Couplage entre un code de calcul méridien instationnaire et un code de calcul 3D dans l'optique de simuler les écoulements transitoires de démarrage dans les turbopompes multiétagées

Coupling an unsteady throughflow calculation and a 3D calculation in order to simulate flow in multistage turbomachines with variable rotating speed

¹ Laboratoire de Mécanique des Fluides et d'Acoustique de l'Ecole Centrale de Lyon
² Metraflu

Abstract

This study deals with a new calculation method which consists in coupling a throughflow calculation with a 3D code. The aim of this development is to simulate flows in multistaged turbomachines with variable rotating speed.

To calculate the steady 3D relative flow of each isolated row embedded in a multistaged configuration, accurate boundary conditions, function of the influence of the other rows, are needed upstream and downstream. In our method, those conditions are imposed in a coupling process, as results of a throughflow calculation. This code solves the circumferentially averaged Euler equations on a multistaged domain. Because the averaging process generates source terms usually known as blades forces and deterministic stresses function of 3D variables fields, the throughflow calculation and the 3D calculations, one per row, are realised in the same process. Periodically during the time-marching evolution of the throughflow calculation, 3D calculations are done using boundary conditions from it. When they are finished, throughflow calculation source terms are restored. The coupling process continues, until the throughflow calculation convergence is obtained.

The 3D code used is CALECHE, which solves the 3D incompressible Euler equations written with the Clebsch variables.

The method has been successfully validated on an axial compressor stage, and preleminary results are presented on isolated row with fast start of rotating speed.