Experimental and Numerical Investigation of an Aggressive Intermediate Turbine Duct: Part 1−Flowfield at Design Inlet Conditions

Demands on lower emissions and reduced noise levels drive the design of modern turbofan engines toward high by-pass ratios. The design of the intermediate turbine ducts, connecting the high- and low-pressure turbines, will become more important as the turbofan engine by-pass ratios are increased. In order to introduce more aggressive designs there is a need to understand the flow features of high aspect ratio and high diffusion ducts. This is part one of a two-part paper, presenting a comparison between an experimental study and a CFD analysis of the flowfield of an aggressive intermediate turbine duct for design inlet conditions. Part one focuses on the on-design conditions and the second part will focus on off-design conditions. The experimental study was performed in a large-scale, low-speed turbine facility. The work presented highlights some of the challenges associated with more aggressive intermediate ducts for the next generation of turbofan engines. The main flow features are successfully reproduced by the CFD, but there are discrepancies found in the predicted local velocity and loss levels. An explanation of the discrepancies between the experimental data and the CFD results is provided and an attempt to track the origin of these differences is made.