• Journal of the Korean Society of Safety
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• v.10 no.3
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• pp.11-20
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• 1995

In recent years, the study on the high efficiency of the internal combustion engine has been mainly proceeding. In this study, we developed rotary valve to achieve the improvement of volumetric efficiency and to be simple construction. And then made a comparative analysis between rotary and poppet valve. In this experiment, rotary valve enlarged the flow area of valve port to minimize the resistance of the fluid flow and to flow smoothly in intake and exhaust process. Indeed, valve timing was controlled properly lest positive pressure in exhaust process should affect intake process. Motoring and firing experiments were using engine speed and air-fuel ratio as the principle parameter and the full opening of throttle valve and minimum spark advance for best torque (MBT) as engine operating variables.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.2
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• pp.17-26
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• 1993

As fundamental step to find the suitable compression ratio of hydrogen fueled engine, performance and combustion characteristics of that engine were analyzed. Qualitative characteristics of the hydrogen fueled engine were similar to that of the gasoline engine, and it was also found that knock limit compression ratio of the hydrogen fueled engine was higher than that of the gasoline engine.

• Journal of the korean Society of Automotive Engineers
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• v.17 no.5
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• pp.1-8
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• 1995

전산유체 해법의 내연기관 3차원 해석에 대한 최근 연구 동향에 대해 소개하였다. 난류유동 해석은 아직 정확성과 신뢰도 면에서 많은 연구가 필요하지만 현재의 상태에서도 직관, 경험, 실험 측정에 의해 파악하기 어렵거나 많은 비용과 시간이 요구되는 부분을 보완해 줄 수 있는 도구로서 인정받고 있다. 연소해석 부분은 현상 자체가 유동, 연소, 분무, 열전달등이 복합적으로 작용하는 어려운 문제로서 공학계산의 가장 첨단 분야 중의 하나라 할 수 있다. 현재 관련 모델로서 스파크 점화기관의 점화 및 화염전파, 배기가스 생성 과정과 디젤기관의 압축착화, 예혼합 및 확산 연소, 매연 등의 생성과정에 대한 모델 개발과 검증이 활발히 이루어지고 있다. 일부 발표된 논문 결과들은 이와 같은 방법이 엔진의 주요 연소 특성을 재현하는데에 성공적으로 활용될 수 있음을 보여주고 있다.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.9-15
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• 1999

A digital CDI(Capacitive Discharge Ignition) system on small two stroke motorcycle engine was developed in this paper, This CDI system with microprocessor as its main part has more flexible spark timing than the conventional CDI system because of its programmable characteristics. The principle of this digital CDI system and the design methods of hardware and software were presented in this paper, Two stroke small engine was tested to investigate the performance of digital CDI system And also this system was investigated to optimize the engine performance. Also comparison between conventional CDI can provide better spark timing variation than the conventional system. The part and full load test results show that the engine power was increased about 10-20% and fuel consumption was decreased about 10-20% simultaneously. Furthermore, this digital CDI system has simple structure, low cost and very little modification are required. It is a promising technology to substitute for the widely used conventional CDI system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.5
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• pp.709-717
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• 2000

Cyclic variability has long been recognized as limiting the range of operating conditions of spark ignition engines, in particular, under lean and highly diluted operation conditions. The cyclic combustion variations can be characterized by the pressure parameters, combustion parameters, and flame front parameters. The coefficient of variation in indicated mean effective pressure ($COV_{IMEP}$) defines the cyclic variability in indicated work per cycle, and it has been found that vehicle driveability problems usually result when $COV_{IMEP}$ exceeds about 10%. For analysis of the cyclic variability in SI engines at idling, the results show that cyclic variability by the $COV_{IMEP}$ or the coefficient of variation in maximum pressure can be explained and may be consequently reduced by the help of the optimum spark timings.

• Journal of the korean Society of Automotive Engineers
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• v.9 no.6
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• pp.53-59
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• 1987

The effect of the three types of fuel vaporizing device on the engine torque and exhaust emission was investigated. Among the three types of fuel vaporizing device designed for the experiments, a 88mm long device with mesh around the inside pipe showed stable lean mixture combustion up to 21:1 air-fuel ratio and reduced the exhaustion of CO and HC. Compared with the general trend in the decrease of engine torque it was observed that the decrease of engine torque in this lean mixture combustion with the new device was small.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.136-140
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• 2009

Vehicle idle has become an increasing quality concern for automobile manufacturers because of its impact on customer satisfaction. As demand for better fuel economy increases, automobile manufacturers are continuously looking for any benefits from different driving conditions. Combustion variability in spark ignition engines was recognized that the stability of engine at idle is affected by the factors of fuel injection timing, ignition timing and air-fuel ratio. Therefore in this research, the results will be shown the effects of stability and the variations at idle according to fuel injection timing, ignition timing and air-fuel ratio as the basic parameters.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.37-46
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• 2016

For the SI engines, at only full load, the pumping loss has a negligible effect, while at part load conditions, the pumping loss increases. To avoid the pumping loss, the spark-ignited engines are designed to inject gasoline directly into the combustion chamber. In the spark-ignited direct-injection engines, ignition probability is important for successful combustion and the flame propagation characteristics are also different from that of pre-mixed combustion. In this paper, a visualization experiment system is designed to study the ignition probability and combustion flame characteristics of spark-ignited direct-injection CNG fuel. The visualization system is composed of a combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. It is found that ambient pressure, ambient temperature and ambient air flow velocity are important parameters which affect the ignition probability of CNG-air mixture and flame propagation characteristics and the injected CNG fuel can be ignited directly by a spark-plug under proper ambient conditions. For all cases of successful ignition, the flame propagation images were digitally recorded with an intensified CCD camera and the flame propagation characteristics were analyzed.

• Fire Science and Engineering
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• v.24 no.4
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• pp.92-97
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• 2010

Fire simulation by using a computational fluid dynamics model and examination of the fires at indoor shooting ranges broken out in the past were conducted, to presume causes of the fire at the indoor shooting range in Busan and suggest fire safety measures. On-site investigations and shooting tests on unburned gunpowder were also carried out. No trace of the muzzle spark and spark at the bullet trap was found in CCTV footage, and the impact of a stray bullet failed to ignite gunpowder. Cigarette was therefore presumed to be the most likely source of ignition among the potential sources. It appeared that the explosion in the shooting area was caused by violent burning of the polyurethane sound absorber and unburned gunpowder accumulated on it. The fire safety measures include prohibit of use of profile polyurethane sound absorber, removal of steel components from bullet trap, clean up and control of unburned gunpowder, etc.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1163-1168
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• 2011

Compared with the spark-ignition gasoline engine, the compression-ignition diesel engine has reduced fuel consumption due to its higher thermal efficiency. In addition, this reduction in the fuel consumption also leads to a reduction in $CO_2$ emission. Diesel engines do not require spark-ignition systems, which makes them less technically complex. Thus, diesel engines are very suitable target engines for using biofuels with high cetane numbers. In this study, the spray characteristics of biofuels such as vegetable jatropha oil and soybean oil were analyzed and compared with those of diesel oil. The injection pressures and blend ratios of jatropha oil and diesel oil (BD3, BD5, and BD20) were used as the main parameters. The injection pressures were set to 500, 1000, 1500, and 1600 bar. The injection duration was set to $500{\mu}s$. Consequently, it was found that there is no significant difference in the characteristics of the spray behavior (spray angle) in response to changes in the blend ratio of the biodiesel or changes in the injection pressure. However, at higher injection pressures, the spray angle decreased slightly.