Numerical and experimental investigation of unsteady flow interaction in alow-pressure multistage turbine

This paper presents results of unsteady viscous flow calculations and corre sponding cold flow experiments of a three-stage low-pressure turbine. The i nvestigation emphasizes the study of unsteady flow interaction. A time-accu rate Reynolds-averaged Navier-Stokes solver is applied for the computations . Turbulence is modeled using the Spalart-Allmaras one-equation turbulence model and the influence of modern transition models on the unsteady flow pr edictions is investigated. The integration of the governing equations in ti me is performed with a four-stage Runge-Kutta scheme, which is accelerated by a two-grid method in the viscous boundary layer around the blades. At th e inlet and outlet, nonreflecting boundary conditions are used. The quasi-t hree-dimensional calculations are conducted on a stream surface around mids pan, allowing a varying stream tube thickness. In order to study the unstea dy flow interaction, a three-stage low-pressure turbine rig of a modern com mercial jet engine is built up. In addition to the design point, the Reynol ds number, the wheel speed, and the pressure ratio are also varied in the t ests. The numerical method is able to capture important unsteady effects fo und in the experiments, i.e., unsteady transition as well as the blade row interaction. In particular, the flow field with respect to time-averaged an d unsteady quantities such as surface pressure, entropy, and skin friction is compared with the experiments conducted in the cold air flow test rig. [ S0889-504x(00)02004-3].