The commercial computational fluid dynamics code ANSYS CFX 12.1 has been employed to carry out Unsteady Reynolds Averaged Navier Stokes (URANS) computations to investigate the fluid mechanics of two different rim-seal geometries in a 3D model of a turbine stage. The mainstream annulus, seal and wheel-space geometries are based on an experimental test rig used at the University of Bath. The calculated peak-to-trough pressure difference in the annulus, which is the main driving mechanism for ingestion, is in good agreement with experimental measurements. There is also good agreement between the computed and measured swirl ratios in the wheel-space. Computed values of concentration-based sealing effectiveness are obtained over a range of sealing flow rates for both an axial-clearance and a radial clearance rim-seal. Good agreement with gas concentration measurements is found for the axial-clearance seal over a certain range of sealing flow rates. Some under-prediction of the amount of ingestion for the radial-clearance seal is obtained. The computed mainstream pressure coefficient increases progressively with mainstream Mach number in moving from quasi-incompressible experimental rig conditions to the compressible flow conditions encountered in engines. It is shown that the minimum sealing flow rate required to prevent ingestion increases as mainstream Mach number increases. A scaling method is proposed to allow sealing flow rates to prevent ingestion obtained from low Mach number experiments to be extrapolated to engine-representative conditions.

In this paper, the flow and heat transfer characteristics of two lines of staggered or inline round jets impinging on a flat plate are numerically analyzed using the CFD commercial code FLUENT. Firstly, the relative performance of seven versions of turbulence models, including the standard k-ε model, the renormalization group k-ε model, the realizable k-ε model, the standard k-ω model, the Shear-Stress Transport k-ω model, the Reynolds stress model and the Large Eddy Simulation model, for numerically predicting single jet impingement heat transfer is investigated by comparing the numerical results with available benchmark experimental data. As a result, the Shear-Stress Transport k-ω model is recommended as the best compromise between the computational cost and accuracy. Using the Shear-Stress Transport k-ω model, the impingement flow and heat transfer under multi-jets with different jet distributions and attack angles are simulated and studied. The effect of hole distribution and angle of attack, etc. on the heat transfer coefficient of the target plate are examined.

In this paper, the heat transfer characteristics of a circular air jet vertically impinging on a flat plate near to the nozzle (H / d ϭ 1 -6, where H is the nozzle-to-target spacing and d is the diameter of the jet) are numerically analyzed. The relative performance of seven turbulent models for predicting this type of flow and heat transfer is investigated by comparing the numerical results with available benchmark experimental data. It is found that the shearstress transport (SST) k Ϫ model and the large Eddy simulation (LES) time-variant model can give better predictions for the performance of fluid flow and heat transfer; especially, the SST k Ϫ model should be the best compromise between computational cost and accuracy. In addition, using the SST k Ϫ model, the effects of jet Reynolds number (Re), jet plate length-to-jet diameter ratio ͑L / d͒, target spacing-to-jet diameter ratio ͑H / d͒, and jet plate width-to-jet diameter ratio ͑W / d͒ on the local Nusselt number (Nu) of the target plate are examined; a correlation for the stagnation Nu is presented.

The commercial computational fluid dynamics code ANSYS CFX 12.1 has been employed to carry out unsteady Reynolds-averaged Navier-Stokes computations to investigate the fluid mechanics of two different rim-seal geometries in a three-dimensional model of a turbine stage. The mainstream annulus, seal and wheel-space geometries are based on an experimental test rig used at the University of Bath. The calculated peak-to-trough pressure difference in the annulus, which is the main driving mechanism for ingestion, is in good agreement with experimental measurements. There is also a good agreement between the computed and measured swirl ratios in the wheel-space. Computed values of concentration-based sealing effectiveness are obtained over a range of sealing flow rates for both an axial clearance and a radial clearance rim seal. A good agreement with gas concentration measurements is found for the axial clearance seal over a certain range of sealing flow rates. Some under-prediction of the amount of ingestion for the radial clearance seal is obtained. The computed mainstream pressure coefficient increases progressively with mainstream Mach number in moving from quasi-incompressible experimental rig conditions to the compressible flow conditions encountered in engines. It is shown that the minimum sealing flow rate required to prevent ingestion increases as mainstream Mach number increases. A scaling method is proposed to allow sealing flow rates to prevent ingestion obtained from low Mach number experiments to be extrapolated to engine-representative conditions.

In this paper, experimental and numerical study has been carried out to investigate impingement cooling with a row of five circular jets, varied between target positions on a realistic leading edge region of a gas turbine blade geometry. Experimental data is collected from a transient thermochromic liquid crystal measurement technique at the target surface.Numerical study was conducted with the geometry using commercial computational fluid dynamics software to analyse the fluid flow. The unique aims of the study are to observe the effects of variation in jet location, and those specific to realistic target and nozzle geometries.Distributions of local and average Nusselt number show that a location targeting the concave surface at 90° demonstrates an overall higher heat transfer coefficient, especially in the stagnation region, and towards the aerofoil sides, with significantly less swirl. The experiment was performed with the following parameters: distance from nozzle to target of 1.7 to 2.1 jet diameters, pitch between jets of 4.4 jet diameters, and concave target diameter of 8.0 jet diameters. The jet Reynolds number range during this test was 20,000 -40,000. A standard flat target plate impingement test is also experimentally conducted and compared against existing literature for method validation.