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TECHNICAL PAPERS

Influence of Loading Distribution on the Off-Design Performance of High-Pressure Turbine Blades

[+] Author and Article Information
D. Corriveau

 Defence R&D Canada (DRDC Valcartier), Quebec City, Quebec Canada G3J 1X5tdaniel.corriveau@drdc-rddc.gc.ca

S. A. Sjolander

Department of Mechanical and Aerospace Engineering, Carleton University, Ottawa, ON K1S 5B6, Canadassjoland@mae.carleton.ca

J. Turbomach 129(3), 563-571 (Aug 12, 2006) (9 pages) doi:10.1115/1.2464145 History: Received June 13, 2006; Revised August 12, 2006

Linear cascade measurements for the aerodynamic performance of a family of three transonic, high-pressure (HP) turbine blades have been presented previously by the authors. The airfoils were designed for the same inlet and outlet velocity triangles but varied in their loading distributions. The previous papers presented results for the design incidence at various exit Mach numbers, and for off-design incidence at the design exit Mach number of 1.05. Results from the earlier studies indicated that by shifting the loading towards the rear of the airfoil an improvement in the profile loss performance of the order of 20% could be obtained near the design Mach number at design incidence. Measurements performed at off-design incidence, but still at the design Mach number, showed that the superior performance of the aft-loaded blade extended over a range of incidence from about 5.0deg to +5.0deg relative to the design value. For the current study, additional measurements were performed at off-design Mach numbers from about 0.5 to 1.3 and for incidence values of 10.0deg, +5.0deg, and +10.0deg relative to design. The corresponding Reynolds numbers, based on outlet velocity and true chord, varied from roughly 4×105 to 10×105. The measurements included midspan losses, blade loading distributions, and base pressures. In addition, two-dimensional Navier–Stokes computations of the flow were performed to help in the interpretation of the experimental results. The results show that the superior loss performance of the aft-loaded profile, observed at design Mach number and low values of off-design incidence, does not extend readily to off-design Mach numbers and larger values of incidence. In fact, the measured midspan loss performance for the aft-loaded blade was found to be inferior to, or at best equal to, that of the baseline, midloaded airfoil at most combinations of off-design Mach number and incidence. However, based on the observations made at design and off-design flow conditions, it appears that aft-loading can be a viable design philosophy to employ in order to reduce the losses within a blade row provided the rearward deceleration is carefully limited. The loss performance of the front-loaded blade is inferior or at best equal to that of the other two blades for all operating conditions.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Pratt & Whitney Canada high-speed wind tunnel

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Figure 2

Summary of the blades’ geometry

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Figure 3

Unstructured mesh used for the computation

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Figure 4

Effect of Mach number on the variation of the total pressure loss coefficient for various incidences

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Figure 5

Comparison of the effect of Mach number on losses measured experimentally and predicted numerically for the three cascades at −10.0deg incidence

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Figure 6

Comparison of the effect of Mach number on losses measured experimentally and predicted numerically for the three cascades at design incidence

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Figure 7

Comparison of the effect of Mach number on losses measured experimentally and predicted numerically for the three cascades at +5.0deg incidence

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Figure 8

Comparison of the effect of Mach number on losses measured experimentally and predicted numerically for the three cascades at +10.0deg incidence

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Figure 9

Effect of Mach number on the variation of the base pressure coefficient for various incidences

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Figure 10

Effect of outlet flow Mach number on the surface Mach number distribution for the three profiles at an incidence of +5.0deg

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Figure 11

Reynolds number effect on losses for the baseline midloaded airfoil (HS1A) at several Mach numbers and an incidence of +10.0deg

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Figure 12

Effect of Mach number on the variation of the axial velocity density ratio for various incidences

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Figure 13

Comparison of loss variation with Mach number for experimental and numerical results at +10.0deg of incidence

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