Investigation Of Heat Transfer Characteristics Of The Blade Tip With Labyrinth Gap

In the modern design of turbine blades, there must be a gap between the blade tip and thecasing, since turbine components were influenced by thermal strain, centrifugal force,technology and other factors when working. Due to the pressure gradient exists between thepressure surface and the suction surface, the gas leakage through the gap will reduce theefficiency of the turbine, the high heat flux on blade tip will also cause the blade oxidation.The labyrinth clearance blade tip is a groove tip with additional film cooling holes, andwith small plates arranged in the downstream of film holes. This paper studies the effect ofgap heights and the effect of blowing ratios on the film cooling effectiveness by experimentaland numerical method.A testing platform to measure the film cooling effectiveness of the tip on the blade wasconstructed. The film cooling effectiveness on the tip was measured by the steady liquidcrystal technique. The experimental results show that:(1) With the increase of gap height, thefilm cooling effectiveness of the both two kinds of tip decreases, but the film coolingeffectiveness of the labyrinth clearance tip decreases more slowly.(2)With the blowing ratioincreased, the film cooling effectiveness of the two kinds of blade tip is increased firstly andthen decreased, the film cooling effectiveness of the labyrinth clearance blade tip changegently.(3)The labyrinth clearance tip structure can significantly improve the effectivenessdistribution on the blade tip.The computation domain is established in agreement with the experimental model. Theresults show that:(1) With the increase of gap height, the film cooling effectiveness of twokinds of tip value gradually decreased.(2) When the blowing ratio change from0.5to2,withthe increase of the blowing ratio, the film cooling effectiveness of the both two kinds of tipsincreases.(3)The labyrinth clearance tip can improve the film cooling effectiveness of bladetip, when the blowing ratio larger and the gap smaller, the improve effectiveness is obvious.(4)change of the number of plates and bettter plates arrangement can improve the cooling efficiency of the distribution tip.