• Journal of the Korean Society of Combustion
• /
• v.21 no.2
• /
• pp.7-14
• /
• 2016

Evaporation and combustion characteristics of fuel droplet with carbon nanoparticle were investigated in a rapid compression machine(RCM). RCM is an experimental equipment to simulate one compression stroke of reciprocating engine. Nitrogen was charged into reaction chamber for evaporation experiment, while oxygen was charged for combustion experiment. N990 carbon black and n-heptane were used to synthesize the carbon nanofluids. Surfactant, span80, was used to make synthesis easier. The droplet pictures were taken using a high speed camera with 500 frames per second. Thermocouple, of which tip is $50{\mu}m$, was used not only to measure transient bulk temperature, but also to suspend the droplet. Reaction chamber temperature was calculated from pressure data. The evaporation rate of nanofluids was improved compared to pure fuel. The ignition delay was promoted due to the nanoparticle, but the burning rate was decreased.

• Textile Coloration and Finishing
• /
• v.32 no.1
• /
• pp.65-71
• /
• 2020

Electrical energy is used for heating and cooling because electric cars do not have engines and cooling water. The downside is that when the heating and cooling system is applied to electric vehicles, about 40 percent of the energy is spent on heating and cooling, which is less efficient in winter. This has increased demand for electric vehicle battery efficiency. In this study, the condensation and dispersion of carbon nanotubes were controlled, and carbon fibers and composite slurry were manufactured without binders to manufacture paper. Manufactured by content showed the highest heat generation characteristic at 143℃ with a carbon fiber content ratio of 20wt% and confirmed that the heat temperature rises with increasing pressure. The plane heaters made through this study can be applied to a variety of products other than electric vehicles because they can be simplified by process and high temperature.

• Journal of Welding and Joining
• /
• v.16 no.1
• /
• pp.52-62
• /
• 1998

Laser beam welding of zinc-coated steel, especially lap joints, has a problem of zinc vapor produced during welding which has a low vaporization temperature of 906.deg. C. It is lower than the melting temperature of steel (1500.deg. C). The high pressure formed by vaporization of zinc during laser welding splatters the molten pool and creates porosities in weld. During laser lap welds of zinc-coated steel sheets with CW CO$_{2}$ laser the gap size has been analyzed and simulated using a FEM. The simulation has been carried out in the range of gap aetween 0 and 0.16 mm. The vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In the case of too small gap size, zinc gas has not ejected and existed between two sheets. Therefore heat was difficult to conduct from the upper sheet to lower sheet and the upper sheet could over-melted. In the case of large gap size the zinc gas has been prefectly ejected but only a part of lower sheet has melted. The optimum range of gap size in the lap welds of zinc-coated steel sheets has been calculated to be between 0.08 and 0.12 mm. According to the comparison of experiment, the simulation is proved to be acceptable and applicable to laser lap welds.

• Journal of the Mineralogical Society of Korea
• /
• v.20 no.4
• /
• pp.261-266
• /
• 2007

A natural FeOOH-goethite was compressed up to 9.5 GPa at room temperature using a DIA-type large volume apparatus with synchrotron radiation. Energy dispersive x-ray diffraction method was employed to measure its compressibility and NaCl was used for high pressure determinations. Bulk modulus was determined to be 131.1 (${\pm}5.8$) GPa by the Birch-Murnaghan equation of state with $K_0'$ fixed to 4. The present result is not in accord with the previous measurements, which vary from 111 to 147.9 GPa.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.10a
• /
• pp.555-559
• /
• 2005

Spinning process is a chipless metal forming method for axis-symmetric parts, which is more economical, efficient and versatile method for producing parts than other sheet metal forming process such as stamping or deep drawing. The large-sized spindle for spinning machine is the equipment to ferm a high-pressure vessel into the demanded shape. The important problem in the spindle system fur spinning machines is to reduce and minimize the thermal effect by motor and bearings. In this study, the effect of heat generation of bearings for the large-sized spindle is considered. Temperature distribution and thermal displacement of the spindle system for spinning machine can be analyzed by using the finite element method. The numerical results are compared with the measured data. The results show that temperature distribution and thermal displacement can be reasonably estimated by using the finite element method and the three dimensional model.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.32 no.1
• /
• pp.78-85
• /
• 2000

Due to environmental proessures there is increasing use of hydrogen peroxide as a total or partial substitute for chlorine based bleaching agents within ECF or TCF sequences. However, to aceive satifactory brightness using peroxide alone, stages having a combination of high temperature, pressure, pH or residence time are required. It may also have negative impact on fiber quality . Therefore, it would be of advantage if vertain means could be found to make hydrogen peroxide more effective in bleacing , via shortening treaction time and allevaiating the need for such forcing reaction conditions. This can be achieve by converting the peroxide in-situ to stronger oxidant through the use of 손 bleach activator. In this study to investigate the influence of additives, such as tetraacetylethylenediamine (TAED) and Molybdate (MO) . addition on peroxide bleaching were carried out. Under alkaline conditions the bleching additives. TAED and Mo. can react H2O2 to form peracetic acid and peroxomolybdate respectively and these generated activators can improve deliginification,. The activators make it possible to bleach the pulp efficiently at low temperature in the range 50 to 7$0^{\circ}C$. Also, addition of TAED and Mo is an environmentally friendly way of enhancing the performance of peroxide bleaching can be incorporated into TCF and ECF sequences.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.320-329
• /
• 2008

The influence of thermodynamic transition associated with transcritical nitrogen injection upon the flow structure was investigated to explore numerical simulation of the injectant dynamics of oxygen/hydrogen coaxial jet in liquid rocket engines. Single and coaxial nitrogen jets were treated by comparing the transcritical and perfect-gaseous conditions, wherein the numerical model was accommodative to the real-fluid thermodynamics and transport properties at supercritical pressures. The model was in the first place validated by comparing the results of transcritical nitrogen injection between calculations and available experiments. For a single jet under the transcritical condition, the nitrogen kept a relatively high density up to its pseudo-critical temperature inside the mixing layer, since it remains less expanding until heated up to its pseudo-critical temperature. Numerical analysis revealed that cryogenic jets exhibit strong dependence of specific enthalpy profile upon the associated density profile that are both dominated by turbulent thermal diffusion. In the numerical model, therefore, exact evaluation of turbulent heat fluxes becomes very important for simulating turbulent cryogenic jets under supercritical pressures. Concerning the coaxial jets due to transcritical/gaseous nitrogen injections, the density profile inside the mixing layer was again affected by the thermodynamic transition of nitrogen. However, hydrodynamic instability modes of the inner jet did not show significant differences by this thermodynamic transition, so that further study is needed for the mixing process downstream of the near injection position.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.866-870
• /
• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1999.10a
• /
• pp.248.1-248
• /
• 1999

Preliminary analysis of in-reactor thermal performance of three MOX fuel rods, which are going to be irradiated in the Halden reactor beginning in the first Quarter of the year 2000 under the framework of the OECD Halden Reactor Programme, have been conducted by using the computer code COSMOS to ensure their safe operation. Parametric studies have been carried out to investigate the effect of uncertainties on in-reactor behavior by considering the four kinds of uncertainties; thermal conductivity, linear power, manufacturing parameters, and model constants. The analysis shows that, in the case of annular MOX -1 fuel, calculation results for thermal performance vary widely depending on the selection of model constants for fission gas release (FGR). On the contrary, the thermal performance of solid MOX - 3 fuel does not depend on the choice of FGR constants to a large extent as MOX-I, because the fuel temperature is very high in the MOX-3 irrespective of the choice of FGR constants and hence the capacity of grain boundaries to retain gas atoms is not large enough to accommodate the number of gas atoms reaching the grain boundaries. It is planned that when the data on microstructure and thermal conductivity for each type of MOX fuel are available, new analysis will be made using these information. In addition, FGR model constants will be derived from the measured fuel centerline temperature, rod internal pressure and other related data.

• Korean Journal of Optics and Photonics
• /
• v.3 no.3
• /
• pp.178-182
• /
• 1992

An air-cooled discharge-heated copper-vapor laser system with its inter-electrode distance of 45 cm has been developed by utilizing an alumina ceramic plasma tube of 1.6 cm in diameter and 50 cm in lengih. For operating the laser, a dc high voltage power supply with output rating of 6 kV and 500 mA, a resonant charging circuitry consisting partly of an 1.8 H inductor assembly and a 5 nF storage capacitor, and a thyratron driver operating up to 7 kHz have also been developed. The present laser system starts lasing at the tube temperature of about $1350^{\circ}C$ and an maximum average output power of 0.7 W has been obtained at 12 kV, 4.5 kHz. 50 mbar of Ne buffer gas pressure, and at the tube temperature of $1460^{\circ}C$.