利用空化现象进行水喷射泵转子叶片尖区流场结构的可视化研究
In this paper, we examine the occurrence of cavitationin the tip region of a waterjet pump, and use theobservations to identify key features of the flowstructure. The rotor, stator and pump casing in ourrecently upgraded facility are made of acrylic, whoserefractive index matches that of the working fluid, aconcentrated aqueous solution of sodium iodide. Suchmatching makes the blades invisible, enabling flowstructure visualization and optical measurementswithout any obstructions. Our initial tests with freshwater focus on cavitation in the vicinity of the tipregion close to design conditions. Near the leadingedge, cavitation inception near the tip corner of thepressure side causes accumulation of bubbles along thepressure side of the corner until mid blade. As roll-upof the tip leakage vortex (TLV) starts in the mid bladeregion, these bubbles travel across the tip-clearance tothe suction side, and become nuclei for cavitationinception in the TLV. As the TLV migrates to thevicinity of the pressure side of the neighboring blade itbursts, generating a cloud of bubbles that spreads overmost of the aft section of the passage. The leakage flowin the tip gap along the aft side of the blade is strongenough to cause sheet cavitation within the gap,starting from the pressure side corner. The paper alsopresents preliminary Particle Image Velocimetry (PIV)data concentrating on the roll-up of TLV. Results areconsistent with observed cavitation phenomena.