High-resolution simulation of film cooling with blowing ratio and inclination angle effects based on hybrid thermal lattice Boltzmann method

Abstract

A series of high-resolution simulations on film cooling with varying blowing ratios and inclination angles are carried out by using in-house code based on hybrid thermal lattice Boltzmann method. Three blowing ratios ranging from 0.2 to 0.8 and four inclination angles from 15? to 60? are chosen for the simulations. The evolutionary mechanism of coherent structure in three domains of film-covering region is studied from the view of space and time. Besides, the influencing mechanism of blowing ratio and inclination angle on flow and heat-transfer features of film cooling is uncovered. Results show that hairpin vortex, hairpin packet and quasi-stream-wise vortex appearing in rotating domain play a key role in heat-transfer process of film cooling. The strong ejection, sweep and vortex rotation resulted from these vortices enhance the convective heat transfer. It is also found that the size of coherent structure varies significantly with blowing ratio and its integral form shows a strong dependence on inclination angle. Moreover, inclination angle of coolant jet has a significant impact on turbulence fluctuation intensity. The influence of blowing ratio on the attachment of coolant film and film-cooling performance is more obvious than that of inclination angle. It is believed that all of these are related closely to the variation of stream-wise and wall-normal jet velocity in the case of various blowing ratios and inclination angles.