Innovative cooling configurations for low emission gas turbine combustors

Abstract

Listen

Translate article

Presently, effective cooling of modern low NOx combustor liners is achieved through combinations of innovative impingement configurations and other heat transfer enhancement methods. An inherent characteristic of conventional impingement configurations is the occurrence of downstream heat transfer degradation due to increased crossflow effects. In the present study, two different impingement configurations are studied. Both impingement configurations examined in this study aim to increase heat transfer effectiveness by reducing the detrimental effects of spent air crossflow. In Part I, a combination technique wherein impingement is combined with ribs placed in between impingement rows is studied. Three configurations with increased rib placements and reduced impingement holes are studied. Each case is compared to a pure impingement configuration for the same jet Reynolds number. In Part II, an innovative impingement configuration, called the zero-crossflow design, is examined. In this design, spent air is directed away from the target surface in an attempt to completely eliminate the detrimental effects of crossflow by reducing its interaction with impingement jets. Three different jet arrays with decreasing numbers of impingement jets are examined in this part of the study. For all test cases, three jet Reynolds numbers (10000, 20000, and 30000) are studied. Detailed heat transfer distributions are obtained through out the study using a transient liquid crystal technique. Results from Part I show that the presence of ribs increases jet impingement heat transfer along the entire target surface. The crossflow improvements of this combination provide higher heat transfer with reduced cooling air requirements, even though some crossflow degradation is still present. In contrast, the zero-crossflow design of Part II shows minimal heat transfer degradation due to crossflow. This design also displays the ability to produce symmetric heat transfer distributions, which are almost completely independent of the exit flow direction. Finally, the sparse arrays of both parts of the study show more efficient cooling by achieving similar levels of heat transfer with greatly reduced coolant flows.