The Experimental Research Of Tip Clearance Flow And Tip Clearance Cavitation

Tip clearance flow effected by the gap width,the relative movement of blade and wall,blade load and inlet velocity exists in the clearance between the blade tip and end wall,which is usually found in ducted propeller?axial pump and aircraft engine.Tip clearance cavitation leading to noise?vibration and loss of mechanical behavior occurs when the flow medium is fluid.In this thesis,the research and analysis work was carried out by experimental method,pointing at tip clearance flow and tip clearance cavitation.First,the velocity field consists of three velocity components measured by 2D-3C PIV at different sections in tip clearance flow field of the hydrofoil with different operating conditions,and analyzing the three-dimensional flow field configuration.Second,the experiments of tip clearance cavitation observation were carried out by high-speed camera and naked eye,and analyzing the relationship of tip clearance cavitation inception and flow field configuration.There are two obvious vorticity regions in the vorticity contour maps,tip detached vortex area and tip leakage vortex area,and the former origin from the pressure side downstream near the leading edge,the latter origin from the suction side downstream near the tip detached vortex.The tip clearance flow configuration would change respectively with the variety of gap width,the intensity of tip leakage vortex core will increase with the reducing of gap width,and decrease quickly with the further reducing of the gap width due to the influence of the wall boundary layer.Through the experiment research and analysis,typical basic structure of tip clearance flow and tip clearance cavitation were acquired,and large number of full and accurate experiment data was obtained,which provide plentiful data resource for further research of tip clearance flow and cavitation.By the research of tip clearance cavitation inception and configuration observation,and the relationship with tip clearance flow field,the foundation for the scale effect research of tip vortex and prediction of cavitation inception is built up.