developed further using slot modifications in Wong et al [16]. Gurram et al [17] used PSP to measure effectiveness on a full blade profile at engine Mach numbers. Telisinghe et al [18] studied the aerodynamics of various engine cutback geometries.…”

“…This limits the direct applicability of the effectiveness measurements taken in this study to a real blade model. However, by comparing to the baseline plain slot geometry, it is still possible to make back-to-back comparisons and judge the suitability of each cross corrugated slot design when applied to trailing edge cooling designs, reducing the number of geometries that must be tested in the high speed facility developed as a continuation of this work and published by Gurram et al [17].…”

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

“…A brief overview of the pressure sensitive paint (PSP) measurement technique is provided here, but the reader is referred to Wong et al [19], Gurram et al [20] and Han and Rallabandi [21] for further details.…”

High Resolution Experimental and Computational Methods for Modelling Multiple Row Effusion Cooling Performance

“…A brief overview of the PSP measurement technique is provided here, but the reader is referred to Wong et al (2016), Gurram et al (2016), and Han and Rallabandi (2010) for further details.…”