| Budget Amount *help |
¥16,940,000 (Direct Cost: ¥14,900,000、Indirect Cost: ¥2,040,000)
Fiscal Year 2007: ¥8,840,000 (Direct Cost: ¥6,800,000、Indirect Cost: ¥2,040,000)
Fiscal Year 2006: ¥8,100,000 (Direct Cost: ¥8,100,000)
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| Research Abstract |
Flame pattern formation was examined for the development of microcombustion devices. Premixed methane-air mixture is introduced at the center of two parallel circular quartz plates separated by a millimeter scale distance (<5mm). Two plates are heated with an external heater to create a positive temperature gradient condition along the flow direction. Main result are as follows.
1) In addition to the general perception of a stable premixed flame front at a radial location, a variety of nonstationary flame propagation modes are observed. For lower mixture flow rates and a range of mixture equivalence ratios, a radial flame propagation mode is observed with simultaneous presence of two circular flames at different radial locations. For higher flow rates, a rotating spiral flame propagation mode is observed. In addition to radial and spiral flame propagation modes, random and unsymmetrical flame oscillations are also observed. The rotational rates of the spiral flame fronts were observed t
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o vary from 28 to 83 Hz. A simple analysis is carried out to describe the formation of spiral flames from a steady circular flame.
2) Comprehensive regime diagrams of flame pattern formation in radial microchannels with temperature gradients were drawn based on experimental findings. A premixed methane-air mixture was introduced at the center of microchannels formed by two parallel circular quartz plates that were heated with an external porous burner to create a positive temperature gradient condition in the direction of flow. Combustion behavior in those microchannels at channel widths of 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mm were experimentally investigated. Regime diagrams of various stable and unstable flame patterns were obtained, confirming that the flame pattern is a strong function of mixture equivalence ratio, inlet mixture velocity, and channel width. Furthermore, some combustion characteristics, such as the rotating frequency of the single pelton-like flame and the triple flame, the radius of the stable circular flame front, and comparison between the major combustion products of the single and double pelton-like flames, were also investigated.
After careful examinations, some of the experimental pattern formations were successfully reproduced by computational two-dimensional modeling. Results are submitted to a journal. Less
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