Masanori Aoki

A Theoretical Analysis of Alternate Blade Cavitation in Inducers

An analysis of alternate blade cavitation on flat plate cascade is made using a singularity method based on a closed cavity model. In the steady flow analysis, it was found that two kinds of steady cavitation patterns exist. One is equal length cavitation in which the cavity lengths of all blades are the same. The other is alternate blade cavitation in which the cavity length changes alternately from blade to blade. Although the present model fails to predict the range of cavitation number where alternate blade cavitation occurs, it predicts alternate blade cavitation fairly well in terms of cavity length. A parameter study shows that the development of alternate blade cavitation is quite different depending on the solidity of cascade. The stability of equal length and alternate blade cavitation is then examined allowing the cavity length freely to change. It was found that alternate blade cavitation is stable for the cascades with larger solidity and unstable for the cascades with smaller solidity. The equal length cavitation is stable in both cases only in the region of cavitation number larger than that where the alternate blade cavitation solution separates from the equal length cavitation

An electromagnetically driven univalved artificial heart

A wide variety of clinical blood pumps including powering systems have been developed and evaluated for totally implantable support systems [1–6]. However, there are still several serious problems, such as thromboembolic episodes, size, and weight, affecting prolonged survival of a total system inside the body.

Appearance of Inlet Reverse Flow and Pressure Distributions on the Surface of a Suction Pipe in a Helical Inducer.

The relationship between the growth of inlet reverse flow and the change in separation point in a suction flow was studied experimentally in a helical inducer. The relationship between the decrease in flow rate and the change in pressure distribution on a suction pipe wall was examined in detail at the point where the inlet reverse flow occurs. Furthermore, flow visualization, with the aid of the streakline method, was carried out to observe the occurrence of flow separation in the suction pipe flow. As a result of the present study, it is confirmed that the separation in a suction pipe occurs just upstream of the inlet reverse flow region. It is also known that the adverse pressure gradient appears in the pipe flow in the partial capacity range, which may be considered as a cause of the suction flow separation.

Inception of Inlet Reverse Flow in Centrifugal Pump Impeller.

In the previous reports, effects of an impeller blade tip clearance and the blade number on the inlet reverse flow starting point were clarified for three and five blades open-type and closed-type impellers with good suction performences. Then, in this paper, for the close-type and open-type impellers with the blade inlet angle decided by conventional design method, the same experiment was carried out to know effects of the blade inlet angle on the inlet flow condition at low flow rates and the inlet reverse flow starting point, and the results were compared with the previous ones. Furthermore, the inlet reverse flow occurrence mechanism of the centrifugal pump impeller was examined based on the experimental results. It was particularly shown that the inlet reverse flow inception point can be predicted by investigating the relative flow along the impeller shroud surface.