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Cavitation instabilities such as rotating cavitation and cavitation surge often occur in high speed turbopumps. In the present study, numerical simulation of cavitation surge, which numerically solves the one-dimensional momentum and... more
Cavitation instabilities such as rotating cavitation and cavitation surge often occur in high speed turbopumps. In the present study, numerical simulation of cavitation surge, which numerically solves the one-dimensional momentum and continuity equations with modelled dynamic cavitation characteristics, is conducted. The phase lag of cavity response against the inlet pressure and the suction flow rate variations is modeled in the form of the first-order lag system considering that the frequency of cavitation surge is small. Differently from linear stability analysis made in our previous study, the equations are solved in time domain with retaining some of non-linear terms. The method is validated through the comparison with the stability analysis. Then the effect of phase lags in dynamic cavitation characteristics is examined.
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ABSTRACT This article describes about various types of cavitation instabilities including rotating cavitation and alternate blade cavitation. In section 1, general characteristics of cavitating flow through turbopump inducers are... more
ABSTRACT This article describes about various types of cavitation instabilities including rotating cavitation and alternate blade cavitation. In section 1, general characteristics of cavitating flow through turbopump inducers are reviewed. In section 2, rotating cavitation in 3- and 4-bladed inducers are discussed focusing on the effect of the number of blades. Section 3 is intended to show the relationship between the operating condition and various types of cavity oscillations in an inducer.
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ABSTRACT Control valves of the main steam flow for power plants are operated under wide range of valve openings and pressure ratios. In the present paper, experimental and numerical investigations are described in order to clarify... more
ABSTRACT Control valves of the main steam flow for power plants are operated under wide range of valve openings and pressure ratios. In the present paper, experimental and numerical investigations are described in order to clarify mechanisms of the valve head vibration. Experiments are conducted with two types of the valve head support. One is a flexible support and the other one is with an exciter. Results show that valve head vibrations with large amplitude appear with the flexibly supported valve head under certain range of valve openings and the pressure ratio. With the valve head exciter, dynamic fluid forces are measured. Results show that the added damping force becomes negative around the condition where the valve head oscillation is observed with flexible support. Numerical analyses are carried out in order to observe the flow field. In the simulations, forced vibrations of valve head are assumed. Results show that the pressure distribution on the valve head surface changes depending on the excitation frequencies, and as a result, the negative damping force occurs.
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Unsteady behaviors of free surface around a rotating vertical shaft in cylindrical stationary casing were investigated. Experiments were carried out with various rotating frequency of the shaft at two initial water levels. An... more
Unsteady behaviors of free surface around a rotating vertical shaft in cylindrical stationary casing were investigated. Experiments were carried out with various rotating frequency of the shaft at two initial water levels. An axi-symmetrical free surface oscillation took place when the rotational speed of the shaft became larger than a certain value. The frequency of the free surface oscillation decreased as the rotating frequency increased. A theoretical model was developed, and the mechanisms of the free surface oscillation were clarified. The oscillation was found to be a sloshing mode excited by the change of fluid angular velocity, caused by the change of wetted areas on the inner rotating shaft and outer stationary casing, associated with the change in free surface height.
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This paper describes experimental and analytical results of rotating cavitation. There are four major sections in this paper. The first section presents the main characteristics of rotating cavitation which was found in the inducer test... more
This paper describes experimental and analytical results of rotating cavitation. There are four major sections in this paper. The first section presents the main characteristics of rotating cavitation which was found in the inducer test using a water tunnel. The second section describes the rotating cavitation which occurred in the development test of an LE-7 liquid oxygen pump for the H-II rocket. Also described in this section is how the rotating cavitation was suppressed. The rotating cavitation was the cause of both super synchronous shaft vibration and an unstable head coefficient curve. The third section presents how the theory of rotating cavitation was developed. The final section shows the measured cavitation compliance and mass flow gain factor of the LE-7 pump inducer for comparison of the experimental and analytical results of the rotating cavitation of the LE-7 pump inducer. Almost all the information presented in this paper has already been reported by Kamijo et al. (1977, 1980, 1993, 1993) and by Shimura (1993). In the present paper, the authors attempt to combine and give a clear overview of the experimental and analytical results described in the previous papers to systematically show their experience and findings on rotating cavitation.
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Research Interests: Materials Science, Mechanics, Instability, Cavitation, Thrust, and 3 moreInertia, Propellant, and Inducer
The singularity method, a kind of boundary element method, is applied to a cross flow fan, which is widely used for household separate types of air-conditioners. A potential flow analysis is carried out for the cross flow fan with a... more
The singularity method, a kind of boundary element method, is applied to a cross flow fan, which is widely used for household separate types of air-conditioners. A potential flow analysis is carried out for the cross flow fan with a complicated shape of casing. The flow is modeled by bound source/vortex distributions on the boundaries and blades, and free vortices shed from the impeller blades following Kelvin’s circulation theorem. Numerical simulation results are in good agreement with experimental results.
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During the firing test of the LE-7A LOX/LH2 engine of the HIIA rocket, a large amplitude rotor vibration of the fuel turbopump occurred at a frequency of about 350 Hz which is about one-half of the shaft rotational frequency V5700 Hz. The... more
During the firing test of the LE-7A LOX/LH2 engine of the HIIA rocket, a large amplitude rotor vibration of the fuel turbopump occurred at a frequency of about 350 Hz which is about one-half of the shaft rotational frequency V5700 Hz. The vibration occurred when the pump inlet pressure was reduced. This vibration caused the failure of the bolts fastening the bearing cartridge. To investigate into this phenomenon, a series of tests were conducted at full speed with liquid hydrogen and the results are reported by Shimura et al. @1#.