Study of Pump Abnormal Characteristics from Prevention toward Suppression and Control

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A variety of unstable characteristics of turbopumps were studied to develop the flow control methods for the stable pump operations. Common factor was tried to find for-various unstable phenomena through the study of five different type unsteady phenomena in turbopumps.[Osaka University Group]: Four bladed inducer was studied on inlet distortion, and then unsteady stress on blades was found to be induced by the interaction between cavities induced by inlet distortion and alternative blade cavitations. And three bladed inducer was found to generate the higher order rotating cavitations.[Nagoya University Group]: Two different specific speed mixed flow pumps were tested to study the decrease in pumping action at low suction pressure. Flow distributions at pump impeller inlet are related to cavitations number.[Kyushu University Group] : Tandem type rotating cascade as well as high blade outlet angle was tested to suppress and control the air lock phenomena at high void ratio. And control system for the blade outlet angle was tested to get the higher pump efficiency.[Kyushu Institute of Technology Group]: Unsteady flow structures were studied to get the pre-unstable signals for the prediction of the occurrence of unstable phenomena of diffuser pump at low discharge.[Yokohama National University Group]: Slit on diffuser wail, the J-Groove, was tested to suppress the rotating vortex core at strong inlet distortion in conical diffuser.The J-Groove was found to be effective for the suppression of pressure fluctuations due to strong rotating flow up to 46 percent.