• 한국자동차공학회논문집
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• 제19권6호
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• pp.46-52
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• 2011

Homogeneous charge compression ignition (HCCI) is the best concept able to provide low NOx and PM in diesel engine emissions. This new alternative combustion process is mainly controlled by chemical kinetics in comparison with the conventional combustion in internal combustion engine. However, HCCI engine's operation have an excessive rate of pressure rising during the combustion process. In this study, stratification condition of EGR exhaust gases was used to reduce the pressure rising during the combustion process in HCCI engine. Also, combustion characteristics and emissions characteristics were investigated using the detailed diesel surrogate reaction mechanism.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.1-8
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• 1998

Waste combustion above a grate is the core process of incineration systems, stability of which should be guaranteed for emission minimization. However, complicated reactions and heat and mass transfer phenomena make understanding the process difficult. One dimensional bed combustor with a numerical combustion model is utilized to investigate the combustion process of the bed, using cubic wood particles as a simulated fuel. Bed combustion behavior is characterized with apparent flame propagation speed, which has close relationship with air supply rate and chemical and physical characteristics of the fuel. Base on the availability of oxygen, two distinct reaction zone is identified; the oxygen-limited and the reaction-limited zone leading to the extinction by excessive convection cooling. The numerical modeling shows good agreement with the experimental results. The transient bed combustion behavior of local temperature and oxygen consumption rate is adequately reproduced. The numerical model is extended to model the waste bed combustion of a commercial incineration plant, which shows meaningful results as well.

• 대한기계학회논문집
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• 제12권2호
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• pp.328-337
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• 1988

본 연구에서는 전보의 연구를 통해 가장 성능이 우수하다고 평가된 형상의 연소시스템을 선택해서, 연소실의 압력변동과 이온전류변동의 동시측정, 압력변동과 온도변동의 동시측정결과를 신호분석기에 의해 통계처리함으로써 아직까지 이해가 대단히 부족한 재착화 및 연소메카니즘, 그리고 공기유동특성에 관한 물리적 현상을 규명하고자 한다.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.259-267
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• 2001

The flow field in a cylinder of a 4-valve pentroof engine is studied using the KIVA-3V code. Turbulence is generated from the jet flow through valves and broken down to the small scale eddies in the compression process. It is known that the tumble effectively keeps turbulence during the compression process. In the combustion process, turbulence is known to enhance flame speed by increasing mass, momentum and heat transfer rates. The effects of the intake port angles on the flow and combustion characteristics are studied in this study. To study the effect of turbulence on the combustion process, Cantore combustion model is applied in this study.

• 동력기계공학회지
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• 제21권3호
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• pp.12-18
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• 2017

Diesel and gasoline engines will be used as main power system of automobiles. Recently, engine downsizing is widely applied to both gasoline and diesel engines in order to improve fuel economy and exhaust emissions. Engine downsizing means small engine combustion chamber with higher combustion pressure. Therefore, spray and combustion process should be investigated under these high pressure and temperature conditions. In this study, constant volume combustion chamber which enables easy optical access from six directions was developed. Combustion chamber was designed to resist maximum pressure of 15 MPa and maximum temperature of 2,000 K. Combustible pre-mixed mixture was introduced into combustion chamber and ignited by spark plugs. High pressure and temperature were implemented by combustion of pre-mixed mixture. Three initial conditions of different pressure and density were tested. High repeatability of combustion process was implemented which was proven by low standard deviation of combustion pressure.

• Journal of Biosystems Engineering
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• 제17권1호
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• pp.5-17
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• 1992

To develop an analytic method of combustion characteristics in a small sized and single cylinder type diesel engine for a power tiller, 1) the theoritical analysis of combustion gas in engine cylinder was performed based on thermoscience and 2) the computer program which could be used to calculate those values of the apparent burning rate, the heat loss, the gas temperature and the fuel-air equivalence ratio with the experimental cylinder pressure data, was developed. This method would provide the practical and quantative data for the diesel combustion process. Through the use of this method, following details would be obtained: 1) the application in the modeling of combustion process without detail knowledeg of combustion process, 2) the basis for the complete modeling of diesel engine, and 3) the basic information for the design of combustion chamber by the prediction of engine performance.

• 한국자동차공학회논문집
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• 제5권1호
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• pp.15-26
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• 1997

The present study is mainly motivated to numerically simulate the autoignition and combustion process of a diesel spray in RCM and effects of design parameters on combustion and engine performance in the DI diesel engine using EGR. In case of the burning spray in RCM, special emphasis is given to the autoignition process coupled with the fluid mechanics and chemical reaction. Computations are carried out for a wide range of operating condition in terms of temperature, concentration of oxygen and carbon dioxide of the intake gas in the DI diesel engine. Numerical results indicate that the mixing process along the edges of spray jet has a crucial role for autoignition and combustion process. Temperature and concentration of O2 and CO2 of intake gas significantly influence the combustion characteristics and engine performance in the diesel/EGR environment.

• 한국기계가공학회지
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• 제10권5호
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• pp.125-130
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• 2011

The characteristics of unsteady combustion were experimentally investigated using confined premixed flames stabilized by a rearward-facing step. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillations and it has usually desirable performance such as high load combustion and low pollutant emission. It is known that combustion oscillation is occurred if Rayleigh's criterion is satisfied. The pressure fluctuation and OH-emission fluctuation were measured using pressure transducer and OH optical fiber respectively and then cross-corelation and phase difference were calculated to apply Rayleigh's criterion.

• International Journal of Automotive Technology
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• 제2권1호
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• pp.25-31
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• 2001

It is necessary to understand the combustion process and cycle-by-cycle variation in combustion to improve the engine stability and consequently to improve the fuel economy and exhaust emissions. The pressure related parameters instead of mass fraction burned were compared for the effect of initial combustion pressures on the following combustion and the analysis of cycle-by-cycle variation in combustion for two pen injected SI engines. The correlation between IMEP and pressures at referenced crank angles showed almost the same trends for equivalence ratios, but the different mixture preparations indicated different tendency. The dependency of IMEP on pressure at the referenced crank angles increases as the mixture becomes leaner for both engines. The mixture distribution in the combustion chamber was varied with the coolant temperature and intake valve deactivation due to the evaporation of fuel and air motion. The correlation between pressure related parameters were also compared for the coolant temperatures and air motion.

• 한국기계가공학회지
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• 제11권5호
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• pp.109-114
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• 2012

The combustion characteristics using forced pulsating flow were experimentally investigated with confined premixed flames stabilized by a reward-facing step. The intermittent combustion has many merits, for instance, such as high load combustion, high heat transfer, low emission gas, compared with those of continuous combustion. For these purposes, data processing of binary image was conducted to reveal the differences between intermittent and continuous combustion. As the results, it was possible to calculate the reaction zone using OH-emission band and, therefore, showed that forced pulsating flow was useful in combustion technology.