Numerical Analysis of Impingement/Effusion Cooling Effectiveness on Flat Plates

The impingement/effusion cooling is a method of using cooling air to protect the hot combustor liner surfaces from high temperature effectively. This paper investigates the impingement/effusion cooling over two perforated flat plates and proposes a better cooling scheme for high temperature combustion liners in aircrafts and electrical power generation application. The adiabatic cooling effectiveness distribution over the liner surface is numerically studied by control volume technique in CFD. In this hybrid scheme the hydraulic diameter (d) of the hole is 1mm and impingement plate is provided with holes normal to the plate over its whole length of 250d. While effusion plate has only 20 rows of holes inclined at 30° to its surface. The effect of blowing ratio (BR) over this hybrid scheme of cooling is studied for different BR of 0.5, 1.0, 1.5 and 2.0. It has been found that the area averaged effectiveness increases steeply for BR 0.5 to 1.0 but further increase in BR results only in a small increase. The results also show that increasing the hole diameter increases averaged effectiveness while increasing the center-to-center spacing decreases averaged effectiveness.