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THE BOUNDARY LAYER OVER TURBINE BLADE MODELS WITH REALISTIC ROUGH SURFACES

THE BOUNDARY LAYER OVER TURBINE BLADE MODELS WITH REALISTIC ROUGH SURFACES.

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THE BOUNDARY LAYER OVER TURBINE BLADE MODELS WITH REALISTIC ROUGH SURFACES

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  1. THE BOUNDARY LAYER OVER TURBINE BLADE MODELS WITH REALISTIC ROUGH SURFACES Background: The surfaces of turbine blades tend to roughen during their operational lifetimes due to deposits and to repeated heating and cooling. This degradation of the surface leads to increased heat transfer loads which further increases roughness, resulting ultimately to the need for replacement. Roughness patterns are irregular thereby making less reliable theoretical estimates of heat transfer processes. Potential Impact: This research could lead to improved MTBO’s for jet engines thereby reducing sustainment costs and increasing affordability. Objective: Arrive at a better understanding of the effects of roughness on the heat loads and frictional losses encountered in jet engine turbine blade flows. PI: Ralph S. Budwig, Mech. Engr., U. of Idaho Donald M. McEligot, Idaho National Engineering and Environmental Laboratory (INEEL) Richard B. Rivir and Major Jeffrey Bons, AFRL-PRTT Students: Hugh McIlroy Jr. - Ph.D. Candidate William Dalling – MSME student Duration: 36 months, ending April 30, 2003 AFOSR Grant Number: F49620-00-1-0265 Technical Approach: Measure fluid velocity in the boundary layer near roughness elements using large scale models of turbine blade surfaces in the Matched Index of Refraction Facility at INEEL. Well-established laser Doppler velocimetry methods will be used. The approach will yield high quality turbulence data in the near wall region. The measurements will support improved direct numerical simulations of the processes and better theoretical predictions.

  2. A flat plate test apparatus that has been developed for use in the Matched-Index-of-Refraction (MIR) Facility. Experiments to measure mean and turbulence quantities within the viscous layer and near wall region of the boundary layer are underway. The outer flow conditions include an elevated free-stream turbulence level and free-stream acceleration chosen to simulate conditions on the suction side of a turbine vane over the first one-third of the vane. A turbulence trip is located just downstream of the leading edge of the flat plate model. The trip was designed to simulate the boundary layer disturbances due to the film cooling jets of a turbine blade. Baseline measurements over a smooth plate have been completed. We are currently completing the detailed design for a realistic rough surface model. The model is patterned after a suction side surface that was evaluated by Major Jeffrey Bons at AFRL. We plan to collect and analyze the rough plate results in the fall of 2002. An additional graduate student has been added to the project team (Mr. William Dalling). He is designing floating element sensors with the objective of obtaining direct measurements of wall shear stress for both the smooth and rough plate models.

  3. Surface roughness plot of the suction-side of a turbine vane (adapted from data supplied by Major Jeffrey Bons, AFRL). We are currently working on a flat plate model based on information from this plot.

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