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Kang-Ki Lee

Bio: Kang-Ki Lee is an academic researcher. The author has contributed to research in topics: Combustion & Natural gas. The author has an hindex of 2, co-authored 3 publications receiving 7 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the measurement method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration were presented to resolve the measurement issue.
Abstract: 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 rpm range of propulsion shafting system. To verify whirling vibration, the measurement should be carried out covering from operating rpm up to target rpm, however, the range is un-measurable generally. In order to resolve the measurement issue, this study shows the measuring method and the assessment method of relevant natural frequency of whiling vibration by using measured harmonic order component of whirling vibration.

7 citations

Journal ArticleDOI
TL;DR: In this paper, a simulation program has been developed to predict NOx emission using two-zone model and Wiebe function for combustion in cylinder and the effects of premixed and diffusive combustion could be simulated by using the excess air ratio as input data.
Abstract: Natural gas for marine diesel engine is considered as an important and clean source of energy because of simultaneously reducing the emission of NOx, SOx and GHG. Especially with a appearance of shale gas, the using of natural gas has been investigated aggressively and expected to expand rapidly. By the reports, gas engine and diesel engine were both in a similar performance in the power aspect, and the SFOC of gas engine was shown a little better than that of diesel engine. But the characteristics of exhaust gas emission were different according to various combustion technologies. And with lean burn technology, the emission of NOx could be reduced to 85% lower than that of diesel engine. In this paper, it was described that a simulation program has been developed to predict NOx emission. The developed program is adopted two-zone model and Wiebe function for combustion in cylinder. The effects of premixed and diffusive combustion could be simulated by using the excess air ratio as input data. And it was confirmed that the results of simulation were agreed with the general trends of exhaust gas emission according to various combustion conditions such as lean burn, premixed and diffusive combustion.

1 citations

Journal ArticleDOI
17 Dec 2022
TL;DR: In this paper , the potential of three molecules NH4NO2, H2O2 and O3 to ignite aqueous solutions of ammonia (25% by mass) as fuel, was investigated using chemical kinetic simulations at conditions representative of a two-stroke marine diesel engine.
Abstract: The potential of three molecules NH4NO2, H2O2 and O3 to ignite aqueous solutions of ammonia (25% by mass) as fuel, was investigated using chemical kinetic simulations at conditions representative of a two-stroke marine diesel engine. The purpose was to address two of the most prominent issues with making ammonia a practical fuel for marine applications: the difficulty of igniting ammonia, and the safety concerns regarding its volatility and toxicity. The ignition simulations carried out to this end used a two-zone reactor model of the engine, representing the ignition zone into which fuel was injected, and the bulk cylinder gases, respectively. The results suggested that all three ignition improving molecules were able to ignite aqueous ammonia reliably and at high combustion efficiency with acceptable levels of NO, N2O and NH3 emissions. Among the three fuel formulations investigated, H2O2 as 12% aqueous solution by mass, promised the lowest emissions of NO and N2O in the exhaust gases. This ignition improver in aqueous solution added in a mole fraction of 0.15 to a mole fraction of 0.85 aqueous ammonia having an ammonia fraction of 25% by mass promised to be the most practical solution, since it is stable and can be stored safely in a separate tank until injected into the engine.

Cited by
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Journal ArticleDOI
TL;DR: In this paper, the characteristics of a ship supporting a propeller shaft with double and single stern tube bearings are compared. And the changes in shaft flexibility and characteristics of the whirling vibration of a corresponding shafting system in a 50-K-DWT petroleum product tanker were explored by applying a single Stern tube bearing.
Abstract: In recently constructed vessels, minimization of engine room volume is required to maximize the volume of cargo to be shipped. Therefore, the main engine and the stern bulkhead mounted on the ship are installed as far as possible in the aftward direction. As a result, the length of the propeller shaft is reduced, along with the stern tube bearing span used to support it. In this case, the shaft flexibility is reduced, the reaction influence number is increased, and the point load of each bearing is easily influenced by change in displacement. Because the point load of each bearing is susceptible to hull deformation and thermal expansion, it is difficult to adjust the shaft arrangement and the bearing load change after large adjustment of the shaft arrangement. Therefore, in the past, the bearing was arranged to support the propeller shaft with two forward and afterward stern tube bearings. However, when the main engine and the stern bulkhead are installed as far aftward as possible to minimize the volume of the engine room, it is necessary to provide shaft flexibility by removing the forward stern tube bearing. As a result, the resonance revolution of the propeller blades during whirling vibration of the propulsion shafting system falls within the range of normal operating revolutions. This means that abnormal wear of the stern tube bearing, damage to the stern tube sealing device, and hull structure vibration may occur due to the whirling vibration. In this paper, the characteristics of shafting alignment and whirling vibration of a ship supporting a propeller shaft with double and single stern tube bearings are compared. Moreover, the changes in shaft flexibility and the characteristics of the whirling vibration of a corresponding shafting system in a 50 K-DWT petroleum product tanker were explored by applying a single stern tube bearing. In addition, the shafting alignment and whirling vibration are determined according to the installation position of the intermediate shaft bearing. A method is suggested for selecting the optimal shafting arrangement by which to secure the shaft flexibility of a ship to which a single stern tube bearing is applied, and to avoid resonance from the whirling vibration.

7 citations

Journal ArticleDOI
25 Feb 2016
TL;DR: In this paper, the dynamic performance of a large floating wave-offshore hybrid power generation platform in extreme conditions was evaluated by measuring motion responses in regular waves and complicated environmental conditions including wave, wind, and current.
Abstract: The present study experimentally considers dynamic performance of large floating wave-offshore hybrid power generation platform in extreme conditions. In order to evaluate the motion performance of the large floating hybrid power generation platform, 1/50 scaled model was manufactured. A mooring line was also manufactured, and free-decay and static pull-out tests were carried out to check the mooring model. A mooring line table was introduced to satisfy the water depth, and environmental conditions were checked. Motion responses in regular waves were measured and complicated environmental conditions including wave, wind, and current were applied to see the dynamic performance in extreme/survival conditions. Maximum motion and acceleration were judged following the design criteria, and maximum offset and mooring tension were also checked based on the rule. The characteristics of hybrid power generation platform are discussed based on these data.

7 citations

Journal ArticleDOI
TL;DR: In this article, the effects of shafting alignment on shafting whirling and bearing vibrations were investigated on a test rig designed by the Wuhan University of Technology (WHUT).
Abstract: The propulsion shafting is one of the main excitation sources of ship vibration and noise. Thus, shafting vibration and alignment are very important issues in the design of a propulsion system. In the present paper, the effects of shafting alignment on shafting whirling and bearing vibrations will be discussed. This study has been carried out experimentally on a test rig designed by the Wuhan University of Technology (WHUT). The results indicated that in design conditions, the effects of shafting alignment on both vibrations are mainly in the horizontal direction. It was found that both shafting whirling and bearing vibrations can be effectively reduced by adjusting the shafting alignment. However, compared to the vertical direction, the vibration in the horizontal direction can be more effectively reduced. Also, the minimum values of whirling vibration and bearing vibration are not in the same shafting alignment state. In addition, the effect of shafting whirling vibration on bearing vibration was little. Also, the bearing vibration changes little when the shafting rotation speed is between 90 and 300 r/min. Finally, it was found that at high rotation speeds, the bearing supporting performance is significantly affected by the shaft whirling effect.

4 citations

Journal ArticleDOI
TL;DR: In this paper , a model of podded propulsor shafting is established, where the shafting was simplified to a heterogeneous variable cross-section beam, while bearings are seen as springs and the influences of bearing stiffness, bearing location, and excitation on vibration characteristics of shafting were analyzed.
Abstract: Podded propulsors are widely used in warships and cruise ships, which have a higher requirement of vibrational and acoustic design. Therefore, studying vibration characteristics and the transmission mechanism of podded propulsor shafting is significant for reducing vibration and ensuring the safe operation of ships. This paper establishes a model of podded propulsor shafting by analytical method. The shafting is simplified to a heterogeneous variable cross-section beam, while bearings are seen as springs. The podded propulsor shafting has one radial-thrust hybrid bearing and one radial bearing. The excitations from the propeller and cabin are considered. The influences of bearing stiffness, bearing location, and excitation on vibration characteristics of shafting are analyzed. The main conclusions are as follows: Based on the analysis of the area that resonance frequency is sensitive to the change of bearing stiffness, the resonance frequencies of the shafting can be adjusted to the proper range. The large span between hybrid bearing and radial bearing leads to low stiffness of shafting and low resonances frequencies. Under radial excitations, the low vibration always occurs at the hybrid bearing, motor shafting, or propeller end of shafting. This research provides theoretical support for the design and optimization of vibration reduction of podded propulsor shafting.

3 citations

Journal ArticleDOI
27 Sep 2017
TL;DR: In this paper, the authors found the whirling speed of the shaft of the ship propeller by using a multi-DOF (degree of freedom) measurement system including engine, gearbox and propeller, flywheel and etc.
Abstract: Finding the whirling speed of the shaft of the ship propeller is presented on this paper Power generated from the engine is transmitted to the propeller directly/indirectly using gearbox This is important to find the natural frequencies of the shafting system in order to prevent resonance So, multi-DOF (degree of freedom) is considered on this study including engine, gearbox and propeller, flywheel and etc connecting by the shaft Whiling speeds of the shaft are determined at various conditions as well as the effect of the shaft torsional stiffness and shaft diameter are presented and discussed

3 citations