Unsteady Aerodynamical Blade Row Interaction in a New Multistage Research Turbine: Part 2 — Numerical Investigation

Abstract

This paper is the second part of a two part paper, which describes in part one the experimental setup and results of a new multistage turbine. Part two presents results of unsteady viscous flow calculations based on cold flow experiments of that three stage low pressure turbine. The present paper emphasizes the investigation of stator-stator interaction of a low pressure turbine section of a commercial jet engine. Different positions for the second and third stator are studied numerically and experimentally with respect to the blade row interaction, unsteady blade loading and unsteady boundary layer effects. A time accurate Reynolds averaged Navier-Stokes solver is applied for the computations. Turbulence is modeled using the Spalart-Allmaras one equation model turbulence model and the influence of modern transition models on the unsteady flow predictions is investigated. The integration of the governing equations in time is performed by a four stage Runge-Kutta scheme, which is accelerated by a two grid method in the viscous boundary layer around the blades and alternatively by a dual time stepping method. At the inlet and outlet reflecting or non-reflecting boundary conditions are used. The quasi 3D calculations are conducted on a stream surface around midspan allowing a varying stream tube thickness. In particular, the flow field with respect to time averaged and unsteady quantities such as surface pressure, vorticity, unsteady velocity field and skin friction are compared with the experiments conducted in the cold air flow test rig.

Impact of clocking on the aero-thermodynamics of a second stator tested in a one and a half stage HP turbine

“…Binder et al [6], studied the effect of the turbulence level in a rotor row created by the preceding rotor wakes migrating across the intermediate stator. It is generally assumed that clocking is a potential mean to control the boundary layer transition in LP turbines and to improve efficiency (Gombert and Hohn [7]; Hohn et al [8]). However, Arnone et al [9] concluded that, because of the three-dimensional environment (geometry and flow), the not-perfect alignment between the first stator wakes and the second stator leading edges over the entire radius is difficult to achieve and the clocking effects are reduced.…”