• Title, Summary, Keyword: Waterjet

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Preliminary power predication of waterjet driven craft (Waterjet 추진선의 초기 성능추정)

  • 최군일
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • pp.90-94
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    • 2001
  • A Waterjet has been widely used for the propulsion of various speed range of marine vehicles due to its many advantages compared with the conventional screw propellers. In this paper, a power prediction based on momentum flux method is presented for the preliminary estimation of required power and selection of propulsion system for the waterjet driven craft. A theoretical basis of the mechanism of the waterjet is given and some of the empirical formulas are given as well. Finally the influence of intake type and nozzle exit velocity on the efficiency will be discussed.

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A Study on Waterjet Fracture Mechanism for Granitic Rocks (화강암에 대한 워터젯 파쇄 메커니즘에 관한 연구)

  • Oh, Tae-Min;Cho, Gye-Chun
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.643-648
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    • 2010
  • Waterjet is a very useful technology for rock excavation because of low level noise and vibration during breaking rocks. To accurately predict the volume and shape excavated by the waterjet, it is important to understand waterjet fracture mechanisms. There have been various theoretical assumptions and approaches in the literature. In this study, waterjet mechanisms are classified into three standards: a mechanism scale, theoretical assumption for a target material, and jet phase. In addition, through a waterjet experimental study for weathered and intact granitic rocks, a fracture shape is observed and analyzed on comparison with the previous mechanisms. As a result, best waterjet mechanisms are selected to explain the fracture pattern of the granitic rocks.

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Design and Analysis for the POD Type Waterjet System (POD형 물분사 추진장치의 설계 및 성능해석)

  • Kim, Moon-Chan;Chun, Ho-Hwan;Park, Won-Kyu;Byun, Tae-Young;Kim, Jong-Hyun;Suh, Sung-Bu
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.3
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    • pp.290-298
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    • 2005
  • A study of design and analysis for the POD type waterjet is conducted. The analysis and design of waterjet system are more difficult than that of conventional propulsor because waterjet is complicatedly composed of many parts which are impeller, stator, inlet, nozzle, etc. The streamline method is traditionally used in the design of pump whose characteristics are similar to those of waterjet. This streamline method, however, has some limitation in analysis of a viscous flow as well as the interaction of inlet part of hull. In the present study, the developed CFD program is applied to the analysis of POD type waterjet. The developed program is first validated by comparing the existed experimental results. The designed waterjet system is also analyzed by the developed CFD program and analyzed results show that the performance of the present POD type waterjet is above the requirement.

Comparative study on the performance of Pod type waterjet by experiment and computation

  • Kim, Moon-Chan;Park, Warn-Gyu;Chun, Ho-Hwan;Jung, Un-Hwa
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.2 no.1
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    • pp.1-13
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    • 2010
  • A comparative study between a computation and an experiment has been conducted to predict the performance of a Pod type waterjet for cm amphibious wheeled vehicle. The Pod type waterjet has been chosen on the basis of the required specific speed of more than 2500. As the Pod type waterjet is an extreme type of axial flow type waterjet, theoretical as well as experimental works about Pod type waterjets are very rare. The main purpose of the present study is to validate and compare to the experimental results of the Pod type waterjet with the developed CFD in-house code based on the RANS equations. The developed code has been validated by comparing with the experimental results of the well-known turbine problem. The validation also extended to the flush type waterjet where the pressures along the duct surface and also velocities at nozzle area have been compared with experimental results. The Pod type waterjet has been designed and the performance of the designed waterjet system including duct, impeller and stator was analyzed by the previously mentioned m-house CFD Code. The pressure distributions and limiting streamlines on the blade surfaces were computed to confirm the performance of the designed waterjets. In addition, the torque and momentum were computed to find the entire efficiency and these were compared with the model test results. Measurements were taken of the flow rate at the nozzle exit, static pressure at the various sections along the duct and also the nozzle, revolution of the impeller, torque, thrust and towing forces at various advance speed's for the prediction of performance as well as for comparison with the computations. Based on these measurements, the performance was analyzed according to the ITTC96 standard analysis method. The full-scale effective and the delivered power of the wheeled vehicle were estimated for the prediction of the service speed. This paper emphasizes the confirmation of the ITTC96 analysis method and the developed analysis code for the design and analysis of the Pod type waterjet system.

A Study on the Waterjet Propulsion in Model Scale (워터제트 추진 모형시험에 대한 연구)

  • 최균일
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.5
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    • pp.474-481
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    • 1997
  • Waterjet propulsion generally refers to propulsion of ships by internally mounted pumps with proper ducting. This arrangement of the actuator component of the system leads to the fundamental differences with respects to screw propeller system. In this paper, the basic hydrodynamic characteristics of waterjet propulsion was outlined to clarify the application consideration and proposal for carrying out model self-propulsion tests with waterjet propelled models was presented. The results of model self-propulsion tests carried out in the Hyundai Maritime Research Institute towing tank with catamaran ship were presented.

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Computational study on turbulent flows inside the duct of marine waterjet propulsor (선박 워터제트 추진기 덕트 내부의 난류유동 해석에 관한 연구)

  • Park Il-Ryong;Kim Wu-Joan;Ahn Jong-Woo;Kim Ki-Sup
    • Proceedings of the KSME Conference
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    • pp.181-184
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    • 2002
  • CFD calculations are carried out to investigate the turbulent flow characteristics inside the duct of marine waterjet propulsors. The Reynolds-averaged Wavier-Stokes equations are solved using a finite-volume method. Standard $k-{\varepsilon}$ model and realizable $k-{\varepsilon}$ model are evaluated with an existing experimental data. Multi-block grid topology is adopted to describe the details of complex duct geometry. The present numerical methods are applied to the preliminary duct design of new waterjet propulsor system. Four different influx conditions are simulated to find out pressure and velocity distribution inside the intake duct. Attention is also paid upon the possible flow separation inside the waterjet duct. It is found that CFD tools can be used for the initial evaluation of inflow condition into the impeller of waterjet propulsor system.

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Characteristics of Cut Surface by Abrasive Waterjet Cutting of Titanium Alloy (티타늄 합금의 연마제 워터 제트 절단에 의한 절단표면 특성)

  • Chung Nam-Yong;Jin Yun-Ho
    • Journal of Welding and Joining
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    • v.23 no.1
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    • pp.86-93
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    • 2005
  • Abrasive waterjet (AWJ) can provide a more effective means for precision of difficult -to-machining materials such as ceramics and titanium alloys. The present study is focused on the surface roughness of abrasive waterjet cut surfaces. This paper investigated theoretical and experimental surface characteristics associated with abrasive waterjet cutting of titanium alloy Gr2. It is shown that the proper variations of several cutting parameters such as waterjet cutting pressure, cutting speed and cutting depth improve the roughness and characteristics on specimen surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of titanium alloy Gr2, the optimal cutting conditions to improve the surface roughness and precision were proposed and discussed.

Development of a Plasma Waterjet Scrubber for the Reduction of PFCs (과불화탄소 제거를 위한 플라즈마 워터젯 스크러버 개발)

  • Lee, Chae-Hong;Chun, Young-Nam
    • Journal of Korean Society for Atmospheric Environment
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    • v.26 no.6
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    • pp.624-632
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    • 2010
  • Perfluorocarbons (PFCs) are widely used in semiconductor industry. These gases need to be removed efficiently because of their strong absorption of infrared radiation and long atmospheric lifetimes which cause the global warming effect. To destruct $CF_4$, a waterjet gliding arc plasma was designed and manufactured. The highest $CF_4$ destruction showed at waterjet plasma case, compared to plasma discharge only or water scrubber only, respectively. In addition, it could be known that the $CF_4$ destruction should be associated with the electron and OH radicals. The operating conditions such as waterjet flow rate, initial $CF_4$ concentration, total gas flow rate, specific energy input were investigated experimentally using a plasma waterjet scrubber. Through the parametric studies, the highest $CF_4$ destruction of 94.5% was achieved at 0.2% $CF_4$, 2.1 kJ/L SEI, 20 L/min total gas flow rate and 18.5 mL/min waterjet flow rate.

Cutting Characteristics of Quartz by Abrasive Waterjet (연마제 워터 제트에 의한 쿼츠의 절단특성)

  • Jin, Yun-Ho;Chung, Nam-Yong;Kim, Kyung-Hoon
    • Proceedings of the KSME Conference
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    • pp.922-927
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    • 2004
  • Abrasive waterjet (AWJ) cutting is an emerging technology for precision cutting of difficult-to-machining materials with the distinct advantages of no thermal effect, high machinability, high flexibility and small cutting forces. This paper investigated theoretical and experimental cutting characteristics associated with abrasive waterjet cutting of quartz GE214. It is shown that the proper variations of several cutting parameters such as waterjet pressure, cutting speed and cutting depth improve the roughness on workpiece surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of quartz GE214, the optimal cutting conditions to improve the surface roughness were proposed and discussed.

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Cutting Characteristics of Quartz by Abrasive Waterjet (연마제 워터 제트에 의한 쿼츠의 절단특성)

  • Chung, Nam-Yong;Jin, Yun-Ho
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.2
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    • pp.118-126
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    • 2005
  • Abrasive waterjet (AWJ) cutting is an emerging technology for precision cutting of difficult-to-machining materials with the distinct advantages of no thermal effect, high machinability, high flexibility and small cutting forces. This paper investigated theoretical and experimental cutting characteristics associated with abrasive waterjet cutting of quartz GE214. It is shown that the proper variations of several cutting parameters such as waterjet cutting pressure, cutting speed and cutting depth improve the roughness on workpiece surfaces produced by AWJ cutting. From the experimental results by AWJ cutting of quartz GE214, the optimal cutting conditions to improve the surface roughness and precision were proposed and discussed.