Turbine through flow design based on time-marching method
To establish reasonable turbine design parameter calculation method and guarantee the accuracy of design work on the basis of quadratic function,an approximate computation method of S2 stream surface circumferential angle and blockage coefficient inside blade row passage was proposed for Euler equation time-marching through design method.The through-flow design method utilized finite volume method to solve 2D unconservative Euler equation in orthogonal curvilinear coordinate.Exact Riemann solution was used to calculate interface parameters of grid element.And third order Godunov scheme with TVD property was implemented.While semi-implicit scheme was employed in temporal discretization.The blade profile loss,secondary loss,and blade tip clearance leakage loss were computed by empirical loss model.Then secondary loss and tip clearance leakage loss could be redistributed radially.On the other hand,shock wave loss was regarded as accurate after solution.A single stage turbine was then designed with the through flow design method.After that,3D blade shapes were profiled according to through flow result.Next,3D viscous CFD software was used to simulate turbine and verify the effectiveness of through flow design method.Given the same inlet and outlet conditions,compared with 3D result,through flow mass flow result was about 1.46％higher,expansion ratio was 0.005 lower,and isentropic efficiency was 0.007 7 higher.Finally,it can be concluded that through flow design method required fewer grid points,featuring higher computation efficiency with favorable convergence.Besides,the calculation method of blade row passage S2 stream surface circumferential angle and blockage coefficient was rational.And also,accurate results of turbine overall performance,as well as dimensionless parameters like flow coefficient,loading coefficient and reaction could be obtained.
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