• Journal of Advanced Marine Engineering and Technology
• /
• v.11 no.3
• /
• pp.31-44
• /
• 1987

Nowadays, the problems of energy and environmental pollution become serious day by day and the diesel engine, which has been proved to be superior to gasoline engine with respect to fuel consumption and ecological problems of exhaust gas, has been adopted widely for various purposes from the marine diesel engine and the dynamo engine to all kinds of engine on land. Therefore, extensive parametric studies on combustion of diesel engine should be done for its desing and improvement. To predict the behavior of diesel engien according to variable operating conditions by means of cycle simulation, the reasonable pattern of heat release rate has to be asumed. But it is necessary to know the actual variation of heat release rate in order to assume the reasonable pattern of heat release rate according to the actual operating conditions. In this paper, on a high speed small bore diesel engine with pre-combustion chamber, experimental investigations were carried out to determine the relationship between the heat release pattern and parameters such as engine load and speed. And also, the theoretical investigations about the performance variations of the above diesel engine according to the predicted pattern of heat release rate variation were performed. From the above observations, it may be said that the Fanboro indicator, which was used to get the cylinder pressure, can be used to estimate a reasonable pattern of heat release rate and it is confirmed that the pattern of heat release rate for the pre-combustion type engine is different from that of the direct injection type engine.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.4
• /
• pp.150-159
• /
• 2018

The present research deals with a finite element analysis and fatigue evaluation of a steam separator of a high-pressure evaporator for the Heat Recovery Steam Generator (HRSG). The fatigue during the expected life of the HRSG was evaluated according to the ASME Boiler and Pressure Vessel Code Section VIII Division 2 (ASME Code). First, based on the eight transient operating conditions prescribed for the HRSG, temperature distribution of the steam separator was analyzed by a transient thermal analysis. Results of the thermal analysis were used as a thermal load for the structural analysis and used to determine the mean cycle temperature. Next, a structural analysis for the transient conditions was carried out with the thermal load, steam pressure, and nozzle load. The maximum stress location was found to be the riser nozzle bore, and hence fatigue was evaluated at that location, as per ASME Code. As a result, the cumulative usage factor was calculated as 0.00072 (much less than 1). In conclusion, the steam separator was found to be safe from fatigue failure during the expected life.

• Transactions of The Korea Fluid Power Systems Society
• /
• v.4 no.3
• /
• pp.1-6
• /
• 2007

The leakage generated from the clearance between the cylinder bore and the piston is one of the most serious problems in the hydraulic piston pump, and it even results in terrible decrease of the volume efficiency at a great velocity and high pressure. In this paper, the lubrication characteristic of the hydrostatic slipper bearing equipped in the hydraulic piston pump has been worked out by experimentation with three model bearings of different shape. Preparatory to this, not only the three models of piston-slipper were designed, but the corresponding experimental apparatus were also manufactured. As a result, it was verified that, according to the supply pressure, the hydrostatic bearing part of the slipper is severely affected by the pocket pressure, land pressure, oil film thickness, and leakage flow.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.22 no.4
• /
• pp.46-54
• /
• 2014

The hollow design of a railway axle is one of the most effective methods to reduce the weight of an axle. However, the conventional hollow axle has the limitation of a lightweight design because it has the same bore diameter along the axial position. The new type of railway axle, the tapered inner surface railway axle, has a different inner diameter between the journal bearing seat and wheel seat. This design method is one way to increase the weight reduction possibility. The purpose of the present study is to establish and evaluate the design of the tapered inner surface railway axle. The case study and Finite Element Method(FEM) are applied to evaluate the strength of the lightweight railway axle according to the European Norm(EN 13103). Finally, the best design case for reducing the weight of the axle is drawn from the results of the case study.

• Journal of the Korean Society of Systems Engineering
• /
• v.2 no.1
• /
• pp.11-17
• /
• 2006

According to the change of customer needs, integration with other systems, and the advent of new technology, it is inevitable for the existing system requirements to be requested to redesign. However, there are actually no methodologies and processes to be able to reorganize the existing requirements or integrate a number of requirements different from each other. The traditional requirements processes do not work when solving such problems. Thus, since the existing approaches to develop requirements are not helpful, many traditional requirement engineering processes can not help falling in Red Ocean. In this paper, in order to solve such the problems, we propose a novel requirements engineering process applying Blue ocean strategy which is used to open a non-competition market not discovered yet. Blue Ocean approach is a novel effective method to elicit and build up new requirements from customers. In order to accomplish the strategy, this paper presents a framework and processes to discover new perspectives and analyze the corresponding requirements. In addition, some pieces of case study are presented to introduce how our approach is applied to practical system developments and the evaluation analysis for how valid it is.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.10
• /
• pp.45-51
• /
• 2010

Electrical discharge drilling (ED-drilling) is a widespread machining method used to bore small holes with a high aspect ratio. This paper presents additional methods by which ED-drilling can improve machining speed, tool wear, and machined surface quality. Firstly, for high machining speed, and low tool wear, a new-type electrode that was ground on one side or both sides of the cylindrical electrodes was suggested to expel debris. The debris which is generated during the machining process can cause sludge deposition and secondary discharge problems: major reasons to decrease machining speed. This new-type electrode also reduced tool wear that was due to the decrease of unstable discharge in a machining gap by helping to expel waste water and debris from the gap. Secondly, to improve the machined surface roughness, an electrolyzation process was included after drilling. This process made the machined surface smooth by means of an electrochemical reaction between an electrode and a workpiece. In this study, the machining speed, electrode wear, and surface roughness were improved by the newtype electrode and the electrolytic process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.10a
• /
• pp.160-163
• /
• 2004

The hub hole in a wheel of vehicles usually formed with hole expansion process. Formability of material, especially the hole expansion ratio, is important to produce a fine hub hole. The hub hole expansion process is different from general forming process or bore expansion process in the viewpoint of forming a thick plate. In the hole expansion process of the plate with a hole, as the hole being expanded, the crack is occurred to outward direction at the boundary of a hole. Therefore, it is need to apply the fracture criterion in the hub hole expansion process. In this paper, the hub hole expansion process is simulated with commercial elasto-plastic finite element code, LS-DYNA3D considering some ductile fracture criteria. Fracture mode and hole expansion ratio is compared with respect to the fracture criteria. Analysis results demonstrate that only the effective plastic strain is not adequate to predict the fracture mode in the hub hole. And the analysis results also indicate that the ductile fracture criteria properly predict the fracture mode but hole expansion ratio is different with the result of each other because of their different characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.549-554
• /
• 2013

For the past years, higher power rating 2 stroke super long stroke diesel engines having more than 8 cylinders and larger cylinder bore are installed mainly on very large containerships to save on fuel consumption. However, these engines are prone to X-mode vibration due to $2^{nd}$ node torsional vibration or the X-type moment, particularly because of the increase in total length and height. Recently, cases of excessive X-mode vibration often occurred on engine's major components. This vibration is manifested also as secondary vibration causing failure in engine-mount large structures. This study investigated the excitations caused by the $2^{nd}$ node propulsion shafting torsional vibration that influence X-mode vibration of the main engine and practical countermeasures are proposed. An 8RT-82RT-flex 8 cylinder engine and 11S90S-ME 11 cylinder engine for a container ship was used as research model.

• Journal of the Korean Wood Science and Technology
• /
• v.11 no.3
• /
• pp.14-22
• /
• 1983

The purpose of this study was to evaluate the effect of short-term paraquat treatment without insecticides on the enhancement in oleoresin of pitch pine (Pinus rigida M.) at various distances from the wound height. The trees were treated with 0.5, 2 and 4% paraquat solutions using the bore-hole technique. Duplicate cores from treated and untreated sides of treated trees were made at 5 height levels (-0.3, 0.0, 0.3, 0.9 and 1.5 m above the wound height) at 3 months after treatment. The alcohol-benzene extractives based on unextracted oven-dry cores were taken as oleoresin contents. The results were as follows: 1. The effect of oleoresin enhancement at wound height were not affected by paraquat concentration. 2. Ascending distance of the enhancing effects above the wound height was directly related to paraquat concentration. Only in 4% paraquat treated trees, the effect extended to 1.5 m above the wound height. 3. As a result of examining descending distance of the enhancing effects at 0.3 m below the wound height, the effects extended to there in 4% and 2% paraquat treated trees.

• New & Renewable Energy
• /
• v.1 no.4 s.4
• /
• pp.30-37
• /
• 2005

Cycle simulation of Ground Source Heat Pump[GSHP] system was carried out to determine the design specification of basic components such as turbo compressor and heat exchangers. Part load operation characteristics of the designed GSHP system was estimated using the compressor and heat exchanger performance data. A 50RT class turbo compressor for GSHP system is now under development, in which R134a refrigerant is adopted as working fluid. The compressor with variable cascade diffusers is designed to work both in cooling and heating modes so that it can actively keep up with the climate change with high efficiency. The normal running speeds of the compressor are 59000rpm for heating mode and 70000rpm for tooling mode respectively. It has two identical impellers at both ends of the rotor so as to minimize aero-induced thrust force effectively. GSHP system was coupled with a vortical type heat exchanger, and heat gain and heat loss from ground were evaluated per a bore hole. For the optimal integration of the heat pump system, its header for circulating fluid was combined with the ground heat exchangers in parallel and series configuration.