As a radial turbine applied to automotive turbochargers, a variable flow capacity turbine becomes very important to satisfy demands of less fuel consumption and emissions, recently. Especially, a variable nozzle, which can control a turbine wheel inflow velocity, is an indispensable component for diesel engines both of passenger and commercial vehicles in order to achieve high boosting and low pressure loss at engine low end to rated power operations.

In order to improve a variable nozzle turbine performance, the author clarified a relation between a nozzle passage profile and a turbine performance. About four different nozzle vane profiles, CFD calculations and turbine performance tests were conducted and it was revealed that nozzle passage length and inlet to outlet area ratio have a large influence to pressure loss coefficient of a variable nozzle and a turbine efficiency.

Rotordynamic fluid forces and a mechanism of their occurrence were examined in experiments and computations for a closed type centrifugal impeller in whirling motion. The force on a front shroud was a main component of the rotordynamic fluid force. Velocity disturbances in a clearance between the front shroud and a casing were caused by an eccentricity of the impeller and a squeeze effect due to the whirling motion of the impeller. Appling the Bernoulli equation to swirling flow in the clearance in a relative coordinate fixed on the whirling motion, the pressure disturbance which generated the rotordynamic fluid force could be reasonably explained.

Downsizing and improvement of efficiency in a centrifugal pump have been required still now. It is well known that the flow instability such as a positive slope in Q-H curve, rotating stall often may appear in case of the above advanced design. Though a lot of studies of flow instability in a pump were carried out by experimental and computational approaches up to now, this generating mechanism was not clarified quantitatively.

In this study, we made the one stage model test facility for measuring both the performance and the internal flow. By use of this test facility, we found the rotating stall in the diffuser influences the positive slope mechanism in Q-H curve. The characteristics of the rotating stall were clarified by experiments and computations. The simulation results have good agreement with the experiments quantitatively.

Three model pump sumps with geometrical similarity are constructed to study the similarity law in the flow of pump sump.Changing the flow rate and water height,the critical submergences for both air entraining vortex and submerged vortex are measured in each sump.For the air entraining vortex, there are two limits of critical submergence,one is proportional to the flow rate or velocity at bell inlet,the other is almost independent from flow rate.The former is mainly under the effect of Froude number,but the similarity on later limit is not clear.For the submerged vortex, the critical line is not clear in the smallest model.The power coefficient, n, for the similarity law estimated from above limits becomes between the same velocity case (n=0) and the same Reynolds number (n=1), both for the air-entraining vortex and for the submerged vortex.

Rocket engine tubopumps adopt balance piston (BP) in order to balance large axial thrust generated from high discharged pressure of the pump. BP is a self-thrust balancing system and quasi-statically stable, but might become unstable due to compressibility of liquid hydrogen, one of the major propellants of rocket. Conventional BP design methods mainly focused on the static characteristics such as thrust balancing ability and volumetric loss. However, a dynamic characteristic, that is stability of axial direction, is not well considered. In this paper the relationship between static and dynamic characteristics are investigated by numerical and theoretical study, and it is concluded that static and dynamic characteristics should be considered simultaneously in BP design.