Increased power output as well as better thermodynamic efficiency levels, can be achieved by higher turbine inlet temperatures. However, higher entry temperatures cause severe demands on materials. For example, lifetime of turbine blades and vanes is highly dependent on gas temperature. In modern gas turbines, a lot of effort is made in order to cool turbines.
A full understanding of the various physical phenomena is vital to improve blade cooling methods. Cooling of blades can be divided into two main fields: inner and outer cooling, both characterized by different flow regimes.
At the outer turbine surface, which is exposed to hot gas, heat transfer should be minimized. Investigations are focused on cooling fluid in a massively accelerated flow regime and shock-boundary-layer interactions. In order to effectively draw heat out of the turbine blade a highly turbulent flow with numerous flow separations is generated on the inside. Depending on the operation point, the temperature of turbine material results from gas temperatures as well as inner and outer surface heat transfer rates.
To accurately predict turbine temperatures, it is necessary to solve the entire system which involves internal/external flow and heat conduction in the material. Therefore the TRACE-Code is coupled with a finite element solver.
For calculating the flow, different turbulence models are employed in TRACE. The range of models reaches from robust one-equation models to complex anisotropic Reynolds-stress-transport models.
To better understand the influence of temperature fluctuations on turbulent heat transfer, autonomous transport models that predict turbulent heat conductivity are studied. It is known that turbulent momentum and temperature fluctuations differ in complex flow fields such as turbomachine flows. Potential for more accurate predictions are expected in flow with separating boundary layer and free shear layers.