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Главная Архив Thermal Letter Оргкомитет Будущие конференции AIHTC
International Heat Transfer Conference 10

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

EFFICIENCY OF FILM COOLING WITH INFLUENCE OF SURFACE ROUGHNESS

M. I. Osipov
Bauman Moscow State Technical University, Moscow, Russia

DOI: 10.1615/IHTC10.1130
pages 95-99

Аннотация

Efficiency of film cooling and distribution of skin friction coefficient on a flat plate and on a wall of a diffuser with different methods of creating the films (blowing through a porous plate, injection through a slot) are analyzed and compared with experimental data. Influence of surface roughness and complex boundary conditions are taken into account. The attention is paid to the results of original experimental investigation and to the development of method of prediction of the efficiency of film cooling. The method is based on the integral approach of calculation of turbulent boundary layer with using experimental data for velocity and temperature distribution in the boundary layers. The relative laws of skin friction Ψr.bl. = f(x/Ks) and heat transfer Ψr.bls. has been developed and presented. Experimental investigation has been carried out at Max number of flow M=0.3÷0.8. Geometry of surface roughness of walls expressed through sand grain roughness varies in the region: Ks=O.4; 0.51; 0.61; 0.74; 1.24; 1.3; 1.7 mm. Intensity of blowing ( j ) through the porous plates and walls was changed from j=O to j=0.012. The variation of relative velocity of injection through the slots was (Us/U0)= 0÷1.2. The values of efficiency of film cooling Θ on the rough porous wall decrease in 1.25 ... 1.6 time for the relation of the sand grain roughness (Ks) to the momentum thickness (δ**) (Ks/δ**)>0.5. The present results of calculation of Θ for porous blowing through porous wall section placed before the smooth adiabatic plate showed good agreement with the experimental data. The main conclusion of this paper is the integral approach of calculation of Θ and Cf for turbulent boundary layers with taking into account the different boundary conditions has been found and confirmed to be quit efficient.

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