For centrifugal compressors with high stage pressure ratio, an unshrouded impeller is generally used. The impeller performance deteriorations are caused by the pressure loss due to the vortex of tip leakage flow and its mixing with impeller's main flow. On the other hand, the amount of tip clearance is varied by the change of the compressor operating conditions. Therefore, in order to ensure the compressor performance, we need to know precisely how much tip clearance exists at the actual centrifugal compressor operating condition.

From these back grounds, authors developed a tip clearance measurement method with capacitive gap sensors. Tip clearance measurements were conducted for several rotational speeds and flow rates to reveal the effect of the compressor operating conditions on the impeller tip clearance. Finally, the transient tip clearance measurement during the surge was also conducted to evaluate the unsteady rotor behavior within the surge cycle.

Balance Piston（BP）Mechanism is used in rocket engine tubopumps in order to balance large axial thrust generated from high discharged pressure of the pump. BP mechanism is a self-thrust balancing system and quasi-statically stable, but might become unstable due to compressibility of the operation fluid in BP. Recently open impeller, which has no front should, is often selected for rocket turbopump because it can be manufactured easily compared to closed impeller. It is concerned about coupling of impeller deformation and acoustic vibration in BP chamber fluid because an open impeller with large diameter has low stiffness. However, coupling of structure（impeller）and acoustic（BP chamber fluid）vibration has not been investigated. In this paper the relationship between static and dynamic characteristics are investigated with simplified model by numerical simulation, and it is concluded that low stiffness of structure and resonance of structure and acoustic frequency causes coupled vibration.

In order to recover hydraulic energy such a discharge channel of small hydropower plant, the performances of an undershot water turbines were experimented by a water tunnel. The width of the channel was much wider than the blade width and the impeller was installed sufficiently apart from the bottom surface of the channel. One of the criteria for the high efficiency turbine was to set the solidity to approximately 0.4. This result could explain that increasing the number of blades and chord length could not necessarily contribute the improvement of the performance. The momentum analysis of the blade element proposed in this study could represent the output of the water turbine with the solidity 0.4 in the vicinity of the design point.

In this study, in order to enhance the effect of circumferential groove casing treatment on the improvement of the aerodynamic performance of axial compressor, the influences of axial location of single groove on the flow field and the loss generation in a low speed axial compressor rotor were investigated numerically. Flows in the compressor with and without the groove were computed and then the comparison of computed results clarified following phenomena. The groove weakens the tip leakage flow by the decrease of the blade loading and consequently shifts the interaction position between the main flow and the tip leakage flow toward the downstream. This trend is intensified when the groove is installed at higher blade loading location. Meanwhile, although the groove decreases the loss generation caused by the tip leakage vortex, the total loss generation is increased due to the additional loss attributed to the application of groove.

Performance conversion methods for hydraulic turbines and pump-turbines have been established as international and domestic standards to transpose from the model performance to the corresponding prototype performance. The up-to-date standards and their performance conversion take into account of the surface roughness of each flow passage component of machines. As a result, the performance conversion methods came to include the complicated calculation and its procedure. Therefore, the simplification of performance conversion methods has been expected by the users and engineers from the practical point of view. In this study, the performance conversion method is simplified considering the general capacity of measuring devices in model test equipment used by domestic manufacturers and the typical surface roughness of the flow passage components of prototype machines.