Aerodynamic and Heat Transfer Validation of LPT-OGVs (TURB34−LTH part) Chenglong Wang, Lei Wang, and Bengt Sundén Department of Energy Sciences, Lund University, Lund, 22100, Sweden

Background Low pressure turbine (LPT) outlet guide vanes (OGVs) are positioned in the turbine rear frame. The purpose of OGVs is to remove the swirl from the incoming flow and straighten the air into an axial outflow (nozzle). OGVs

Challenges The flow around OGVs is challenging because it requires tight separation margins and low pressure losses. However, at some conditions (e.g., ground idle), the inlet incidence angles are far from what the OGV is designed for and fully separated flow would be expected. The accurate prediction of the thermal load on the OGVs is essential for aerodynamic designers, both for on- and off-design conditions.

Objectives To investigate the heat transfer on the suction side of an OGV for both on- and off-design conditions. More specifically, it is of interest to know the effects of incoming flow velocity and incidence angle of an OGV on the heat transfer coefficient. Liquid crystal thermography (LCT) was used to measure the temperature and obtain the heat transfer coefficients on the OGV.

Linear cascade flow In the linear cascade, the flow velocity and incidence angle with respect to OGVs can be changed. The cross section of the working part of the facility is 200 by 1200 mm.

Profile of an OGV The axial chord of an OGV is 243.51 mm, the spanwise width is 200 mm.

Re-Calibration of LCT

Preliminary test: test rig in Lund

Nusselt contours on the Suction side. Preliminary results: α = -10° for Re = 160,000 Camera viewing angle 45° (b) Camera viewing angle 90° Nusselt contours on the Suction side.

Measurements in situ: Chalmers

On-design I : α = 25° for Re = 300,000 (a) Nusselt contours and (b) Nusselt distribution along the central line on the Suction side.

On-design II: α = 25° for Re = 450,000 (a) Nusselt contours and (b) Nusselt distribution along the central line on the Suction side.

Off-design III: α = 40° for Re = 300,000 (a) Nusselt contours and (b) Nusselt distribution along the central line on the Suction side.

Comparisons Case 1: α = 25° for Re = 300,000 Case 2: α = 25° for Re = 450,000 Case 3: α = 40° for Re = 300,000 Comparison of Nusselt distributions along the central line on the Suction side.

Summary The incoming flow velocity and incident angle have significant effects on the heat transfer of the OGV. Due to the impingement effect, the leading edge has the highest heat transfer coefficient. The peak in the Nusselt distribution on the suction side implies the flow transition from laminar to turbulent boundary layer. Compared to the on-design condition, it is found that the position of flow transition in the off-design condition is significantly displaced upstream.

The leading and trailing edges of the OGV are of interest. Future works Apart from the suction side, it is imperative to obtain the heat transfer coefficients on the pressure side, especially for the off-design case where the full flow separation might occur. The leading and trailing edges of the OGV are of interest. The heat transfer coefficients on the endwall of the OGVs will be measured.

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