The purpose of the air delivery system is to provide the blade with air of the required temperature and pressure. In gas-turbine engines, pre-swirl air delivery systems, in which the air is pre-swirled in the rotating turbine disk direction, are used to deliver cooling air to the blade. In this case, total air temperature and pressure decrease, while the frame of reference changes from absolute to relative. After leaving the pre-swirl nozzle, the air flows through a mixing cavity to the rotor-rotor rotating cavity formed by the turbine disk and cover-plate and then through the blade cooling rim slots feed the blade cooling channels. This paper reports a combined theoretical and computational study of the adiabatic flow in pre-swirl turbine cooling air delivery system. Theoretical investigations were performed to find maximum temperature decreasing after pre-swirl nozzles as system potential with variation of pre-swirl nozzles radius. It was shown that taking into account free vortex law of the flow in rotating cavity optimal radius of the pre-swirl nozzles could be theoretically defined. Computations are performed within the parameter range similar to gas-turbine engine operating conditions: 0.375<λT<0.98; 0.548<β0<2.5; 1.69×107<Reφ<2.33×107; 2.79×105<Cw<5.73×105. Numerical simulation was performed with commercial code Ansys CFX. To solve the Reynolds Averaged Navies-Stokes (RANS) a finite volume coupled algebraic multi-grid solver was used. The second order accurate advection scheme was used for computations. The energy equation is solved including the viscous work term. For validating purposes we used the experimental data obtained during real engine turbine assembly tests and while testing individual delivery system elements, as well. It was shown that the maximum range of error of nondimensional pressure and temperature values near the stator walls was within 0.5% of the measured values. It was shown that the selection of optimum radius of pre-swirl nozzle location is determined by different factors and depends on design and boundary conditions. As a result of conducted theoretical and computational study five steps were developed to find optimal radius of pre-swirl nozzles.
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