Investigations On Heat Tranfer Characteristics Of Jet Arrays Impingementwith Inclined And Ribbed Target Surfuce

With the development of the high efficient engine,there are much more urgent demands including high component efficiencies, long service life and high reliability. The turbine tip clearance control is one of the most important factors to achieve those goals above. Aimed at the cooling air feeding structuresof a multistage low pressure turbine(LPT)active clearance control system,typical heat transfer configurations were abstracted with some reasonable simplifications. Heat transfer characteristics were experimental studied to support the future revised design of LPT active clearance control system.Firstly, the local and average heat transfer coefficient(Nusselt number) of impinging inclined target with single and multiple coolant feeding tubes were investigated respectively. Reynolds number Re(6000,9000,12000),the jet impingement distance to the hole diameter ratio H/D(2.73, 455, 6.36) were changed in experiments to get the effects on Nusselt number. Different heat transfer characteristics between impingement with single coolant feeding tube and multiple tubes were also discussed to reveal the effects of the crossflow induced byneighbors' impingement. It was found that Nusselt number decreased at the beginning and then increased because of the jet mass flow rate variation through the tube in the streamwise direction along the cooling pipe. The local and average heat transfer were enhanced when multiple coolant feeding tubes were applied for the crossflow induced by the adjacent jets. The experiments show that heat transfer is improved distinguished with Re increasing and H/d decreasing. The highest Nusselt number is achieved when H/d equals 2.73 in this study.Then the irregular array jet impingement on ribbed target surface were investigated. Reynolds number Re(2000-15000), the jet impingement distance to the hole diameter ratio Sz/d(6, 8, 10), the hole spacing to hole diameter ratio Sy/d(4-20) were changed in experiments to get the effects on heat transfer.It was found the distribution of Nusselt number on target surface was changed greatly because of the high ribs and inclined impingements. High Nusselt number was observed in the region of 5 times diameters distance from the jet stagnation point. The experimental data indicates the average Nusselt number increaseswith the increase of Re and discrease of the hole spacing to hole diameter ratio Sy/d. However the relationship between Nusselt number and Sz/d is complicated. Higher Nusselt number can be achieved with larger Sz/d when Re is low, while small Sz/d leads to larger Nusselt number if Re is higher...