• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.774-779
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• 2012

MILD (Moderate and Intense Low Oxygen Dilution) combustion is a technology that uses the recirculation of combustion gas to increase thermal efficiency not only by keeping down the concentration of Nitric Oxides and temperature but also by uniformizing the internal temperature of the combustion furnace. This study is a trial to obtain MILD combustion characteristics by adjusting the equivalence ratio with the air flow rate in the conical combustor while keeping the fuel flow rate and measuring the exhaust gas of the combustion furnace.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.97-104
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• 2002

The conventional regenerative system has a high thermal efficiency as well as energy saving using the high preheated combustion air. in spite of these advantages, it can not avoid high nitric oxide emissions. Recently, flameless combustion has received much attention to solve these problems. In this research, numerical analysis is performed for flow-combustion phenomena in the self regenerative burner. In this analysis we used Fluent 6.0 code. the that is developed for commercial use, Methane gas is used as a fuel and two-step reaction model for methane and Zeldovich mechanism for NO generation are used. the velocity of the preheated combustion air is used as a parameter and we analyze the characteristics of flow-field, temperature distributions and NO emissions. Due to the increased recirculation rate, the maximum temperature of flame is significantly increased and NOx emissions is reduced

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.7
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• pp.1111-1122
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• 2004

An idea to suppress the self-excited combustion oscillation was applied to the flames. The characteristics of unsteady combustion were examined and the unsteady combustion was driven by forced pulsating mixture supply that can modulate its amplitude and frequency. The self-excited combustion oscillation having weaker flow velocity fluctuation intensity than that of the forced pulsating supply can be suppressed by this method. The effects of the forced pulsation amplitude and frequency on controlling self-excited combustion oscillations were also investigated comparing with the steady mixture supply. The unsteady combustion used in this experiment plays an important role in controlling self-excited combustion oscillation. Symptoms of self-excited combustion oscillation were also studied in order to predict the onset of combustion oscillation before it proceeded to a catastrophic failure For the purpose, the unique measures to observe the onset of self-excited combustion oscillations based on the careful statistics of fluctuating properties in flames, such as pressure or emission of OH radicals, have been proposed.

• Journal of Hydrogen and New Energy
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• v.29 no.6
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• pp.635-641
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• 2018

To select the operating condition of 0.5 MWth chemical looping combustion system, minimum fluidization velocity, transition velocity to fast fluidization and solid circulation rate were measured using mass produced new oxygen carrier (N016-R4) which produced by spray drying method for 0.5 MWth chemical looping combustion system. A minimum fluidization velocity decreased as the pressure increased. The measured transition velocity to fast fluidization was 2.0 m/s at ambient temperature and pressure. The measured solid circulation rate increased as the solid control valve opening increased. We could control the solid circulation rate from 26 to $93kg/m^2s$. Based on the measured minimum fluidization velocity and transition velocity to fast fluidization, we choose appropriate operating conditions and demonstrated continuous solid circulation at high pressure condition (5 bar-abs) up to 24 hours.

• Transactions of the Korean Society of Automotive Engineers
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• v.11 no.6
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• pp.65-72
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• 2003

In order to clarify turbulent combustion characteristics of hydrocarbon mixtures by hydrogen addition, turbulent burning velocities in a constant volume vessel were measured for both lean and rich hydrocarbon mixtures. Moreover, the configuration characteristics of turbulent flame was investigated in the wrinkled laminar flame region. A laser tomography technique was used to obtain the images of turbulent flame, and quantitative analyses were performed. As a result, the characteristics of turbulent burning velocity was shown a distinct difference with the addition rate of hydrogen between lean and rich mixtures. On the other hand, the obtained tomograms showed that the surface area of turbulent flame depends almost only on the turbulence intensity.

• Journal of the Korean Society of Industry Convergence
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• v.6 no.2
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• pp.149-153
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• 2003

Besides the fuel spray behavior and combustion chamber shape. an air motion has a key role on exhaust gas emission and performance in a DI diesel engine. A swirl ratio represents the ratio of the intake swirl velocity to the engine speed. The main purpose in this work is to investigate the effects of the swirl ratio to the combustion characteristics. A shroud valve machined to change the swirl ratio. Test was carry out by changing the engine speed, nozzle diameter and swirl ratio in a single cylinder diesel engine. From this study, the optimized combustion was found at swirl ratio 2.7. And it was also found that the increasing the maximum cylinder pressure with an increasing swirl ratio lead to decrease a smoke and to increase NOx.

• Journal of the Korean Society of Combustion
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• v.7 no.3
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• pp.37-46
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• 2002

Characteristics of lifted flames in axisymmetric laminar coflow jets have been investigated experimentally. Approximate solutions for velocity and concentration accounting virtual origins have been proposed for coflow jets to analyze the behavior of liftoff height. From the measurement of Rayleigh intensity for probing the concentration field of propane, the validity of the approximate solutions was substantiated. From the images of OH PLIF and CH chemiluminescence and the Rayleigh concentration measurement, it has been shown that the positions of maximum luminosity in direct photography coincide with the tribrachial points, which were located along the stoichiometric contour. The liftoff height in coflow jets was found to increase highly nonlinearly with jet velocity and was sensitive to coflow velocity.

• Journal of the Korean Society of Combustion
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• v.5 no.2
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• pp.69-78
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• 2000

Reattachment characteristics of laminar flames in partially premixed jets are studied for propane fuel mixed with air. As the flow rate decreases, liftoff height is decreased nonlinearly and the flame reattaches to a nozzle at a certain liftoff height. Using a jet theory by taking into account a virtual origin, it is predicted that flow velocity along a stoichiometric contour has a maximum value near nozzle. With this velocity characteristics, it is shown that reattachment mechanism can be explained by a balance between flame speed and flow velocity. Predicted displacement speeds at reattachment and liftoff agree qualitatively well with experimental findings.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.159-162
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• 2012

Combustion in a narrow space has been interested as a model of meso-scale combustors (or micro-combustors). Premixed flames have been used to overcome flame quenching in a narrow space and non-premixed flames have been used to improve flame stabilization. In this study, overall characteristics of premixed flame and non-premixed flame in narrow combustion spaces were reviewed. Various effects such as the flow velocity distribution, thermal interaction, enhanced mass diffusion were discussed and an eventual structure of the flame at the extinction limit was introduced.

• Journal of ILASS-Korea
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• v.21 no.1
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• pp.37-46
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• 2016

For the SI engines, at only full load, the pumping loss has a negligible effect, while at part load conditions, the pumping loss increases. To avoid the pumping loss, the spark-ignited engines are designed to inject gasoline directly into the combustion chamber. In the spark-ignited direct-injection engines, ignition probability is important for successful combustion and the flame propagation characteristics are also different from that of pre-mixed combustion. In this paper, a visualization experiment system is designed to study the ignition probability and combustion flame characteristics of spark-ignited direct-injection CNG fuel. The visualization system is composed of a combustion chamber, fuel supply system, air supply system, electronic control system and data acquisition system. It is found that ambient pressure, ambient temperature and ambient air flow velocity are important parameters which affect the ignition probability of CNG-air mixture and flame propagation characteristics and the injected CNG fuel can be ignited directly by a spark-plug under proper ambient conditions. For all cases of successful ignition, the flame propagation images were digitally recorded with an intensified CCD camera and the flame propagation characteristics were analyzed.