• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.35-41
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• 2003

Propagation speeds of turbulent premixed flames have been measured in a pulsed-flame flow reactor which generates flames propagating in nearly isotropic turbulent flow field with U'/$S_L$ ranging from 1.2 to 5.3. The measurement involved a high-speed digital imaging at 1000 frames/second to capture the flame propagation motion. In addition to the flame speed measurements, flame perimeter ratio was measured for comparison. The observed flame propagation speed is high ranging from 5 to 20 times the laminar flame speed for the range of U'/$S_L$. The flames observed at extreme equivalence ratios exhibit intermittent propagation in that only a small fraction of ignited flame kernel resulted in full propagation of the flame. Also, at low equivalence ratios the flame speed decreased substantially even at high turbulence intensities.

• 한국가스학회지
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• 제15권3호
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• pp.6-10
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• 2011

실린더형 챔버내에서 정전기 방전에너지 변화에 따른 가솔린-공기 혼합물의 화염전파에 관한 영향을 조사하기 위해 실험적 연구를 수행하였다. 3개의 서로 다른 정전기 방전 에너지(1 mJ, 50 mJ 및 98 mJ)를 실험변수로 사용하였으며, 점화원 전극 주변의 미연소가스 유동장을 가시화하기 위해 고속 PIV 시스템을 적용하였다. 정전기 방전 에너지가 증가할 때, 점화원 핵은 찌그러면서 초기화염에 영향을 미치는 것으로 나타났다. 초기화염 동안에 화염속도는 점화에너지가 높을수록 증가하는 것으로 나타났으나, 초기화염 이후에 시간이 증가할수록 화염속도는점화에너지에 관계없이 거의 유사하였으며, 이는 문헌[5]에서 보여진 전산유체 모델링 결과의 경향과 거의 유사하였다. 또한, 점화에너지가 증가할 때 전파하는 화염 전면의 미연소가스 속도장은 증가하는 것으로 나타났다.

• 대한기계학회논문집
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• 제13권1호
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• pp.135-139
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• 1989

본 연구에서는 이러한 예혼합기체의 유한두게의 고온기체에 의한 점화현상을 일차원 평면적으로 다룸에 있어 점화를 일으키는 고온기체의 두께와 기체의 물리적 성질의 비를 나타내는 Lewis수의 영향을 알아 보고자 한다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.47-57
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• 1998

Characteristics of evaporation, flame propagation at moment of ignition and steady state combustion, and flow characteristics of combustible mixture have been investigated by experiments and computational simulation for the evaporation pot type kerosene burner. The results show how to design the evaporation pot in order to minimize the sticking of residual tar, and also indicate that symmetrical flame propagation along the flame ring from the kernel of ignition is achieved by modication of the shape of ignition part. In the case of steady state combustion, the uniform distribustion of flame at each flame hole is accomplished by proper modification of the piping instruments. The improved design of the structure and parts of the kerosene burner make up enhancement of flame stability and considerable reduction of CO and bad smell emission at moment of ignition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.864-870
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• 2001

Flame propagation along vortex tube was experimentally investigated. The vortex tube was generated by the ejection of propane from a nozzle through a single stroke motion of a speaker and the ignition was induced from a single pulse laser. Non-reactive flow fields were visualized using shadow technique. From these images, vortex ring size and translational velocity were measured in order to determine the ignition time and position. Flame structure and flame speed were measured using high speed CCD camera. Flame speed was accelerated during the initial stage of flame kernel growth, and reached near constant value during steady propagation period. Near the completion of propagation, flame speed was decelerated and then extinguished. Flame speed along the non-premixed vortex tube was found to be linearly proportional to circulation, which was similar to that of the flame propagation along premixed vortex ring. Ignition position minimally affects the propagation characteristics. These imply that flame is propagating along the maximum speed locus expected to be along stoichiometric contour and also support the existence of tribrachial flames.

• 한국가시화정보학회지
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• 제14권3호
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• pp.51-58
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• 2016

New concept spark plug was developed to study its influence on the combustion characteristics of SI engine. It has pre-ignition chamber at the lower end of spark plug and flame hole, in which fresh mixture gas can be put in through the flame hole without any fuel supply system. This spark plug was tested in a single cylinder engine dynamometer for different air fuel ratio to measure the fuel consumption rate, emission gases, and MBT timing. And constant volume combustion chamber was made to understand flame characteristics of spark plug. New spark plug induced fast burn compared to the conventional spark plug and its effects were increased in lean air fuel ratio. Pre-ignition chamber spark plug with 5 holes which had adjusted size was more stable and effective in combustion performance than pre-ignition chamber spark plug with 1 hole. And its effects showed larger differences in lean air fuel ratio than stoichiometric condition. Flame kernel and flame growth process of conventional spark plug and pre-ignition chamber spark plug studied by flame visualization of schlieren method.

• 대한기계학회논문집B
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• 제33권9호
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• pp.682-687
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• 2009

In order to investigate the effects of three different electrostatic discharge energies on gas explosions, a high-speed PIV system has been applied. The present study paid attention to the flame initiation by the gas explosions and its propagation at the existence of an obstacle within a chamber. Three different ignition energies such as 0.56 mJ, 52.87 mJ and 112.5 mJ were used. It is found that the ignition kernel is bent by the electrostatic discharge during the flame initiation. Tangential velocities of unburnt mixture ahead of initially propagating flame fronts are increased with increasing ignition energy, which makes the flame propagation faster before it reaches the obstacle. Although the flame speed was found to be less sensitive to the ignition energies, the flame developments were different. The effects of the energies on explosion pressures were also discussed.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.49-51
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• 2015

In this research, engine performance and emission variation according to equivalence ratio and ignition time is calculated by validated analysis model. LNG engine ignite by spark plug and spark ignition modeled using DPIK model and G-equation that modeled initial flame surface called kernel and velocity and position of flame front. Engine pressure and emission was validated with experimental data.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.9-16
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• 2002

In plasma jet ignition, combustion enhancement effects occur toward the plasma jet issuing direction. Therefore, when the igniter is attached at the center of a cylindrically shaped combustion chamber, plasma jet should issue toward the round combustion chamber wall. The plasma jet igniter that had an annular circular orifice has been developed. The purpose of this study is to elucidate the relationship between the newly developed plasma Jet igniter configuration and combustion enhancement effects. In this newly developed plasma Jet igniter, flame front wrinkle appears on the flame front and flame propagates rapidly. Plasma Jet influences on the flame propagation far long period when the plasma jet igniter has issuing angle 90 degrees and large cavity volume, because the plasma jet only lasts several ms. However, in the early stage of combustion, flame front area of issuing angle 45 degrees is larger than that of 90 degrees, because the initial flame kernel is formed by the plasma jet.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.289-294
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• 2006

Better fundamental understanding of the interactions between the in-cylinder flows and combustion process is an important requirement for further improvement in the fuel economy and emissions of internal combustion(IC) engines. Flow near a spark plug at the time of ignition plays an important role for early flame kernel development(EFKD). Velocity data measurements in this study were made with a two-component laser Doppler velocimetry(LDV) near a spark plug in a single cylinder optical spark ignition(SI) engine with a heart-shaped combustion chamber. LDV velocity data were collected on an individual cycle basis under wide-open motored conditions with an engine speed of 1,000rpm. This study examines and compares the flow fields as interpreted through ensemble, cyclic and discrete wavelet transformation(DWT) analysis. The energy distributions in the non-stationary engine flows are also investigated over crank angle phase and frequency through continuous wavelet transformation(CWT) for a position near a spark plug. Wavelet analysis is appropriate for analyzing the flow fields in engines because it gives information about the transient events in a time and frequency plane. The results of CWT analysis are provided and compared with the mean flows of DWT first decomposition level for all cycles at a position. Low frequency high energy found with CWT corresponds well with the peak locations of the mean velocity. The high frequency flows caused by the intake jet gradually decay as the piston approaches the bottom dead center(BDC).