Effects of free-stream turbulence and surface roughness on laterally injected film cooling
Film cooling with laterally directed holes on a flat surface was studied experimentally, with particular attention on the effects of high free-stream turbulence and surface roughness. The free-stream used in these experiments, with a turbulence level of 17% and large turbulence scales, was representative of the turbine environment; and the rough surfaces simulated roughness representative of turbine airfoils after extensive hours of operation. Adiabatic effectiveness levels were measured using a coolant to mainstream density ratio of DR = 2.0, and heat transfer coefficients were measured using a density ratio of DR = 1.0. The performance of a row of holes laterally directed at 90{degree} to the mainstream was compared to a row of streamwise directed holes for a wide range of blowing rates, and for a distance extending 90 diameters downstream of the holes. For low free-stream turbulence, the laterally and streamwise directed holes had comparable adiabatic effectiveness at lower blowing rates, but the laterally directed holes had distinctly superior adiabatic effectiveness at higher blowing rates. For high free-stream turbulence, with smooth and rough surfaces, the blowing rate for maximum film cooling performance increased by a factor of three for streamwise and laterally directed holes. When subjected to high free-stream turbulence, adiabatic effectiveness values were similar for the streamwise and laterally directed holes for the full range of blowing rates. However, increases in heat transfer coefficients when film cooling with laterally directed holes led to decreased overall performance quantified in terms of a net heat flux reduction. Maximum net heat flux reduction was consistently achieved with streamwise directed holes for high free-stream turbulence conditions with smooth and rough surfaces.
- Research Organization:
- Univ. of Texas, Austin, TX (US)
- OSTI ID:
- 20014399
- Resource Relation:
- Conference: 32nd National Heat Transfer Conference, Baltimore, MD (US), 08/08/1997--08/12/1997; Other Information: PBD: 1997; Related Information: In: ASME proceedings of the 32nd national heat transfer conference (HTD-Vol. 350). Volume 12: Fundamental experiment techniques in heat transfer; Thermal hydraulics of advanced nuclear reactors; Heat and mass transfer in supercritical liquid systems; Heat transfer in energy conversion; Heat transfer equipment; Heat transfer in gas turbine systems, by Beasley, D.E.; Hassan, Y.A.; Cheung, F.B.; Yang, B.; Presser, C.; Olsen, D.A.; Tong, W.; Phelan, P.; Swanson, L.W.; McEligot, D.W.; Bogard, D.G. [eds.], 261 pages.
- Country of Publication:
- United States
- Language:
- English
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