An analysis of the exhaust diffuser section of a gas turbine is presented by incorporating the reduced order mathematical model "actuator disc concept" that represents the last stage of the turbine. The actuator disc model is one of the simplified numerical methods for analyzing the aerodynamic performance of axial turbine stage. In which, the rotor and the stator of the turbine stages are modeled as zero thickness discs with a specified blade speed and zero speed respectively. Finite volume based commercial CFD package ANSYS FLUENT was employed for the numerical investigation of the applicability of the proposed simplified model. The compressible Navier-Stoke equations along with k- turbulent model were solved in the computational domain by incorporating suitable boundary conditions. The implementation of actuator disc boundary conditions is described in detail. The numerical results obtained from the proposed model are in good agreement with the experimental data available in the literature. The effect of casing angle on the performance of diffuser is presented.
Aerodynamic aspects of train shapes suitable for Vacuum Tube Train System are investigated in this paper. Three feasible geometries for the vacuum tube train system have been considered and modelled in three dimensions and have been computationally studied using the commercial software Ansys Fluent. Aerodynamic drag loads on these geometries have been calculated under different tube pressures and speeds of the train, which provide insight on various operating parameters that need to be considered while designing the vacuum tube train system. The present computational research shows that, the suitable vacuum pressure, and different shapes of head and tail of the train have significantly effects the drag force of the vacuum train in the tunnel. Overall, the elliptical train shape with a height to base ratio of 2:1 is more efficient for aerodynamic drag reduction of the vacuum tube train at the vacuum tube pressure of 1013.25 Pa.
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