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首页> 外文期刊>Combustion Science and Technology >NUMERICAL MODELING OF CONVECTIVE EFFECTS ON PILOTED IGNITION OF COMPOSITE MATERIALS
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NUMERICAL MODELING OF CONVECTIVE EFFECTS ON PILOTED IGNITION OF COMPOSITE MATERIALS

机译：复合材料污染点火对流效应的数值模拟

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A combined solid and gas-phase numerical model has been developed and used to simulate the piloted ignition of a radiatively heated composite material in a boundary layer oxidizer flow. Condensed phase processes (oxidative and thermal pyrolysis, phase change, and in-depth radiation absorption) are simulated with a pyrolysis model developed by the authors. The solid-phase model is coupled to a modified version of the CFD code Fire Dynamics Simulator (FDS), which provides a transient solution to the low Mach number, reactive, buoyant, Navier Stokes equations. The condensed phase and gaseous chemical kinetics are simplified with one-step Arrhenius reactions. Ignition occurs when a premixed flame propagates upstream from the igniter and forms a diffusion flame anchored at the surface of the solid fuel. Numerical simulations have been performed for a polypropylene/fiber glass blended composite slab with a glass concentration of 30% by mass and thickness of 3.2mm. The influence of the incident radiant heat flux, oxidizer flow velocity, and gravitational acceleration on piloted ignition of this composite material has been investigated. Emphasis is given to low-velocity microgravity flows expected in spacecraft. Ignition delay time predictions are compared with experimental data for several external heat flux levels and two flow velocities. The ignition time, pyrolysis rate at ignition, and surface temperature at ignition are considerably lower in a 0.09 m/s microgravity flow than in a 1.0 m/s normal gravity flow. This has important fire safety implications because it indicates that piloted ignition of solid combustibles will occur more easily under the conditions expected in spacecraft.
机译：已经开发了固相和气相的组合数值模型，并用于模拟边界层氧化剂流中辐射加热的复合材料的引燃。作者开发的热解模型模拟了冷凝相过程（氧化和热解，相变和深度辐射吸收）。固相模型与CFD代码Fire Dynamics Simulator（FDS）的修改版本耦合，后者为低马赫数，反应性，浮力的Navier Stokes方程提供了瞬态解决方案。一步式Arrhenius反应简化了冷凝相和气态化学动力学。当预混合火焰从点火器向上游传播并形成锚定在固体燃料表面的扩散火焰时，就会发生点火。已经对玻璃浓度为30质量％，厚度为3.2mm的聚丙烯/纤维玻璃混合的复合板进行了数值模拟。研究了入射辐射热通量，氧化剂流速和重力加速度对该复合材料引燃的影响。重点介绍了航天器中预期的低速微重力流。将点火延迟时间的预测与几种外部热通量水平和两种流速的实验数据进行比较。 0.09 m / s微重力流的点火时间，点火时的热解速率和点火时的表面温度明显低于1.0 m / s的正常重力流。这具有重要的消防安全意义，因为它表明在航天器预期的条件下更容易发生固体可燃物的引燃。

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