• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.93-96
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• 2012

The spontaneous ignition mechanism of high pressure hydrogen gas released into tube is well-deduced from previous studies. However, those results have a limit because the studies have been conducted at low burst pressure of about 10 MPa. In this study, the process or ignition feature are investigated with higher burst pressure of up to 30 MPa through numerical analysis. The results show that the trend of ignition became to be different with a burst pressure. While two reaction regions is important to initiate the ignition when burst pressure is about 10 MPa, the reaction of the core region does not play a role in ignition inside the tube when a burst pressure is above 20 MPa.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.1
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• pp.75-85
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• 1996

The gas pressure acting on the rings in internal combustion engine influences the friction, wear and HC emission. In order to understand their characteristics, it is necessary to measure the interring gas pressure during engine operations. In this study, miniature type pressure transducer was developed to measure inter-ring gas pressure. And measurements of cylinder and inter-ring gas pressure were made on a gasoline engine running at full and part load conditions. Finally the characteristics of inter-ring gas pressure variation during engine operation were obtained form analysis of measured date.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.8
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• pp.2561-2571
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• 1996

The flow in the turbomachinery is very unsteady due to the stator-rotor interaction. It has been indicated that the stator-rotor interaction has three distinct causes of unsteadiness: that is, the viscous vortex shedding, wake rotor interaction and potential stator-rotor interaction. In this paper, the mechanism of unsteady potential interaction and wake interaction in the stator-rotor stage flow is numerically investigated in two-dimensional view point. The numerical technique used is the upwind scheme of Van Leer's Flux Vector Splitting(FVS) and cubic spline interpolation is applied on zonal interface. Then, the flow field of a compressor stage composed of NACA 65410 is analyzed. Flow fields are found to be simulated reasonably by this method and the sensitivity due to back-pressure variation is more stronger than rotor-velocity variation.

• Journal of Korea Foundry Society
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• v.31 no.4
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• pp.198-204
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• 2011

The present study was aimed to investigate the dependence of fatigue property on microporosity variation of low-pressure die-cast (LPDC) A356 alloy. The fatigue property of A356 alloy was evaluated through high cycle fatigue test, and the microporosity-terms used were the fractographic porosity measured from SEM observation on fractured surface and the volumetric porosity obtained through the density measurement using Archimedes's principle. The number of cycles to failure of A356 alloys depends obviously upon the variation of fractographic porosity, and can describe in terms of the defect susceptibility which depends on the microporosity variation at a given value of stress amplitude. The modified Basquin's equation was suggested through the combination of microporosity variation and static maximum tensile stress to fatigue strength coefficient. Using modified Basquin's equation, it could suggest that the maximum values of fatigue strength coefficient and exponent achievable in defect-free condition of A356 alloy are 265 MPa, -0.07, respectively.

• Journal of Korean Port Research
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• v.6 no.2
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• pp.43-64
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• 1992

This study discusses the interacting with deep water waves approaching from deep water based on the linear wave theory and steep sloping sea bottom floor by the numerical procedure. The results of particular interest are particle velocity and acceleration in x, y, z direction wave height amplification factor reflection coefficient and dimensionless pressure distribution on the steep sloping bottom with respect to the various incident wave angle. The wave loads relative to various bottom slopes, incident wave angles and wave periods on submerged breakwater and pipe are represented in comparison with mild sloping bottom the wave load parameters on the steep sloping bottom seemed to be influenced by variation of incident wave angle. In general the particle velocities and accelerations in x, y, z directions on the steep sloping bottom represented larger value or about two than those on the mild sloping bottom according to incident wave angle. However, the wave height amplification factors did not show distinct difference, but the slight variation with respect to the various incident angle showed on mild sloping bottom. The reflection coefficient increased with respect to increase of the incident angle on the steep sloping bottom the results also indicate that the very steep sloping beach produces a rather substantial amount of reflection as we expected. No significant variation of wave pressure was shown on the steep sloping bottom but it represented a certain amount of variation on the mild sloping bottom according to the various incident wave angle. The analysis at the OTEC site also showed similar results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.57-58
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• 2008

• Journal of computational fluids engineering
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• v.2 no.2
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• pp.89-96
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• 1997

High injection pressure system has been developed as a measure to reduce harmful exhaust gases. In order to understand the effect of pressure on diesel spray injection process, wide range of high injection pressure was tested. The gas phase is modelled by the Eulerian continuum conservation equations of mass, momentum, energy and fuel vapour fraction. The liquid phase is modelled following the discrete droplet model approach in Lagrangian form. The droplet distributions, vapor fractions and gas flows are analyzed in various injection pressure cases. The distributions of spray and vapor increase and the Sauter mean diameter decreases with increasing injection pressure quickly in a low pressure area but slowly in a high pressure area.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1042-1050
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. The external and internal pressure of rolling stock have been measured by using the running test with atmospheric pressure sensors and portable data acquisition system in high speed train. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.329-334
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• 2003

Design of pre-compression region(trapping region) of the valve plate is an important element to minimize the pressure fluctuation in a cylinder and in discharge process, and pump noise. In this study, we tried to prove what the characteristics of the oil hydraulic pump would be according to the angle of the trapping region. Three kinds of asymmetrical valve plates were used. As a result, we found that by designing the trapping region, the slope of the pressure rise in the cylinder port from low-pressure suction region to high-pressure discharge region is relaxed and the pressure fluctuation width and the discharge pressure pulsation are reduced. Therefore, because the pump gets smooth pressure fluctuation and low fluid Impact, the pump noise is reduce.

• Journal of the Society of Naval Architects of Korea
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• v.46 no.2
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• pp.105-113
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• 2009

A theoretical study on the pressure fluctuation induced by a propeller was carried out in this study. The main objective of this study is to analyze the source mechanism of the pressure fluctuation induced by propeller sheet cavitation. To analyze the pressure fluctuation induced by propeller sheet cavitation, modern acoustic theory was applied. Governing equation of pressure fluctuation induced by sheet cavitation was derived using Ffowcs Williams proposed time domain acoustic approaches. Several factors affecting pressure fluctuation were analyzed based on the derived governing equation. Pressure fluctuation result was represented by combined results of the far field term and near field term. Finally, the physical mechanism of pressure fluctuation at the blade rate frequency was analyzed using numerically generated cavitation volume variation.