Unsteady blade force computation sensitivity in a transonic turbine to rotor tip gap, hub and shroud cavity model detail

• The influence of including geometric detailing features on blade forcing predicted by CFD calculations is investigated. Various features such as rotor tip gap, rotor tip shroud cavity with substantial leakage flow and large rotor upstream hub rim cavity are investigated. The test case is based on a single stage transonic test turbine rig in which the unsteady aerodynamics and blade forcing have previously been investigated numerically.Including the tip gap and the tip shroud leakage in the computational model resulted in an overall increase in unsteady forcing. The change in forcing is mainly due to a change in secondary flow structure, but also due to a change of the stage flow condition. Conversely, it is shown that including the hub cavity in the computational model, even without the presence of purge-flow, reduces the unsteady force. Lastly, even though there are changes in unsteady blade loading, the blade response amplitude is only changed marginally (maximum 7%) due to forcing variations alone.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering (hsv//eng)

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