Turbine flows

One of the most important challenges today for turbine designers is the prediction of heat transfer on engine blade walls. The life duration of the turbine components directly depends on the wall heat transfer levels and therefore designers imperatively need an accurate estimation tool. To give an idea, a 15 K difference on the temperature prediction at mid-span of a blade corresponds to a reduction of its life duration by a factor 2. The difficulty is that complex flows observed in the turbine environment can not be efficiently computed with classical steady methods. For example, laminar to turbulent transition, hot spot incoming from the combustion chamber, temperature gradient at walls are among the difficulties that CFD solvers have to address.

Recently the CFD team has engaged in a new area of research focused on heat transfer in High Pressure Turbine. Since hot streaks coming from the combustor are transported in the turbine, the temperature field is highly heterogeneous and thus the prediction of the blade temperature is challenging. The main studied topics concern the transport of hot streaks in high pressure turbines, the influence of clocking between vanes and hot streaks and the effects of coolant devices on heat transfer. In order to better model this complex problem, simulation involving coupling between different codes will be necessary. Actually a better prediction of wall temperature may be achieve by coupling a solid thermal and a fluid aero-thermal code. Moreover the complex task of specifying an inlet boundary condition for the high pressure turbine can be avoid by coupling an aerodynamic and a combustion code.

Contacts: Fabien Wlassow, Thomas Leonard, Nicolas Gourdain