• Journal of the Korean Society of Combustion
• /
• v.1 no.2
• /
• pp.21-29
• /
• 1996

Flame propagation characteristics of propane-air mixtures were experimentally investigated in constant-volume combustion chambers. Flame propagation process was observed as a function of mixture strength, initial mixture temperature and initial mixture pressure in quiescent mixtures. A cylindrical combustion chamber and a spherical combustion chamber contain a pair of parallel windows through which optical access into the chamber can be provided. Laser two beam deflection method was adopted to measure the local flame propagation, which gave information on the flame size and flame propagation speed. Pressure development was also measured by a piezoelectric pressure transducer to characterize combustion in quiescent mixtures. Burning velocity was calculated from flame propagation and pressure measurements. The effect of flow on flame propagation was also investigated under flowing mixture conditions. Laser two beam method was found to be feasible in measuring flame propagation of quiescent mixtures. Flame was observed to propagate faster with higher initial mixture temperature and lower initial pressure. Combustion duration was shortened in the highly turbulent flowing mixtures.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.1 no.1
• /
• pp.14-21
• /
• 1993

The effect of coolant flow pattern on the metal temperature of the combustion chamber was studied in 1.5L and 1.8L gasoline engines. One of the main important points in the design of the water jacket is the increase of the coolant flow velocity. In this paper, the water jackets of the cylinder head and the cylinder block were visualized for the purpose of improving the coolant flow pattern. By the use of this technique, the optimal design of the size and th location of the water transfer fole was possible. And, to lower the metal temperatures of the thermally critical parts, the drilled water passages were employed. To investigate of effect of the improved flow pattern and the drilled water passages, the metal temperatures of the combustion chamber were measured. As a result of the temperature measurement, it was found out that both the change of flow pattern and the drilled water passages have significant effect on the reduction of the peak metal temperature.

• Particle and aerosol research
• /
• v.4 no.1
• /
• pp.9-20
• /
• 2008

The effect of light intensity on the ozone formation and the aerosol number concentration during the photochemical reactions of ambient air was investigated in an indoor smog chamber. The smog chamber consists of a housing, 64 blacklights, and a $2.5-m^3$ reaction bag made of Teflon film. The bag was filled with the unfiltered ambient air in Seoul from January 10 to March 18, 2002. In this work, the photolysis rate of $NO_2$, $k_1$ was used as an index of light intensity. Three levels of light intensity were controlled by changing the number of blacklights turned on among 64 blacklights: $0.29min^{-1}$ (50%), $0.44min^{-1}$ (75%), $0.57min^{-1}$ (100%). The ozone concentration increased rapidly within 10 minutes after irradiation irrespective of light intensity, thereafter it increased linearly during the irradiation. The ozone production rate seems to be dependent on both the light intensity and the quality of ambient air introduced into the reaction bag. The change in aerosol number concentration also depended on both the light intensity and the ambient air quality, especially aerosol size distribution. Based on the initial ambient aerosol size distributions, the photochemical potential for aerosol formation and growth is classified into two cases. One is the case showing aerosol formation and growth processes, and the other is the case showing no apparent change in particle size distribution.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.15 no.1
• /
• pp.49-55
• /
• 2007

The characteristics of auto-ignition and combustion process of a single droplet of emulsified fuel suspended in a high-temperature air chamber have been investigated experimentally with various droplet sizes, surrounding temperatures, and water contents. The used fuels was n-Decane and it was emulsified with varied water contents whose maximum is 30%. The high-speed camera has been adopted to measure the ignition delay and flame life time. It was also applied to observe micro-explosion behaviors. The increase of droplet size and chamber temperature cause the decrease of the ignition delay time and flame life-time. As the water contents increases, the ignition delay time increases and the micro-explosion behaviors are strengthened. The starting timings of micro-explosion and fuel puffing are compared for different droplet sizes and the amount of water contents.

• Aerospace Engineering and Technology
• /
• v.7 no.2
• /
• pp.103-109
• /
• 2008

A study has been conducted on the bulging process of regenerative cooling nozzle which is essential for the manufacturing of liquid rocket thrust chamber. Tension tests have been performed for the material to be used for the development of the bulging process and mechanical properties are obtained by the test. Two or three bulging tools were required to complete the bulging process. The necking of the material was a major failure encountered in the bulging process and a research has revealed that grain size of the material has considerable effect on its occurrence. The presently developed bulging process with a controlled grain size material has been successfully applied to the manufacturing of subscale and 30-tonf full scale regeneratively cooled nozzle while demonstrating the applicability and usefulness of the presently developed bulging process.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.22 no.1
• /
• pp.91-105
• /
• 2020

This study is the basic study for improving the range of influence and potency of mixing bars in the chamber of Shield TBM. Currently, there are many studies on disk cutters, cutter bits and segments in the study of the domestic Shield TBM. However, studies that mix soil and rocks that come from the membrane during the Shield TBM excavation and scatter them with screw conveyors are not as good as those abroad. In this study, the existing Shield TBM Chamber was manufactured as a miniature and the experiment. Inside the chamber, different sizes (4 mm, 6 mm, 8 mm, 10 mm) and colors (black, white, red, and blue) were used to form layers. This experiment was carried out by different shapes and sizes of RPM and mixing bars. In addition, the difference between a miniature model and a reclining one was checked to determine the effect of the direction of gravity on the mixing efficiency. This was done in the same way for all other conditions other than differences in the direction of gravity. Through this experiment, we identified the orientation of the chamber model, the size and shape of the mixing bar inside, and the mixing effect and torque depending on RPM. A comparative review of the mixing effect and torque confirmed that the shape and size of the mixing bar affect the mixing of samples, and that the direction of gravity affects torque.

• Journal of Powder Materials
• /
• v.11 no.4
• /
• pp.328-332
• /
• 2004

Fe nanopowders were successfully synthesized by plasma arc discharge (PAD) process using Fe rod. The influence of chamber pressure on the microstructure was investigated by means of X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The prepared particles had nearly spherical shapes and consisted of metallic cores (a-Fe) and oxide shells (Fe$_{3}$O$_{4}$), The powder size increased with increasing chamber pressure due to the higher dissolution and ejection rate of H$_2$ and gas density in the molten metal.

• Journal of Korean Society for Atmospheric Environment
• /
• v.20 no.E1
• /
• pp.35-41
• /
• 2004

Aerosol wall loss is an important factor affecting smog chamber experiments, especially with chambers made of Teflon film. In this work, the aerosol wall loss was investigated in 2.5 and $5.8-m^3$ cubic-shaped Teflon film chambers filled with ambient air. The natural change in the particle size distribution was measured using a scanning mobility particle sizer in a dark environment. The rate of aerosol wall loss was obtained from the deposition theory suggested by Crump and Seinfeld (1981). The measured rates of aero-sol wall loss were In a good agreement with the theoretical and experimental values given by McMurry and Rader (1985), implying that the electrostatic effect enhances particle deposition on the chamber wall. The significance of aerosol wall loss correction was demonstrated with the photochemical reaction experiments using the ambient air.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.26 no.1
• /
• pp.74-81
• /
• 2002

Combustion phenomena in a sub-millimeter scale combustor have been investigated. To evaluate scale effect on flame propagation characteristics, a cylindrical combustion chamber with variable depth was built in-house. The combustor was charged with premixed gas of hydrogen and air and ignited electronically. A piezo electric pressure transducer recorded transient pressure after the ignition. Measurements were made at different test conditions specified with chamber depth and initial pressure as parameters. Visual observation was made through a quartz glass window on top side of the combustion chamber using high speed digital video camera. From the pressure data, available work was estimated and compared with energy input required for stable ignition. The preliminary results suggested that the net thermal energy release is sufficient to generate power and enables a combustor of the size in the present study to be used as the energy source of a micro power devices .

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.28 no.1
• /
• pp.16-23
• /
• 2004

Acoustic characteristics of unbaffled and baffled combustion chamber are experimentally investigated under atmospheric condition to preliminarily determine baffle for mitigation of combustion instability. To investigate the effect of the baffle which has several configurations such as radial baffles and hub/blade baffle, resonant-frequency shift and damping factors of the chamber were analyzed and compared quantitatively with those of the unbaffled combustion chamber. From a view of acoustic characteristics, radial baffles with several configurations have not much difference in resonant-frequency shift and damping factor ratio with each other. On the other hand, hub and blade baffle is very effective to suppress the first tangential mode which was found to be the most harmful acoustic mode in KSR(Korean Sounding Rocket)-III engine. But more study on design parameters such as hub size and axial length should be done for complete optimization of hub and blade baffle. The present study based on linear acoustic analysis is expected to be a useful confirming tool to predict acoustic field and design a passive control devices such as baffle and acoustic cavity.