For long time operation of general-use turbopumps with inducer, instability-free operation is expected as well as improved suction performance in the wide operating range from shut-off to over flow rates. However, the cavitation surge with strong inlet backflow often occurs in the low flow rate range. In our previous study, the effectiveness of the connecting with reduced-diameter suction pipe to inducer on the cavitation surge was experimentally investigated. Connecting with reduced-diameter suction pipe seems to have two effect : one is reducing the incidence angle by contracting the cross sectional area, another one is blocking the inlet backflow which extends along the casing wall. On the other hand, the same effects can be realized by the inducer design with small incidence angle. In the present paper, the effectiveness of the reduced-diameter suction pipe and that of the inducer designed with small incidence angle are compared in terms of the suction performance and the suppression of cavitation surge. As a result, the employment of reduced-diameter suction pipe achieves suction performance at moderate and higher flow rates with the narrowed onset region of cavitation surge. Further investigation is necessary for the quantitative assessment of suction performance at low flow rates due to the existence of strong swirling back flow.

The characteristics of a gyro-mil wind turbine whose rotating blades are elastically deformable are presented. The each blade consists of ordinal rigid wing and elastically deformable thin plates. The performance tests are performed under the wind generated by 6 fans. This type of gyro-mill turbine has very large torque when the rotation speed is low, but the torque drops sharply when the rotating speed becomes larger. In order to prevent the sharp drop of the torque, the deformation of the elastic plate in outside direction due to the centrifugal force must be prevented and rigid plates for preventing the deformation are shown to be successful. When the wind is discontinuous or fluctuates like the natural wind, the performance of presented wind turbine with elastic plates is shown to be much higher.

Blowdown wind tunnels have been utilized not only in the fields of fluid dynamics research and also in industrial fields as automobiles, railways and aircraft. A dust-proof filter may be attached to the wind tunnel suction to protect precision measuring equipment. It is known that flowrate is reduced and the turbulence intensity of the flow is increased by its attachment. There is no design guideline on how to attach it. In the present paper, effects of mesh and filter attachments to the blowdown wind tunnel suction on its performance such as flowrate and turbulence intensity are investigated experimentally for two types of meshes and four types dust-proof felts. As the result, one guideline on dust-proof felt attachment with low resistance and low turbulence intensity will be proposed.

This paper describes how to design turbo-pump inducers for a micro satellite launcher. The authors organized NASA's design criteria (NASA SP series) and some current design studies. To evaluate the design procedures and the design criteria, we designed inducers and conducted performance tests using a cavitation tunnel. As a result of the test, it was confirmed that we successfully developed high performance inducers that caused no severe cavitation instability phenomena, at the design flow coefficients of 0.09 and 0.1.

The cavitation that occurs in fluid machinery using hydraulic oil is of a different form than the cavitation that occurs in water. The cavitation in hydraulic oil is dominated by gaseous cavitation caused by the separation of dissolved air. However, the cause of separation of dissolved air and the threshold values in flow field are still completely unclear. The author's research group developed a numerical model that defines the threshold value for determining the occurrence of gaseous cavitation in terms of “dynamic air separation pressure” which changes according to the unsteady flow field co cavitation. The practicality of this approach was verified in the cavitating flow field around cascade hydrofoil in hydraulic oil, which shape is for a torque converter. The gaseous cavitation model is added to commercial software Simcenter STAR-CCM+. The validity of the gaseous cavitation model is verified by comparing the numerical results with the experimental results.

It is requested that the hydroturbine be a small size and have high performance. Therefore, the contra-rotating rotors are suitable for a small hydroturbine, because it can be expected to achieve compactification of radial direction and high performance. However, a conventional contra-rotating rotor was composed of two axial flow rotors, so it had a specification suitable for high flow rate and low head. In order to achieve small hydroturbine suitable for low flow rate and high head, we propose a new type of contra-rotating rotors, which are composed of a hybrid rotor and a centrifugal rotor. In order to verify the feasibility of the small hydroturbine, we manufactured an experimental apparatus and investigated the performance of the hydroturbine. In the present paper, we compare the experimental results with the numerical analysis results, and the feasibility of the small hydroturbine was examined.