Hidetaka Okui

Three Dimensional Design and Optimization of a Transonic Rotor in Axial Flow Compressors

This paper presents a 3-D optimization of a moderately loaded transonic compressor rotor by means of a multi-objective optimization system. The latter makes use of a Differential Evolutionary Algorithm in combination with an Artificial Neural Network and a 3D Navier-Stokes solver. Operating it on a cluster of 30 processors enabled the optimization of a large design space composed of the tip camber line and spanwise distribution of sweep and chord length. Objectives were an increase of efficiency at unchanged stall margin by controlling the shock waves and off-design performance curve. First, tests on a single blade row allowed a better understanding of the impact of the different design parameters. Forward sweep with unchanged camber improved the peak efficiency by only 0.3% with a small increase of the stall margin. Backward sweep with an optimized S shaped camber line improved the efficiency by 0.6% with unchanged stall margin. It is explained how the camber line control could introduce the forward sweep effect and compensate the negative effects of the backward sweep. The best results (0.7% increase in efficiency and unchanged stall margin) have been obtained by a stage optimization that also considered the spanwise redistribution of the rotor flow and loading to reduce the Mach number at the stator hub.Copyright

Study on the Effect of Asymmetric Vane Spacing on Vibratory Stress of Blade

It is well known that asymmetric vane spacing can result in decreased levels of the excitation at specific frequencies. In this paper, the resonant response reduction of compressor blades due to asymmetric vane spacing is studied both theoretically and experimentally for the most probable asymmetric vane in which the vane count of the upper and lower half is slightly different. First, a method for predicting the vibratory stress of the blade for the asymmetric spacing vane is proposed. Secondly, using a simple model of the asymmetric vane, a parametric study is carried out to clarify the influence of blade damping and vane count on the blade resonant response reduction. Finally, experiments are carried out to verify the validity of the proposed method and the effect of asymmetric vane spacing on resonant stress response using a 3 stage scaled-model compressor.Copyright

Numerical Analysis of Passive Control of Pseudo-Shock.

Oscillation of the pseudo shock in the rectangular duct with the porous wall was investigated numerically. In the simulation, 2nd order accurate, Harten Yees upwind TVD scheme was used for high resolution and numerical stability, and Chiens κ-e two equation model was used as the turbulence model. To simulate the effect of the blowing and suction on the porous wall, Darcys law was used on the porous wall boundary. The boundary layer thickness under the first shock wave oscillates due to the shock oscillation, which changes the strength of the first shock wave changes, so that it suppresses the pressure fluctuation downstream of the first shock wave. The effects of some parameters of the passive control on the pseudo-shock oscillation were investigated.