• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.1-9
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• 1999

Liquid Petroleum Gas (LPG) has been widely used for commercial light-duty vehicles worldwide. Since LPG has a higher octane number and a lower maximum combustion temperature than gasoline , it becomes more popular fuel for reducing exhaust emissions. In tihs study, mathematical models of air intake and fuel delivery system are presented, and a PI-controller is designed for air-fuel ratio control. Hardware and software of an engine control module (ECM) are designed for an LPG engine. The ECM is built using a Motorola MC68HC05. In order to control the air-fuel ratio at stoichiometry, the PI-control algorithm is implemented in the ECM. The experiment results show the proto LPG ECM and its control scheme perform well to meet the stoichiometric air-duel ratio requirement.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.787-790
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• 2017

This study is a preliminary research on characterization of methane - oxygen combustion used in bipropellant thruster. The limit of combustion stability and flame shape of methane - oxygen non-premixed flame injected by shear coaxial injector in the model combustion chamber Experimental studies have been carried out. A direct image of the flame was photographed using a DSLR camera, and combustion characteristics and flame length were quantified through image post-processing. As a result, it was confirmed that the stabilized flame was generated at the stoichiometric ratio as the oxidizer Reynolds number ($Re_o$) was increased, and the length of the turbulent flame was increased under the same injector diameter condition.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.233-240
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• 2008

The reductive precipitation of platinum and palladium in hydrochloric acid solution using hydrazine as a reducing agent was investigated. The reductive precipitation ratios of platinum and palladium increased when increasing the stoichiometric ratio for reducing agent, precipitation time, and pH. The precipitation ratio of platinum was much lower than that of palladium. This is the reason the reaction rate of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}$ at the reduction reaction step of $PtCl{_6}^{2-}{\rightarrow}PtCl{_4}^{2-}{\rightarrow}Pt$ is very slow. The purity of platinum precipitated was very affected by metallic impurities, while it was possible to precipitate the high purity palladium since the precipitation rate of palladium was relatively fast. At the pH of 1.3, the precipitation temperature of $25^{\circ}C$, and the addition amounts of the hydrazine of 10 and 1.75 times the stoichiometric ratio, the reductive precipitation ratios of platinum and palladium from their hydrochloric acid solutions containing 2,000 ppm were 98.5% and 99.9% in 30 min, respectively.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2207-2212
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• 2012

Dimethylaluminum isopropoxide (DMAI, $(CH_3)_2AlO^iPr$) as a single precursor, which contains one aluminum and one oxygen atom, has been adopted to deposit non-stoichiometric aluminum oxide ($AlO_x$) films by low pressure metal organic chemical vapor deposition without an additional oxygen source. The atomic concentration of Al and O in the deposited $AlO_x$ film was measured to be Al:O = ~1:1.1 and any serious interfacial oxide layer between the film and Si substrate was not observed. Gaseous by-products monitored by quadruple mass spectrometry show that ${\beta}$-hydrogen elimination mechanism is mainly contributed to the $AlO_x$ CVD process of DMAI precursor. The current-voltage characteristics of the $AlO_x$ film in Au/$AlO_x$/Ir metalinsulator-metal (MIM) capacitor structure show high ON/OFF ratio larger than ${\sim}10^6$ with SET and RESET voltages of 2.7 and 0.8 V, respectively. Impedance spectra indicate that the switching and memory phenomena are based on the bulk-based origins, presumably the formation and rupture of filaments.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.1-12
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• 2021

The present study proposes the modified-stoichiometric model for describing hydration of sodium silicate-based alkaliactivated slag(AAS), and compares the results with the thermodynamic modelling-based calculations. The proposed model is based on Chen and Brouwers(2007a) model with updated database as reported in recent studies. In addition, the calculated results for AAS are compared to those for hydrated portland cement. The maximum difference between the proposed model and the thermodynamic calculation for AAS was at most 20%, and the effects of water-to-binder ratio and activator dosages were identically described by both approaches. In particular, the amount of non-evaporable water was within 10% difference, and was in excellent agreement with the experimental results. Nevertheless, notable deviation was observed for the chemical shrinkage, which is largely dependent on the volume of hydrates and pores.

• Journal of Powder Materials
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• v.8 no.1
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• pp.13-19
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• 2001

Ni and NiO particles were made by a combustion synthesis process. The characteristics of synthesized powders were investigated with various kinds and amounts of fuels such as urea, citric acid and glycine. Ni phase particles without NiO phase were obtained through combustion synthesis process in air atmosphere with-out further calcinations process, when the content of glycine was 2.44 times of the stoichiometric ratio in the precursor solution. Primary particle sizes of synthesized Ni and NiO particles were about 20∼30 nm.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.66-76
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• 1997

In order to investigate the generation of carbon monoxide and heat loss of incomplete combustion in compartment fires, an experiment was conducted in a small scale compartment by using methanol as a fuel. The concentration of carbon monoxide and the toxicity parameter showed high values when the mass air - to - fuel stoichiometric ratio is under 1.0. The constitution of the combustion gas was showed to estimate it from the . The heat loss due to incompleteness of combustion is about one third of heat of combustion in case of under 1.0.

• Bulletin of the Korean Chemical Society
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• v.18 no.10
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• pp.1071-1075
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• 1997

Detonation characteristics of acetylene were studied behind reflected shock waves in the temperature range 800-1350 K by monitoring OH emission and pressure profiles. For a comprehensive measurement of ignition delay time, the mixture composition was varied in a wide range of Ar mole % was varied from 0.625 to 2.5 in stoichiometric ratio of C2H2-O2-Ar. A computer simulation study was also performed to elucidate the important elementary steps determining ignition behavior. The 33-reaction mechanism provides a good agreement in delay time between the observed and the calculated ones.

• Journal of the Korean Society of Combustion
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• v.16 no.3
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• pp.52-58
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• 2011

The purpose of this paper is to investigate the effect of equivalence ratio on the combustion and emission characteristics of a compression ignition engine fueled with biodiesel. In this research, a single-cylinder direct injection engine with 373.3 cc of displacement volume was tested on DC dynamometer. In order to investigate the effect of biodiesel equivalence ratio on combustion characteristics, the experiments were conducted at various equivalence ratios and injection pressures of 40~120 MPa. For investigating engine performance, lambda meter was connected and equivalence ratios was varied from 0.6 to 1.0. In addition, the exhaust emissions such as oxides of nitrogen($NO_X$), hydrocarbon(HC) and carbon monoxide(CO) were measured by exhaust gas analyzer under the various air/fuel ratios. The experimental results show that maximum IMEP was measured at the 0.8 of equivalence ratio. Furthermore, $NO_X$ emission was rapidly decreased as the increase of equivalence ratio. However soot emission was significantly increased according to the increase of equivalence ratio.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.369-372
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• 1996

We prepared LiMn$_2$O$_4$ by reacting stoichiometric mixture of LiOH.$H_2O$ and MnO$_2$ (mole ratio 1 : 1) and heating at 80$0^{\circ}C$ for 24h, 36h, 48h, 60h and 70h. We obtained through X-ray diffraction that lattice parameter varied as function of heat treatment time. heated cathode active materials at 80$0^{\circ}C$ for 36h, (111)/(311) peak ratio was 0.37. It expected good charge/discharge characteristics. When (111)/(311) peak ratio was 0.37, it will be that crystal structure is farmed very well. In the result of charge/discharge test When heated at 80$0^{\circ}C$ for 36h, charge/discharge characteristic of LiMn$_2$O$_4$is the most property. It agree with our expectation.