• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.411-416
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• 2005

Nowadays, diesel power plant using low speed two stroke diesel engine is widely used in islands and restricted areas. Considerations were given to its benefit of high thermal efficiency, reliability and durability compared to the other prime movers. However, various types of engine vibration affect neighboring buildings to their structural vibration. For this, diesel power plant are held liable for the troubles caused by these vibration. These are mainly due to the X- and H-type engine vibrations which we excited by the X- and H- guide force moment. Authors have identified a structural vibration of new pattern called ‘T-mode vibration’ due to the torsional vibration of shafting system. In this paper, T-mode vibration is analyzed through an experimental method based on the global vibration measurement.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.3
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• pp.563-572
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• 2001

With the results of calculation for natural frequencies the reponses of forced coupled vibration of propulsion shafting system were investigated by the modal analysis method. For the forced vibration response analysis, the axial exciting forces, the axial damper/detuner, propeller exciting forces and damping coefficients were extensively considered. As the conclusion of this study, some items are cleared as follows.-The torsional vibration amplitudes are not influenced by the radial excitation forces of the crank shaft. -The axial vibration amplitudes are influenced by the tangential exciting forces as well as the radial exciting forces of the crank shaft. The increase of the amplitudes is observed in the speed range at the neighbourhood of any torsional critical speed. 1The closer the torsional and axial critical speed. the larger coupling effect becomes. -The axial exciting force of propeller is relatively strong comparing with axial exciting forces of cylinder gas pressure and oscillating inertia of reciprocating mechanism. Therefore, the following conclusions are obtained. -Torsional vibration calculation with the classical one dimensional model is still valid. -The influence of torsional excitation at each crank upon the axial vibration is improtant. especially in the neighbourhood of a torsional critical speed. That means that the calculation of axial vibration with the classical one dimensional model is inaccurate in most of cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.90-95
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• 2008

Medium and high speed marine diesel engines have been widely used as prime mover in small car ferries and fishing vessels with reduction gear. These propulsion shafting system should be installed and matched the elastic coupling between engine and reduction gear to isolate the vibratory torque. In this paper, the elastic dynamic characteristics of coupling with rubber type circular segments is confirmed by the theoretical analysis using the FEM and the hydraulic exciting test at shop. And its adaptation is investigated in the torsional vibration test in factory shop.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2529-2534
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• 2000

Torsional vibration analysis in a large two -stroke low speed diesel engine and generator system for stationary power plants is performed to verify that the vibration characteristics of shafting system meet design requirements. Our own developed S/W is employed for the analysis, whose results are evaluated comparing with measurements. Vibration analysis results of the system are presented according to the change of loading(unload, 100%load, 110% load) and operating(mis-firing, uneven firing) conditions of the stationary power plants.

• Journal of KSNVE
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• v.10 no.4
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• pp.655-661
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• 2000

Diesel power plant can be used as a power supplier for the isolated place where consumption of electric power is variable. The reason is that mobility and durability of diesel engine is superior to those of other thermal engines. However, there are some disadvantages for using these diesel engines such as bigger vibratory excitation force comparing to the others, which result from high combustion pressure of cylinders and inertia force of piston reciprocating masses. In this paper, control and optimization of torsional vibration of 12K90MC-S engine for diesel power plant using uneven crank angles is identified by theoretical analysis and vibration measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.316-323
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• 2003

The gear system is commonly applied in the marine propulsion shafting system using the diesel engine with the power take off/in system and it also is necessary to reduce propeller revolution increasing the propulsion efficiency. The diesel engine has the advantage more than other thermal engines in high thermal efficiency and mobility. But the large vibratory torque which induced by higher combustion pressure is transmitted to these gears. In this paper, the surface durability and bending stress of gear system considering vibratory and transient torque is evaluated by ISO and AGMA regulation. And the influence of these in gear design is investigated with the theoretical analysis and onboard measurement result of torsional vibration.

• Bulletin of the Society of Naval Architects of Korea
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• v.7 no.2
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• pp.61-70
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• 1970

Since there has been no analytical method to calculate principal dimensions of the axial vibration damper of marine diesel engine shaftings in design state, it has often happened to install the axial vibration damper after the ship's trial trip. In this paper a method to calculate the coefficient of equivalent damping of the axial vibration damper is introduced and with this value one can calculate fairy accurate vibrating amplitudes of the crankshaft that is fitted with an axial vibration damper, by using author's matrix methods.[1][2][3][4] A comparison of the calculated amplitudes with measured ones is shown and its result is fairy good, except values of the case where the damper nozzle is almost closed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.786-791
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• 2006

Two stroke low speed diesel engines are mainly used for marine propulsion or power plant prime mover. These have many merits such as higher thermal efficiency, mobility and durability. However various annoying vibrations sometimes occur in ships or at the plant itself. Of these vibrations, torsional vibration is very important and it should be carefully investigated during the initial design stage for engine's safe operation. In this paper authors suggest a new estimation method of for shaft's can be calculated equivalently from accumulated fatigue cycles number due to torsional vibration. The 6S70MC-C($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study, and the accumulated fatigue cycles numbers for shafting life time converted from the measured angular velocity and torsional vibration stress was calculated. This new method can be realized and confirmed in test model ship with two stroke low speed diesel engine.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.5
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• pp.626-634
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• 1998

Controllable pitch propeller(CPP) is usually adopted for easy and effective engine controls of a ship in a port. Unfortunately the torsional vibration may occur by a certain variation of engine torque and the major resonance peak may exist within the maximum continuous rating(MCR) In these cases an additional stress concentration on the oil passages such as longitudinal slots notches and circular holes of an oil distributor shaft(ODS) occurs by the torsional vibration of the CPP shaft. In this paper an analysis for the fatigue limit of an ODS system of the 5S70MC engine in a crude oil carrier is done by applying FEM and empirical formulas. Furthermore the additional stress on the ODS is investigated by analyzing the torsional vibration of the shaft system and a control method in which a tuning damper is adopted is introduced in the case of the additional stress exceeds the fatigue limit. The validity of analysis method is verified by comparing the results acquired by an actual measurement of the vibratory torque for the above ODS

• Journal of the Society of Naval Architects of Korea
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• v.57 no.3
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• pp.160-167
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• 2020

A two-stroke diesel engine and a propeller normally adopted in large merchant ships are regarded as major ship vibration sources. They are directly connected and generate various excitation components proportional to the rotating speed of diesel engine. Among the components, the magnitude of two excitation components with the same frequency generated by both engine and propeller can be compensated by the adjustment of their phase difference. It can be done by the optimization of propeller assembly angle but requires a number of burdensome trials to find the optimal angle. In this paper, the efficient estimation method to determine optimal propeller assembly angle is proposed. Its application requires the axial vibration measurement in sea trial and the numerical vibration analysis for propulsion shafting which can be substituted by additional vibration measurement after one-trial modification of propeller assembly angle. In order to verify the validity of the proposed method, the phase difference between two fifth order excitation components generated by both diesel engine and propeller of a real ship is calculated by the finite element analysis and its result is indirectly validated by the comparison of axial vibration responses at intermediate shaft obtained by the numerical analysis and the measurement in sea trial. Finally, it is numerically confirmed that axial vibration response at intermediate shaft at a resonant speed can be decreased more than 87 % if the optimal propeller assembly angle determined by the proposed method is applied.