In this work the flow regime within a generic turbine cooling system is investigated numerically. The main objective is to validate the performance of various turbulence models with different complexity by comparing the numerical results with experimental data. To maximize surface heat transfer rates, present-day cooling systems of high pressure turbines have highly complex shapes generating high turbulence levels and flow separations. These flow structures lead to higher requirements of CFD-techniques for sufficient prediction. To simulate complex flows in the industrial design process, Reynolds averaged Navier-Stokes (RANS) techniques are applied instead of computationally expensive LES and DNS simulations. Therefore, higher order turbulence models are necessary to predict flow field and heat transfer performance in such complex motion. The DLR standard flow solver for turbomachinery flows, TRACE, is used to solve the RANS equations. Four turbulence models have been analysed: the one equation model of Spalart and Allmaras, the two equation k – ω model of Wilcox, the two equation k – ω SST model of Menter and the anisotropy resolving Explicit Algebraic Reynolds Stress model (EARSM) of Hellsten. The investigated cooling geometry consists of a two-pass smooth channel with a 180 degree bend. At the DLR institute of propulsion technology PIV measurements in a rotating cooling channel test bed for Rotation numbers up to 0.1 have been performed. This work uses the experimental data for Re = 50,000 and Ro = 0 without rotation for comparison. For all models adiabatic and diabatic calculations have been performed. In order to accurately apply the turbulence models, a study concerning the turbulent boundary conditions has been performed prior to the calculations. The results obtained through RANS simulations are presented in comparison with the experiments along planes in the flow direction and in the orthogonal direction to study the velocity field, the shape and size of the separation bubbles and the wall shear stress. The EARSM predicts the flow field overall more accurately with improved agreement between all relevant parameters compared to the other models. The diabatic simulations reflect the adiabatic results. However, it can be noticed that higher complexity in turbulence modelling is related to increased heat transfer. Our work confirms the EARSMs ability to predict complex flow structures better than the more elementary approaches.

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In this paper the influence of a non-symmetrical sidewall-contour on the flow field of an axial compressor is investigated. In earlier studies, carried out at the DLR Institute of Propulsion Technology in Cologne, it has been shown that it is possible to influence secondary flow regimes by a non-symmetrical sidewall contour. With the help of the contour a vortex is generated that serves as an aerodynamic barrier and thus reduces the flow transport orthogonal to the main flow direction. In this paper the described method of flow manipulation is investigated for the compressor rotor at the hub wall. It turns out that despite the unsteady inflow conditions the vortex is stably generated and works as an aerodynamic separator. The rotor hub region increases its flow capacity. A higher pressure ratio is achieved at a highly loaded operating point. The efficiency at this point remains unchanged. List of Symbols and Abbreviations m M-relative mass flow, y +-dimensionless wall distance, η-isentropic efficiency, π-total pressure ratio, ω-vorticity , BPrVar-back pressure variation, MVDRmeridional velocity density rate, OP-operating point, PR-pressure ratio, TVD-Total Variation Diminishing

The application of Reduced Order Models (ROMs) in the simulation of complex, time-dependent flows in turbomachines provides a means to significantly reduce the cost, both in terms of preprocessing and computational overhead, of numerical simulations. In this work the development and combination of two ROMs for the simulation of the unsteady, time-periodic flow and heat transfer in a film-cooled turbine are presented. For the simulation of the unsteady flow an alternating frequency/time domain Harmonic Balance (HB) method is applied. To allow the efficient preprocessing and simulation of film-cooled blades a second, volume source based, ROM is incorporated into the underlying nonlinear solver of the HB method. Through the application of the volume source model the time consuming and error prone resolution and specification of individual cooling holes is no longer necessary. To validate the newly implemented volume source model a number of simple academic test cases are presented and analyzed in detail. Following the basic validation of the cooling model the approach is combined with the HB method to simulate the unsteady flow in the first one and half stages of a high-pressure turbine.