Numerical investigations of the 3D transonic field and heat transfer at the over-tip casing in a HP-turbine stage

Aiming to increase engine efficiency, the trend of turbine entrance temperature is still towards higher levels. Since heat transfer experiments under realistic operating conditions are both costly and time consuming. To reduce the design cost and time a combined complementary numerical and experimental approach is more frequently used nowadays. To improve this procedure at the test facility for Rotating Cascades (RGG) at DLR wind tunnel measurements were carried out assisted by 3D numerical simulations applying TRACE a CFD code developed at DLR. After a successful validation of the numerical code this combination provides quantities which are very difficult or impossible to measure. With courtesy of MTU Aero Engines during the German research program E3E a high pressure turbine stage test rig was developed. At DLR this test rig was slightly modified to enable heat transfer measurements at the over-tip casing. A matrix of operating points was selected and filled up with numerical simulation results focusing on the over-tip casing region of the rotor. Aerodynamic characteristics as well as heat transfer parameters such as wall heat transfer coefficients were investigated.