• Journal of the Korean Institute of Navigation
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• v.15 no.3
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• pp.73-97
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• 1991

The analysis and investigation are described for White's[2] equations compared to the equations of Runeburg[3] and Milano[5] for continuous icebreaking mode, Tunik[8-1] and Ghoneim[8-2] for ramming icebreaking mode. Calculation results compare reasonably well with published model-scale and full-scale icebreaker data by Baker[1] and Dick[11]. During continuous and ramming mode operation, using characteristics of an incebreaker, down ward force on ice and standard ice thickness broken are predicted. Additionally draft, trim and extraction difficulty are also predicted. The bow part line of an icebreakin $g^{ply}$ vessel is designed aiming to maximize the ice breaking capabiltiy as following conditions-low bow angle[20 degrees] at designed waterline, small spread angle complement [6 degrees] at designed waterline, small spread angle complement [6 degrees] and high propeller thrust [220tons]. with plow, two reamers and wave type bumper.

• Journal of Korea Ship Safrty Technology Authority
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• s.22
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• pp.34-53
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• 2007

In the case of hull material. large sized merchant ships are made of steel, on the other hand FRP or wood are used for small sized fishing boats. At present in Korea approximately 88,500 fishing boats are in operation of which 70% are made of FRP In the meantime, stainless steel is frequently used as shaft materials of the small-size FRP fishing boat. Namely, the kinds of shaft materials are STS 304(18Cr-8Ni), STS 316(18Cr-12Ni-2.5Mo steel) and STS 630(17Cr-Ni-Nb steel)etc. Among these things, STS 304 which is the cheapest and having ordinary corrosion resistance is most widely used as 2nd class shaft material. But, using STS 304 for shaft system material of the small-size FRP fishing boat on seawater environments entails a severe corrosion which causes shaft system troubles. Particularly, the corrosions tend to be concentrated of the stern and bow side, propeller shaft surface of inside of stern tube and the boat having no stern cooling pipe line system. As a solution for those problems, research on the ways to mitigate corrosion on the part of 2nd class stainless steel shaft have been undertaken. In the result, not only clarification for the reason of corrosion of the part of stainless steel shaft used mainly for the small-size FRP fishing boat was done, but also most optimal corrosion protection system was developed by experimenting shaft's protection simulation based of the electrochemical cathodic protection principle. In addition, verification through the field test on the optimal cathodic corrosion protection method by means of aluminum sacrificial anode was carried out. In this study, effective and economical shaft's protection system is suggested to the small-size FRP fishing boat operator by substantiating the results obtained from the research on the optimal cathodic protection.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.1
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• pp.46-58
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• 1997

The energy saving is one of the most important factors for profit in marine transportation. In order to reduce the fuel oil consumtion the ship's propulsion efficiency must be increased as possible. The propulsion efficiency depends upon a combination of an engine and a propeller. The propeller has better efficiency as lower rotational speed. This situation led the engine manufacturers to design the engine that has low speed, long stroke and a small number of cylinders. Consequently, the variation of rotational torque became larger than before because of the longer delay-time in fuel oil injection process and an increased output per cylinder. As this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variation of the delay-time and the parameter perturbation. In this paper we consider the delay-time and the perturbation of engine parameters as the modeling uncetainties. Next we design the robust servo controller which has zero offset in steady state engine speed, based on H sub($\infty$) control theory. The validity of the controller was investigated through the response simulation. We used a personal computer and an analog computer as the digital controller and the engine (plant) part respectively. And, we could certify that the designed controller maintains its robust servo performance even though the engine parameters may vary.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.3
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• pp.430-436
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• 2008

Recently, there are many cases to use a ship's engine performance analyzer(SEPA) to measure pressure in cylinder and top dead center(TDC) of piston of engine, and analyze its performance such as fuel injection time and horsepower as well as wear of piston ring. But, SEPA needs TDC pulses($T(1){\sim}T(n)$) generated when pistons of engine are located to the TDC position ($TDC(1){\sim}TDC(n)$), these pulses are gathered from sensors connected to gear wheel of the propeller shaft in the remote distance from the measurement point. Therefore, operators need a long wire cable(WRC) to TDC detecting sensor to get these pulses, but this method is a very uncomfortable and expensive in case of installation, and it might decrease user's purchase desire. In this paper, we design and fabricate a small and inexpensive MODEM cable(M0C) so that it may be available to transmit TDC pulse generated from sensor in propeller shaft through existing power line. We also verify the facts that this MOC can be applied to SEPA and the effectiveness of the system through the experiments.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.3
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• pp.71-78
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• 1998

Recently, modern long-stroke diesel engines with small number of cylinders have been installed for energy saving and simpler maintenance. These kinds of low speed diesel engine produce large torsional vibration in the shafting, which induces the excessive vibratory stresses in the shafting and large propeller thrust variation. This thrust variation excites vibrations of the shafting and superstructure in the longitudinal direction. Up to now the deteriministic analysis of coupled vibration of marine shafting system has been performed. In this paper probabilistic analysis method of the marine diesel propulsion shafting system under coupled axial and torsional vibrations is presented. For the purpose of this work, the torsional and axial vibration excitations of engine and propeller are assumed to be probabilistic while the lateral excitation is assumed to be deterministic. The probabilistic analysis is based on a response surface and Monte-Carlo simulation. Numerical results based on the proposed method are compared with results calculated using the conventional deterministic analysis method. The results obtained make it clear that the proposed method gives a substantial increase in information about shafting behaviour as compared with the deterministic method.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.3
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• pp.193-210
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• 1991

For the deckhouse or superstructure, attention is directed to the reduction of vibration from a human susceptibility point of view. The two basic requirements for obtaining a low vibration level in the accommodation are to ensure that excitation forces from propeller and/or main engine are small and to avoid resonance excitation of the hull and superstructure. In recent years increased attention has been directed towards the problems of vibration and noise in deckhouse, which have caused major problems with regard to the environmental quality in the living quarters for crews. Accordingly, in this paper, the characteristic of the vibration of deckhouse of fishing boat, of which the length/height ratio is also relatively high, are studied systematically with regard to the shape and modelling of deckhouse based on finite element method of 1-dimensional, 2-dimensional and 3-dimensional model. This study is divided into 4-part. 1st part is the global deckhouse vibration, 2nd part is the local deckhouse vibration, 3rd part consists of the estimation for stiffness of foundational support and 4th part is the application to TUNA LONG LINER of 416 ton class. For the global vibration analysis, the severity of the vibration depends on the longitudinal shear and bending stiffness of the deckhouse, on the vertical deckhouse support(fore, aft and sides). However, even if the design is technically sound, vibration problems may arise due to vertical or longitudinal hull girder or afterbody resonances. Author applied the method of this study to the analysis of, deep-sea fishing vessel of G.T. 416 ton class with relatively low height and long deckhouse, and investigated the vibrational characteristic of the fishing vessel with earlier structural feature. According to this investigation, the vibration, response of above vessel was confirmed of which main hull and deckhouse behave as one body. It is at the bottom of vibrational trouble which a accommodation part of the fishing vessel is raised, that is the local vibration for side wall, fore-aft wall and deck plate of deckhouse rather than thief fect of fore-aft vibration of deckhouse for above fishing vessel. and the resonance of main hull, deckhouse and driving system such as the main engine, propeller in exciting source is mainly brought up as the trouble.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.2
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• pp.150-162
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• 2010

Assessment of hydrodynamic performance of a ship hull has been focused on a model ship rather than a full-scale ship. In order to design the propeller of a ship, model-scale wake is often extended to full-scale based upon an empirical method or designer's experience, since wake measurement data for a full-scale ship is very rare. Recently modern CFD tools made some success in reproducing wake field of a model ship, which implicates that there are some possibilities of the accurate prediction of full-scale wakes. In this paper firstly the evaluation of model-scale wake obtained by Fluent package was performed. It was found that CFD calculation with the Reynolds-stress model (RSM) provided much better agreement with wake measurement in the towing tank than with the realizable k-$\varepsilon$ model (RKE). In the next full-scale wake was calculated using the same package to find out the difference between model and full-scale wakes. Three hull forms of KLNG, KCS, KVLCC2 having measurement data open for the public, were chosen for the comparison of resistance, form factor, and propeller plane wake between model ships and full-scale ships.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.1
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• pp.60-70
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• 1995

In the field of marine transportation the energy saving is one of the most important factors for profit. In order to reduce the fuel oil consumption the ship's propulsion efficiency must be increased as much as possible. The propulsion efficiency depends upon a combination of an engine and a propeller. The propeller has better efficiency as lower rotational speed. This situation led the engine manufacturers to design the engine that has lower speed, longer stroke and a small number of cylinders. Consequently the variation of rotational torque became larger than before because of the longer delay-time in the fuel oil injection process and an increased output per cylinder. As this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variation of the delay-time and the parameter pertubation. In this paper we consider the delay-time and the perturbation of engine parameters as the modeling uncetainties. Next we design the controller which has zero offset in steady state engine speed, based on the two-degree-of-freedom control theory and $\mu$-synthesis. Thd validity of the controller is investigated through the response simulation. We use a personal computer and an analog computer as the digital controller and the engine (plant) part respectively. And, we certify that the designed controller maintains its performance even though the engine parameters may vary.

• The KSFM Journal of Fluid Machinery
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• v.11 no.5
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• pp.44-49
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• 2008

As the alternative energy, renewable energy should have been developing by many techniques, in order to substitute the fossil fuel which will be disappeared in the near future. One of the small hydropower generator, main concept of tubular turbine is based on using the different water pressure levels in pipe lines, energy which was initially wasted by using a reducing valve at the end of the pipeline, is collected by turbine in the hydro power generator. A propeller shaped hydro turbine has been used in order to use this renewable pressure energy in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the guide vane opening angle are examined in detail. First, it ensures the reliance of CFD by that of compared with experiment data. After all, the results of performance characteristics of the CFD and experiment show to confirm the data that power, head and efficiency of less than 4%, 2% and 5% respectively. Moreover influences of pressure, tangential and axial velocity distributions on turbine performance are investigated.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2839-2844
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• 2007

Micro hydraulic power generation of which the output is less or equal to a 100kW is attracting considerable attention. This is because of its small, simple, renewable, and abundant energy resources. By using a small hydropower generator of which main concept is based on using the different water pressure levels in pipe lines, energy which was initially wasted by use of a reducing valve at the end of the pipeline, is collected by turbine in the hydropower generator. A propeller shaped hydroturbine has been used in order to use this renewable pressure energy. In this study, in order to acquire basic design data of tubular type hydraulic turbine, output power, head, efficiency characteristics due to the flow coefficient are examined in detail. Moreover influences of pressure and velocity distributions with the variations of runner vane angle on turbine performance are investigated by using a commercial CFD code.