Direct Numerical Simulations of transsonic turbine tip gap flow

Started: 1st April 2012
Investigators: Richard Sandberg

Turbine blade tips can experience significant degradation throughout the engine life-cycle due to the high mechanical and thermal stresses in the tip region. The high thermal loads are largely due to the tip-leakage flow, which forms in the gap between the moving rotor blade tips and the casing of the machine. Turbine tip flows are also responsible for up to 30% of stage losses for newly installed engines. In-service, the blade-tips are eroded due to chemical attack, fatigue and creep which are all exacerbated by the high gas temperatures, and this causes further performance degradation. Predicting the correct heat transfer to the tip is consequently a critical part of the turbine design process. Shroudless high-pressure turbine blades can have peak Mach numbers within the tip-gap of 1.8. Supersonic effects tend to occur over the aft region of the tip where the blade loading is highest and cannot be ignored. In the current project, we employ direct numerical simulations (DNS) of a transonic turbine tip flow at engine-representative Mach and Reynolds numbers and compare the results with modern RANS based CFD methods.

Computational Modelling Group

Direct Numerical Simulations of transsonic turbine tip gap flow

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