Improved modelling capabilities of the airflow within turbine case cooling systems using smart porous media

Impingement cooling is commonly employed in gas turbines to control the turbine tip clearance. During the design phase, Computational Fluid Dynamics is an effective way of evaluating such systems but for most Turbine Case Cooling (TCC) systems resolving the small scale and large number of cooling holes is impractical at the preliminary design phase. This paper presents an alternative approach for predicting aerodynamic performance of TCC systems using a “smart” porous media to replace regions of cooling holes. Numerically (CFD) defined correlations have been developed, which account for geometry and local flow field, to define the porous media loss coefficient. These are coded as a user defined function allowing the loss to vary, within the calculation, as a function of the predicted flow and hence produce a spatial variation of mass flow matching that of the cooling holes. The methodology has been tested on various geometrical configurations representative of current TCC systems and compared to full cooling hole models. The method was shown to achieve good overall agreement whilst significantly reducing both the mesh count and the computational time to a practical level.