Session: 12-03 Experimental techniques and scaling

Paper Number: 125674

125674 - Impact of Blowing and Density Ratio on the Film Cooling and Heat Transfer in an Aggressive Turbine Center Frame 

It was shown that the aft purge flows from the last stage of the high-pressure turbine (HPT) have a significant film cooling potential in the downstream turbine center frame (TCF) [1]. The TCF is a stationary duct that guides the flow from the high-pressure turbine (HPT) outlet to the low-pressure turbine (LPT) inlet and is after the combustion chamber and HPT, the third most thermally loaded engine component. This paper investigates the impact of different purge-to-mainstream blowing ratios and density ratios on the film cooling effectiveness and the heat transfer coefficient in the TCF. The experiments were conducted in a product-representative 1.5-stage HPT-TCF-LPT vane configuration under Mach-similarity in the transonic test turbine facility (TTTF) at Graz University of Technology.

The blowing ratio has been demonstrated to be the dominant parameter for purge film cooling in TCFs since HPT purge flows typically have very low momentum. Even at twice the nominal blowing ratio, no cooling film detachment was observed on the TCF hub or shroud surface. Varying the density ratio in the experimentally possible range delivered no significant differences in the results. With increasing purge blowing ratio, the film cooling effectiveness in the TCF increased as expected, but also, the heat transfer intensification due to purge injection increased accordingly. The gain in film cooling effectiveness, however, outweighed the heat transfer intensification as the heat transfer reduction on the hub monotonically increases with the blowing ratio. The circumferentially averaged film cooling on the hub and shroud scales relatively well with an offset version of the well-known Hartnett correlation [2] that takes into account the ingress-induced premixing of the purge flow in the cavities.

 

[1]        P. R. Jagerhofer, T. Glasenapp, B. Patzer, and E. Goettlich, “Heat Transfer and Film Cooling in an Aggressive Turbine Center Frame,” Journal of Turbomachinery, pp. 1–26, Sep. 2023, doi: 10.1115/1.4063515.

[2]        J. P. Hartnett, R. C. Birkebak, and E. R. G. Eckert, “Velocity Distributions, Temperature Distributions, Effectiveness and Heat Transfer for Air Injected Through a Tangential Slot Into a Turbulent Boundary Layer,” Journal of Heat Transfer, vol. 83, no. 3, pp. 293–305, Aug. 1961, doi: 10.1115/1.3682263.

Presenting Author: Patrick Jagerhofer Graz University of Technology

Presenting Author Biography: Patrick completed his PhD in 2023 at TU Graz, where he is now starting a research group on heat transfer and combustion in turbomachinery. He currently leads or consults on two government-funded research projects that address heat transfer and film cooling in turbine center frames, including the presence of combustor hot streaks. In addition to heat transfer and film cooling measurements, his main interest lies in the development and improvement of innovative thermal measurement techniques.

Authors:

Patrick R. Jagerhofer Graz University of Technology
Tobias Glasenapp MTU Aero Engines AG
Bastian Patzer MTU Aero Engines AG
Emil Göttlich Graz University of Technology