59150 - Ddes Numerical and Experimental Investigations on Film Cooling Characteristics of the Trailing-Edge Cutback With Upstream Cylinder Hole at Different Blowing Ratios 

The trailing edge cutback is often applied when designing the film cooling structure of a high-pressure turbine. Previous studies have demonstrated strong unsteady film mixing process which is indeed influenced by the vortex shedding from the pressure side lip. Thus, adiabatic film cooling effectiveness on cutback rapidly declines at streamwise direction. To obtain high film cooling performance, this paper arranges a cylinder hole on pressure side upstream of the trailing edge cutback flat-plate model. The film cooling characteristics of combined configuration are investigated by DDES Numerical and Experiments. DDES turbulence model has been proved to capture the vortex shedding well. Reasonably good agreement between DDES and experiments were obtained for adiabatic film-cooling effectiveness. Seven simulations with the blowing ratio M varying as the only parameter were performed over a range from M = 0.35 to 1.3. The results indicate that the mainstream temperature and velocity greatly reduce due to hole coolant ejection. The vortex shedding downstream of lip is weakened contributing to less film mixing on the trailing edge cutback. The lateral-averaged adiabatic film cooling effectiveness increases especially downstream of cutback. Within a limited range of blowing ratios, an increase in the blowing ratio results in a counter-intuitive decrease of the cooling effectiveness. The present work suggests a mechanism that can explain this behavior. The visualization and analysis of large coherent structures showed that there exist dominant clockwise-rotating structures that can give rise to a combined upstream- and wall-directed turbulent heat flux. The introduction of upstream hole coolant ejection will change the map of film cooling effectiveness of the cutback.