• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.179-182
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• 2014

A comparative DNS study of the ignition characteristics of dual-fueled reactivity controlled compression ignition (RCCI) and stratification charge compression ignition (SCCI) is investigated using a 116-species reduced primary reference fuel (PRF) mechanism. In the RCCI combustion, two PRF fuels (n-heptane and iso-octane) with opposite autoignition characteristics are separatedly supplied and in-cylinder blended such that spatial variations in fuel reactivity, fuel concentration and temperature are achieved. In the SCCI combustion, however, just a single fuel (PRF50) is used such that only fuel concentration and temperature inhomoginieties are obtained. Because three factors, rather than only two as in SCCI combustion, govern the overall RCCI combustion, combustion timing and combustion duration or heat release rate of RCCI combustion are flexibly and effectively controlled. It is found that the overall RCCI combustion occurs much earlier and its combustion duration is longer compared to SCC combustionI. Moreover, the negative temperature coefficient (NTC) has a positive effect on enhancing RCCI combustion by inducing a shorter combustion timing and a longer combustion duration as a result of the occurrence of a predominant low-speed deflagration-combustion mode.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.1-9
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• 2006

Recently, there has been an interest in premixed diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to conventional diesel engines. Because this concept reduced NOx and smoke emissions simultaneously. Early studies are shown that in a HCCI(Homogeneous Charge Compression Ignition) engine, the fuel injection timing and intake air temperature affect the mixture formation. The purpose of this study is to investigate characteristics of combustion and mixture formation according to injection timing and intake air temperature in a common rail direct injection type HCCI engine using an early injection method called the PCCI(Premixed Charge Compression Ignition). From this study, we found that the fuel injection timing and intake air temperature affect the mixture formation and in turn affects combustion in the PCCI engine.

• 한국화재소방학회논문지
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• 제18권2호
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• pp.27-33
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• 2004

화학물질의 최소자연발화온도의 정확한 지식은 산업화재를 예방하고 제어하는데 중요하다. 최소자연발화온도(AIT)는 화염이나, 스파크 없이 주위로부터 충분한 에너지를 받아서 스스로 점화할 수 있는 최저온도를 말한다. AIT는 실험 개시온도, 압력, 농도, 용기의 크기, 양론혼합비, 촉매, 증기의 농도, 발화지연시간 등 많은 인자에 영향을 받는다. 본 연구에서는 1994년에 제작된 ASTM E659-78 장치를 이용하여 산류(Acids) 발화지연시간과 AIT관계를 측정하였고, 실험에서 얻은 자료는 본 연구에서 제시한 예측 모델과 적은 오차 범위에서 일치하였다.

• 한국위험물학회지
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• 제6권2호
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• pp.23-29
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• 2018

The fire and explosion properties necessary for waste, safe storage, transport, process design and operation of handling flammable substances are lower explosion limits(LEL), upper explosion limits(UEL), flash point, AIT( minimum autoignition temperature or spontaneous ignition temperature), fire point etc., An accurate knowledge of the combustion properties is important in developing appropriate prevention and control measures fire and explosion protection in chemical plants. In order to know the accuracy of data in MSDSs(material safety data sheets), the flash point of phenol was measured by Setaflash, Pensky-Martens, Tag, and Cleveland testers. And the AIT of phenol was measured by ASTM 659E apparatus. The explosion limits of phenol was investigated in the reference data. The flash point of phenol by using Setaflash and Pensky-Martens closed-cup testers were experimented at $75^{\circ}C$ and $81^{\circ}C$, respectively. The flash points of phenol by Tag and Cleveland open cup testers were experimented at $82^{\circ}C$ and $89^{\circ}C$, respectively. The AIT of phenol was experimented at $589^{\circ}C$. The LEL and UEL calculated by using Setaflash lower and upper flash point value were calculated as 1.36vol% and 8.67vol%, respectively. By using the relationship between the spontaneous ignition temperature and the ignition delay time proposed, it is possible to predict the ignition delay time at different temperatures in the handling process of phenol.

• 한국안전학회지
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• 제37권6호
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• pp.18-24
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• 2022

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

• 동력기계공학회지
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• 제13권2호
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• pp.5-10
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• 2009

In recently, studies concerned to the diesel engine uses a natural gas as a fuel oil whose infra has been built already was approached to PCCI or HCCI with keeping a high thermal efficiency and reducing NOx and PM have been researching actively in normally single cylinder. An ignition source is required to bum the natural gas by a spark plug in gasoline engines, due to a higher auto-ignition temperature of natural gas. Then gas oil and DME were introduced as the ignition source. In this study as basic data for practical use of natural gas PCCI and HCCI engines, combustion characteristics and emission characteristics on 4-cylinders natural gas PCCI and HCCI engines with gas oil and DME as ignition sources were analyzed and the engine load range that is main object for practical use of PCCI and HCCI engines was made clearly by empirical experiment.

• Journal of Advanced Marine Engineering and Technology
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• 제26권1호
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• pp.132-137
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• 2002

Recently, impinging spray is used for atomization of diesel engine, but it bring on adhesion of fuel. Therefore, we studied about droplet behavior on high temperature plate changing the size of droplet, surface temperatures, and surface roughness of plate. In this study, We studied to confirm experimentally about mechanism of evaporation and ignition process of single fuel droplet. We observed evaporation time, evaporation appearance and ignition delay time by the photopraphs of 8mm video camera. Experimental results are summarized as follows: 1. The boiling point of fuel affect a evaporation and ignition process. 2. The surface roughness affect a evaporation time. 3. The ignition delay time relate to evaporation characteristic.

• 대한기계학회논문집
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• 제16권12호
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• pp.2376-2384
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• 1992

본 연구에서는 액적들의 분포상태가 비균일 분포 즉 비균일 액적크기 및 수밀 도 분포를 갖는 액적군에 대하여 집단점화 현상을 이론적인 해석을 통하여 규명한다. 이를 위하여 분사직후부터 점화순간까지의 과정 즉, 액적의 온도상승-증발-혼합기 형 성-반응의 진행-점화의 과정에 초기 액적들의 크기 및 수밀도 분포상태와 기체상의 조 건들이 중요 제변수들, 즉 온도, 속도, 성분질량농도 및 액적의 크기 분포등에 미치는 영향 등은 물론 액적군의 증발특성, 점화특성 등을 이론적 모델을 구성하여 해석한다. 결과들은 현재 사용되고 있는 집단연소 모델의 초기조건으로 사용하며, 액적들의 분포 상태에 따른 점화시의 액적군의 상태 및 점화 특성은 보다 향상된 연소시스템의 운전 및 설계에 분사조건으로서 활용될 것이 기대된다.

• 한국결정성장학회지
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• 제19권6호
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• pp.324-327
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• 2009

Mg 합금에서 Ca 첨가가 발화 및 연소 특성에 미치는 영향을 조사하였다. 주조 상태에서 순 Mg은 표면과 내부에 균열과 게재물들이 관찰되었지만 Ca이 첨가된 Mg-Ca 합금에서는 관찰되지 않았다. Mg 합금에 Ca가 첨가됨에 따라 1.5 wt%Ca까지는 발화 온도가 급격히 증가하다가 포화되는 경향을 보였다. 이러한 경향은 Mg-Ca 합금에서 Ca의 고용도와 관련이 있었다. Mg-Ca 합금의 연소 표면에 형성된 MgO 산화층이 발화와 연소를 억제하는 역할을 하였다.

• 한국분무공학회지
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• 제8권3호
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• pp.33-40
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• 2003

The low-emission and high-performance diesel combustion is an important issue in the combustion research community, In order to understand the detailed diesel flame involving the complex physical processes, it is quite desirable to diesel spray dynamics, auto-ignition and spray flame propagation. Dynamics of fuel spray is a crucial element for air-fuel mixture formation, flame stabilization and pollutant formation, In the present study, the diesel RCM (Rapid Compression Machine) and the Electric Control injection system have been designed and developed to investigate the effects of injection pressure, injection timing, and intake air temperature on spray dynamics and diesel combustion processes, In terms of the macroscopic spray combustion characteristics, it is observed that the fuel jet atomization and the droplet breakup processes become much faster by increasing the injection pressure and the spray angle, With increasing the cylinder pressure, there is a tendency that the of spray pattern in the downstream region tends to be spherical due to the increase of air density and the corresponding drag force, Effects of intake temperature and injection pressure on auto-ignition is experimently analysed and discussed in detail.