Effect of Holes Array on Effusion Cooling Characteristics of a Three-Nozzle Model Combustor Liner

Abstract

Effusion cooling performance for a simulated three-nozzle annular combustor under both non-reacting and reacting flow conditions is experimentally investigated. Under this realistic swirling flow, cooling behavior shows the remarkable difference with that under uniform flow case. Mainstream air is electrically heated to a certain temperature level (180 °C) under non-reacting conditions, while methane-air premixed combustion is performed under reacting conditions at the equivalence ratio of 0.7. Especially, the effect of effusion holes array is discussed for the in-line and staggered layouts. Infrared thermography is used to record the temperature distribution on the two bent cooling test panels equipped with the outer and inner liners respectively after individual in-situ calibration process. Local and average overall cooling effectiveness results are then analyzed as a vital parameter to weigh the cooling performance. Results show that no matter under non-reacting or reacting flow conditions, the temperature distribution is skewed, which is closely related to the multi-nozzle swirling flow structure inside the combustor. In addition, an elliptic region area of relatively low cooling effectiveness appears at the downstream the injector outlet due to swirling jets impingement effect when the reaction is activated, however, this is not observed under cold flow cases. The impinging swirling flame on the combustor wall also leads to the local blowing ratio declining, so the effusion film will be not easy to issue through the holes. Influence of holes layout on the cooling characteristics are also different on the outer and inner liners. It is assumed to be caused by the interaction of effusion jets and main swirling flow. This reminds us that in the annular combustor, effusion cooling optimization should be considered according to the curvature. Generally, staggered effusion cooling holes arrangement presents better cooling performance than the in-line arrangement.