Session: 41-07 Turbine Secondary Flows and Interactions II

Paper Number: 101889

101889 - Boundary Layer Analysis of a Transonic High-Pressure Turbine Vane Using Fast-Response Temperature-Sensitive Paint 

The flow physics of a high-pressure turbine nozzle guide vane (HPT-NGV) is challenging. It undergoes high acceleration to cope with inhomogeneous flow from the combustor. The high acceleration may reach relaminarization and reduces the portion of turbulence in the boundary layer. The overall losses are therefore reduced by a boundary layer that is close to a laminar state. Downstream of the acceleration region appearing pressure discontinuities and even shocks at the passage that are disturbing the flow. A deceleration causes flow separation and additional shocks may appear downstream until the trailing edge.

The vane investigated in this work was designed within the EU-Project TFAST. The main focus of the TFAST-Project laid on the aspect to reduce adverse effects on separation, unsteadiness and shock separation (Doerffer, et al. 2020) by tripping the boundary layer close to the shock region. The design criteria for the TFAST-NGV was a high acceleration downstream of the leading edge. Hence, a high acceleration that attempts to reach relaminarization in order to minimize the overall losses. This vane is intended as baseline for a series of investigations, where a former work analyses the influence on the transition location and a separation bubble at a blade with generic film cooling (Petersen 2017). This paper addresses how an engine relevant 7YSZ-Thermal barrier coating (TBC) influences the boundary layer due to roughness. The blade is modified so that the shape is not influenced by the thickness of the TBC. The roughness is expected to solely effects the transition. The effects that are influencing the transition next to the roughness are a positive and negative pressure gradient, separation and interacting shocks.

The experiments are conducted in the Wind Tunnel for Straight Cascades (EGG) in Göttingen at a subsonic and transonic exit Mach number (Ma_2,is = 0.5 and 1.05). The Reynolds numbers are in the region of Re₂ ≈ 0.75 – 1.25∙10⁶. The separation and transition location on the suction side are evaluated by an infrared camera. The different convective heat transfers of the laminar and turbulent boundary layer are visualized by changing the temperature of the main flow. For the time resolved analysis of the surface temperature on the suction side iTSP (ultra-fast-response temperature sensitive paint) was applied. Temperature unsteadiness caused by fluctuating shocks can be found up to f = 2000 Hz.

The influence of the TBC will be discussed on the appearance of turbulent wedges, the position of the separation bubble as well as the transition location. Together with the previous investigations, this study creates a comprehensive picture of the aero-thermodynamics of a turbine vane. This data set will be used as a benchmark for innovative future turbine vane designs including TBC and extensive cooling. Additionally, the results will be used as a validation data set for numerical models and their improvement.

References

Doerffer, P., J.-P. Dussauge, P. Grothe, A. Petersen, und F. Billard. Transition Location Effect on Shock Wave Boundary Layer Interaction. Springer Nature, 2020.

Petersen, A. „Influence of Cooling on the Transition Location in a Straight High Pressure Turbine Cascade.“ Proceedings of 12th European Conference on Turbomachinery Fluid dynamics & Thermodynamics ETC12, 2017.

 

Presenting Author: Anna Petersen German Aerospace Center (DLR)

Presenting Author Biography: The author studied aeronautical engineering at the HAW Hamburg in Germany and is working as a researcher at the German Aerospace Center (DLR) since 2012 at the institute of propulsion technology, department turbine. The PhD was finished in 2021 at TU Braunschweig (ISM) in experimental and numerical investigations of influencing a NGV turbine by air jet vortex generators. Since 2021 the author is head of the project 3DCeraTurb, where new materials (CMC: SiC-SiC) and additive manufacturing is applied at a NGV turbine combined with thermal and environmental barrier coating and tested at a wind tunnel and at a thermo-chemical oven.

Authors:

Anna Petersen German Aerospace Center (DLR)
Michael Hilfer German Aerospace Center (DLR)