| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 96 === The increasing demand for micro-power systems for the world-wide extensive applications in microelectromechanical systems (MEMS) and personal utility systems has given a significant impetus on investigations of micro-propulsion and micro-combustion. Concepts of micro-scale detonation systems were proposed recently to resolve the heat loss problems in the micro-combustion system by means of high speed flame propagating in the chamber. Furthermore, the detonation system has much higher thermal efficiency compared to the other traditional low speed combustion systems. In view of these advantages, the micro detonation power systems deserve further in-depth research and developments..
Generation of the detonation in the manner of deflagration-to-detonation transition (DDT) in macro-scales has been shown feasible and successful. However, the research of DDT in a microscale tube is scarce and with challenges so far. Accordingly, in this study we will discuss the phenomenon of DDT in a micro-tube with experimental measurements and further propose the novel design of the pre-chamber to promote flame acceleration and to stabilize the onset of detonation. Experimental parameters include tube sizes, pre-chamber dimensions, and initial pressure of the mixtures.
Results show that the pre-chamber set-up is definitely helpful for flame acceleration, and occurrence of DDT in the stoichiometric hydrogen- oxygen mixture in the 1mm-diameter to 2mm-diameter tubes at atmospheric pressure. Besides, DDT induction distance can be decreased depending on increaseof the initial pressure. For the fixed tube size cases, the effects of pre-chamber are not pronounced in the smaller tube, whereas this influence become significant in the larger 2mm-diameter tube cases. In this study, the shortest detonation induction distance of 116mm was reached at the case of 1mm-diameter tube with 9mm-diameter pre-chamber at 34.5 psia.
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