Numerical and experimental analysis of the flow in an aggressive intermediate turbine duct

Multi-spool turbofan engines have intermediate ducts connecting the high-pressure turbine with the low-pressure turbine. The demands for more efficient and environmentally friendly jet engines force future turbofan engines to have higher by-pass ratios. This leads to that the radial off-set between the turbine stages increases and therefore the radial off-set of the intermediate duct has to increase. In order to save fuel consumption it is desirable to decrease engine weight and thus the duct should be made as short as possible. The flow in the intermediate duct is complex, so safely shortening the duct requires a thorough understanding of the flow physics in order to be able to accomplish this in a controlled manner. The present investigation focus on a joint experimental and numerical investigation of an intermediate duct configuration. The main purpose of the numerical simulation is to obtain an insight into the current capabilities of numerical simulations for these kinds of complex flow. The conclusion is that the numerical simulations manage fairly well to capture the total pressure and swirl angle profile from about 20% to 80% span. Also, the hub and shroud pressure profiles are well predicted while the total pressure loss is overpredicted in the numerical simulations