Rotordynamic Fluid Force Moments on an Open-type Centrifugal CompressorImpeller in Precessing Motion

[摘要] In recent years, increasing interest has been given to the rotordynamic fluid forces on impellers, from the view point of the shaft vibration analysis. Previous experimental and analytical results have shown that the fluid-induced forces and moments on closed type pump impellers contribute substantially to the potential destabilization ofsubsynchronous shaft vibrations. However, to date few papers are known of therotordynamic fluid forces on open-type centrifugal impellers. This paper reports aboutexperimental investigations of the rotordynamic fluid force moments on an open-typecentrifugal compressor impeller in precessing motion. For open-type impellers, thevariations of the tip clearance and the clearance between the back shroud and casing dueto the precessing motion contribute to the rotordynamic fluid force moments.Experiments were conducted to measure the rotordynamic fluid force moments directlyusing the 4-axis sensor, and the unsteady pressure on the front and back casing wall.In this paper, following results are obtained: (1) The fluid force moment becomesdestabilizing in the region of negative precessing speed ratio(-0.3<Ω/ω<0), at the design flow rate; (2) At reduced flow rate, the destabilizing fluid force moments occurred at small positive precessing speed ratio(0.2<Ω/ω<0.4); (3) From the comparison of direct measured fluid force moments with those estimated from the unsteady pressure measured on the front and back casing walls, it was found that the destabilizing moments in the backward precession are mainly caused by the fluid forces on the front surface of the present impeller, where there is large clearance between the back shroud and casing.

[学科分类] 力学，机械学