Characterization of Pt catalytic combustor in microchannel

• Main Authors: Shun-Yi Li, 李順義
• Other Authors: Tzong-Shyng Leu
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/45183784584118710660

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 92 === 　　One of the problems faced in micro-scale combustion is the limit of quenching length. The factors that influencing quenching length limit include the loss of heat, the friction loss and the depletion of free radical. This research can utilize the characteristic that the catalyst surface on the little channel reduced the activation energy. The research take advantage of the quality that the activation energy can be reduced by the catalyst surface on the micro channel to carry out the experiment. There are three platinum catalyst micro channels which have different width ,such as 1000μm , 400μm and 40μm. The platinum catalyst micro channel reactor is fabricated by MEMS technology. The reactor uses the exothermic reaction of hydrogen and oxygen on the platinum catalyst plate as the heat source and the platinum thin film resistance deposited on a glass chip by face micro machining process as catalyst and temperature sensor. The channel is bonded with a cover plate etched by bulk micromachining technology to become a mico- channel reactor. Moreover, a micro catalytic column structure fabricated on channel with 400μm in width by LIGA-like technology to increase the reaction surface for catalyst. The research is focused on the catalytic exothermic reaction in the micro channel under different warm-up temperature and equivalents. Due to the decrease of the catalytic surface for the unit volume of fuel, the micro exothermic catalytic reaction is more violent than the macro exothermic catalytic reaction. The preliminary analysis reveals that the platinum catalyst micro channel reactor with 1000μm in width produces appropriate heat under appropriate fuel supply and the maximal wall temperature reaches more than 1000 K. There are two operation limits in the reactor with 40μm in width. Under considerably small flow rate, the heat loss is so big that the reaction cannot hold. The reaction will also blow off when the flow rate is considerably big. In the reactor with 400μm in width, the catalytic column structure increase the surface volume ratio from 7 mm-1 to 20.25 mm-1 and the maximal temperature will reach 790K and 1050K when the flow rate are 10m/s and 30m/s respectively. 　　In order to understand the influence of flow rate, channel size and fuel gas concentration on reaction, three time scales are presented in this thesis to stand for the three factors. They are residence time, diffusion time and characteristic time. According to our studies, three time scales will compete with each other and influence the reaction efficiency of micro catalyst channel. In micro combustion, how to improve the heat loss on wall is also worthy to be studied.