It is a common practice to use closed impeller in radial inflow turbine against the flow leakage from tip clearance of impellers, especially in small volume flow condition. It utilizes labyrinths between the shroud and the case to abate the higher pressure leakage. Experimental and computational investigations of shroud clearance flow in a radial inflow turbine with labyrinth seals are presented in this paper. Compared with the result without leakage, numerical computation result including the leakage of labyrinth seals agrees better with that of the experiment result, which indicates that the leakage of labyrinth seals cannot be neglected. Several geometrical arrangements with a series of different clearance of labyrinth seals are investigated experimentally and numerically, and the dimensionless shroud clearance is of 0%, 0.6%, 1.2%, 1.8%, 2.7%, 3.6%. Finally, the character of flow and loss is analyzed by computational fluid dynamics (CFD) tools. The results indicate that the labyrinth seal flow has no effect on the main flow passage and mainly causes different leakage mass flow.

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