Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

Abstract

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data was taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short duration turbine test facility. The data consists of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, 2-D, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modelling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

Unsteady Flow in a Single Stage Turbine

“…A Uint WE sharp spike is seen in the measured heat transfer at the first point on the suction surface and similar measurements by Abhari et al (1992) and Rao et al (1994b) suggest that this is due to impingement of the ngv shock wave. The compression model, based on measured pressure levels, has reproduced this feature, while the UNSFLO model (which did not include a ngv exit shock) did not.…”

“…In Figure 18 a sharp spike in heat transfer is seen embedded in a more gentle increase at 5% surface distance. Abhari et al (1992) and Rao et al (1994b) both report similar features in time resolved heat transfer measurements made in transonic turbines and attributed them to the ngv trailing edge shock wave impinging first on the crown of the blade and the point of impact then moving towards the leading edge. Rao et al also recorded sharp increases in the unsteady pressure levels and the measurements of Abhari et al were backed up by schlieren analysis of shock impingement taken by Doorly and Oldfield (1985).…”

“…Abhari et al (1992) compared the time resolved heat transfer measurements on a turbine rotor blade with predictions from UNSFLO and found them in reasonable agreement. UNSFLO predictions of the unsteady pressure measured at mid-span on another rotor blade (Moss et al, 1995(Moss et al, , 1997a showed good agreement concerning the amplitude of the pressure fluctuations and the time averaged Mach number, but there were discrepancies in phase and waveform of the unsteady signals.…”

Improving the unsteady aerodynamic performance of transonic turbines using neural networks

“…The stator airfoil shock interacts with the other stator and rotor airfoils to set up a complex pattern of direct and reflected shock waves within the stage (ref. 5,6). The rotor airfoil trailing edge shock on the other hand interacts with the downstream LP stage.…”

Effect of Film Injection Location on Local Heat Transfer Coefficient on a Gas Turbine Blade

“…Also, the injectant to mainstream density ratio There have been many studies to investigate the effect of upstream unsteady wake and mainstream turbulence on heat transfer coefficients from a turbine blade without film cooling. Dunn [1986], Dunn et al [1986Dunn et al [ ,1989Dunn et al [ ,1994, Blair et al [1989aBlair et al [ , 1989b, Abhari et al [1992], and Blair [1994], conducted experiments in rotor-stator blade rows; whereas, Pfeil et al [1983], Doorly and Oldfield [1985], Wittig et al I1987,1988, Priddy and Bayley [1988], O'Brien and Capp [1989], Dullenkopf et al [1991 ], Dullenkopf and Mayle [1994], Liu and Rodi [1992], and Han et al [1993] did laboratory simulations of upstream unsteady wake conditions. They reported significant increases in heat transfer due to unsteady wake as well as an earlier and longer transition region on suction surface.…”