• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1692-1701
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• 2001

This study describes the combustion characteristics under various condition of air excess ratio and ignition timing in a 2-valve SI optically accessible engine with swirl control valve(SCV). It adapted three different types of SCV(open ratio 72.5%, 78%, 59%) to strengthen a swirl flow. Pressure data were acquired using pressure sensor to investigate the effect of swirl flow on combustion, and from these pressure data, IMEP(indicated mean effective pressure) and MFB(mass fraction burnt) were calculated to explain burn rate and flame speed. From acquired flame images, we inspected the flame propagation direction, flame area, and flame centroid. Flame propagation direction showed different tendency between with/without SCV, and flame area with SCV was faster and larger than that of conventional engine. Finally, the representative flame images at each crank angle were acquired by PDF method to verify flame growth process. It is found that strengthened swirl flow is more beneficial for faster and stable combustion.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.659-669
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• 1996

To clarify the effects of equivalence ratio, initial pressure and temperature on the flame propagation and radicals characteristics, a series of the experimental study were conducted in a quiescent methane-air premixture using a constant volume chamber. The development of the flame was visualized following the start of ignition using high speed schlieren photo and radical images by intensified CCD camera. Combustion pressure and ion current were recorded simultaneously according to the experimental conditions which were equivalence ratio with 0.7 to 1.2, initial pressure with 0.08 MPa to 0.40 MPa and initial premixture temperature with 3l3.2K to 403.2K. The results showed that the flame speed by ion current and mass fraction burned by combustion pressure characterized the effects of flame propagation very well. And increased combustion duration due to lean combustion condition that was below equivalence ratio, 0.8 caused cycle variation and decreasing the power of engine.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.2
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• pp.155-163
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• 1999

In this study, single cylinder engines with different tumble ratio were made to find out in-cylinder fluid motion and flame propagation. Tumble ratio derived from the steady state flow rig test. Flame propagation speed was obtained using cylinder head gasket ionization probe and the piston ionization probe. And the combustion pressure in cylinder was measured to analyze the combustion characteristics. In case of high tumble engine, BSFC and BSHC were decreased and BSNOx was increased at part load test. Also BMEP and combustion peak pressure was increased at full load test. Tumble flow motion had an great effects on initial burning period rather than main burning period in part load test.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.22-28
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• 2005

Exhaust gas emissions from internal combustion engines are one of the major sources of air pollution. And, it is extremely difficult to increase gasoline engine efficiency and to reduce $NO_X$ and PM(particulate matter) simultaneously in diesel combustion. This paper offers some basic concepts to overcome the above problems. To solve the problems, a recommended technique is CAI(controlled auto-ignition) combustion. In this paper, a flame trap was used to simulate internal EGR(exhaust gas recirculation) effect. An experimental study was carried out to find combustion characteristics using homogeneous premixed gas mixture in the constant volume combustion chamber(CVCC). Flame propagation photos and pressure signals were acquired to verify the flame trap effect. The flame trap creates high speed burned gas jet. It achieves higher flame propagation speed and more stable combustion due to the effect of geometry and burned gas jet.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.389-396
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• 1994

It is very important to clarify the ignition and flame propagation processes of methanol fuel in the Spark-ignition engine. High speed Schlieren photography and pressure trace analyses were used to study on combustion characteristics of methanol fuel in a constant volume chamber. Methanol-air mixtures equivalence rations from lean limit to 1.4 were ignited at initial pressure (0.1, 0.3, 0.5 MPa), temperature (313 343, 373 K) and ignition energy (40, 180 mJ). As the result of this study, we verified the characteristics such as ignition delay, effective thermal efficiency, flame propagation velocity, lean limit, ignitability and combustion duration. Obatained results are as follows. (1) The time to 10% reach of maximum pressure was 40-50% of the total combustion duration for this experimental condition hardly affected by equivalence ratio. (2) The Effective thermal efficiency, as calculated from maximum pressure was the highest when the mixture was slightly lean $({\phi} 0.8-0.9)$ and maximum pressure was the highest when the mixiture was slightly rich $({\phi} 1.2-1.2).$

• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.70-77
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• 2012

Experimental investigations were performed to examine the characteristics of propagating flame fronts around multiple bars within a rectangular chamber. The explosion chamber is 400 mm in height, $700{\times}700mm^2$ in cross-section and has a large top-venting area, $A_v$, of $700{\times}210mm^2$. This results in a value of 0.44 for $A_v/V^{2/3}$ and a L/D value of 0.57. The multiple obstacles of length 700 mm with a blockage ratio of 30 % were placed within the chamber. Temporally resolved flame front images were recorded by a high speed video camera to investigate the interaction between the propagating flame and the obstacles. Results showed that the flame propagation speeds before the flame impinges onto the obstacle almost equal to the laminar burning velocity. As the propagating flame impinged on the obstacle, the central region of flame began to become concave, this resulted in the flame deceleration in the region. As the flame interacted with the modified flow filed generated behind the central obstacle, the probability density functions(PDFs) of the local flame displacement speed were extensively distributed toward higher speeds.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.173-181
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• 2014

The propagation behavior and structural variation of a premixed propane/air flame with frequency change in an ultrasonic standing wave at various equivalence ratios were experimentally investigated using Schlieren photography and pressure measurement. The propagating flame was observed in high-speed Schlieren images, allowing local flame velocities of the moving front to be analyzed in detail. The study reveals that the distorted flame front and horizontal splitting in the burnt zone are due to the ultrasonic standing wave. Vertical locations of the distortion and horizontal stripes are intimately dependent on the frequency of the ultrasonic standing wave. In addition, the propagation velocity of the flame front bounded by the standing wave is greater than that of the flame front without acoustic excitation. As expected, the influence of the ultrasonic standing wave on premixed-flame propagation becomes more prominent as the frequency increases.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.891-899
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• 2000

The flame speed may be decomposed into the burning speed and the flame transport speed. The flame transport speed is affected considerably by the flow direction, variation rate of flow direction, and flow speed in the combustion chamber. Especially, the flow direction and the variation rate of flow direction at the spark plug location during the ignition period have an important effect on the ignition process and the early flame propagation process. We measured the flow direction component and the variation rate of flow direction with a hot wire probe at the spark plug location. It was shown that the representative flow direction of ignition period is the right-vertical direction of crank shaft and it was used to investigate the variation rate of flow direction.

• Fire Science and Engineering
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• v.28 no.3
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• pp.43-48
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• 2014

The purpose of this study is to analyze the flame propagation speed, radiation range, diffusion pattern and combustion completion time of a fire by filling a divided space with single combustible substance. It was found that the flame propagation speed was the fastest (0.2 s) for kerosene and the lowest (82.1 s) for alcohol. In the case of paint thinner, it took 19.0 s for the flame to reach its peak at the fastest speed after ignition while in the case of alcohol, it took 138.6 s for the flame to reach its peak at the lowest speed. In the case of the combustion of 200 ml of flammable liquids, the combustion completion time was 79.9 s for paint thinner, which is the shortest, 135 s for gasoline, 170 s for kerosene, 231.4 s for diesel and 337.0 s for alcohol. In addition, when flammable liquids are combusted, the lower part of the flame is governed by laminar flow pattern and the upper part of the flame showed turbulence pattern. In the case of a test performed for bean oil, it could be seen that if the fire source was removed, the flame was automatically extinguished without further combustion and that white smoke was generated due to incomplete combustion.

• Journal of the Korean Society of Industry Convergence
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• v.11 no.1
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• pp.5-10
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• 2008

A flame speed of methane mixture of water vapor and air have been measured to study the process of flame propagation using schlieren photographs. The quantity of water vapor contained were changed 5% and 10% of total mixture, and equivalence ratio of mixture between 0.8 and 1.2 were tested under the ambient temperature 323K and 373K. The results showed that the burning velocity was decreased by increasing the water vapor contents due to the interruption of flame development. And, the reduction rate of burning velocity was smaller by increasing the water contents under the same ambient temperature. The effects of ambient temperature on burning velocity was decreased by increasing the water vapor contents.