The effect of vertical flows for the performance of gyro-mill wind turbines are studied. Pumping air into the inside of the rotating blades has negative effect. However the suction flow from the same region is effective. In the latter case, the total flow volume into the wind-mill increases, and the three-dimensional flow is expected to drive the rear-side blades. The present study is performed by a motored fan, but the same flows should be obtained by motor-free low pressure generators such as a diffuser and so on.
A left ventricular assist device (LVAD) is also used for right ventricular assist because a right ventricular assist device (RVAD) does not exist. In that case, the LVAD is operated at off-design point and can damage the blood. Therefore, our research group has been working on the development of the RVAD in recent years. In the present study, we investigated the effects of the clearance of dynamic pressure bearings and the mass of the impeller on the motion of the impeller of the RVAD under development. Performance tests of the RVAD were carried out and the motion of the impeller was analyzed by two laser displacement sensors and a high-speed video camera. The time-averaged motion of the impeller was a revolution on a circular orbit centered on a position eccentric to the outlet direction of the casing. The predominant frequency of the impeller motion was about the half of the rotational frequency, which was thought to be due to the so-called oil whirl observed in general journal bearings. The impeller rotated without mechanical contact when the clearance of the bearing was 60, 70, and 80 mm for a titanium impeller and 80 mm for a stainless steel impeller. From this fact, it was found that the optimum value exists in the clearance of the bearing, and the lighter the impeller, the wider its range.
The diffuser rotating stall (DRS) is one of the biggest problems in pumps because unstable flow and pressure fluctuations are induced and the pump operating range is severely limited. The objective of this research is to suppress pressure fluctuation by machining slits to the diffuser vanes and confirm the effect on pump characteristics. In the experiment, two kinds of vaned diffuser, with and without slits, were investigated and time history of static pressure in the two diffuser passages were measured. Then, the data processing of wave form was conducted by Fast Fourier Transform (FFT) analysis. The shaft rotating speed dependency on the instability phenomena, the amplitude of pressure fluctuation and the onset flow rate of DRS was summarized.