Research On Cavitation Performance Of An Axial Pump With Adjustable Inlet Guide Vanes

Cavitation phenomenon exists widely in hydraulic machinery,which often causes performance deterioration,erosion,vibration and noise.The methods to improve the cavitation performance of hydraulic machinery have always been the research emphasis of experts.The axial pump is a kind of common hydraulic machinery and the cavitation in axial pumps also cannot be ignored.In this paper,a kind of adjustable inlet guide vanes(IGVs)is presented to improve cavitation performance of axial pumps.Both experiment approach and numerical simulation method are conducted to analyze the impact of adjustable IGVs on cavitation performance under off-design conditions.The main work and results are as follows:(1)A closed test rig is established to obtain cavitation performance with and without IGVs in an axial pump,and to record and analyze the pressure pulsations in pump inlet and outlet.The results indicate that when the angle of IGVs is negative,pump head increases and cavitation performance is decreased,meanwhile,when the angle is positive,the cavitation performance is improved.Time domains of pressure pulsation show that,as equipped with IGVs the pressure amplitude increases when cavitation incepts and decreases when cavitation further develops.The frequency spectrums of pressure pulsation show that the pulsation amplitude appears mainly in blade frequency and its harmonic frequencies in cavitation inception,and as cavitation develops,the amplitude is centered on low frequencies in inlet and appears broadband characteristics in outlet.(2)The numerical simulation is conducted to obtain inner flow field and to reveal the mechanism of IGVs to cavitation performance.The results show that when the angle of IGVs is 0°,the pump performance is poorer than that without IGVs.As the angle of IGVs is adjusted from negative values to positive values,the cavitation performance is improved.The pressure distribution and vapor distribution shows that 1%efficiency drop is more proper to predict critical cavitation state compared with 3%head drop.And the increase of vapor fraction in impeller can predict cavitation performance well.