Experimental investigation of sequential narrow impingement channels for turbine cooling

Sequentially stacked impingement channels allow for a more effective use of the cooling fluid and can limit the heat transfer reduction due to the crossflow when the number of jets increases. In this paper, sequential impingement channels are experimentally investigated using the transient liquid crystal technique. Twelve configurations are tested: the baseline consists in a double rectangular channel with 5 jets per channel; other configurations feature different number of jets, variations of the jet-to-jet spacing and of the transition zone length, reduction of the cross-section in the transition zone and addition of a bypass between the channels. Results show that heat transfer coefficients (HTC) in the 2nd channel are similar to the 1st, and that the cross-section reduction in the transition zone allows for an increase of the HTC in this critical zone with only a moderate increase of pressure losses.