• 한국연소학회지
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• 제8권3호
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• pp.31-37
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• 2003

The objective of this work is to investigate the effect of swirl, injection pressure and pilot injection on D.I.Diesel combustion by using a transparent engine system. The test engine is equipped with common rail injection system to obtain high pressure and to control injection timing and duration. In this study, the combustion analysis and steady flow test were conducted to estimate the heat release rate from in-cylinder pressure and pilot injection was investigated by using LII technique. As the results, high injection pressure was found to shorten ignition delay as well as enhance peak pressure and heat release rate was greatly affected by injection timing and pilot injection. In addition, the results showed that the period of soot formation corresponded to the diffusion flame.

• 한국해양공학회지
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• 제21권1호
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• pp.40-44
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• 2007

This paper presents the experimental results on slamming phenomenon. The air pressure cylinder was used to ensure repeatability of the impact. The results showed that the adopted experimental technique was excellent in terms of repeatability, compared to that of the free drop tests. The pressure time histories, magnitude of peak pressure and the behavior of jetspray were obtained. The flat specimen was tested for various incident angles. To estimate the incident speed of the specimen, a high-speed camera was used. The high-speed camera was also a useful tool in understanding the behavior.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.41-47
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• 2007

Scattering fields of two dimensional acoustic waves by a circular cylinder are investigated. The present numerical approach for the acoustic scattering problem has difficulties of numerical robustness, long-time stability and suitability of far-field boundary treatments. The time-dependent periodic acoustic source is used to analyze Interference patterns between incident waves and waves reflected by the cylinder. Characteristic boundary algorithms coupled with 4th order Modified-Flux-Approach ENO(essentially non-oscillatory) schemes are employed in generalized coordinates to examine the effect of the wane frequency on the interference patterns. Non-reflecting boundary conditions, which is crustal for accurate computations of aeroacoustic problems, are used not to contaminate scattering fields by reflected waves at the outer boundary. Computed scattering fields show the circumferential acoustic modes generated by interacting between acoustic sources and scattered waves. At a lower frequency, the wave passes almost straight through the cylinder without Interacting with circular cylinder. Simulation results are presented and compared with the analytic solution. Computed RMS-pressure distribution on the cylinder wall is good agreement with exact solution.

• 한국자동차공학회논문집
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• 제19권3호
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• pp.146-153
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• 2011

American NREL (National Renewable Energy Laboratory) reported that BDF20 could reduce PM, CO, SOx, and cancerogenic matters by 13.6%, 9.3%, 17.6%, and 13% respectively, compared to diesel fuel. BDF20 has been being tested on garbage trucks and official vehicles at Seoul City, which is positive on air environment, but negative on combustion by higher viscosity in winter season. This study investigated the combustion characteristics by applying pilot injection for improving the deterioration of combustibility caused by the higher viscosity of the BDF20 with the combustion flames taken by a high-speed camera and the cylinder pressure diagram. A 4-cycle single-cylinder diesel engine was remodeled to a visible 2-cycle engine taking the flame photographs, which has a common-rail injection system. The test was done laboratory temperature at $5{\sim}6^{\circ}C$. The results obtained are summarized as follows, (1) In the case of without pilot injection, the flame propagation speed was slowed and the maximum combustion pressure became lower. The phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of with pilot injection, early stage of combustion such as rapid ignition timing and flame propagation was activated since intermediate products formed by pilot injection act as a catalyst for combustion of main fuel.

• 한국소음진동공학회논문집
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• 제17권9호
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• pp.826-834
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• 2007

A 7K60MC-S low speed diesel engine in a power plant has frequently experienced high vibration since the unit completed construction works. Up to date, no fundamental vibration solutions were reached. Hence, several vibration tests and analyses were conducted to identify the root cause of this high vibration and to suggest the optimal countermeasures for diesel engine. The 9.25 Hz and 25.4 Hz vibrations have been observed on main body during operation. The magnitude of engine upper structural vibration is generally similar in horizontal transverse direction. However, differences in the 'Fore' and 'After' vibration magnitude with the same vibration phase angle at 9.25 Hz occur due to the explosion pulsations of 7 cylinders and the Inertia momentum added by the SCR (selective catalytic reduction) duct system. It was analyzed that the excess structural vibration occurred when the natural frequency of engine body is affected by the exciting sources due to the explosion pressure and the discharge pulsation of the seven cylinders in resonance range.

• Journal of Advanced Marine Engineering and Technology
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• 제39권9호
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• pp.911-917
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• 2015

본 논문에서는 함정용 디젤연료를 단기통 커먼레일 디젤엔진에 적용하여 연료분사압력 변화에 따른 분사율 특성, 거시적 분무 특성 및 연료분사시기와 연료압력변화에 따른 연소 및 배기가스 배출특성을 분석하는데 초점을 두었다. 분사율 특성은 Bosch법을 적용한 분사율 측정 시험 장치를 이용하여 분석하였고, 거시적 분무 특성은 정적용기 및 초고속 카메라를 이용하여 분석하였다. 또한, 연료분사시기 및 연료압력 변화를 정밀하게 제어할 수 있는 단기통 엔진을 이용하여 연소 및 배기가스 배출특성을 분석하였다. 30MPa과 50MPa의 분사조건에서 초기 분사율은 50MPa의 분사조건에서 크게 나타났으며, 분무 발달(투과) 또한 동일시간대에서 큰 것으로 분석되었다. 연료분사시기가 지각될수록 실린더 내부 최대 압력과 최대 열발생량은 떨어지는 경향으로 나타났으며, 고압분사조건에서 실린더 내부 최대압력과 최대 열발생량은 다소 큰 것으로 분석되었다. 고압분사조건에서 도시평균유효압력은 낮은 것으로 분석되었고, 연료분사시기가 TDC 쪽으로 지각될수록 도시평균유효압력 및 토크는 증가하는 것으로 나타났다. 연료분사시기가 $BTDC20^{\circ}$(30MPa)와 $BTDC15^{\circ}$(50MPa)에서 질소산화물 발생수준이 가장 높았으며, 일산화탄소는 $BTDC30^{\circ}$를 기준으로 지각될수록 저감되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제22권1호
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• pp.42-51
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• 1998

A 150 m$\^$3//hr, 30 kg/cm$\^$2/, air-cooled 3-stage reciprocating air compressor is designed to be used in starting large diesel engines of ships. A basic design procedure is presented to meet the targeted pressure and flow rate, and especially a volumetric efficiency of 80%. Temperature and stress analysis of the 1st stage cylinder are performed using axisymmetric FEM modelings. The dynamics of valve system is analyzed and stress at the 1st stage valve seat caused by valve impact is evaluated. To reduce friction loss and wear at the compressor engine system tribological design issues are reviewed and good design practices are suggested. Finally, forced-air pin-type interstage coolers are designed to dissipate generated compression heat at each stage.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
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• pp.61-67
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• 2000

Many research works for improving a boundary lubrication performance have been executed by using solid lubricants, and been tried to apply an engine lubrication. However those general lubricants like MoS$_2$ or PTFE have not been applied on engines due to the extreme conditions such as very high temperature and pressure by combustion process in a cylinder. A copper nickel alloy fine particle has been introduced and studied. In this Paper the lubricant using the alloy Particles is applied on a marine diesel engine and assessed by the engine performance test The results showed the increase of cylinder pressure related strongly to the engine efficiency as well as the improving the engine lubrication performance.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.110-115
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• 1999

Experimental study is conducted to clarify the pneumatic characteristics of brake system for freight car. KNR(Korean National Railroad)'s freight cars have the laden-tare type control valve of brake system. But, laden-tare type control valve has some shortcomings to match the high speed freight car. Newly developed diaphragm type control valve is introduced to adopt freight car for speed-up. The test using the formated train set consisted of 21 cars is conducted to estimate the pneumatic braking efficiency of the mixed train set. From the results of experiment, the pressure characteristics of each brake cylinder show similar patterns qualitatively. But, in the case of release and brake application, quantitative pressure values of brake cylinder are different.

• Journal of Advanced Marine Engineering and Technology
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• 제12권1호
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• pp.28-36
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• 1988

Since the oil shocks of 1970s, the quality of the fuel oil for marine diesel engines has become more degarded than ever. When the poorer quality fuel is burned, carbon residues of the fuel oil cause blockage of the fuel injection valve nozzle and troubles of fuel injection system. The mis-firing of engine occurs due to the decrease of fuel quantity injected, the decrease of compression pressure in the slow speed range, the increase of fuel leaked and the high ignition temperature of degraded fuel etc. This paper is to investigate theoretically the effects of mis-firing on the crankshaft axial vibration of diesel engine. The cylinder pressure in operation is calculated by the computer aided simulation of closed cycle for a large two-stroke diesel engine and also the exciting force of axial vibration and the resonance amplitudes are calculated. And then, the condition of normal state, misfiring and one-cylinder cut-off operation are analyzed. The results of calculations show good agreements with those of the actual measurements.