Enhancement of full coverage film cooling performance with opposite injection holes

Abstract

In the present work numerical study of effusion cooling on an adiabatic flat plate is carried out for three different configurations of cylindrical holes namely forward injection, reverse injection and opposite injection. Opposite injection configuration comprises of holes with both forward and reverse injections where holes just in front of the other inject in opposite directions. The holes are arranged in an array of 20 rows with spanwise hole-to-hole pitch (p) of 4.9d and streamwise hole-to-hole pitch (s) of 4.9d.Diameter (d) of the cylindrical holes is 1.0 mm. The injection angles are 30° for forward injection and 150° for reverse injection holes. Numerical simulations are carried out for a wide range of velocity ratios (VR) ranging from 0.25 to 5.0 and at density ratio (DR) of about 1.0. Laterally averaged adiabatic film cooling effectiveness is calculated to study the film cooling performance of the three configurations. Opposite injection demonstrates higher and more uniform cooling than forward and reverse injections especially at high velocity ratio. At higher velocity ratio, area weighted average of film cooling effectiveness for opposite injection is found around 30% higher than that for forward injection and around 10% higher than that for reverse injection configurations. Opposite injection also supports early growth of developed effusion film layer from developing stage