Experimental Study of Transition in a Turbine Rear Structure

Conference contribution, 2020

In modern commercial aviation engines, the low-pressure turbine (LPT) has a high outlet swirl to maximize turbine power to weight ratio. Downstream of the last LPT rotor is the turbine rear structure (TRS) that with relatively few low-aspect-ratio outlet guide vanes (OGV), de-swirls the flow to maximize the thrust. In the wide operational envelope of the TRS, both transition location and mode can change during a normal operating cycle. Hence, accurately predicting transition is critical for the development of future TRS modules. This work discusses the experimental method and results of laminar-turbulent transition in a TRS module at engine representative conditions at Reynolds Number of 235,000. This was done in Chalmers 1.5 stage LPT-OGV facility. The transition was measured on the entire span using IR-thermography. The technique was specially developed at Chalmers for this particular purpose and validated by boundary layer hot-wire measurements. The technique provides both steady-state heat transfer with high confidence of 2-8% and time-resolved temperature fluctuations. This paper describes a collection of how this data can be used for transition detection, how it compares to fundamental correlations and as a tool for flow visualization. The facility was built thanks to the financial support of Energimyndigheten, Nationella flygtekniska forskningsprogrammet, the EU Commission, GKN Aerospace Sweden AB and the department of Mechanics and Maritime Sciences at Chalmers. The aerosurface of the LPT and TRS is designed by GKN Aerospace solely for the experimental rig and is not related to any GKN Aerospace product characteristics.