The Effect of Wake Passing on Turbine Blade Film Cooling PDF Download

Author: James D. Heidmann
Publisher:
ISBN:
Category : Airplanes
Languages : en
Pages : 272

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Author: James D. Heidmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 14

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Presented at the International Gas Turbine & Aeroengine Congress & Exhibition, Orlando, FL, Jun 2 - Jun 5, 1997.

Author: James D. Heidmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 18

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Author:
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Category :
Languages : en
Pages :

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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781725097346
Category :
Languages : en
Pages : 28

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The effect of wake passing on the showerhead film cooling performance of a turbine blade has been investigated experimentally. The experiments were performed in an annular turbine cascade with an upstream rotating row of cylindrical rods. Nickel thin-film gauges were used to determine local film effectiveness and Nusselt number values for various injectants, blowing ratios, and Strouhal numbers. Results indicated a reduction in film effectiveness with increasing Strouhal number, as well as the expected increase in film effectiveness with blowing ratio. An equation was developed to correlate the span-average film effectiveness data. The primary effect of wake unsteadiness was found to be correlated by a streamwise-constant decrement of 0.094.St. Steady computations were found to be in excellent agreement with experimental Nusselt numbers, but to overpredict experimental film effectiveness values. This is likely due to the inability to match actual hole exit velocity profiles and the absence of a credible turbulence model for film cooling. Heidmann, James D. and Lucci, Barbara L. and Reshotko, Eli Glenn Research Center NASA-TM-107425, NAS 1.15:107425, E-10671 RTOP 505-62-10...

Author: M. J. Rigby
Publisher:
ISBN:
Category : Turbines
Languages : en
Pages : 252

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Category :
Languages : en
Pages : 66

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Author: Kristofer Michal Womack
Publisher:
ISBN:
Category : Marine engines
Languages : en
Pages : 109

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The combined effects of pulsed film cooling and upstream wakes were studied. In film cooling, compressed air is routed around the combustion chamber of a gas turbine engine and bled through holes on the surface of the turbine blades. This compressed air creates a protective film of relatively cool air that reduces the heat transfer between the combustion gases and the blades. Diverting air from the combustor reduces the power and efficiency of the turbine; however, pulsing the air may provide equivalent or acceptable protection for the turbine blades with less cooling air. Previous pulsed film cooling studies have been completed with a simplified, continuous freestream flow. In an actual turbine, the combustion gases pass through a cascade of rotor blades and stator vanes, which interrupt the flow, sending wakes downstream to subsequent rows of turbine blades. In this study, periodic wakes were added to the mainstream flow. A large test plate was constructed with a row of holes through which film cooling air could be pulsed. A wind tunnel provided a wall jet at a controlled velocity across the test plate. A wake generator was located upstream of the test plate to simulate the effect of upstream turbine blades, so that the resulting flow field, film cooling effectiveness, and heat transfer could be studied. Continuous film cooling resulted in better blade protection than pulsed film cooling at equivalent wake frequencies. For the cases with a continuous freestream and the cases with lower wake frequencies, continuous film cooling jets blowing at half the freestream velocity provided the best protection. For the highest wake frequency tested, continuous film cooling jets blowing at a velocity equal to the freestream velocity provided the best protection. Finally, when comparing pulse timing relative to the wake passing, there was some improvement in blade protection when the cooling jet was on as the wake passed over the cooling holes; however in most cases, differences were small. This study suggests that, for the geometry tested, continuous film cooling provides better protection for gas turbine blades for the same amount of cooling air.

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721933846
Category :
Languages : en
Pages : 228

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Unsteady wake effect, with and without trailing edge ejection, on detailed heat transfer coefficient and film cooling effectiveness distributions is presented for a downstream film-cooled gas turbine blade. Tests were performed on a five-blade linear cascade at an exit Reynolds number of 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.4 to 1.2; air and CO2 were used as coolants to simulate different density ratios. Surface heat transfer and film effectiveness distributions were obtained using a transient liquid crystal technique; coolant temperature profiles were determined with a cold wire technique. Results show that Nusselt numbers for a film cooled blade are much higher compared to a blade without film injection. Unsteady wake slightly enhances Nusselt numbers but significantly reduces film effectiveness versus no wake cases. Nusselt numbers increase only slic,htly but film cooling, effectiveness increases significantly with increasing, blowing ratio. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher 0 effectiveness at lower blowing ratios (M = 0.8). Trailing edge ejection generally has more effect on film effectiveness than on the heat transfer, typically reducing film effectiveness and enhancing heat transfer. Similar data is also presented for a film cooled cylindrical leading edge model. Han, J. C. and Ekkad, S. V. and Du, H. and Teng, S. Glenn Research Center NAG3-1656; RTOP 714-01-4A

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781720482284
Category :
Languages : en
Pages : 64

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The detailed heat transfer coefficient and film cooling effectiveness distributions as well as tile detailed coolant jet temperature profiles on the suction side of a gas turbine blade A,ere measured using a transient liquid crystal image method and a traversing cold wire and a traversing thermocouple probe, respectively. The blade has only one row of film holes near the gill hole portion on the suction side of the blade. The hole geometries studied include standard cylindrical holes and holes with diffuser shaped exit portion (i.e. fanshaped holes and laidback fanshaped holes). Tests were performed on a five-blade linear cascade in a low-speed wind tunnel. The mainstream Reynolds number based on cascade exit velocity was 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. The wake Strouhal number was kept at 0 or 0.1. Coolant blowing ratio was varied from 0.4 to 1.2. Results show that both expanded holes have significantly improved thermal protection over the surface downstream of the ejection location, particularly at high blowing ratios. However, the expanded hole injections induce earlier boundary layer transition to turbulence and enhance heat transfer coefficients at the latter part of the blade suction surface. In general, the unsteady wake tends to reduce film cooling effectiveness.Han, J. C. and Teng, S.Glenn Research CenterHEAT TRANSFER COEFFICIENTS; COOLANTS; TEMPERATURE PROFILES; SUCTION; TURBINE BLADES; HEAT MEASUREMENT; FILM COOLING; BOUNDARY LAYER TRANSITION; CASCADE WIND TUNNELS; CYLINDRICAL BODIES; EJECTION; GAS TURBINES; HOLE DISTRIBUTION (MECHANICS); LIQUID CRYSTALS; LOW SPEED; THERMAL PROTECTION; THERMOCOUPLES; WIND TUNNELS