CUED Publications database

Parasitic loss due to leading edge instrumentation on a low pressure turbine blade

Ng, HCH and Coull, JD (2016) Parasitic loss due to leading edge instrumentation on a low pressure turbine blade. In: UNSPECIFIED.

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© 2016 by ASME. During the testing of development engines and components, intrusive instrumentation such as Kiel head Pitot probes and shrouded thermocouples are used to evaluate gas properties and performance. The size of these instruments can be significant relative to the blades and their impact on aerodynamic efficiency must be considered when analysing the test data. This paper reports on such parasitic losses for instruments mounted on the leading edge of a stator in a low pressure turbine, with particular emphasis on understanding the impact of probe geometry on the induced loss. The instrumentation and turbine blades have been modeled in a low Mach number cascade facility with an upstream turbulence grid. The cascade was designed so that the leading edge probes were interchangeable in-situ, allowing for rapid testing of differing probe geometries. RANS calculations were performed to complement the experiments and gain more understanding about the flow behaviour. A horseshoe vortex-like system forms at the join of the probe body and blade leading edge, generating pairs of streamwise vortices which convect over the blade pressure and suction surfaces. These vortices promote mixing between the freestream and boundary layer fluid, and promote the transition of the boundary layer from laminar to turbulent flow. The size and shape of the leading edge probes relative to the blade varies significantly between applications. Tests with realistic probe geometries demonstrate that the detailed design of the shroud bleed system can impact the loss. A study of idealised cylinders is performed to isolate the impact of probe diameter, aspect ratio and incidence.

Item Type: Conference or Workshop Item (UNSPECIFIED)
Divisions: Div A > Turbomachinery
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:00
Last Modified: 22 May 2018 08:16