• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.646-652
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• 2016

Biomass is regarded as one of the promising energy sources to deal with the depletion of fossil fuels and the global warming issue. Biocrude-oil can be produced through the fast pyrolysis of biomass feedstocks such as wood, crops, agricultural and forestry residues. It has significantly higher viscosity than that of conventional petroleum fuel and contains solid residues, which can lower the spray and atomization characteristics when applied to the burner. In addition, biocrude-oil consists of hundreds of chemical species derived from cellulose, hemicellulose and lignin, and evaporation characteristics of the biocrude-oil droplet are distinct from the conventional fuels. In the present study, a numerical study was performed to investigate the evaporation characteristics of biocrude-oil droplet using a simplified composition of the model biocrude-oil which consists of acetic acid, levoglucosan, phenol, and water. The evaporation characteristics of droplets were compared at various surrounding air temperatures, initial droplet diameters, and ethanol mixing ratios. The evaporation time becomes shorter with increasing air temperature, and it is much sensitive to the air temperature particularly in low temperature ranges. It was also found that the biocrude-oil droplet evaporates faster in cases of the smaller initial droplet diameter and larger ethanol mixing ratio.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.1
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• pp.132-137
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• 2002

Recently, impinging spray is used for atomization of diesel engine, but it bring on adhesion of fuel. Therefore, we studied about droplet behavior on high temperature plate changing the size of droplet, surface temperatures, and surface roughness of plate. In this study, We studied to confirm experimentally about mechanism of evaporation and ignition process of single fuel droplet. We observed evaporation time, evaporation appearance and ignition delay time by the photopraphs of 8mm video camera. Experimental results are summarized as follows: 1. The boiling point of fuel affect a evaporation and ignition process. 2. The surface roughness affect a evaporation time. 3. The ignition delay time relate to evaporation characteristic.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.7
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• pp.89-96
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• 2006

The combustion temperature in gas generator should be kept below around 1,000K to avoid any possible thermal damages to turbine blade by adopting either fuel rich or oxidizer rich combustion. Thus, non-equilibrium chemical reaction dominates in the gas generator. Meanwhile, Kerosene is a compounded fuel mixed with various types of hydrocarbon elements and difficult to model the chemical kinetics. This study focus to model the non-equilibrium chemical reaction of kerosene/LOX with detailed kinetics developed by Dagaut using PSR(Perfectly stirred reactor) assumption. Also, droplet evaporation time is taken into account by calculating for the residence time of droplet and by decoupling reaction temperature from the reactor temperature. In Dagaut’s surrogate model for kerosene, chemical kinetics of kerosene consists of 1592 reaction steps with 207 chemical species. The comparison of calculation results with experimental data could provide very reliable and accurate numbers in the prediction of combustion gas temperature, species fraction and other gas properties.

• Journal of ILASS-Korea
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• v.26 no.2
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• pp.73-80
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• 2021

Evaporation characteristics of single butanol gel fuel were investigated in different mass ratios of gellant and ambient temperatures. Gel fuel was made by adding the pure water and hydroxypropylmethyl cellulose (HPMC) into the 1-butanol. Increase of viscosity was observed when the loading of HPMC increased. The evaporation process of gel droplet could be divided into three stages: droplet heating, micro-explosion and crust formation. Elevation of ambient temperature helped boost the evaporation in all experimental cases, but the effect was mitigated when the mass ratio of HPMC increased. Increase of HPMC weight ratio reduced the evaporation rate.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.652-659
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• 1999

The trend of poisoning of reforming catalyst along with the position of anodic catalyst bed was studied. Keeping the conditions that steam to carbon ratio was 2.5, operating voltage was 0.75 V, current density was $140mA/cm^2$, the unit cell was operated during 24 hrs at a steady state. And then the cell was stopped, the catalysts packed in the position of inlet, middle and outlet were sampled individually and then the amount of carbon, Li and K poisoned were analysed. After 100 hrs operated, the catalysts at the same positions were analysed at the same manner. The result of this experiment was as followings. After 24 hrs operated, the poisoning amounts of Li and K in the catalyst were 0.27 wt% at inlet, 0.23 wt% at middle and the highest value 1.59 wt% at outlet. After 100 hrs, the amount of poisoning is the highest in the catalyst packed at the inlet of unit cell. The performance simulation of unit cell explained these trends of poisoning catalysts. The simulation told that the catalyst in the region of the inlet of unit cell treated the 90% of initial methane flow rate and the highest electrochemical reaction happened in this region. So the catalysts of this region were the most poisoned with carbon, Li and K and also the rate of poisoning is faster than that of the catalyst at other regions. The temperature at the region of outlet of unit cell was $30^{\circ}C$ higher than that of other regions, so more Li, and K vaporized than at other regions and little reforming reaction at this region made the catalysts poisoning rate low.

• Fire Science and Engineering
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• v.13 no.1
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• pp.37-47
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• 1999

The spreading fire of very small floating particles after they are ignited is fast and t therefore dangerous. The research on this area has been limited to experiments and global simulations which treat them as dusts or gaseous fuel with certain concentration well m mixed with air. This research attempted micro-scale analysis of ignition of those particles modeling them as liquid droplets. For the beginning, the in-line array of fuel droplets is modeled by two-dimensional, unsteady conservation equations for mass, momentum, energy and species transport in the gas phase and an unsteady energy equation in the liquid phase. They are solved numerically in a generalized non-orthogonal coordinate. The single step chemical reaction with reaction rate controlled by Arrhenius’ law is assumed to a assess chemical reaction numerically. The calculated results show the variation of temperature and the concentration profile with time during evaporation and ignition process. Surrounding oxygen starts to mix with evaporating fuel vapor from the droplet. When the ignition condition is met, the exothermic reactions of the premixed gas initiate a and burn intensely. The maximum temperature position gradually approaches the droplet surface and maximum temperature increases rapidly following the ignition. The fuel and oxygen concentration distributions have minimum points near the peak temperature position. Therefore the moment of ignition seems to have a premixed-flame aspect. After this very short transient period minimum points are observed in the oxygen and fuel d distributions and the diffusion flame is established. The distance between droplets is an important parameter. Starting from far-away apart, when the distance between droplets decreases, the ignition-delay time decreases meaning faster ignition. When they are close and after the ignition, the maximum temperature moves away from the center line of the in-line array. It means that the oxygen at the center line is consumed rapidly and further supply is blocked by the flame. The study helped the understanding of the ignition of d droplet array and opened the possibility of further research.

• Journal of the Korean Institute of Gas
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• v.22 no.4
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• pp.1-6
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• 2018

An LNG bunkering system stores LNG in a horizontal IMO's C-Type tank insulated with perlite powder, and $10^{-2}$ Torr vacuum in the annular space between the double walls. Current storage tanks have high heat leakage, evaporating over 2.0% daily. A more efficiently insulated storage tank reducing the evaporation rate is required to develope. This research carried out thermal analysis on a new effective insulation method, i.e. double shield insulation system, that separates high super vacuum in the annular space between two tanks with a perlite vacuum in the back side of outer tank. This highly efficient insulation system obtained an evaporation rate of 0.16% per day under a $10^{-4}$ Torr vacuum. Even if the space loses its vacuum, the new insulation system showed a lower evaporation rate of 5.23% than the present perlite system of 4.9%.

• Applied Chemistry for Engineering
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• v.35 no.1
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• pp.16-22
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• 2024

Polymer electrolyte membrane fuel cells have the advantage of low operating temperatures and fast startup and response characteristics compared to others. Simulation studies are actively researched because their cost and time benefits. In this study, the resistance of water residual in the gas diffusion layer (GDL) of the unit cell was added to the existing equation to compare the actual data with the model data. The experiments were conducted with a 25 cm² unit cell, and the samples were separated into stopping times of 0, 10, and 60 minutes following primary impedance measurement, activation, and polarization curve data acquisition. This gives 0, 10, and 60 minutes for the residual water in the GDL to evaporate. Without the rest period, the magnitude of the performance improvement was not significantly different at the same potential and flow rate, but the rest period did improve the performance of the membrane electrode assembly when measuring impedance. By changing the magnitude of the resistance reduction to an overvoltage, the voltage difference between the fuel cell model with and without residual water was compared, and the error rate in the high current density region, which is dominated by concentration losses, was reduced.

• Fire Science and Engineering
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• v.16 no.1
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• pp.1-7
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• 2002

Halogen-based fire suppressing agents have environmental problems because they cause the stratospheric ozone depletion and globe warming. Hence, fire suppression system using fine water mist became the center of interest as a substitution of halon. As a study about this, it is in progress to make the optimum droplet size by using water mist nozzles and to improve the extinguishing performance of water mist by using additives. Before this study, the extinguishing time of ethanol and n-heptane pool fire was measured with changing of water mist droplet size, flow density, discharge pressure, and fire size. In this study, on adding the additives to improve physical and chemical extinguishing performance of water mist, the extinguishing performance would evaluate and the optimum condition would find out. As a result, in case of ethanol pan 1 pool fire, the extinguishing time of the water mist by adding of 2.5 wt% NaCl and 0.3% AFFF got shorter 27% and 60% than the pure water mist. Adding of AFFF was to decrease the flame temperature by forming thin film on the fuel surface and to decrease the evaporation of n-heptane fuel. In case of NaCl, alkali salt crystals showed on the flame surface.

• Elastomers and Composites
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• v.42 no.1
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• pp.20-31
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• 2007

Material characteristics and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. In this paper, the NBR compound was prepared by sulfur-cure system, and was used in predicting the lifetime of rubber gasket made by the compound. The accelerated material aging was investigated at different temperatures at 120, 140 and $160^{\circ}C$ and aging time from 3 hours to 600 hours at 5, 6, 7 vol %. of $H_2SO_4$ concentrations The rubber strips were placed in acid solution using pyrex g1ass tube. Both ends of pyrex g1ass tube were sealed to avoid evaporation of solution during heating at given time. The material test and accelerated acid-heat aging test were carried out to predict the useful life of NBR rubber gasket for a fuel cell stack. In order to investigate the effects of acid-heat aging on the properties of the NBR, tensile strength, elongation at break, hardness and crosslink-density were measured. The tensile strength decreases as the $H_2SO_4$ concentrations and temperature increase. Results were evaluated using Arrhenius equation.