Evaluation of the flow in an intermediate turbine duct at off-design conditions

Intermediate turbine ducts are used in modern turbofan engines for connecting the highpressure turbine with the low-pressure turbine. The demands for engines with higher by-pass ratios require these ducts to be more "aggressive", i.e., to have a larger radial off-set and to be shorter. However, the flow in the intermediate turbine ducts are complex and therefore difficult to predict. Therefore a better understanding of the flow physics is necessary and measurements for CFD validation are needed. This paper presents time-averaged measurements of the flow in a state-at-the-art intermediate turbine duct with an upstream high-pressure turbine present. The investigation focuses on the intermediate turbine duct flow field development for different turbine conditions. The measurements consist of area traverses with a five-hole pressure probe at different axial locations within the intermediate turbine duct. In addition, a discussion of the endwall static pressure distribution and the overall pressure losses for the different conditions are done