Effects of Variable Pressure Outlets for Array Jet Impingement Cooling With a Bidirectional Exit Air Scheme

Array jet impingement in conjunction with other cooling methods such as effusion cooling is used in gas turbine combustion zones to provide optimized cooling in the form of double wall cooling around a combustion chamber. Utilizing a transient liquid crystal (TLC) technique an experimental investigation into the effects of pressure gradients and single versus multiple exits for array jet impingement crossflow is evaluated in the form of a detailed heat transfer analysis. In this study, four pressure gradients to bias mass flow ratios as (1:1), (2:1), (3:1), and (1:0), two jet array configurations either inline or staggered with jet to jet spacings (x/D = y/D) of 1.4, 1.9, and 2.2, three jet to target distances (z/D) ranging from 2 to 4, and three Reynolds number from 5000 to 15,000 are considered. In total, a test matrix of 72 different performance conditions was evaluated. Results are presented as local and area averaged Nusselt number plots along with local heat transfer coefficient contours. Overall, Nusselt number decreases with increased (z/D) and increased pressure gradient bias toward a single exit from (1:1) to (1:0). There is also slightly better performance from inline jet array configurations compared to staggered configurations.