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To prevent ingestions of the combustion gas into the cavity between the stationary components and rotating disks, coolant flow from the compressor is used to seal and purge the area against the hot gas. Specific geometries are used to improve the performance of those rim seals in order to save coolant while maintaining a save operation condition for the rotating components. Therefore accurate performance predictions in the early design steps are important to save time and costs. But numerical performance predictions for rim seal applications are still challenging especially for small and mediate enterprises (SME’s). Therefore the authors of this paper are looking for methods to reduce time and costs of numerical performance predictions for rim seal geometries, whereas this paper initiates this proposition by investigating the current limits of the available methods for SME’s. This paper compares steady and unsteady RANS (URANS) simulations. The investigations are based on measurement and geometry data taken from a test rig design of a single stage test turbine at RWTH Aachen University. The RANS simulations did not show a significant ingestion of hot gas whereas the URANS approach has shown increased hot air ingestion. In order to achieve a converged flow field in the URANS simulations, a large number of full rotation cycles have to be calculated. The results show, that pressure oscillations driven by the blade pressure field, as well as acoustics frequencies have been captured by the URANS approach. Nevertheless the investigated URANS simulation approach still shows significant deviation in the prediction of the hot gas ingestion compared to the experimental test data. This is due to the fact that the fundamental equations and the applied closure by isentropic turbulence models are not capable of resolving sufficiently characteristic flow phenomena inside the wheels space and the sealing gap. Another limitation is by the chosen sector model with regard to flow phenomena in circumferential direction.

Exploration of Unsteady and Steady Calculation Methods for Wheel Space Sealing Applications