Experimental Investigation of the Aerodynamics and Heat Transfer in an Intermediate Turbine Duct

Licentiate thesis, 2014

In today’s aero engines with large bypass ratios, the difference in diameter between the high pressure turbine and the downstream turbine, being either an intermediate or low pressure turbine, is large. There is also scope to further increase it, in order to increase the efficiency of the downstream turbine and enabling use of larger diameter fans. Hence, there is a need to guide the flow in between these two entities. This is carried out through an intermediate turbine duct. The flow through the duct includes a number of complex phenomena, affecting the performance of this component. This includes secondary flow structures, risk of separations, strong vorticity, high temperatures etc. This thesis investigates two different designs of the intermediate turbine duct, which have been tested in two different experimental facilities, the Chalmers Large-Scale Low-Speed Turbine Facility and the Oxford Turbine Research Facility. Both configurations consists of a full high pressure turbine stage (stator and rotor) and an intermediate turbine duct with a low turning vane. At Chalmers, the emphasis was at steady aerodynamic measurements, including static pressure, total pressure and flow angles within the duct. In Oxford, the experimental campaign mainly regarded heat transfer measurements, on the intermediate turbine duct vane surface at discrete positions. However, the results included in this thesis are mainly static pressure distributions from the first part of the campaign, along with some heat transfer results. This set of experimental data, from two different facilities and designs, enables the validation of current and future numerical methods to well-defined test cases.