• 한국자동차공학회논문집
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• 제4권2호
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• pp.147-157
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• 1996

Natural gas is gaining more attraction as a future fuel in particular both for environmental protection and energy conservation. In order to bring about more widespread use of gaseous engines, the technology capable of achieving output and efficiency performance equivalent to that of diesel engines needs to be developed. In the present paper, the requirements of the pilot torch from pre-chamber for ensuring ignition and promoting combustion are discussed by means of taking high-speed flame photography and system can run with leaner mixture of various fuels comparing to the electric plug ignition system cause the ignition delay period ignited with the torch and the combustion period are very short in spite of changing A/F of gaseous fuels in the main chamber. However, the suitable piston-cavity design for the use of lower-hydrocarbon fuels such as propane and butane must be discussed increasingly in the mear future.

• 에너지공학
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• 제24권3호
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• pp.61-66
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• 2015

Homogeneous charge compression ignition (HCCI) engine combines the combustion characteristics of a compression ignition engine and a spark ignition engine. HCCI engines take advantage of the high compression ratio and heat release rate and thus exhibit high efficiency found in compression ignition engines. In modern research, simulation has be come a powerful tool as it saves time and also economical when compared to experimental study. Engine simulation has been developed to predict the performance of a homogeneous charge compression ignition engine. The effects of compression ratio, cylinder pressure, rate of pressure rise, flame temperature, rate of heat release, and mass fraction burned were simulated. The simulation and analysis show several meaningful results. The objective of the present study is to develop a combustion characteristics model for a homogeneous charge compression ignition engine running with isooctane as a fuel and effect of compression ratio.

• Journal of Advanced Marine Engineering and Technology
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• 제32권4호
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• pp.506-513
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• 2008

The engine containing a radical injector has been studied to improve the performances of efficiency and to reduce the exhaust emissions recently. The engine is far different from general compression ignition engines or spark ignition engines for the concept of combustion process. The inflow characteristic from main chamber into radical chamber during compression stroke is important because the radical chamber must have enough fresh air to generate appropriate radicals. The numerical simulation is performed in each specific shape and the engine speed by using KIVA code. The result shows that the fresh air inflow from main chamber into the radical chamber is the best at 45 degree of the hole angle.

• 한국분무공학회지
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• 제13권1호
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• pp.28-33
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• 2008

The present study is mainly motivated to investigate the vaporization, auto-ignition and combustion processes in high-pressure diesel engines. In order to realistically simulate the dimethyl ether (DME) fueled diesel engine, the high pressure vaporization model is utilized and the interaction between turbulence and chemistry is treated by employing the Representative Interactive Flamelet (RIF) model. The detailed chemisty consisted of 336 elementary reaction steps and 78 species is used for DME/air reaction. Numerical results indicate that the RIF model with high pressure vaporization model successfully predicts the essential feature of the combustion processes and pollutants formations in the DME fueled diesel engines.

• 드라이브 ㆍ 컨트롤
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• 제16권3호
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• pp.16-22
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• 2019

Due to the rise in energy consumption and natural resource prices, the demand to improve energy efficiency in the construction machine has been highlighted. Even though many researchers have contributed to the development of the technology, CO2 gas emissions of heavy machinery remains high. One of the most significant problems of the novel excavator with internal combustion engines is the emission of harmful gas. To reduce emissions in the construction machine, it is necessary to replace the internal combustion engines with the alternative one. To overcome those problems, this paper focuses on the adoption of PEMFC hybrid engine for the excavator system. An internal combustion engine is replaced by new structures with fuel cell, battery and ultra capacitor. The proposed system has been designed and modeled using Simcenter Amesim software and compared with the conventional one through simulation results.

• 대한기계학회논문집B
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• 제30권7호
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• pp.671-681
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• 2006

This study focuses on the development of numerical procedure to analyze the nonlinear combustion instabilities in liquid rocket engine. Nonlinear behaviors of acoustic instabilities are characterized by the existence of limit cycle in linearly unstable engines and nonlinear or triggering instability in linearly stable engines. To discretize convective fluxes with high accuracy and robustness, approximated Riemann solver based on characteristics and Euler-characteristic boundary conditions are employed. The present procedure predicts well the transition processes from initial harmonic pressure disturbance to N-like steep-fronted shock wave in a resonant pipe. Longitudinal pressure oscillations within the SSME(Space Shuttle Main Engine) engine have been analyzed using the pressure-sensitive time lag model to account for unsteady combustion response. It is observed that the pressure oscillations reach a limit cycle which is independent of the characteristics of the initial disturbances and depends only on combustion parameters and operating conditions.

• 한국분무공학회지
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• 제1권2호
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• pp.24-32
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• 1996

Most of the research of small engines to date focused on developing spark ignition engines occupied much parts. Recently the number of a small direct injection diesel engine applied in small cars has been increased and considered as a next generation power source for passenger cars because of its high efficiency. Therefore the combustion chamber becomes smaller and the fuel injection pressure goes higher, which makes fuel sprays impinged easily on the combustion chamber walls. When strong swirls are not induced, the fuel may not mix with air because of fuel deposition on the wall. As a positive way, the combustion chamber systems which is using spray wall impaction has been introduced and assessed by an experimental or a simulate manner. In these systems the raised lands are positioned in tile chamber for spray impaction in order to break up the fuel drops into much smaller and direct them into desirable direction. This study addresses to the effects of rho position and size of the raised land or glow plug to help the chamber design using spray wall impaction. The characteristics of the spray impinged on various lands are investigated and compared with each other. Then the chamber shapes are discussed with the characteristics and their proper position and size is proposed in any chamber volume.

• 한국분무공학회지
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• 제16권4호
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• pp.167-175
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• 2011

The HCCI engines have been known with high efficiency and low pollution and can be actualized as the new internal combustion engines. However, As for(??) the ignition and combustion depend strongly on the oxidation reaction of the fuel, so it is difficult to control auto-ignition timing and combustion duration. Purpose of this paper is creating the database for development of multi-dimensional simulation and investigating the influence of different molecular structure. In this research, the effect of n-heptane mole ratio in fuel (XnH) on the ignition delay from homogeneous charge compression ignition(HCCI) has been investigated experimentally. By varying the XnH, it was possible to ascertain whether or not XnH is the main resource of ignition delay. Additionally, the information on equivalence ratio for varying XnH was obtained. The tests were performed on a RCM (Rapid Compression Machine) fueled with n-heptane and iso-octane. The results showed that decreasing XnH (100, 30, 20, 10,0), the ignition delays of low temperature reaction (tL) and high temperature reaction (tH) is longer. And the temperature of reaction increases by about 30K. n-heptane partial equivalence ratio (fnH) affect on tL.and TL. When ${\phi}$nH was increased as a certain value, tL was decreased and TL was increased.

• 한국분무공학회지
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• 제15권3호
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• pp.140-149
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• 2010

The spray-wall impingement in diesel engines is important to mixture preparation, engine performance and pollutant emissions. The purpose of this paper is to study the effects of spray-wall impingement on fuel distribution, combustion and emission characteristics by using both experimental and numerical methods. To investigate the spray-wall impingement process, an impingement-chamber was designed and a visualization experiment system was also developed. The images of impinged spray and free spray were digitally recorded with an intensified CCD camera. To investigate the fuel distribution, combustion and emission characteristics of impinged spray in a real diesel engine, the fuel injection and combustion processes of an engine with impingement-chamber were simulated by CFD software. Equivalence ratio distribution results were obtained to understand the fuel distribution characteristics of the impinged spray. Some combustion and emission characteristics were also acquired and the results showed that ignition delay of impinged spray was shorter than that of free spray; NO emission of the impinged spray was significantly less than that of free spray, but soot emission of impinged spray was more than that of the free spray. This study found that the diesel engine with spray-wall impingement has significant potential to reduce NO emission.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.21-30
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• 2005

Heat release analysis is a very importent method in understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the mesured cylinder pressures of an IDI(indirect injection), a HSDI(high speed direct injection) and a SI(spark ignition) engine. It has benefits of simple equation, fast speed, reliability. The object of the study is to compare the combustion characteristics among an IDI, a HSDI and SI engine. Result of analysis, the maximum heat release rate of a HSDI is higher than an IDI because of long ignition delay period. The heat release curve of a IDI is more linear than an HSDI, so the combustion characteristics of a IDI is similiar to that of an SI engine. There is a suggestion here that the combustion efficiency of a HSDI is highest of that of all engines because of the smallest heat transfer loss of all engines.