The characteristics of cycloidal propellers, which is aimed to be installed on airships, were analyzed numerically with two and three dimensional vortex methods. Three dimensional calculated results of the thrust and flows around the propeller explained the experimental results and also suggested the importance of the wing tip vortices on the flows. Calculations for propellers with the elliptic wings and rectangular wings of large aspect ratio were carried out to find an efficient wing shape. It was clarified that thrust values obviously increased in case of the large aspect ratio wings.
For the further improvement of aerodynamic performance of a radial turbine with the variable nozzle system. which is designed for the application of automotive turbocharger, the clarification for the influence of the setting angle of nozzle vane on the internal flow of the radial turbine is required. However, it is very difficult to perfom the experimental measurements for the internal flow of a radial turbine because of the small size and the high rotational speed of a radial turbine. In this study, the numerical computations were carried out for the flow in the radial turbine model at three inlet flow angles which were estimated from the setting angle of nozzle vane. The computed results revealed that the behaviors of flow in the nozzle region near the turbine inlet and the complex secondary flow and the associated loss generation in the radial turbine were affected by the inlet flow angle.
A prototype pump performance converted from its model pump performance shows an increase in efficiency compared with that of the model pump. This paper discusses if this increase results in an increase in pump head or in a decrease in input power, based on the relationship between tangential force on impeller blades, head loss and input power. It was clarified that a part of the efficiency increase brings about input power decrease, as the tangential force on the blades constitute a part of input power of a pump.
Experiments on Savonius rotor and Bent-blade rotor with two curved plate blades which were bent twice by two corners were conducted to confirm characteristics and to augment output power. From the results of experiments, the rotors with different bend angle showed some interesting behaviors to develop the action region in the rotational speed, and to augment the output power coefficient compared with the normal rotor. At the bend angle of 60 degrees, the output power coefficient reached the value of 1.13 times that of the normal Savonius rotor.
The aim of this investigation was to improve power performance of Savonius hydraulic turbine utilizing small stream for electric generation. An attempt was made to increase the power coefficient of runner by use of a flat shield plate placed upstream of the runner. The difference of the power coefficient is discussed in relation to a rotation direction of the runner and with/without the shield plate. The flow field around the runner was also examined visually to clarify influences of installation conditions on the power performance. From this study it was found that the power performance of the Savonius runner is drastically changed by the use of shield plate and with the rotation direction, and then the maximum power coefficient of runner is achieved for 47 %.
Three inducers were designed to avoid cavitation instabilities. This was accomplished by avoiding the interaction of tip cavity with the leading edge of the next blade. The first one was designed with extremely larger leading edge sweep, the second and third ones were designed with smaller incidence angle by reducing the inlet blade angle or increasing the design flow rate, respectively. The inducer with larger design flow rate has larger outlet blade angle to obtain sufficient pressure rise. The inducer with larger sweep could suppress the cavitation instabilities in higher flow rates more than 95% of design flow rate, owing to weaker tip leakage vortex cavity with stronger disturbance by backflow vortices. The inducer with larger outlet blade angle could avoid the cavitation instabilities at higher flow rates owing to the extension of the tip cavity along the suction surface of the blade. The inducer with smaller inlet blade angle could avoid the cavitation instabilities at the flow rates larger than the design flow coefficient, owing to the occurrence of the cavity first in the blade passage and its development upstream. The cavity shape and suction performance were reasonably simulated by three dimensional CFD computations under the steady cavitating condition, except for the backflow vortex cavity. The difference in the growth of cavity for each inducer is explained from the difference of the pressure distribution on the suction side of the blades.