• Title/Summary/Keyword: Propellers

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Setup Data Generation for Positional 5-axis Machining of Die and Mold (금형의 고정형 5축 가공 시 공구자세 셋업 정보 산출시스템 개발)

  • Lee, Jung-Geun;Yang, Seong-Jin;Park, Jung-Whan
    • Korean Journal of Computational Design and Engineering
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    • v.13 no.5
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    • pp.382-390
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    • 2008
  • Five-axis machining has been applied to manufacture of turbine blades, impellers, marine propellers. Nowadays it extends to mold & die machining, where more productivity as well as added value is expected. The five-axis machining can be divided into positional and continuous, according to the variableness of tool orientation during material removal process. The positional five-axis machining is commonly applied to the regional machining on a whole part surface in mold manufacturing industry, where the tool orientation for each region (area) should be determined to be feasible, that is, avoiding any interference such as machine tool collision, etc. Therefore it is required for a CAM programmer to decide a feasible tool orientation in generating tool-paths on a designated area, because it is a very tedious job to obtain such information by utilizing a commercial CAM system. The developed system generates feasibility data on tool orientation and machining region, which facilitates the CAM programmer's decision on a feasible tool orientation.

Analytic study of a new conceptual propulsion device for ships

  • Muscia, Roberto;Sciuto, Giacomo
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.2 no.2
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    • pp.75-86
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    • 2010
  • In this work the possibility of obtaining a rectilinear motion of bodies partially or totally submerged without using propellers is evaluated. The system propulsion is based on a pair of counter rotating masses that generate the thrust. The fluid-body system has been schematized in order to carry out a very simple model. Using this model an evaluation of the body motion along a longitudinal direction was performed. The motion equations of the system were written and integrated. The external forces applied to the body depend on its velocity in relation to the water. These forces were obtained by fluid dynamic simulations. Regarding the mechanical configuration suggested, the results obtained show that a certain displacement of the body along a fixed direction is obtainable.

Numerical Analysis of Underwater Propeller Noise(Part 1. Non-Cavitating Noise) (수중 프로펠러의 소음 예측에 관한 연구(Part 1. 비공동 소음))

  • 설한신;이수갑;표상우;서정천
    • Journal of the Society of Naval Architects of Korea
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    • v.41 no.2
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    • pp.21-32
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    • 2004
  • The non-cavitating noise of underwater propeller is considered numerically in this study. The main purpose is to analyze non-cavitating noise from underwater propellers in various operating conditions with different configurations. Noise is predicted by using time-domain acoustic analogy, boundary element method, and computational hydro-acoustics. The flow field is analyzed with potential-based panel method, and then time-dependant pressure data are used as the input for Focus Williams-Hawkings formulation to predict far field acoustics. Furthermore, boundary element method and computational hydro-acoustics are also considered to investigate duct propeller and ducted multi-stage propeller to consider the reflection and diffraction of sound waves. With this methodology, noise intensity and directivity of each noise sources could be well analyzed.

CL-data Optimization of 5-axis Face-milling Via C-space and Effective-radius Map (C-space 및 유효반경-맵을 이용한 5축 페이스 밀링의 공구자세 최적화에 관한 연구)

  • 박정환;이정근
    • Korean Journal of Computational Design and Engineering
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    • v.7 no.1
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    • pp.34-41
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    • 2002
  • Five-axis NC machining, in general, is utilized in fabricating impellers, turbine blades, marine propellers that can be machined more effectively rather than three-axis machining. There have been many researches concerning tool interference avoidance, optimization of tool orientation. The C-space or Configuration-space was originated from the robotics area, which depicts interference-free joint-values in motion planning. In the paper we propose an optimizing scheme by which the maximum effective-radius of a face-milling cutter can be achieved for each CC(cutter-contact) point. Also the concept of a C-space for a CC point, the effective-radius map for 5-axis face-milling, and some illustrative examples of marine propeller machining, are presented.

On the Model Tests for POD Propulsion Ships

  • Go Seokcheon;Seo Heungwon;Chang Bong Jun
    • Journal of Ship and Ocean Technology
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    • v.9 no.1
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    • pp.1-10
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    • 2005
  • The procedures of model test and performance prediction for the CRP-POD propulsion ships, are studied. At the CRP-POD system, which are highly applicable to ultra large container carriers, RPM ratio of two propellers is not fixed, unlike conventional CRP system, and hence the power of each propeller must be predicted respectively. In this paper, a CRP-POD system is designed for 10,000 TEU class ultra large container carriers, and the characteristics of the CRP-POD system are experimentally studied. Finally, based on this study, the procedure of powering performance evaluation for CRP-POD propulsion ships is suggested. However, further studies on quantitative correction of the present procedure are required.

SIMULATION OF CAVITATING FLOW PAST CYLINDERS WITH STRONG SIDE-FLOW (측류유동을 고려한 실린더 주위의 캐비테이션 유동 현상 해석)

  • Lee, B.W.;Park, W.G.;Lee, K.C.
    • Journal of computational fluids engineering
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    • v.14 no.4
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    • pp.78-85
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    • 2009
  • Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. The present work has focused on the simulation of cavitating flow past cylinders with strong side flows. The governing equation is the Navier-Stokes equation based on the homogeneous mixture model. The momentum and energy equation is in the mixture phase while the continuity equation is solved liquid and vapor phase, separately. An implicit dual time and preconditioning method are employed for computational analysis. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained. After the code validation, the strong side flow was applied to include the wake flow effects of the submarine or ocean tide.

Inclination angle influence on noise of cavitating marine propeller

  • Bal, Sakir
    • Ocean Systems Engineering
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    • v.10 no.1
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    • pp.49-65
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    • 2020
  • In this study, the effects of inclined shaft angle on the hydro-acoustic performance of cavitating marine propellers are investigated by a numerical method developed before and Brown's empirical formula. The cavitating blades are represented by source and vortex elements. The cavity characteristics of the blades such as cavitation form, cavity volume, cavity length etc., are computed at a given cavitation number and at a set advance coefficient. A lifting surface method is applied for these calculations. The numerical lifting surface method is validated with experimental results of DTMB 4119 model benchmark propeller. After calculation of hydrodynamic characteristics of the cavitating propeller, noise spectrum and overall sound pressure level (OASPL) are computed by Brown's equation. This empirical equation is also validated with another numerical results found in the literature. The effects of inclined shaft angle on thrust coefficient, torque coefficient, efficiency and OASPL values are examined by a parametric study. By modifying the inclination angles of propeller, the thrust, torque, efficiency and OASPL are computed and compared with each other. The influence of the inclined shaft angle on cavity patterns on the blades are also discussed.

Numerical simulation of cavitating flow past axisymmetric body

  • Kim, Dong-Hyun;Park, Warn-Gyu;Jung, Chul-Min
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.4 no.3
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    • pp.256-266
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    • 2012
  • Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, torpedoes, etc. The present work has developed the base code to solve the cavitating flows past the axisymmetric bodies with several forebody shapes. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with hemispherical, 1-caliber, and 0-caliber forebody and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. It has been concluded that the present numerical code has successfully accounted for the cavitating flows past axisymmetric bodies. The present code has also shown the capability to simulate ventilated cavitation.

Modeling and Development of an Integrated Controller for a Ship with Propellers and Additional Propulsion Units (프로펠러와 부가추력장치를 갖는 특수선의 모델링 및 통합제어기 개발)

  • Kim Jong Hwa;Lim Jae Kwon;Lee Byung Kyul
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.2
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    • pp.236-242
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    • 2005
  • Dynamic Positioning(DP) system maintains ship's position (fixed location or predetermined track) exclusively by means of CPPs and thrusters. To generate the control input adequate to various situation an integrated controller for CPPs and thrusters is required. The integrated controller is composed of a thrust calculation algorithm and a thrust allocation algorithm. The thrust calculation algorithm generates thrusts in the surge direction and the sway direction from the desired forward and lateral speed and generates a moment about the yaw axis from desired heading angle. The thrust allocation algorithm allocates the generated thrusts and moment to each CPP and thruster. Computer simulations are executed to confirm the effectiveness of the suggested controller.

Vibration Analysis & Prevention of Vibration for a Large Ro-Ro Ferry (대형 Ro-Ro Ferry의 진동 해석 및 방진 설계)

  • Um, Jae-Kwang;Han, Sung-Yong;Kwon, Hyuk;Lee, Ju-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.1050-1054
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    • 2001
  • Relatively high rotating speed propulsion shafting system of the large Ro-Ro Ferry has a greate risk of the resonance of the many wide local panels as well as the high frequency global vibratory modes. Therefore, from the initial design stage, it is necessary to control the vibration characteristics of the wide panels with detail so as not to be resonant with the blade number order excitation due to the propellers in the normal operating speed range. The procedure of the vibration analysis and the structural redesign for prevention of vibration is introduced.

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