Session: 32-06 Purge and Cooling Flows

Paper Number: 153075

Aerodynamic Interaction Between Main Annulus Flow and Injected Secondary Air in Transonic High-Pressure Turbine Stage 

This study explored the effects of secondary air blowing on the main annulus flow field and performance of a transonic high-pressure turbine (HPT) experimentally and numerically.

The test section featured a single-stage, unshrouded turbine with a blading consistent with modern low-aspect ratio HPTs. The full annular, rotating, continuous turbine test rig in the Japan Aerospace Exploration Agency (JAXA) was used for the whole testing campaign. This resulted in the most accurate and unparalleled matching of the similarity parameters to reality for both the primary and secondary air streams. An elaborate secondary air system built into the hardware enabled it to simulate all the critical coolant/purge air streams typically found in advanced hot sections: full coverage film-cooling on stator and rotor airfoils/endwalls, disk wheelspace purge air blown forward and aft of the rotor, and coolant ejection from the over-tip casing. Detailed three-dimensional flow field and efficiency measurements for various secondary air flowrates were conducted by traversing a pneumatic thermometric combination probe at the stage exit.

A complete set of numerical simulations was conducted in parallel with the testing to assess how effectively they capture the flow physics, particularly the interaction between mainflow and ejected secondary air streams. The JAXA in-house code, UPACS, and its best practice settings—which are based on previous verification and validation efforts—were applied without any intentional adjustments to better fit the data. Important features that impact the interactions, such as discrete coolant holes or internal air feeding plenums/cavities, were all directly resolved in the computation rather than simplified by source-term modeling or boundary conditions.

The stage exit survey in the experiment suggests that film-coolant ejection from stator vanes intensifies passage vortices in the cascade, especially at the hub. Rotor blade film-cooling and rotor forward purge air appear to have the similar enhancing effect on rotor-induced passage vortices, although vortex intensity in the region of stator-rotor vortex interaction is not further enhanced or even suppressed. Blade coolant also appears to enhance tip leakage flow, which then reduces work extraction. The enhanced tip leakage discharges into the mainstream, boosting tip clearance vortices and the resultant mixing and dissipation losses. Coolant blown from over-tip casing also appears to enhance passage vortices at the tip, however it is indicated that a positive effect also results from the blowing, diminishing the tip leakage vortices.

Presenting Author: Takashi Yamane Japan Aerospace Exploration Agency (JAXA)

Presenting Author Biography: Dr. Yamane received his PhD in Aeronautical and Astronautical Engineering from University of Tokyo.
Now, he is a researcher in Aviation Safety Innovation Hub, JAXA.

Major areas of interest and expertise:
> Heat transfer/cooling technology for aeroengine hot section.
> Numerical simulation of complex flow fields.

Authors:

Yoji Okita Japan Aerospace Exploration Agency (JAXA)
Junichi Kazawa Japan Aerospace Exploration Agency (JAXA)
Takashi Yamane Japan Aerospace Exploration Agency (JAXA)
Nozomi Tanaka IHI Corporation
Kazutaka Fuchigami IHI Corporation
Hiroki Sato IHI Corporation
Masaaki Hamabe IHI Corporation
Haruyuki Tanimitsu IHI Corporation