• Title/Summary/Keyword: Propulsion shafting system

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Nonlinear Forced Torsional Vibration for the Engine Shafting System With Viscous Damper (점성댐퍼를 갖는 엔진 축계의 비선형 비틀림강제진동)

  • Park, Y.N;Song, S.O;Kim, U.K;Jeon, H.J
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.4
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    • pp.372-372
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    • 1996
  • The torsional vibration of the propulsion shafting system equipped with viscous damper is investigated. The equivalent system is modeled by a two mass softening system with Duffing's oscillator and the vibratory motion is described by non-linear differential equations of second order. The damper casing is fixed at the front-end of crankshaft and the damper's inertia ring floats in viscous silicon fluid inside of the camper casing. The excitation frenquency is proportional to the rotational speed of engine. The steady state response of the equivalent system is analyzed by the computer and for this analyzing, the harmonic balance method is adopted as a non-linear vibration analysis technique. Frequency response curves are obtained for 1st order resonance only. Jump phenomena are explained. The discriminant for the solutions of the steady state response is derived. Both theoretical and measured results of the propulsion shafting system are compared with and evaluated. As a result of comparisions with both data, it was confirmed that Duffing's oscillator can be used in the modeling of the propulsion shafting system attached with viscous damper with non-linear stiffness.

Excitation Response Estimation of Polar Class Vessel Propulsion Shafting System (대빙 등급 선박 추진 시스템의 기진 응답 평가)

  • Barro, Ronald D.;Lee, Don-Chool
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1166-1176
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    • 2011
  • The prospect in opening the arctic trade transportation route on a year-round basis offers vast opportunity of exploring untapped resources and shortened navigational routes. In addition, the environment's remoteness and lack of technical experiences remains a big challenge for the maritime industry. With this, engine designers and makers are continually investigating, specifically optimizing propulsion shafting system design, to meet the environmental and technical challenges of the region. The International Association of Classification Society, specifically machinery requirements for polar class ships(IACS UR13), embodies the propulsion shafting design requirements for ice class vessels. However, the necessity to upgrade the various features of the unified rules in meeting current polar requirements is acknowledged by IACS and other classification societies. For the polar class propulsion shafting system, it is perceived that the main source of excitation will be the propeller - ice load interaction. The milling - and the impact load, in addition to the load cases interpreted by IACS, contribute greatly to the overall characteristic of the system and due considerations are given during the propulsion design stage. This paper will expound on the excitation load estimation factors affecting the dynamic response of the different propulsion shafting system design. It is anticipated that detailed understanding of these factors will have a significant role during propulsion shafting design in the future.

A theoretical investigation of misfiring effects on the crankshaft torsional vibration of diesel engine (디젤기관 착화실패가 크랭크축계 비틀림 진동에 미치는 환경의 이론적 고찰)

  • 전효중;임영복
    • Journal of Advanced Marine Engineering and Technology
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    • v.10 no.3
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    • pp.94-106
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    • 1986
  • Since the oil shock of '70s the engine makers have developed new types of diesel engine with low fuel consumption. There is an obvious tendency towards the use of poorer quality fuels, such as the residual oil from chemical processes of refinery. The shaft driving generators is also widely adopted on behalf of the auxiliary diesel engines, which are driving on the expensive diesel oil and have high fuel oil consumption rates, and some mania propulsion diesel engines are equipped with reduction gear systems to get better propulsive efficiency by slower propeller revolutions. The propulsion shafting system equipped with the shaft driving generator or the geared diesel engine shafting system has flexible couplings, and it requires extensive investigations of the torsional vibration and torque fluctuation in order to ensure the acceptable operation range in service. The characteristics of misfiring must be especially examined for the high viscosity fuels to be used. Both torsional vibration and fluctuating torque resulted from misfiring, should be examined for thier effects on the flexible coupling and propulsion shafting system. This paper is to investigate and solve the above mentioned problems which must be predicted on the design-stage of marine propulsion shafting system. A computer program is developed to calculate the indicated diagram, fluctating torque and torsional vibration for both normal and misfiring conditions.

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Development of Analysis Program of Dynamic Characteristic for the Propulsion Shafting System (선박추진축계 동특성 분석 프로그램 개발)

  • Ha, Jeong-Min;Lee, Jeong-Myeong;Lee, Jeong-Hoon;Kim, Yong-Whi;Ahn, Byeong-Hyun;Choi, Byeong-Keun;Kim, Won-Chul
    • Journal of Power System Engineering
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    • v.18 no.2
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    • pp.57-61
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    • 2014
  • Due to the changes of marine transportation industry, it requires ship in larger scale and high speed. In order to operate efficiently, the engine should be work in high power and high horse power. The increase of the number of the propeller blades and the pitch of the screw and the weight, vibration of shafting problems occurs. To evaluate the safety of the system through analyzing the dynamic characteristics propulsion shafting system, was used to prove or to verify the Lalanne & Ferraris model validation.. It indicates that the Program through Campbell diagram and Critical speed map, Root rocus map, to ensure the reliability of the experimental model.

A study on the whirling vibration measurement (횡 진동 측정에 관한 연구)

  • Sun, Jin-Suk;Oh, Joo-Won;Kim, Yong-Cheol;Kim, Ue-Kan
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2012.06a
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    • pp.184-184
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    • 2012
  • Recently, as a result of the application of large and multi-blade propellers with high efficiency for large vessels, the vertical bending stiffness of propulsion shafting system tends to be declined. For some specific vessels, the shaft arrangement leads to the forward stern tube bearing to be omitted, decreasing vertical bending stiffness. In this respect, decreased vertical bending stiffness causes the problem which is the blade order resonance frequency to be placed within the operational range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering the range of MCR, however, the range is un-measurable. To resolve the measurement issue, this study shows the measuring method and the estimating method of whiling vibration by using resonance frequency of sub harmonic.

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Propulsion Shafting Alignment Analysis Considering the Interaction between Shaft Deflection and Oil Film Pressure of Sterntube Journal Bearing (축 처짐과 선미관 저널 베어링 유막 압력의 상호작용을 고려한 추진축계 정렬 해석)

  • Cho, Dae-Seung;Jang, Heung-Kyu;Jin, Byung-Mu;Kim, Kookhyun;Kim, Sung-Chan;Kim, Jin-Hyeong
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.6
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    • pp.447-455
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    • 2016
  • Precise propulsion shafting alignment of ships is very important to prevent damage of its support bearings due to excessive reaction forces caused by hull deflection, forces acted on propeller and crankshaft, and so forth. In this paper, a new iterative shafting alignment calculation procedure considering the interaction between shaft deflection and oil film pressure of Sterntube Journal Bearing (SJB) bush with single or multiple slopes is proposed. The procedure is based on a pressure analysis to evaluate distributed equivalent support stiffness of SJB by solving Reynolds equation and a deflection analysis of shafting system by a finite element method based on Timoshenko beam theory. SJB is approximated with multi-point biaxial elastic supports equally distributed to its length. Their initial stiffness values are estimated from dynamic reaction force calculated by assuming SJB as single rigid support. Then, the shaft deflection and the support stiffness of SJB are sequentially and iteratively calculated by applying a criteria on deflection variation between sequential calculation results. To demonstrate validity and applicability of the proposed procedure for optimal slope design of SJB, numerical analysis results for a shafting system are described.

Reduction Gear Stability Estimation due to Torque Variation on the Marine Propulsion System with High-speed Four Stroke Diesel Engine (고속 4행정 디젤엔진을 갖는 선박 추진시스템에서 토크변동에 의한 감속기어 안정성 평가)

  • Kim, InSeob;Yoon, Hyunwoo;Kim, Junseong;Vuong, QuangDao;Lee, Donchool
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.25 no.12
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    • pp.815-821
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    • 2015
  • Maritime safety has been more critical recently due to the occurrence of shipboard accidents involving prime movers. As such, the propulsion shafting design and construction plays a vital role in the safe operation of the vessel other than focusing on being cost-efficient. Smaller vessels propulsion shafting system normally install high speed four-stroke diesel engine with reduction gear for propulsion efficiency. Due to higher cylinder combustion pressures, flexible couplings are employed to reduce the increased vibratory torque. In this paper, an actual vibration measurement and theoretical analysis was carried out on a propulsion shafting with V18.3L engine installed on small car-ferry and revealed higher torsional vibration. Hence, a rubber-block type flexible coupling was installed to attenuate the transmitted vibratory torque. Considering the flexible coupling application factor, reduction gear stability due to torque variation was analyzed in accordance with IACS(International Association of Classification Societies) M56 and the results are presented herein.

Optimum design of propulsion shafting system considering characteristics of a viscous damper applied with high-viscosity silicon oil (고점도 실리콘오일 적용 점성댐퍼 동특성을 고려한 추진축계 최적 설계)

  • Kim, Yang-Gon;Cho, Kwon-Hae;Kim, Ue-Kan
    • Journal of Advanced Marine Engineering and Technology
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    • v.41 no.3
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    • pp.202-208
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    • 2017
  • The recently developed marine engines for propulsion of ships have higher torsional exciting force than previous engines to improve the propulsion efficiency and to reduce specific fuel oil consumption. As a result, a viscous damper or viscous-spring damper is installed in front of marine engine to control the torsional vibration. In the case of viscous damper, it is supposed that there is no elastic connection in the silicon oil, which is filled between the damper housing and inertia ring. However, In reality, the silicon oil with high viscosity possesses torsional stiffness and has non-linear dynamic characteristics according to the operating temperature and frequency of the viscous damper. In this study, the damping characteristics of a viscous damper used to control the torsional vibration of the shafting system have been reviewed and the characteristics of torsional vibration of the shafting system equipped with a corresponding viscous damper have been examined. In addition, it is examined how to interpret the theoretically optimal dynamic characteristics of a viscous damper for this purpose, and the optimum design for the propulsion shafting system has been suggested considering the operating temperature and aging. when the torsional vibration of the shafting system is controlled by a viscous damper filled with highly viscous silicon oil.

Passenger & Car Carrier's Superstructure Vibration induced by the 1st order Excitation of Whirling Vibration on the Propulsion Shafting System (추진축계 횡진동 1차 기진력에 의한 여객.차도선의 선체 상부진동)

  • Lee, D.C.;Ko, J.Y.;Kim, J.R.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.11a
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    • pp.301-306
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    • 2000
  • Small passenger and car carrier ships are mainly used as a connection way between land and small islands. And these ships should be designed to enlarge the capacity of passenger and car loading within limited space and draft. So the resonances of various vibrations exist in normal operation range of engine and propulsion shafting. In this paper, hull's superstructure vibration which was especially induced by the 1st order excitation of whirling vibration on the 2-engines and 2-propulsion shafting systems is introduced. Also these are verified via the theoretical analysis using transfer matrix method and FEA software ANSYS and its vibration measurement.

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Whirling Vibration Analysis & Measurement of the propulsion shafting system of l000P Ro-Ro Ferry (1000인승 대형 Ro-Ro Ferry 의 축계 whirling 진동 해석 및 계측/분석)

  • Kwon, Hyuk;Han, Sung-Yong;Um, Jae-Kwang
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.05a
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    • pp.143-148
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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 whirling vibration within the operating speed range. Therefore, it is necessary to control the whirling vibration characteristics of the shafting system in the initial design stage so as not to be resonant with the blade number order excitation in the normal operating speed range. The results of the whirling vibration analysis for l000P Ro-Ro Ferry with SHI's in-house program and the measured results during the sea trial are introduced. Additionally the outline of the program and the calculation method of the major properties are presented.

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