Influence of Tip Clearance Size on Tip Clearance Flow of a Transonic Turbine

The influence of the tip clearance height of turbine rotor blades on tip clearance flow of an axial turbine stage was investigated by numerical simulation and different tip clearance heights were taken into account.Results show that the leakage flow rate would increase markedly due to the increase of the tip clearance height.The ratio of the leakage flow rate and total flow rate would increase 2.1% as the tip clearance height increased 1% of the blade height.From analyzing the flow field,it indicates that as the height of tip clearance increases,the flow structure in the tip clearance changes.When the height of tip clearance is small,the size of the separation bubble increases quickly as the height of tip clearance increases,meanwhile,the size of the leakage vortex gets larger as well as the flow rate of high speed leakage flow.The passage vortex and the leakage vortex are pushed off from the blade,the flow structure of secondary flow near the tip clearance changes while the height of tip clearance increases.