• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.4
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• pp.410-416
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• 1983

This study presents the combustion characteristics and flame structure of annular swirling flow when there were changes the equivalence ratio and swirl number of swirling jet of fuelair mixture. The conclusions of this study are as follows; During the investigations in which the change of equivalence ratio and swirl number were studied, three basic shapes of flame were observed in this study. Visible flame lengths of swirling jet results in the decrease with increasing of swirl number and air-fuel ratio of mixture. Radial distribution of flame temperature with strong swirl is higher than that of weak swirl at the same equivalence ratio of mixture. The angle of spread of the annular jet increases with the increase of swirl number. When the swirl intensity is increased in a jet, the decay of concentration of carbon dioxide is decreased with the distance from nozzle exit of burner.

• Journal of the Korean Society of Combustion
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• v.11 no.3
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• pp.18-25
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• 2006

The present studying is aimed to establish the relationship between flame chemiluminescence$(OH^*,\;CH^*,\;C_2^*)$ intensities and combustion conditions such as $NO_x$ emission characteristics. Measurements are made for $OH^*,\;CH^*,\;C_2^*$ radicals in gas & light oil diffusion flames. At turbulent nonpremixed combustion mode, the equivalence ratio is varied. The optical emissions were measured by photomultiplier(PMT) using optical band pass filter and spectrometer system. The experimental results showed that the ratio of radicals and $NO_x$ emission characteristics have exponential correlations and equivalence ratio characteristics have linear correlations at this experimental conditions.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2308-2315
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• 1995

We studied the effects on the ignitability of mixture, the combustion duration, and the maximum combustion pressure, of various initial combustion factors such as temperature, pressure, and each equivalence ratio in order to identify the combustion characteristics of lean mixture and improve ignitability through the proper control of the ignition energy. It is concluded that there is an optimum turbulent intensity that enables the combustion to have the best ignitability and the shortest duration under each equivalent ratio, and the combustion duration is only dependent upon the distribution and magnitude of discharge energy within the limit of inflammability.

• Journal of the Korean Society of Combustion
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• v.6 no.1
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• pp.29-35
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• 2001

The surface flames in porous ceramic burner are experimentally characterized to investigate the effects of equivalence ratio and firing rates. The results show that the surface flames are classified into green, red radiant and blue surface flame as decrease of equivalence ratio. And each flame is maintained very stably and shows the same flame characteristics at any orientation of ceramic burner. Particularly the blue surface flame was found to be very stable at very lean equivalence ratio at 200 to $800\;kw/m^2$ firing rates. And the exhausted NOx was analysed to find out which flame has lower NOx emission. The blue surface flame showed the lowest NOx emission regardless of the location of burner since it sustained very stable at lean mixture ratio.

• 한국연소학회:학술대회논문집
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• 2006.10a
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• pp.209-219
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• 2006

The supersonic combustion experiments are carried out using T3 free-piston shock tunnel. Different shock tube fill pressures have various inflow conditions. $15^{\circ}$ inclined hydrogen fuel injection is located before the cavity. Oblique shock is generated at the trailing edge of the cavity and reflects off the top and bottom wall. For non-reacting flow, static pressures in low equivalence ratio are similar to those in no fuel injection. As equivalence ratio is increased, static pressures are increased in the duct. In the similar equivalence ratio, static pressures are increased when total enthalpy is decreased. For reacting flow, the flame is occurred near the cavity. The combustion is weak locally in the middle of the duct. The up and down pressure distribution in the duct means that the supersonic combustion is generated.

• Journal of the Korean Society of Combustion
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• v.22 no.2
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• pp.42-49
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• 2017

A premixed combustion has many advantages including low NOx and CO emission, high thermal efficiency and a small volume of combustor. This study focused on combustion characteristics in a premixed combustion burner using the nickel based metal foam. The results show that the blue flame is found to be very stable at heating load 6,300-25,200 kcal/h by implementing the proper nickel based metal foam and baffle plate. The premixed flame mode is changed into green flame, red flame, blue flame and lift off flame with decreasing equivalence ratio. NOx emission was measured 80 ppm(0% oxygen base) from 0.710 to 0.810 of equivalence ratio and CO emission is 90 ppm(0% oxygen base) under the same equivalence ratio. It is also found that the stable blue flame region in flame stability curve becomes wider with increasing the heat load.

• Journal of Advanced Marine Engineering and Technology
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• v.27 no.5
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• pp.624-632
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• 2003

In the gasoline engine industry. there has been a trend towards the development of high performance engines with improved fuel efficiency, reduced weight and smaller sizes. These trends help to solved engine problems related to thermal load and abnormal combustion. In order to investigate these Problems, a thin film-type probe for instantaneously measuring temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and the heat flux was obtained through Fourier analysis. A peak instantaneous temperature was obtained after 55∼60 ms from ignition and the temperature increased according to an equivalence ratio and varied differently according to the position of the probe. Total heat loss during combustion period was affected by the equivalence ratio and differed widely in accordance to the position of the probe.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.1
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• pp.76-88
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• 1995

The effects of exhaust gas recirculation(EGR) on the characteristics of NOx emissions and specific fuel consumption rate have been investigated using an eight-cylinder. four cycle. direct injection diesel engine operating at several loads and speeds. The theoretical NO formation concentration is calculated with the equivalence ratio as a parameter of flame temperature to study the effect of EGR on NOx emissions in the diesel combustion. The experiments in this study are conducted on the fixed fuel injection timing of $38^{\circ}$ BTDC regardless of experimental conditions. It is found that the specific fuel consumption rate is slightly increased with EGR rate. and NOx emissions are markedly reduced owing to the drop of the incoming oxygen concentratio and the increase of equivalence ratio as the EGR rate increases.

• Journal of the Korean Society of Combustion
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• v.4 no.2
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• pp.35-41
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• 1999

The purpose of this study is to establish the flame structure and NOx emission characteristics of the swirl flow coaxial diffusion combustion in the model gas turbine combustor. The mean temperature, ion currents and NOx emission measurement technique showed the effect of equivalence ratio into flame length and flame stability. As a result of this study, NOx emission was increased by increasing the equivalence ratio, and the peak value of the NOx was appeared near the flame front.

• 한국연소학회:학술대회논문집
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• 2002.06a
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• pp.133-139
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• 2002

The lean premixed technique has been proven very efficient in reducing NOx emissions from gas turbine combustors. However combustion instability is susceptible to occur in lean premixed combustor. So laboratory-scale dump combustor was used to understanding the underlying mechanisms causing combustion instabilities. In this study, tests were conducted at atmospheric pressure and inlet air was up to $360^{\circ}C$ with natural gas. The observed instability was a longitudinal mode with a frequency of ${\sim}341.8Hz$. At selected unstable conditions, phase-resolved OH chemiluminescence images were captured to investigate flame structure with various equivalence ratio. Combustion instability was observed to occur at higher value of equivalence ratio(>0.69). This study was performed to investigate the effects of equivalence ratio and fuel split measuring NOx and acoustic wave. The results reveal the effect of fuel-air unmixedness on lean premixed combustor.