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.