Combination of Impingement and Trip Strips for Combustor Liner Backside Cooling

Effective cooling of modern low NOx combustor liners is achieved through combinations of impingement and other heat transfer enhancement methods. In the present study, a combination of impingement and trip strips is studied to determine the optimum location of trip strips with respect to impingement jet arrays. Heat transfer with pure impingement has degradation downstream due to increased cross-flow effects. To counter the cross-flow induced heat transfer degradation, a combination technique wherein impingement is combined with ribs placed in between impingement rows or downstream of the impingement array is studied. Three configurations with increased rib placements and reduced impingement holes are studied and compared with pure impingement cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Re_j = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. Results show that the presence of ribs increases jet impingement heat transfer on the surface with lower mass flows. The effectiveness of the combination ribs and impingement can provide higher heat transfer with reduced cooling air requirements.