Demands on improved efficiency, reduced emissions and lowered noise levels result in higher by-pass ratio turbofan engines. The design of the intermediate turbine duct, connecting the high-pressure and low-pressure turbines in a two-spool engine, becomes thus more critical. The radial offset between the high-pressure core and the low-pressure system will increase, which leads to a higher aspect ratio (Δr/L) of the turbine duct. In order to improve the low-pressure turbine performance the turbine duct exit axial velocity could be reduced by increasing the duct area ratio (Aout/Ain). In order to keep the turbine frame weight as low as possible, it is also desirable to keep the duct short, i. e. keep the non-dimensional length (L/hin) as low as possible. Therefore, there is a need to improve the knowledge about the flowfield and heat transfer in aggressive (high aspect ratio/high area ratio) turbine ducts. The work presented here has been performed within the EU FP6 project AITEB-2, focusing on heat transfer in turbines. In a two-part paper the aerothermal behavior of a fairly aggressive intermediate turbine duct with nine non-lifting vanes has been studied. The flowfield and heat transfer data was acquired in the Chalmers Turbine Facility. The first part of the paper focuses on the experimental investigation and results. In this second part of the paper comparisons between experimental data and numerical results are made. The work highlights the challenges associated with numerical predictions of flowfield induced heat transfer in turbine ducts. The numerical analysis was performed using Chalmers in-house compressible flow solver. The experimental results are compared to CFD analyzes using two different turbulence models; k-ε with wall functions and low-Re k-ω SST, and using the measured inlet conditions to the duct as boundary conditions. Previously presented flowfield comparisons showed good agreement between experiments and CFD. The main flow features, such as vorticity and pressure gradients, are reasonably well reproduced by the CFD. The heat transfer results show reasonable agreement on the hub and on the downstream part of the shroud. The heat transfer agreement is, however, poor on the shroud in the region between the duct inlet and the leading edge of the vane.

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