1,721,179 research outputs found
Scaling and Evaluation of Pt/Al2O3 Catalytic Reactor for Hydrogen Peroxide Monopropellant Thruster
No full textA scaling methodology of hydrogen peroxide monopropellant thruster is described. As the decomposition process of the hydrogen peroxide on the surface of catalyst bed is extremely complex, empirical method was taken for design purposes. A small-scale thruster was fabricated and important design parameters, including temperature at different locations of the catalyst bed, were measured. Based on the measurement, the catalyst bed size as a function of the propellant flow rate was estimated. Using the scaling methodology, a catalyst bed configuration for a thruster capable of delivering 50 N was estimated. The thruster built on this design produced 42 N at sea level and specific impulse of 123 s.This work was supported by the Korea Science and Engineering
Foundation (KOSEF) grant funded by the Korea Ministry of
Education, Science and Technology (MEST) through the National
Research Laboratory (NRL) (no. R0A-2007-000-20065-0)
MEMS fuel cell system integrated with a methanol reformer for a portable power source
No full textMEMS fuel cell system was designed and fabricated for a portable power source in the present study. The system consists of a methanol-steam reformer, catalytic combustor, preferential oxidation (PROX) reactor, and polymer electrolyte membrane fuel cell (PEMFC). Methanol reformer is an essential part for hydrogen supply, in which a pre-heater, vaporizing/reforming channels and catalytic combustor were integrated. All components were fabricated using MEMS fabrication technologies combined with catalyst loading processes. Performance of the MEMS fuel cell system was measured with the optimal conditions of the reformer and PROX. Power density was 195 mW/cm(2) when the potential was 0.64V. The performance was low compared to the result for pure hydrogen because the feed at the fuel cell included undesired CO, CO(2), and N(2). MEMS fuel cell system with a weight specific energy density of 225 W h/kg was accomplished as an alternative micro power source. (C) 2008 Elsevier B.V. All rights reserved
A practical design approach for a single-stage sounding rocket to reach a target altitude
No full textA new type of design domain for a sounding rocket is suggested in this study, which is more intuitive, simplified, and conducive to a single-stage sounding rocket development process. Among the various operation parameters, this study identifies several effective variables, which are also among the most practical in a sounding rocket design process. Of the many design variables considered for peak altitude optimisation, arguably the three most effective in shaping the whole system and conferring the most practicality in the design process of a sounding rocket were determined. A simulation-based study was conducted to establish: the effect of the selected parameters on flight performance, and the optimum design conditions of a single-stage sounding rocket in terms of its peak altitude. The simulation result was compared with randomly chosen experimentally tested flight data and validated. With the clear performance curves varying depending on the variables, the combination of the considered design inputs was effective. The new type of design domain and design procedure proposed is expected to constitute a useful reference and deliver practical benefits to the development process for a target-altitude-optimised single-stage sounding rocket.
TEMPERATURE DISTRIBUTION OF METHANOL-HYDROGEN PEROXIDE AUTOTHERMAL REFORMING FOR PEM FUEL CELL IN SPACE EXPLORATION
No full textA STUDY ON THE IMPROVEMENT OF IGNITION AND THRUST REPEATABILITY OF A MICRO SOLID PROPELLANT THRUSTER ARRAY
No full textCatalyst preparation for fabrication of a MEMS fuel reformer
No full textFabrication procedures for a micro fuel reformer including catalyst preparation, coating, and patterning on a wafer are described. CU/ZnO catalyst was selected for the steam reforming of methanol. The catalysts were prepared by three different procedures according to the precipitation sequence and temperature. The effect of precipitation conditions on the catalyst characteristics was investigated by BET, XRD and SEM analysis. Catalytic activity and coating quality were tested to find the optimum precipitation condition for the uniform and crack-free catalyst layer on a wafer. For coating purpose, the prepared catalyst was ground by ball-mill into powder and mixed with binder in the deionized water. Simultaneous precipitation of catalyst and binder on the wafer produced a catalyst layer that is uniform and rigidly found to the wafer surface. The amount of the coated catalyst was 5-8 mg/cm(2) and the thickness was 30 mu m. By repetition of the coating procedure, the catalyst mass up to 15 mg/cm(2) was obtained with increased reactivity. Patterned catalyst layer was obtained by a novel lift-off process of the PVA sacrificial layer. The process consists of the PVA decomposition by heating instead of etching the wafer. A micro fuel reformer was fabricated using a typical lithography procedure including catalyst coating and patterning process and its performance was measured. The catalyst-coated micro fuel reformer had higher performances than the packed-bed reactor. (c) 2006 Elsevier B.V. All rights reserved.This work is supported by the NANOFINE program funded
by the Ministry of Commerce, Industry, and Energy. Their support
is gratefully acknowledged
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