A Loosely Coupled Unsteady Flow Simulation of a Single Stage Compressor

Abstract

A steady/unsteady, three-dimensional Navier- Stokes solver that utilizes a semi-implicit, pressure-based solution procedure is developed to simulate the three-dimensional, incompressible flow through a single stage compressor. The present numerical scheme features the implementation of a second-order plus fourth-order artificial dissipation formulation to prevent the numerical oscillation due to central differencing schemes. A low-Reynolds-number form of the two-equation turbulence model is used to account for the turbulence effects. For unsteady flow computations, the coupling between the mean flow properties and the turbulence is enhanced by an inner-iteration procedure during each time step. The steady flow field in the rotor passage is computed first. This is used as input for the computation of the unsteady flow in the subsequent stator. The predicted unsteady pressure on the stator blades and unsteady velocities at several locations inside the passage are compared with the experimental data. The unsteady pressures on the stator blade surfaces are in good agreement with the experimental data. The predicted unsteady velocity components at various locations inside the stator blade rows are generally smaller than the measured values in the endwall regions. The phase, angle variations of the unsteady velocity are in good agreement with the measured values. The effects of the rotor wake, secondary and tip clearance flows on the unsteady flow through the subsequent stator are studied. An attempt is also made to quantify the contributions of incoming tip leakage flows and the endwall boundary layers on the unsteady flow through the downstream stator. It was found that the endwall boundary layers and tip leakage flows have a much stronger influence on the unsteady flow development than the wake.