A Novel Package for Turbomachinery Throughflow Analysis

Throughflow methods still represent a key tool for turbomachinery designers. In this work, a novel CFD-based throughflow method is proposed and demonstrated for realistic industrial applications: a single-stage axial fan, where the performance of the method is thoroughly discussed, and a multistage low pressure steam turbine which demonstrates the potential of the code also for transonic flows in a fully three-dimensional configuration. The key feature of the proposed method is that the impermeability condition in bladed regions is prescribed by exploiting some concepts used in immersed boundary methods. The resulting algebraic force model circumvents the introduction of an additional constraint equation in bladed regions, resulting in a highly simplified implementation into an existing CFD code. To account for the effect of aerodynamic losses, further source terms proportional to the local entropy gradient are introduced. To estimate the losses and deviation angles, a number of correlations have been implemented into the code. The code can deal with highly non-ideal flows governed by very accurate (though complex) equations of state, as required for the simulation of low pressure and supercritical steam turbines and, more generally, for turbomachinery operating with dense gases as working fluids. The throughflow solver is coupled with a fully automated blade modeler and grid generator, which can be used to design the geometry of the meridional channel and of the blades and for the generation of triangular as well as quadrilateral meshes of the entire bladed meridional domain.