Effects of LoD and PoD in combined-hole film cooling

• Main Authors: Hassan, Haswira, Abdullah, Mohammad Kamil
• Format: Article
• Language: English
• Published: Asian Research Publishing Network (ARPN) 2017
• Subjects: TJ Mechanical engineering and machinery
• Online Access: http://eprints.uthm.edu.my/5407/1/AJ%202017%20%28790%29.pdf; http://eprints.uthm.edu.my/5407/

Film cooling technique was used to provide thermal protection for turbine components from the hot combustion gases. Combined-hole film cooling system was introduced as a way to improve the film cooling performances. In the present work, a batch of simulations using combined-hole unit involving two round hole of film cooling with opposite compound-angle were carried out. The aim is to determine the arrangement of combined-hole which will produces highest film cooling effectiveness. The influence of geometrical and flow parameters; distance between two holes in mainstream direction, LoD, distance between two holes in lateral direction, PoD and blowing ratio, M were considered in the present study. The present study had been carried out using steady state Reynolds Averaged Navier Stokes (RANS) analysis of ANSYS CFX, at Reynolds number, Re = 4200 and blowing ratios, M = 0.5, 1.0, and 1.5. Nine different computational models with combination of three different values of PoD and LoD have been considered. The results shows that as the PoD and M increase, the lateral coverage of film cooling also increases, while increase on LoD shows minimal impact on the spread of the coolant downstream of the cooling hole. However, the increase of PoD and M also resulting drastic decrease of film cooling effectiveness downstream of the cooling hole as a result of the lift-off phenomena. Weak interaction between the two jets along the mainstream direction cause separation and lift-off of the coolant at further downstream. In addition to laterally average film cooling effectiveness, the results of area average film cooling effectiveness were also presented to determine the optimal arrangement of combined-hole. Overall, the combined hole film cooling provide better thermal protection in comparison with the single hole configuration.