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首页> 外文会议>A safer space for a safer world >UNDERSTANDING PILOTED IGNITION OF SOLID COMBUSTIBLES IN SPACECRAFT ENVIRONMENTS THROUGH NUMERICAL MODELING
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UNDERSTANDING PILOTED IGNITION OF SOLID COMBUSTIBLES IN SPACECRAFT ENVIRONMENTS THROUGH NUMERICAL MODELING

机译：通过数值建模理解立体燃烧在空间环境中的燃烧

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Space exploration vehicles can present internalrnatmospheres different from sea level standardrnatmospheric conditions (100 kPa, 21%O2). In NASA'srnmost recent human space exploration crew vehicles therncabin environments were designed to have reducedrnambient pressure and increased oxygen concentrationrn(around 55 kPa, 32%O2,). These distinct ambientrnconditions, in addition to the absence of gravity, mayrnincrease the fire risk of combustible materials on board.rnEnhancing the oxygen concentration will lead to higherrnflame temperatures. Reducing the ambient pressure willrndecrease convective heat losses from heated surfacesrnbut also will reduce the amount of pyrolyzate requiredrnto reach a flammable mixture near the pilot. This studyrnexplores the effect of ambient variables such as reducedrnpressure, oxygen concentration or microgravity on thernphysical mechanisms that lead to the piloted ignition ofrnsolid combustibles through numerical analysis.rnTwo-dimensional simulations of piloted ignition ofrnthermally irradiated samples of PMMA (polymethylmethacrylate)rnwere performed with the Fire DynamicsrnSimulator (FDS5) code. Finite-rate single-steprncombustion kinetics is used in the gas-phase and arnsingle step Arrhenius type reaction rate describes thernsolid pyrolysis. Oxidative pyrolysis is not consideredrnand the in-depth formed pyrolyzate is assumed to flowrnunrestricted through the PMMA. The model correctlyrndescribes the thermo-physical mechanisms leading tornthe piloted ignition of solid fuels. It is shown that as thernambient pressure is reduced or the oxygen concentrationrnenhanced, both the time to ignition and the fuel massrnloss rate at ignition are reduced, increasing the firernhazard of the material when externally heated.rnThe calculated ignition times and mass loss rates atrnignition are compared to those measured experimentallyrnin a laboratory-scale combustion wind tunnel. It is alsornshown that with appropriate kinetic parameters thernmodel agrees qualitatively well with the experimentalrndata.
机译：太空探索飞行器可以呈现与海平面标准大气条件（100 kPa，21％O2）不同的内部大气。在美国宇航局最近的人类太空探索飞行器飞行器中，客舱环境被设计为具有降低的环境压力和增加的氧气浓度（约55 kPa，32％O2）。除了没有重力以外，这些独特的环境条件还可能增加船上可燃材料的着火危险。增强氧气浓度将导致更高的火焰温度。降低环境压力将减少受热表面的对流热损失，但也将减少到达引燃器附近的易燃混合物所需的热解产物量。这项研究通过数值分析探索了诸如变压，氧气浓度或微重力之类的环境变量对导致引燃固体可燃物的物理机制的影响。通过火对PMMA（聚甲基丙烯酸甲酯）的热辐照样品进行引燃的二维模拟DynamicsrnSimulator（FDS5）代码。气相采用了有限速率的单步燃烧动力学，并且以阿涅尼斯型反应速率描述了固体热解。不考虑氧化热解，并假定深度形成的热解产物不受限制地流过PMMA。该模型正确描述了导致固体燃料引燃的热物理机制。结果表明，随着环境压力的降低或氧气浓度的增加，点火时间和点火时燃料质量损失率均降低，从而增加了材料在外部加热时的着火危险.rn比较了计算得到的点火时间和燃烧时的质量损失率。在实验室规模的燃烧风洞中进行实验测量的结果。还表明，在适当的动力学参数下，模型与实验数据在质量上吻合良好。

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  • 会议地点 Versailles(FR)
  • 作者

    Sonia Fereres; Carlos Fernandez-Pello; Gary Ruff; David Urban;

  • 作者单位

    Department of Mechanical Engineering, University of California at Berkeley,60A Hesse Hall, Mailstop 1740, Berkeley, CA 94720, USA, Email: sfereres@gmail.com;

    Department of Mechanical Engineering, University of California at Berkeley,60A Hesse Hall, Mailstop 1740, Berkeley, CA 94720, USA, Email: ferpello@me.berkeley.edu;

    NASA John H. Glenn Research Center, Cleveland, OH 44135, USA, Email: gary.a.ruff@nasa.gov;

    NASA John H. Glenn Research Center, Cleveland, OH 44135, USA, Email: david.l.urban@nasa.gov;

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