In order to investigate fundamental characteristics of three-dimensional corner separations of decelerating cascade flow, a channel flow around a NACA65 blade in a decelerating flow by turning was examined. Five-hole probe survey showed that the exit flow of the blade had a few similar points to the cascade flow in that the accumulation of the low-energy fluid on the corner part, the secondary flow and the pitchwise periodicity of the wake. PIV measurement showed that the focus-type separation was seen in the momentary streamline along the suction surface of the blade, whereas no apparent separation was seen in the flow along the endwalls. SD diagram consideration showed that the present case of the study was consistent with the relation between the stall indicator S and the diffusion parameter D proposed by Lei et al.

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Stall stagnation phenomena in the system of axial-flow compressors and ducts are studied on the basis of analytical results by a code on surge transients analysis and simulation with respect to a variety of delivery duct configurations coupled　with either a nine-stage compressor or a single stage fan. The stall stagnation boundary was found to be formed mainly by two zones, B- and A-boundaries. The B-boundary occurs for short and fat plenum-type delivery ducts. It is related with some limiting conditions of E.M. Greitzer's B parameter. The A-boundary, a newly-found one, occurs for narrow and long delivery ducts in the case of the suction duct with relatively short length. The boundary duct lengths are found to be compact compared with the wavelength of the fundamental resonance frequency of the system. More detailed features of the stagnation boundaries and the related flow behaviors will be presented in the next reports of this study.

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Phase resonance in Francis type hydraulic turbine is studied. Experimental and numerical studies have been carried out using a centrifugal fan. In the present study, comparisons between the pump mode and the turbine mode operations are made. The results show that the rotational direction of the rotor does not affect characteristics of the pressure fluctuation but the propagation direction of the rotor-stator interaction mode plays an important role. Flow rate fluctuations through the stator are examined numerically. It has been found that the blade passing flow rate fluctuation component can be evaluated by the difference of the fluctuating pressure at the inlet and the outlet of the stator. It was demonstrated that that the pressure fluctuation in the volute and connecting pipe normalized by using the flow rate fluctuation becomes the same for pump and turbine mode operations, and depends on the rotational direction on the interaction mode.

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In theis present paper, the authors we have particularly evaluated the influence of bubble coalescence and break-up in the “Multi-process Cavitation Model”, which takes the various elementary processes in cavitation into account based on the moment method, using CFD analysis around the hydrofoil of NACA0015. Although the coalescence and break-up changed the value of void fraction in the sheet cavity, the influence on the cavitation pattern and the surface pressure distribution was trivial. This result suggested that the modeling of coalescence and break-up under the assumption of the homogeneous medium is not so important for the improvement of the prediction accuracy of cavitation CFD.

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The newly invented “Dual Pressure Radial Turbine” has been developed and studied on the efficiency and non-dimensional flow rate characteristics. The radial turbine wheel has two radial inlets and one axial outlet, through those two inlets flows with high pressure and low pressure are induced. The characteristics of the turbine efficiency has small change from that of the design condition, with about 40%change of pressure and about 70%change of temperature at the low pressure turbine inlet. The “Dual Pressure Radial Turbine” is expected to be applied to low temperature waste heat recovery systems for any plants and reciprocating engines and to geothermal plants.

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In order to improve the performance of a forward curved fan, a dual stacked forward curved fan (DS fan) which is stacked impeller of the same diameter ratio is proposed. The internal flow of the fan is analyzed by the numerical simulation; the effect of the internal flow in the diffuser on the aerodynamic characteristics is considered. The results of the simulation indicated that the fan could create the high dynamic pressure at the vicinity of the end of the scroll diffuser because the uniform outward flow was formed over the wide span domain. Furthermore, the simulation gave the information that the static pressure of the DS fan increased 28.3%than the current forward curved fan when the outlet angle of the diffuser was 20°.

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