• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.20 no.10
• /
• pp.3282-3292
• /
• 1996

Flow velocity was measured using a hot wire anemometer. Turbulence intensity was in proportion to mean flow velocity regardless of swirl velocity. And integral length scale has proportional relation with swirl velocity regardless of measurement position. Flame speed calculated by radius of visualized flame was increased and then decreased according to lapse of time from spark. Maximum flame speed was increased according to increase of turbulence intensity. Burning speed and flame transport effect increased with increase of swirl velocity, but ratio of burning speed to flame speed decreased with increased of swirl velocity. Mass fraction burned versus volume fraction burned was increased in proportion to the increase of turbulence intensity, caused by increase of combustion promotion effect according to increase of turbulence intensity and scale.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 1997.11a
• /
• pp.154-161
• /
• 1997

Several studies have developed upward flame spread models which use somewhat different features. However, the models have not considered the transient effects of the igniter and the burning rate. Thus, the objective of this study is to examine a generalized upward flame spread model which includes these effects. We shall compare the results with results from simpler models used in the past in order to examine the importance of the simplifying assumptions. We compare these results using PMMA, and we also include experimental results for comparison. The results of the comparison indicate that flame velocity depends on the thermal properties of a material, the specific model for flame length and transient burning rate, as well as other variables including the heat flux by igniter and flame itself. The results from the generalized upward flame spread model can provide a prediction of flame velocity, flame and pyrolysis height, burnout time and position, and rate of energy output as a function of time.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.29 no.11 s.242
• /
• pp.1277-1284
• /
• 2005

The combustion characteristics of methane oxygen diffusion flames have been investigated to give basic information for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since the small amount of nitrogen is included from the current low cost oxygen production process. Flame lengths decreased with increasing fuel or oxygen velocity because of the enhancement of mixing effect. Correlation equation between flame length and turbulent kinetic energy was proposed. NOx concentration was reduced with increasing fuel or oxygen velocity because of the enhanced entrainment of the product gas into flame zone as well as the reduction of residence time in combustion zone.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.11a
• /
• pp.35-36
• /
• 2022

In order to supplement the flame-retardant performance of oil stain, which can prevent wooden buildings from contamination, (NH4)2HPO4, a phosphorus flame-retardant, was added to oil stain and applied for each type of plywood, and an experiment was conducted. The addition rate was set to 0-60%, but white powder appeared on the surface of plywood from 40% and thus it was impossible to experiment, so the maximum addition rate was selected as 30%. As a result of the experiment, acacia plywood had the best performance. As the rate of addition of the flame retardant increased, the remaining time and carbonization length of all plywood decreased, but the carbonization length of the MDF plywood was not met with the standards.

• Journal of ILASS-Korea
• /
• v.9 no.4
• /
• pp.31-37
• /
• 2004

This paper presents spray and combustion characteristics of hydrocarbon fuel injected from pressure-swirl nozzles. Three commercial nozzles with orifice diameters of 0.256, 0.308 and 0.333mm and injection pressures ranging from 0.7 to 1.3 MPa were selected f9r the experiments. Spray characteristics such as breakup length. spray angle and drop size (SMD) were analyzed using photo image analyses and Malvern Panicle Size Analyzer. The drop size was measured with and without a blower at the same measuring locations. The flame length and width were measured using photo image analyses. The temperature distribution along the axial distance and the gas emission such as CO, $CO_2\;and\;NO_x$ were studied. The breakup length decreased with an increase in injection pressure for each nozzle but increased with an increase in nozzle orifice diameter. The spray angle increased and SMD decreased with an increase in injection pressure. The flame with an increased linearly with an increase in injection pressure and in nozzle orifice diameter. The flame temperature increased with an increase in injection pressure but decreased along the axial distance. The maximum temperatures occurred closer to the burner exit and flame at axial distance of 242mm from the diffuser tip. The experimental results showed that the level of CO decreased while that of $CO_2\;and\;NO_x$ increased with an increase in injection pressure and nozzle orifice diameter.

• Journal of the Korean Society of Combustion
• /
• v.10 no.3
• /
• pp.34-41
• /
• 2005

Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

• 한국연소학회:학술대회논문집
• /
• 2005.10a
• /
• pp.207-214
• /
• 2005

Hydrogen safety is one of the key technical issue with growing attention on utilization of hydrogen energy. This study is aimed to predict behavior of momentum-controlling buoyant jet and flame caused by hydrogen leakage from a high pressured tank. Approximate solutions were derived for the case of turbulent buoyant jet and diffusion flame in still air. In case of hydrogen jet with low Froude number (100-4000), computed jet trajectories were compared with experimental data and showed good agreement with them. Jet and flame trajectories and flame length of hydrogen are predicted and compared with the buoyant flame of propane. The results well show that buoyancy is dominant in the range of low Froude number, while initial momentum is dominant in the range of high Froude number. That effect is more distinct for hydrogen flame than the case of propane.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.8
• /
• pp.2030-2038
• /
• 1995

In this study, three turbulent flame propagation models are compared using experimentally measured data of a 4 valves/cylinder spark-ignition engine. First two conventional models are B.K model and GESIM combustion model. The burning rates calculated from the two models are compared with the burning rates calculated from measured pressure data using the one-zone heat release analysis. GESIM combustion model predicts burning rates closer to the data acquired from the experiment in wide operating ranges than B-K model does. The third model is refined based on GESIM combustion model by including the effect of flame stretch, turbulent length scale band pass filter and a variable that considers flame size and the area of flame contacting the cylinder wall surface. The refined combustion model predicts burning rates closer to experimental results than GESIM combustion model does. Also, the refined combustion model predicts flame radius close to the experimental result measured by using optical fiber technique.

• Journal of the Korean Society of Combustion
• /
• v.11 no.1
• /
• pp.11-18
• /
• 2006

In this work, $TiO_2$ nanoparticles were synthesized using $N_2-diluted$ and Oxygen-enriched coflow hydrogen diffusion flames. The effect of flame temperature on the characteristics of the formed $TiO_2$ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103 K for oxygen-enriched flame to 1,339 K for $N_2-diluted$ flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The characteristics of synthesized $TiO_2$ nanoparticles were analyzed by SEM and TEM images. From these images, it was evident that the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700 K, $TiO_2$ nanoparticles having spherical shapes with diameters about 60 nm were synthesized. In the lower temperature region, below the 1,600 K, the diameters of formed nanoparticles having unclear boundaries were ranged from 35 - 50 nm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.25 no.5
• /
• pp.79-84
• /
• 2011

In this study, breakdown characteristics of a vertical sphere-plane air gap in the presence of combustion flame were examined under the application of a.c. and d.c. high-voltages in order to investigate the effect of flame on the dielectric strength of air. Propane gas is used as the fuel of the flame, and the temperature distribution of air around the flame is measured. The polarity effects for the d.c. voltages and breakdown voltages of air when applied both of a.c. and d.c. voltages were examined in the case of the variation of the gap length and the horizontal distance between the flame and the high-voltage sphere electrode. The influence of relative air density, electrification and shape changes of the flame as factors that affect the breakdown voltages were discussed.