• 한국자동차공학회논문집
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• 제25권3호
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• pp.336-343
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• 2017

Intake air conditions, such as air temperature, pressure, and humidity, are very important parameters that influence engine performance including combustion and emissions characteristics. The purpose of this study is to investigate the effects of intake air temperature on combustion and exhaust emissions characteristics in a single cylinder diesel engine. In this experiment, an air cooler and a heater were installed on the intake air line and a gas flow controller was installed to maintain the flow rate. It was found that intake air temperature induced the evaporation characteristics of the fuel, and it affects the maximum in-cylinder pressure, IMEP(indicated mean effective pressure), and fuel consumption. As the temperature of intake air decreases, the fuel evaporation characteristics deteriorate even as the fuel temperature has reached the auto-ignition temperature, so that ignition delay is prolonged and the maximum pressure of cylinder is also reduced. Based on the increase in intake air temperature, nitrogen oxides(NOx) increased. In addition, the carbon monoxide(CO) and unburned hydrocarbons(UHC) increased due to incomplete fuel combustion at low intake air temperatures.

• 한국안전학회지
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• 제27권3호
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• pp.83-88
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• 2012

For the safe handling of n-tridecane, the lower flash points and AITs(auto-ignition temperatures) by ignition delay time were experimented. Also lower explosion limits by the lower flash points were calculated. The lower flash points of n-tridecane by using closed-cup tester were experimented $92^{\circ}C$ and $96^{\circ}C$. The lower flash points and fire point of n-tridecane by using open cup tester were experimented 100 oC and 103 oC, respectively. This study measured relationship between the AITs and the ignition delay times by using ASTM E659 apparatus for n-tridecane. The experimental AIT of n-tridecane was 223 oC. The calculated lower explosion limit by using measured lower flash point 92 oC for n-tridecane was 0.6 Vol.%.

• 한국화재소방학회논문지
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• 제27권6호
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• pp.50-56
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• 2013

대향류 비예혼합 연료-공기 유동장에서 고온연료의 점화특성과 형성된 화염의 소화특성에 미치는 복사효과에 대해 수치계산을 통해 검토하였다. 화학반응의 계산을 위해 GRI-v3.0의 상세화학반응기구를 사용하였으며, 단열계산과 광학적으로 얇은 복사모델을 적용하여 계산을 수행하였다. 대향류 유동장의 점화와 소화점을 정확히 찾기 위하여 화염제어 연속계산법을 적용하였다. 결과를 통해 스트레인율 변화에 대해 최고 온도보다는 최고 H 라디칼 농도가 점화와 소화거동을 이해하는데 더 적합하다는 것을 확인하였다. 최고 H 라디칼 농도변화 거동을 통해 기존에 알려진 S-곡선, C-곡선 및 O-곡선 등을 확인하였다. 복사열손실 분율($f_r$)과 공간에 대해 적분된 열발생률(IHRR)을 통해 $f_r$이 가장 큰 점에서 복사효과에 의한 소화가 발생하였으며, 화염신장 소화점에서는 IHRR이 가장 높지만 화염에서의 전도에 의한 열손실로 인해 소화가 되는 것을 확인하였다. 복사는 화염신장 소화점에는 거의 영향이 없지만 복사 소화점과 점화점에는 큰 영향을 주는 것을 알 수 있었다. 또한 연료의 온도가 높아질수록 복사에 의한 소화점의 스트레인율과 화염신장에 의한 스트레인율 사이의 영역이 넓어지게 되어 화염 안정성이 향상되고 있음을 알 수 있었다.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.29-34
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• 2011

This study investigates the potential of DME/Diesel dual fuel engine for reducing emissions with same power. Dual fuel engine controls the combustion using two different fuels, DME and diesel with different auto-ignition timings. In the previous work, the caracteristics of combustion and emissions under single cylinder engine and ignition is done by compression ignition. Pre-mixture is formed by injecting low-pressure DME into an intake manifold and high-pressure fuel (diesel or DME) is injected directly into the cylinder. Both direct diesel injection and port fuel injection reduced the significant amount of Smoke, CO and NOx in the homogeneous charge compression ignition engine due to present of oxygen in DME. In addition, when injecting DME directly in cylinder with port DME injection, there is no changes in emissions and energy consumption rate even operated by homogeneous charge compression ignition.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.80-86
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• 2008

Recently, controlled auto ignition(CAI) in gasoline engines are drawing more attentions due to its extremely low level of NOx emissions and potentials in lowering the fuel consumption rate. The one of the key techniques for realizing CAI combustion in engines is the control of valve system. Since the valve linkage system with higher complexity, or even earn-less valve systems, such as electro-hydraulic and electro-magnetic system, are adopted in CAI engines, it is not easy to estimate the valve lift profile from earn profiles. Therefore new measurement techniques for valve lift in CAI engines have been tried and tested. In this paper, hole type valve lift sensor was developed and tested to check the applicability in CAI engines. The valve lifts could be obtained from the sensor signal, which depends on the distance from the sensor to magnet attached to valve. Various engine speeds, ranging from 2,000 to 6,000 rpm, and valve lifts, maximum up to 9.7 mm, were tested. It was found that the sensor output for valve lift had accuracy of 98% in comparison with the basic specifications of valve lift through improvements of sensor driving circuit.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.51-58
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• 2003

A cycle simulation method is developed by coupling a commercial code, Ricardo's WAVE, with the SENKIN code from CHEMKIN packages to predict combustion characteristics of an HCCI engine. By solving detailed chemical kinetics the SENKIN code calculates the combustion products in the combustion chamber during the valve closing period, i.e. from IVC to EVO. Except the combustion chamber during the valve closing period the WAVE code solves thermodynamic status in the whole engine system. The cycle simulation of the complete engine system is made possible by exchanging the numerical solutions between the codes on the coupling positions of the intake port at IVC and of the exhaust port at EVO. This method is validated against the available experimental data from recent literatures. Auto ignition timing and cylinder pressure are well predicted for various engine operating conditions including a very high ECR rate although it shows a trend of sharp increase in cylinder pressure immediate after auto ignition. This trend is overpredicted especially for EGR cases, which may be due to the assumption of single-zone combustion model and the limit of the chemical kinetic model for the prediction of turbulent air-fuel mixing phenomena. A further work would be needed for the implementation of a multi-zone combustion model and the effect of turbulent mixing into the method.

• 한국분무공학회지
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• 제10권2호
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• pp.41-47
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And. it is extremely difficult to increase gasoline engine efficiency and to reduce NOx and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper. internal EGR(exhaust gas recirculation) effect is suggested to realize CAI combustion. An experimental study was carried out to achieve CAI combustion using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). A flame trap was used to simulate internal EGR effect and to increase flame propagation speed in the CVCC. Flame propagation photos and pressure signals were acquired to verify internal EGR effect. Flame trap creates high speed burned gas jet. It achieves higher flame propagation speed due to the effect of geometry and burned gas jet.

• 한국화재소방학회논문지
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• 제31권5호
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• pp.1-6
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• 2017

가연성물질의 화재 및 폭발 특성치는 안전한 취급, 저장, 수송, 처리 및 폐기하는데 반드시 필요하다. 공정 안전을 위한 대표적인 연소특성치로 최소자연발화온도(AIT)를 들 수 있다. 최소자연발화온도는 가연성 액체의 안전한 취급을 위해서 중요한 지표가 된다. 최소자연발화온도는 가연성물질이 주위의 열에 의해 스스로 발화하는 최저온도이다. 본 연구에서는 ASTM E659 장치를 이용하여 가연성 혼합물인 n-Pentanol과 p-Xylene 혼합물의 최소자연발화온도와 발화지연시간을 측정하였다. 2성분계를 구성하는 순수물질인 n-Pentanol과 p-Xylene의 최소자연발화온도는 각각 $285^{\circ}C$, $557^{\circ}C$로 측정되었다. 그리고 측정된 n-Pentanol과 p-Xylene 혼합물의 최소자연발화온도와 AIT에서의 발화지연시간의 실험값은 제시된 식에 의한 계산값과 적은 평균절대오차에서 일치하였다. 따라서 본 연구에서 제시한 예측식들을 이용하여 n-Pentanol과 p-Xylene 혼합물의 다른 조성에서도 최소자연발화온도와 발화지연시간을 예측이 가능하다.

• 한국분무공학회지
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• 제18권4호
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• pp.188-195
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• 2013

An investigation on spray characteristics of fuels which diesel and di-methyl ether (DME) with change of injection pressure used the multi-injection in constant volume combustion chamber (CVCC). Diesel was already used famous fuel which we could use. DME showed similar features with diesel like as cetane number, auto-ignition temperature. High cetane number of diesel and DME could make possible to compression ignition. DME showed different atomization from diesel due to evaporating pressures and boiling points. Experiments were carried out in CVCC equipped with Delphi solenoid 6-hole type injector and the spray characteristics of diesel and DME were tested the various pre and pilot injection. Terms of injections and a number of injections in multi-injection has been controlled. Experiments were performed in 2 types that 1500 rpm, 2000 rpm and under the condition of injection ranging from 100 bar to 500 bar. From the results of this experiment diesel showed longer spray penetration than DME. That result showed different of atomization speed DME and diesel. Result of high injection pressure condition showed similar spray characteristics diesel and DME. After this investigation, new conditions and experiments using laser light to go forward and add the fuels like as the biodiesel and diesel and DME blend.

• 한국수소및신에너지학회논문집
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• 제26권5호
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• pp.393-401
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• 2015

The characteristics of diesel and biodiesel are similar like as cetane number and auto-ignition temperature. High cetane number of diesel and BD could make possible to compression ignition. but BD showed different atomization from diesel due to component like density, viscosity and iodine value etc. Because of this, the biodiesel requires validation. This study using diesel and BD20 investigated effect to durability injector. Durability test were used common rail and bosch solenoid type 5-hole injector. Total test was 672hr but actual running time was 200hr. Spray experiments for spray characteristics were carried out using constant volume combustion chamber. Spray characteristics of diesel and BD showed different result up to durability test time. After 100hr, diesel showed spray shapes were stable but BD was not. After 200hr, difference of diesel and BD spray shapes were grow serious.