• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.235-239
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• 2005

We analyzed the thermal and mechanical behaviors of micro reformer for the purpose of design verifications and modification of micro channels. The reformer designed for hydrogen generation from methanol is essential to PEM(Proton Exchange Membrane) type fuel cell. For the mobile applications, the size and the simplicity would be the most critical issues. We utilized silicon process for micro reformer to obtain the thickness thinner than 2 mm thick. We have used commercial simulation software, IDEAS, to analyze the thermal and mechanical characteristics of micro reformer structure. The heat generation rates of heaters, heat transfer rates, and fluid temperatures are derived from thermal equilibrium relation and these values were used for thermal boundary conditions. We also analyzed the thermal stresses, thermal deformations to examine the possibility of failure.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.3
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• pp.217-225
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• 2008

A new micro reformer system consisted of a micro reformer, a microcombustor and a micro evaporator was studied experimentally and computationally. In order to satisfy the primary requirements for designing the microcombustor integrated with a micro evaporator, i.e. stable burning in a small confinement and maximum heat transfer through a wall, the present microcombustor is simply cylindrical to be easily fabricated but two-staged (expanding downstream) to feasibly control ignition and stable burning. Results show that the aspect ratio and wall thickness of the microcombustor substantially affect ignition and thermal characteristics. For the optimized design conditions, a premixed microflame was easily ignited in the expanded second stage combustor, moved into the smaller first stage combustor, and finally stabilized therein. A micro reformer system integrated with a modified microcombustor based on the optimized design condition was fabricated. For a typical operating condition, the designed micro reformer system produced 22.3 sccm hydrogen (3.61 W in LHV) in an overall efficiency of 12%.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2238-2243
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• 2007

A new microcombustor configuration for a micro fuel-cell reformer integrated with a micro evaporator was studied experimentally and computationally. The present microcombustor is simply cylindrical to be easily fabricated but two-staged, expending downstream, to feasibly control ignition and stable burning. Results show that the aspect ratio of the first stage and the wall thickness of the microcombustors substantially affect ignition and thermal characteristics. For the optimized design conditions, a premixed microflame was easily ignited in the expanded second stage combustor, moved into the smaller first stage combustor, and finally stabilized therein. The measured and predicted temperature distributions across the microcombustor walls indicated that heat generated in the microcombustor is well transferred. Thus, the present microcombustor configuration could be applied to the practical micro reformers integrated with a micro evaporator for use of fuel cells.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.225-229
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• 2005

We have designed micro-fuel processor system, which consists of a steam reforming area and a PROX(preferential oxidation) area. Micro-fuel processor system generates $H_2$ rich gas from a methanol. In our experiment, we have integrated micro-fuel processor system using low temperature cofired ceramics (LTCC) process because LTCC is superior to other materials principally due to their high thermal and chemical stability, simpler fabrication processes, and lower materials cost. Therefore, we have studied and integrated micro-fuel processor system containing embedded heaters, cavities, and 3D structures of micro-channel with LTCC. Also we have optimized the LTCC process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.551-552
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• 2006

The miniature fuel cells have emerged as a promising power source for applications such as cellular phones, small digital devices, and autonomous sensors to embedded monitors or to micro-electro mechanical system (MEMS) devices. Several chemicals run candidate at a fuel in those systems, such as hydrogen. methanol, ethanol, acetic acid, and di-methyl ether (DME). Among them, hydrogen shows most efficient fuel performance. However, there are some difficulties in practical application for portable power sources. Therefore, more recently, there have been many efforts for development of micro-reformer to operate highly efficient micro fuel cells with liquid fuels such as methanol, ethanol, and DME In our experiments, we have integrated a micro-fuel processor system using low temperature co-fired ceramics (LTCC) materials. Our integrated micro-fuel processor system is containing embedded heaters, cavities, and 3D structures of micro- channels within LTCC layers for embedding catalysts (cf. Figs. 1 and 2). In the micro-channels of LTCC, we have loaded $CuO/ZnO/Al_2O_3$ catalysts using several different coating methods such as powder packing or spraying, dipping, and washing of catalyst slurry.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.615-616
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• 2006

A micro-fuel processor system integrating steam reformer and partial oxidation reactor was manufactured using low temperature cofired ceramic (LTCC). A CuO/ZnO/$Al_2O_3$ catalyst and Pt-based catalyst prepared by wet impregnation were used for steam reforming and partial oxidation, respectively. The performance of the LTCC micro-fuel processor was measured at various operating conditions such as the effect of the feed flow rate, the ratio of $H_2O/CH_3OH$, and the operating temperature on the LTCC reformer and CO clean-up system. The catalyst layer was loaded with "Fill and Dry" coating for small volume. The product gas was composed of $70\sim75%$ hydrogen, $20\sim25%$ carbon dioxide, and $1\sim2%$ carbon monoxide at $250\sim300^{\circ}C$, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.12 s.255
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• pp.1196-1202
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• 2006

A MEMS methanol reformer was fabricated and its performance was evaluated in the present study. Catalytic steam reforming of methanol was selected because the process had been widely applied in macro scale reformers. Conventional Cu/ZnO catalyst that was prepared by co-precipitation method to give the highest coating quality was used. The reactor structure was made by bonding three layers of glass wafers. The internal structure of the wafer was fabricated by the wet-etching process that resulted in a high aspect ratio. The internal surface of the reactor was coated by catalyst and individual wafers were fusion-bonded to form the reactor structure. The internal volume of the microfabricated reactor was $0.3cm^3$ and the reactor produced exhaust gas with hydrogen concentration at 73%. The production rate of hydrogen was 4.16 ml/hr that could generate power of 350 mW in a typical PEM fuel cell.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.739-740
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• 2007

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.613-614
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• 2006

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.689-696
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• 2010

The Because of its high thermal efficiency, the direct injection (DI) diesel engine has emerged as a promising potential candidate in the field of transportation. However, the amount of nitrogen oxides ($NO_x$) increases in the local high-temperature regions and that of particulate matter (PM) increases in the diffusion flame region during diesel combustion. In the de-$NO_x$ system the Lean $NO_x$ Trap (LNT) catalyst is used, which absorbs $NO_x$ under lean exhaust gas conditions and releases it in rich conditions. This technology can provide a high $NO_x$-conversion efficiency, but the right amount of reducing agent should be supplied to the catalytic converter at the right time. In this research, the emission characteristics of a diesel engine equipped with a micro-reformer that acts as a reductants-supplying equipment were investigated using an LNT system, and the effects of the exhaust-gas temperature were also studied.