Aerodynamics and Heat Transfer Investigations on a High Reynolds Number Turbine Cascade

Effect of unsteady wakes on aerodynamic and heat transfer characteristics of a turbine blade in a cascade were analyzed both experimentally and theoretically. Comprehensive aerodynamic data were collected for different wake passing frequencies that are typical of turbomachinery. Hot-wire probes were used for collection of boundary layer data on suction and pressure surfaces of the turbine blade. Heat transfer measurements were made using steady liquid crystal techniques. Boundary layer data were analyzed through intermittency function to get insight into the transition process under unsteady wake flow conditions. The experimental and theoretical results presented in this paper confirm the general validity of the unsteady boundary layer transition model developed by Chakka and Schobeiri (1997). This model is based on a relative intermittency function, which accounts for the effects of periodic unsteady wake flow on the boundary layer transition. Three distinct quantities are identified as primarily responsible for the transition of an unsteady boundary layer. These quantities, which exhibit the basis of the transition analysis presented in this paper, are: (1) relative intermittency, (2) maximum intermittency, and (3) minimum intermittency. To validate the developed transition model, it is implemented in an existing boundary layer code, and the resulting heat transfer coefficients are compared with the experimental data.

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“…1. Since this facility was already described by Schobeiri et al(1995a) only a brief description will be given below.…”

Section: Experimental Investigationsmentioning

confidence: 99%

“…The free-stream turbulence intensity of steady flow into the test section is 1.0%. As explained by Schobeiri et al(1995a), the facility was designed to generate a turbulence intensity about 0.75% without wakes. For unsteady flow cases, however, higher free stream turbulence intensities are established by wakes.…”

Section: Experimental Investigationsmentioning

confidence: 99%

Unsteady Wake Effects on Boundary Layer Transition and Heat Transfer Characteristics of a Turbine Blade

Schobeiri

Chakka

Pappu

1998

Volume 1: Turbomachinery

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“…3). The geometry of these blades are similar to the SSME (Space Shuttle Main Engine) blades described by Schobeiri et al (1990). The second turbine cascade incorporated five General Electric blades of high flow deflection.…”

Section: Fig 1 Trailing Edge Ejection and Mixing Downstream Of A Coomentioning

confidence: 99%

Optimization of Trailing Edge Ejection Mixing Losses: A Theoretical and Experimental Study

Pappu

Schobeiri

1997

Volume 1: Aircraft Engine; Marine; Turbomachinery; Microturbines and Small Turbomachinery

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The aerodynamic effects of trailing edge ejection on mixing losses downstream of cooled gas turbine blades were experimentally investigated and compared with an already existing one-dimensional theory by Schobeiri (1989). The significant parameters determining the mixing losses and therefore the efficiency of cooled blades are the ejection velocity ratio, the cooling mass flow ratio, the temperature ratio, the slot thickness ratio and the ejection flow angle. To cover a broad range of representative turbine blade geometry and flow deflections, a General Electric power generation gas turbine blade with high flow deflection and a NASA-turbine blade with intermediate flow deflection and different thickness distributions were experimentally investigated and compared with the existing theory. Comprehensive experimental investigations show that for the ejection velocity ratio μ = 1, the trailing edge ejection reduces the mixing losses downstream of the cooled gas turbine blade to a minimum which is in agreement with the theory. For the given cooling mass flow ratios that are dictated by the heat transfer requirements, optimum slot thickness to trailing edge thickness ratios are found, which correspond to the minimum mixing loss coefficients. The results allow the turbine aerodynamicist to minimize the mixing losses and to increase the efficiency of cooled gas turbine blades.

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“…Several researches (Simonich and Moffat, 1984;Crane and Sabzvari, 1989;You et al, 1989, andSchobeiri et al, 1991) (1993) proved that the Inconel 600 foil was a more uniform heater sheet by determining that the error for the heat transfer coefficient was approximately +/-3.7%. Therefore, the heater sheet in this investigation is Inconel 600.…”

Section: Heat Transfer Measurementsmentioning

confidence: 99%

“…However, none are applicable to an unsteady flow situation. Gaugler (1985) and Schobeiri et al (1991) proved that existing correlations for external aerodynamic applications cannot correctly predict the unsteady transition behavior of gas turbine blades. Thus, more research is needed to correct this situation.…”

Section: Introductionmentioning

confidence: 99%

Periodic Unsteady Flow Aerodynamics and Heat Transfer: Studies on a Curved Surface, Combined Part I and II

Schobeiri

Wright

Chakka

2000

International Journal of Rotating Machinery

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Aerodynamic and heat transfer investigations were done on a constant curvature curved plate in a subsonic wind tunnel facility for various wake passing frequencies and zero pressure gradient conditions. Steady and unsteady boundary layer transition measurements were taken on the concave surface of the curved plate at different wake passing frequencies where a rotating squirrel-cage generated the unsteady wake flow. The data were analyzed using timeaveraged and ensemble-averaged techniques to provide insight into the growth of the boundary layer and transition. Ensemble-averaged turbulence intensity contours in the temporal spatial domain showed that transition was induced for increasing wake passing frequency and structure. The local heat transfer coefficient distribution for the concave and convex surface was determined at those wake passing frequencies using a liquid crystal heat transfer measurement technique. Detailed aerodynamic and heat transfer investigations showed that higher wake passing frequency caused transition to occur earlier on the concave surface. Local Stanton numbers were also calculated on the concave surface and compared with Stanton numbers predicted using a differential boundary layer and heat transfer calculation method. On the convex side, no effect of wake passing frequency on heat transfer was observed due to a separation bubble that induced transition.

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Aerodynamics and Heat Transfer Investigations on a High Reynolds Number Turbine Cascade

Cited by 15 publications

References 5 publications

Unsteady Wake Effects on Boundary Layer Transition and Heat Transfer Characteristics of a Turbine Blade

Unsteady Wake Effects on Boundary Layer Transition and Heat Transfer Characteristics of a Turbine Blade

Optimization of Trailing Edge Ejection Mixing Losses: A Theoretical and Experimental Study

Periodic Unsteady Flow Aerodynamics and Heat Transfer: Studies on a Curved Surface, Combined Part I and II

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