The Numerical Investigation About Effects Of Inlet Fogging On Rotating Stall In A Transonic Compressor Rotor

The unstable flow of compressor can worsen working performance. Rotating stall is themost common instability phenomenon in an axial flow compressor. As well as the interactionof the tip leakage vortex and shock wave, flow blockage caused by breakdown of tip leakagevortex near stall point is considered to have a lot to do with rotating stall. In recent years, anumber of numerical studies have been performed to investigate the unsteady mechanism oftip leakage flow and the stall inception with the numerical simulation. Using various means toimprove tip clearance flow in a near stall operating point, they want to find the right methodto expand stability.In order to find the effects of inlet fogging on rotating stall in a transonic rotor, with thesimulation model of this transonic compressor, a full three-dimensional calculation of dry andwet compression under different operation conditions is conducted by utilizing Ansys-CFX ofa NASA transonic compressor stage-Rotor35.The purpose of the present work is to elucidatethe tip clearance flow field in a transonic axial compressor rotor,.and the inducing factor oftransonic rotor rotating stall. Meanwhile the effect of inlet fogging on stall boundary and theform to stall in the rotor is studied.The results that summed up by steady simulations can be described in these aspects. At anear-stall condition, the breakdown of tip leakage vortex occurred after downstream of theshock wave. With inlet fogging, the dispersed phase droplets which get past the blade andflow together with the tip clearance leakage will control the breakdown and extend the stallboundary and delay the appearance of shock wave. The measure of inlet fogging can expandcompressor stall boundary, but can not make stall characteristics change. In the conditions ofdifferent injected water flow rates and droplet diameters, it will make the best effect when thedroplet is5microns in diameter and2%water quantity.In unsteady simulations, these conclusions can be summarized. The breakdown of the tipleakage vortex leads to not only the large blockage effect near the tip but also the unsteadyflow phenomena in the rotor passage. From the multi-passages unsteady computation, whenthe rotating stall cell is far developed, leading egde spillage appears,while LE spillage belowblade tip provide an additional path for the tip clearance fluid to be displaced upsteam by thebackflow. With the the inlet fogging, compressor stall boundary is expand, the unsteady periodic of static pressure at the rotor tip becomes irregular.