3D-simulation of multi-stage turbomachinery by means of a non-reflecting mixing plane interface

Abstract

Turbomachines have experienced a fast development over the last years, and are present in a wide range of devices involved in the generation of electricity and the transportation sector. Current challenges in both sectors have driven quite a number of developments regarding the increase of efficiency and use of new types of devices. Those changes have also affected turbomachinery design, and new innovative approaches are being used in order to solve current problems. As the design of those machines is sometimes done without lot of prior knowledge, new design techniques are required. Design optimization is usually involving a wide range of disciplines. When it comes to turbomachinery applications, this becomes more challenging as there are lot of parameters involved in the design. The heterogeneous range of applications imposes challenges from the designer point of view as different architectures may need to be considered, different working fluids, different number of stages, etc. In this Master Thesis, the problem of multi-stage turbomachinery analysis will be undertaken. Simulation of multi-stage turbomachinery presents a number of limitations when it comes both to modelling of the problem and the use of CFD codes, among which the main one is the modelling of the stator-rotor interface. To overcome this problem, a number of solutions are proposed, of which some are presented in the present report. The Mixing-Plane interface is one of the most used, especially when design optimization is considered. The Mixing-Plane interface creates an artificial interface between turbomachinery blade rows which forces the match of the average of physical quantities at both upstream and downstream sides of the interface. However, since in general specialised turbomachinery solvers are multi-block structured, current approaches based on the Mixing-Plane interface are not adapted to unstructured edge based solvers. This imposes limitations in the mesh types that can be used for simulating turbomachinery, and add some design constrains. In this Master Thesis the existing methods are analysed and extended to the edge based unstructured solver SU2. After implementing the proposed approach, a multi-stage turbine for which experimental data is available is simulated. By comparing the results with the experiments and simulations with another CFD solver, the implemented method is validated.