A LOOSELY-COUPLED UNSTEADY-FLOW SIMULATION OF A SINGLE-STAGE COMPRESSOR

A steady/unsteady, three-dimensional Navier-Stokes solver that utilize s a semiimplicit, pressure-based solution procedure is developed to si mulate the three-dimensional, incompressible flow through a single sta ge compressor. The present numerical scheme features the implementatio n of a second-order plus fourth-order artificial dissipation formulati on to prevent the numerical oscillation due to central differencing sc hemes. A low-Reynolds-number form of the two-equation turbulence model is used to account for the turbulence effects. For unsteady flow comp utations, the coupling between the mean flow properties and the turbul ence is enhanced by an inner-iteration procedure during each time step . The steady flow field in the rotor passage is computed first. This i s used as input for the computation of the unsteady flow in the subseq uent stator. The predicted unsteady pressure on the stator blades and unsteady velocities at several locations inside the passage are compar ed with the experimental data. The unsteady pressures on the stator bl ade surfaces are in good agreement with the experimental data. The pre dicted unsteady velocity components at various locations inside the st ator blade rows are generally smaller than the measured values in the endwall regions. The phase angle variations of the unsteady velocity a re in good agreement with the measured values. The effects of the roto r wake, secondary and tip clearance flows on the unsteady flow through the subsequent stator are studied. An attempt is also made to quantif y the contributions of incoming tip leakage flows and the endwall boun dary layers on the unsteady flow through the downstream stator. It was found that the endwall boundary layers and tip leakage flows have a m uch stronger influence on the unsteady flow development than the wake.