• 한국가스학회지
• /
• 제14권6호
• /
• pp.7-14
• /
• 2010

본 연구에서는 자착화특성이 다른 DME와 n-Butane을 이용하여 다양한 흡기공급방식에 따른 HCCI엔진연소에서 압력상승률의 저감특성에 대하여 조사하였다. 연소실내부의 가스압력측정, 광학측정용 엔진을 이용한 화학발광법의 측정 그리고 화학반응수치계산을 통하여 연소실내부에서 각 국소부분의 연소특성을 파악하였다. 최대압력상승률은 DME와 n-Butane의 혼합 상태에 의해 결정되어진다. DME가 성층화되고 n-Butane이 균일하게 분포되진 조건에서 가장 많이 감소되는데 두 연료가 균일한 경우에 비해서 최대압력상승률은 0.25MPa/ms 로 저감되었고 CA50도 5deg 지각되었다.

• 한국자동차공학회논문집
• /
• 제12권1호
• /
• pp.32-38
• /
• 2004

To evaluate the durability of direct injection diesel engine using biodiesel fuel, a small D. I. diesel engine was operated on a blend(BDF 20) of 20％ biodiesel fuel and 80％ diesel fuel for 200 hours. Engine dynamometer test was performed at a load of 90％ and a speed of 1900 rpm to monitor the engine performance and exhaust emissions. Engine performance parameters and exhaust emissions were sampled at 1 hour interval for analysis. The combustion maximum pressure and the crank angle at this maximum pressure as a combustion variation factor were considered to study the combustion characteristics of BDF 20 in diesel engine during durability test. As the results, the standard deviations and errors of combustion variation factors on BDF 20 were very little and combustion characteristics were very stable during the durability test. BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions with special increase of nitrogen oxides compared to diesel fuel. There was no also unusual change in engine oil composition from using BDF 20. Most of engine parts were clean and showed little wear, but soots were detected around the hole of fuel injector when BDF 20 was used in direct injection diesel engine for 200 hours.

• 한국자동차공학회논문집
• /
• 제19권2호
• /
• pp.105-110
• /
• 2011

Through this study, the performance evaluation on the addition of low-pressure loop EGR(Exhaust Gas Recirculation) in a 6.0 L commercial diesel engine was carried out using WAVE modeling and simulation. Since the key technology of advanced diesel engine combustion such as low-temperature combustion is to steadily supply high rates of EGR in a wide operating range, the current study could be effectively contribute to the design and development processes of up-to-date diesel engine systems as real-world reference data. The current simulation results show that the system in which low-pressure loop EGR is added shows almost 2.3 times increase in maximum EGR rate at 1000 rpm as well as almost 1.6 times increase at 2200 and 1600 rpm in comparison with an engine system employing high-pressure loop EGR only. Also, both turbocharger axis speed and charging pressure level did not deteriorate due to the addition of low-pressure loop EGR at 2200 and 1000 rpm, but they were fairly decreased at 1600 rpm.

• 동력기계공학회지
• /
• 제17권6호
• /
• pp.18-24
• /
• 2013

An experimental study was performed to investigate the characteristics of combustion pressure and exhaust emissions when the pilot injection timing and EGR rate were changed in a CRDI 4-cylinder diesel engine. The pilot injection timing and EGR rate have a significant impact on the combustion and emission characteristics of diesel engine. In this study, the pilot injection timing and EGR rate variation were conducted to 2000rpm of engine speed with torque 50Nm. Combustion pressure and heat release rate were decreased under high EGR rate conditions but increased under the pilot injection timing $20^{\circ}$(BTDC). IMEP and the maximum pressure in cylinder(Pmax) were decreased under the same injection timing with the increase of EGR rate. The NOx emission was decreased with increasing the EGR rate. On the other hand, in the same injection timing conditions, CO, HC, $CO_2$ emissions were increased with increasing the EGR rate.

• 한국자동차공학회논문집
• /
• 제13권5호
• /
• pp.35-41
• /
• 2005

The effects of cooled-ECR on the characteristics of combustion and exhaust emissions were investigated in a single cylinder HCCI diesel engine The premixed charge (gasoline or diesel) was obtained with premixing chamber and high-pressure (5.5MPa) injection system. Exhaust pressure control and cooled ECR system were used in order to reduce pressure fluctuation and to mix the exhaust gas well with the fresh intake air. The experimental results show that NOx emissions from conventional diesel engine are steeply decreased by HCCI diesel combustion with cooled-EGR in both case of gasoline and diesel premixing. But soot emissions are rapidly increased with the increase of ECR rate. The recycled exhaust gas increased the ignition delay of mixture and decreased maximum combustion pressure. HC and CO emissions of HCCI combustion are increased with ECR rate.

• 한국농업기계학회:학술대회논문집
• /
• 한국농업기계학회 2005년도 동계 학술대회 논문집
• /
• pp.76-82
• /
• 2005

This paper presents the combustion characteristics of hydrocarbon fuel from a conventional pressureswirl nozzle of a small-scale burner. The nozzle has orifice diameters of 0.256 mm and liquid flow rates raging from 50 to 64 mL/min were selected for the experiments. The furnace temperature distribution along the axial distance, the gas emission such as CO, $CO_2,\;NOx,\;S0_2,$ flue gas temperature, and combustion efficiency were studied. The local furnace and flue gas temperatures decreased with an increase in air velocity. At injection pressures of 1.1 and 1.3 MPa the maximum furnace temperatures occurred closer to the burner exit, at an axial distance of 242 mm from the diffuser tip. The CO and $CO_2$ concentrations decreased with an increase in air velocity, but they increased with an increase in injection pressure. The effect of air velocity on NOx was not clearly seen at low injection pressures, but at injection pressure of 1.3 MPa it decreased with an increase in air velocity. The effect of air velocity $SO_2$ concentration level is not well understood. The combustion efficiency decreased with an increase in air velocity but it increased with an increase in injection pressure. It is recommended that injection pressure less than 0.9 MPa with air velocity not above 8.0 m/s would be suitable for this burner.

• 한국연소학회지
• /
• 제2권1호
• /
• pp.17-27
• /
• 1997

It is well known that NOx formation has a strong dependence on the maximum temperature and correspondingly with the maximum chamber pressure of a closed combustion system. However, in a case of impinging-jet-flame (IJF hereafter) combustion with opposed dual pre-chambers, low $NO_x$ formation with high pressure could be achieved, but its mechanism has not been clearly understood so far. In this study, a three-dimensional analysis is adopted to resolve time-variant local properties that might indicate the mechanism of IJF combustion. Numerical results are verified by comparing them with experiments. The IJF combustion in a vessel with no pre-chamber, with single pre-chamber, and with dual pre-chambers is studied. The orifice diameter and the volumetric ratio of pre-chamber are used as geometric parameters. The effects of main-chamber ignition delay time and combustion time of main-chamber, orifice exit velocity, orifice exit temperature, turbulent kinetic energy of main-chamber and spatial distribution of temperature in the latter stage of combustion are investigated. A longer main-chamber ignition delay and a shorter main-chamber combustion time suppress the formation of high temperature region with respect to mean temperature, which consequently results in less NO production.

• Journal of Advanced Marine Engineering and Technology
• /
• 제29권2호
• /
• pp.154-160
• /
• 2005

The result of combustion experiment by using the methanol-gasoline blended fuel showed that the supplying pressure appeared the maximum pressure between equivalent rate 1.1 and 1.2. and the evaporation of the fuel has been known to have been greatly influenced by surrounding temperature and the combustion chamber temperature after being injected from the injector And it is confirmed that the rate of evaporation had been suddenly dropped according to the temperature in the combustion chamber though the injected foe) had been fully evaporated Such tendency has visibly appeared when the zone is leaner. and we recognize that the rich fuel supply is needed in the operation of cold operating.

• International Journal of Automotive Technology
• /
• 제6권4호
• /
• pp.323-332
• /
• 2005

A cylindrical constant volume combustion chamber was used to investigate the flow characteristics at the spark electrode gap and the combustion characteristics of a homogeneous charged methane-air mixture under various overall charge pressures, excess air ratios and ignition times. The flow characteristics, including the mean velocity and turbulence intensity, were analyzed with a hot wire anemometer. Combustion pressure development measured by piezoelectric pressure transducer, a flame propagation image acquired by ICCD camera and exhaust emissions measured by 2-valve gas chromatography were used to investigate effects of initial pressures, excess air ratios and ignition times on the combustion characteristics. It was found that the mean velocity and turbulence intensity had the maximum value around 200-300 ms and then decreased gradually to a near-zero value after 3000 ms and that the combustion duration was shorten and the flame speed and laminar burning velocity had the highest value under the condition of an excess air ratio of 1.1, an overall charge pressure of 0.15 MPa and an ignition time of 300 ms in the present study. The $CO_2$ concentration was proportional to the ignition time and overall charge pressure, the $CO_2$ concentration was proportional to the excess air ratio, and the UHC concentration was inversely proportional to the ignition time and overall charge pressure.

• 한국자동차공학회논문집
• /
• 제12권3호
• /
• pp.75-82
• /
• 2004

The allowable exhaust standard has been intensified as a part of the countermeasure to decrease air pollution in the world. As the cars with an alternative fuel starts to get into the spotlight, the cars with low emission has been introduced and exhaust gas regulation forced in this country. These days, LPG vehicles, which infrastructure of fuel was already built up, and CNG vehicles are recognized for alternative fuel cars in this country. In this study, the constant volume combustion chamber was manufactured and used for experiments to obtain the ignition characteristics of LPG fuel and the optimal ignition energy. The experiment measured the combustion characteristics, in regard to the change of combustion variable, and the change of ignition energy. During the combustion of fuel, the maximum temperature inside the combustion chamber is higher when the initial pressure is higher. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux did not change much with the theoretical correct mixture but the various initial temperature of the combustion chamber. The heat flux got faster and ignition energy bigger as the dwell time of the ignition system expanded. When the dwell time get longer, the ignition energy also increased then fixed. The ignition energy increased as the initial pressure inside the combustion chamber higher. The heat flux got faster as the dwell time expanded.