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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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🏛️國立陽明交通大學機構典藏

Author: search.filters.author.Lin, PHSubject: search.filters.subject.flame spread

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    Numerical analyses for radiative autoignition and transition to flame spread over a vertically oriented solid fuel in a gravitational field
    (2000)
    Lin, PH
    ;
    Chen, CH
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    This study numerically investigates the ignition behaviors of vertically oriented cellulosic materials subjected to a radiant heat flux in a normal gravitational field. The entire process is delineated into two distinct stages. In the heating up stage, the maximum temperature increases with time but at a decreasing rate because of the pyrolysis reaction. The flame development stage consists of ignition and transition processes. In the ignition process, the maximum temperature in gas phase increases dramatically within a short period of time because a large amount of heat is generated from chemical reaction of the accumulative, flammable mixture. The flame is in a transition from a premixed flame to a diffusion one, except for the small region around the flame front. For the effect of varying the heating duration on ignition behavior, prolonging the imposed radiative heat time leads the ignition from a transition one to a persisting ignition. The effect of varying the solid fuel thickness indicates that the ignition delay time increases with an increase of solid fuel thickness while delta(S)less than or equal to 1.802. For 1.802 less than or equal to delta(S)less than or equal to 3.244, the ignition delay times remain constant. Finally, if the external heating rate is the same order as the heat diffuse rate, the ignition delay time increases with an increase in solid fuel thickness.
  • Thumbnail Image
    Item type:Item,
    Numerical analyses for radiative ignition and transition to flame spread over a horizontally oriented solid fuel in a gravitation field
    (2001)
    Lin, PH
    ;
    Fan, WF
    ;
    Chen, CH
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    This study numerically investigates the ignition behaviors of horizontal-oriented cellulosic materials subjected to radiant heat flux under a natural convective environment. This process can be divided into two stages: (1) the heating-up stage, during which the maximum temperature increases with time and (2) the flame development stage, consisting of the ignition and transition processes, The ignition process is marked with a sharp increase in maximum temperature. Meanwhile, the flame is in a transition from a premixed flame into a diffused one. In the transition process, the flame propagates upstream, forming a so-called opposed flame spread. There is a time lag between solid fuel pyrolysis and the gas-phase chemical reaction. The pyrolysis front overtakes the flame front in the initial heating-up process. As soon as the flammable mixture ahead of the flame front is ignited, the flame moves forward quickly, moving ahead of the pyrolysis front. The ignition delay time is shorter for a horizontal solid fuel than for a vertical solid fuel under the same environment, because the resultant high-temperature region is not cooled and the flammable mixture is not diluted by the induced flow in a horizontal solid fuel. For the effect of changing gravity, the ignition delay time decreases with a decrease in gravity level, owing to the smaller induced flow velocity.