Effects Of Tip Clearance Leakageon The Flow And Heat Transfer Characteristics Of Turbine Outer Ring Surface

The turbine shroud plays an important role in maintaining the integrity of the turbine casing structure and also protecting it from hot gas.The cooling structure of turbine shroud can affect the temperature of engines directly.Moreover,the clearance leakage flow from the turbine blade tips significantly affects the heat transfer efficiency of the outer ring,which could impact the performance of the engine.In this paper,we have studied the effects of the Reynolds number Re,blowing ratio M,gap height ratio ?/H on the heat transfer efficiency of GE-E3 outer ring by combining numerical and experimental methods.Firstly,the effects of Reynolds number Re(60000?70000?80000?90000 and 100000),blowing ratio M(1?1.5?2 and 4)and gap height ratio ?/H(1%?1.6% and2.7%)on the flow field in the channel,and the convective heat transfer efficiency of the outer ring is studied under two different conditions of those with gas film cooling and without gas film cooling.It was found that the gap separation vortex and leakage vortex were formed in the blade tip regions due to the gap leakage flow.The fluid hits the wall under the vertical uplift generated by the pressure,leading a higher heat transfer efficiency of the router ring.Whereas,in the gap,the separation and re-attachment of the leakage flow made the heat transfer efficiency at the corresponding position on the outer ring surface higher.As the leakage flew from the leading edge pressure side of blade into the gap separation,the boundary layer thickness grew,leading a lower heat transfer efficiency.This study has designed a test rig and the test element is consistent with that used inthe simulation.The paper has studied the influence of the parameters mentioned above to outer surface heat exchange characteristics by liquid crystal transient temperature measurement technology.The results show: the heat transfer characteristics of the turbine outer ring surface are greatly affected by the gap leakage flow;its efficiency increases with increasing the Reynolds number(Re),while Reynolds number has a relatively weak influence on the adiabatic cooling efficiency;with increasing blow ratio M,the heat exchange of out ring changes little,but the outer ring adiabatic coolingchanges a lot;when fixingthe gap height and the mainstream Reynolds number,the change in blowing ratio has little impact on the outer ring surface heat transfer;the gap leakage flow is complicated and is sensitive to the gap height.When the gap height ratio is 1.6%,the heat transfer of theouter ring surface performs best.