• Journal of the Society of Naval Architects of Korea
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• v.41 no.5
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• pp.21-27
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• 2004

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious military vehicles because of a good maneuverability at low speed, good operating ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. Especially, compact design is important for the tracked-vehicle because of buoyancy in water and available space inside the tracked vehicle. The experiment is parametrically performed for various impeller diameters for more compact design. The experimental results are analyzed according to the ITTC 1996 standard analysis method as well as the conventional propulsive factor analysis method. The full-scale effective and delivered power of the tracked-vehicle are evaluated according to the variation of impeller diameter. This paper emphasized the effect of impeller diameter on the performance of waterjet system.

• The KSFM Journal of Fluid Machinery
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• v.4 no.3 s.12
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• pp.39-45
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• 2001

It is reported recently that the pump head deterioration near the best efficiency point, from single-phase flow to the choke due to air entrainment became less in a screw-type centrifugal pump than in a general centrifugal pump. Moreover, at a narrow tip clearance, the pump head became partially higher in two-phase flow than that in single-phase flow. However, the internal pressure fluctuations on this pump due to air entrainment have not been studied yet. For that reason, we have examined the influences of void fraction, flow coefficient and impeller tip clearance on pressure fluctuations in the casing. The void fraction became larger, the influence of tip clearance on pressure distribution became less.

• The KSFM Journal of Fluid Machinery
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• v.6 no.3 s.20
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• pp.58-63
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• 2003

The performance of turbo pump drops rapidly and it gets into break-down when the void fraction reaches above the threshold value because the impeller flow passage is choked up with air bubbles. Phenomenological understanding of break-down and pumping recovery mechanisms under air-water two-phase flow conditions are therefore important for pump designers and essential assignment for researchers. In this paper, we investigated the characteristics of break-down and pumping recovery due to entrained air occurring inside a screw-type centrifugal pump which has a wide flow passage mainly through the findings of suction and discharge pressures, rotational speed, flow rate measurements and visualization.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.150-155
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• 2012

Water jet propulsion system has low efficiency than screw propeller at low speed, but has been applied in high speed ship due to its better cavitation performance and high rotation capacity. In this study, a numerical analysis was conduct to understand the flow in the propulsion system of 200HP grade water jet for small ship. As the result, it could be confirmed that total pressure and force of the flow was increased through the impeller and the straight-ability of discharging flow to outlet was improved by guide vane. Also, the reliability of numerical analysis was secured by comparing peripheral velocity calculated by design values with that calculated by numerical analysis.

• Proceedings of the IEEK Conference
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• 2002.06e
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• pp.219-222
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• 2002

There are screw, reciprocating type turbo compressor by structure in an air compressor which is essential equipment on the industrial spot. Recently, the application range of a turbo compressor tend to be wide gradually. And this type of compressor needs high speed rotation of impeller in structure so high ratio gearbox and conventional induction motor driving required. This mechanical system have results of increased moment of inertia and mechanical friction loss. Recent studies of modern turbo compressor have been applied to developing super high speed BLDC motor and driver which remove gearbox that make its size small and mechanical friction loss minimum. To accomodate this tendency, we tried to develope a super high speed motor drive system for 150Hp, 70,000rpm direct drive Turbo compressor using DSP(Digital Signal Processor) and SVPWM(Space Vector Modulation PWM) technique. The results of this specific application show that super high speed driver and controller could be implemented well with digital electronics.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.6
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• pp.879-884
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• 2002

There are screw, reciprocating and turbo compressor by structure in an air compressor, essential equipment on he industrial spot. Resently it is wide that the range of turbo compressor's use in gradual, turbo compressor needs high speed rotation of impeller in structure, high rated gearbox and conventional induction motor. This mechanical system increased the moment of inertia and mechanical friction loss. Resently the study of turbo compressor applied super high speed motor and drive, removing gearbox made its size small and mechanical friction loss minimum. In this study we tried to develope variable super high speed motor drive systems for 150Hp, 70,000rpm drect drive Turbo compressor. The result of study is applied to a 150Hp direct turbo compressor and makes it goods.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.197-204
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• 2005

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious armored wheeled vehicles because of a good maneuverability at low speed, good operation ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. The POD type waterjet is adequate for the present wheeled vehicle because the weight is lighter and L/B is longer than the conventional armored amphibious vehicle. Resistance and self-propulsion tests with a 1/3.5-scale model are conducted at PNU towing tank. Based on these measurements, the performance is analyzed according to ITTC 96 standard analysis method and also according to the conventional propulsive factor analysis method. Based on these two methods, the full-scale effective and delivered powers of amphibious armored wheeled vehicle are estimated. This paper emphasizes the analysis method of model test of the waterjet propulsion system for a amphibious armored wheeled vehicle and the model test technique together with the comparison of the two analysis methods.