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Microchannel combustion dynamics of low gas, environmentally friendly time delay compositions.

机译：低气体，环保延时成分的微通道燃烧动力学。

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摘要

The purpose of this study is to investigate environmentally friendly time delay compositions. Replacement reactive systems for the widely used tungsten delay composition (W/BaCrO4/KClO4/diatomaceous earth) are needed due to concerns over the toxicity of hexavalent chromium and perchlorates. The ideal system is environmentally benign and gasless in nature (<10 mg of gas formed per gram of reactive) with burning rates in the range of the W/BaCrO4/KClO4 composition (0.6 to 150 mm·s--1). In this work, condensed phase reactives (e.g, Ti/C-3Ni/Al and Ti/C-Ni/Al-Al2O3), Si/metal-oxide reactives and Mn/MnO2 are systematically explored as potential time delay compositions. Additionally, combustion performance predictions from a 2-D axisymmetric COMSOL 4.3a Multiphysics model using measured thermal properties and experimentally determined Arrhenius kinetics are presented.;Systems based on condensed phase reactions, that are typically used in combustion synthesis (e.g., Ti/C or Ni/Al) are of interest as replacements due to their wide range of combustion velocities and potentially low environmental impact. The combustion characteristics of the Ti/C-3Ni/Al reactive system were examined in microchannels with inner diameters ranging from 3.0 -- 6.0 mm (i.e., similar to that of a common delay housing). It was found that this reactive system could be tailored to overcome the heat losses associated with small diameter microchannels by changing the relative amounts of Ti/C and 3Ni/Al. At 40 wt.% Ti/C content, the failure diameter was found to be between 3.0 and 4.0 mm, while at 30 wt.% Ti/C the failure diameter was between 4.8 and 6.0 mm. Measured combustion temperatures in metal microchannels were approximately 1700 K while those of unconfined pellets were around 100 K greater. Increasing Ti/C content resulted in faster combustion velocities while decreasing microchannel diameter resulted in slower combustion velocities. At these small sizes the effects of adding a thermal barrier (specifically Grafoil(TM)) to minimize radial heat losses to the microchannel were shown to be minimal with respect to combustion velocity. The Ti/C-3Ni/Al system was shown to be a suitable delay fuze composition with tunable combustion velocities ranging from 2.1 - 38.1 mm•s-1 in aluminum microchannels with diameters ranging from 4.0 -- 6.0 mm.;The Mn/MnO2 reactive system was also investigated as a suitable replacement for the traditional W/BaCrO4/KClO4/diatomaceous earth delay composition. The delay performance, ignition sensitivity, and aging characteristics were examined in aluminum microchannels similar in diameter to common delay housings (4.7 mm). Stoichiometries with measured combustion temperatures between 1358 and 2113 K were self-sustaining with combustion velocities ranging from 2.4 to 7.3 mm•s-1. The Mn/MnO 2 system produced less gas than W/BaCrO4/KClO4/diatomaceous earth compositions allowing consideration for use in sealed delay housings. Accelerated aging at 70°C and 30% relative humidity for eight weeks resulted in no measurable loss of performance. Safety characterization showed that this composition is not sensitive to ignition by friction or electrostatic stimuli. The combustion products (as determined by X-ray diffraction) appear to be benign based on current regulations. Therefore, the Mn/MnO2 system appears to be a suitable low gas-producing, non-sensitive, less toxic delay composition with good longevity.;Predictive computational models to complement laboratory experiments could help to rapidly develop new pyrotechnic systems. Typically a time intensive experimental approach is necessary to demonstrate applicability. In this effort, a simplified model is developed for the Mn/MnO2 reactive system and compared to experimental data taken previously. First, kinetic parameters and thermal properties were experimentally determined. Effective thermal properties of a Mn/MnO2 powder compact were measured using the transient plane source method and kinetic parameters were obtained using the Boddington method. An effective activation energy of 56.2 +/- 11.7 kJ/mol was determined. A 2-D axisymmetric COMSOL 4.3b Multiphysics model was then developed using global one step first order Arrhenius kinetics. By using this approach, a model of a reacting unconfined pellet predicts combustion velocities similar to those observed experimentally. However, simulations were not able to predict the effect of metal microchannel confinement, changing channel diameter or channel material to those observed experimentally. In order to more accurately simulate these effects, a considerably more complex model with multiphase heat transfer effects would likely be needed.
机译：这项研究的目的是调查环境友好的延时成分。由于担心六价铬和高氯酸盐的毒性，需要用于广泛使用的钨延迟组合物（W / BaCrO4 / KClO4 /硅藻土）的替代反应体系。理想的系统本质上对环境无害且无气体（每克反应物生成的气体少于10 mg），燃烧速率在W / BaCrO4 / KClO4组成的范围内（0.6至150 mm·s--1）。在这项工作中，系统地探索了凝相反应物（例如Ti / C-3Ni / Al和Ti / C-Ni / Al-Al2O3），Si /金属氧化物反应物和Mn / MnO2作为潜在的时间延迟成分。此外，还提出了使用测量的热性质和实验确定的Arrhenius动力学从二维轴对称COMSOL 4.3a Multiphysics模型进行的燃烧性能预测。;基于凝聚相反应的系统，通常用于燃烧合成（例如Ti / C或由于Ni / Al的燃烧速度范围广且对环境的影响可能很小，因此作为替代品受到关注。 Ti / C-3Ni / Al反应系统的燃烧特性在内径范围为3.0-6.0毫米（即类似于普通延迟壳体的内径）的微通道中进行了检查。已经发现，可以通过改变Ti / C和3Ni / Al的相对量来定制该反应体系以克服与小直径微通道相关的热损失。在40重量％的Ti / C含量下，发现破坏直径在3.0和4.0mm之间，而在30重量％的Ti / C下，破坏直径在4.8到6.0mm之间。在金属微通道中测得的燃烧温度约为1700 K，而无限制球团的燃烧温度约高100K。 Ti / C含量的增加导致更快的燃烧速度，而微通道直径的减小导致较慢的燃烧速度。在这些小尺寸下，显示出相对于燃烧速度而言，增加隔热层（特别是Grafoil TM）以使向微通道的径向热损失最小化的影响是最小的。 Ti / C-3Ni / Al系统被证明是合适的延迟引信组成，在直径为4.0-6.0 mm的铝微通道中，燃烧速度可调节为2.1-38.1 mm•s-1。还研究了反应体系作为传统W / BaCrO4 / KClO4 /硅藻土延迟成分的合适替代品。在直径类似于普通延迟罩（4.7毫米）的铝微通道中检查了延迟性能，点火灵敏度和老化特性。燃烧温度在1358和2113 K之间的化学计量比是自持的，燃烧速度在2.4到7.3 mm•s-1之间。 Mn / MnO 2系统产生的气体少于W / BaCrO4 / KClO4 /硅藻土成分，因此考虑用于密封延迟壳体中。在70°C和30％相对湿度下加速老化八周不会导致性能的明显下降。安全性表征表明该组合物对摩擦或静电刺激引起的点燃不敏感。根据现行法规，燃烧产物（通过X射线衍射确定）似乎是良性的。因此，Mn / MnO2系统似乎是一种合适的低产气，不敏感，毒性较小的延迟成分，且具有长寿性。补充实验室实验的预测计算模型可以帮助快速开发新的烟火系统。通常，需要大量时间的实验方法来证明其适用性。在这项工作中，为Mn / MnO2反应系统开发了一个简化的模型，并将其与先前的实验数据进行了比较。首先，通过实验确定动力学参数和热性质。使用瞬态平面源法测量Mn / MnO2粉末压块的有效热性能，并使用Boddington方法获得动力学参数。测定的有效活化能为56.2 +/- 11.7kJ / mol。然后使用全局一阶一阶Arrhenius动力学开发了二维轴对称COMSOL 4.3b多物理场模型。通过使用这种方法，反应性无侧限颗粒的模型预测的燃烧速度类似于实验观察到的速度。但是，模拟无法预测金属微通道限制，将通道直径或通道材料更改为实验观察到的效果。为了更准确地模拟这些效应，可能需要具有多相传热效应的更为复杂的模型。

著录项

  • 作者

    Miklaszewski, Eric J.;

  • 作者单位

    Purdue University.;

  • 授予单位 Purdue University.;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 140 p.
  • 总页数 140
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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