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<p>The ignition of solid materials is strongly influenced by environmental conditions, including flow velocity, oxygen concentration, and ambient pressure. Understanding ignition behaviors at low flow velocities is of paramount importance for spacecraft fire safety. In this study, the ignition process of thermally thick solid fuels is systematically investigated using a narrow-channel apparatus, with a specific focus on low-flow-velocity regimes. Within the tested parametric range, transient flame flashes are observed, the duration of which depends on the flow velocity, indicating a complex transport phenomenon driven by limited oxygen supply. Both the ignition delay time and the corresponding critical mass flux exhibit a non-monotonic dependence on flow velocity; that is, they decrease, reach minimum values at approximately 5&#xa0;cm/s, and subsequently increase until ignition fails. This paper proposes an improved model for predicting the critical mass flux for ignition by explicitly accounting for the unique mass transport characteristics in low-flow-velocity environments. The model predictions demonstrate good agreement with both the present experimental results and existing literature data. Furthermore, by integrating this critical mass flux criterion with a comprehensive solid-phase degradation model, a one-dimensional transient ignition model is developed. By incorporating the additional heat feedback from the transient flashing flame at low velocities, this comprehensive model successfully reproduces the observed non-monotonic trend of the ignition delay time. The proposed modeling framework can also be extended to predict flame spread rates, thereby establishing a quantitative link between ignition and flame spread process.</p>

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An Experimental Study on Piloted Ignition of Solid Materials Under Low-Velocity Flow Environment

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Kai Zhang,
  • Feng Zhu,
  • Zhanbin Lu,
  • Shuangfeng Wang

摘要

The ignition of solid materials is strongly influenced by environmental conditions, including flow velocity, oxygen concentration, and ambient pressure. Understanding ignition behaviors at low flow velocities is of paramount importance for spacecraft fire safety. In this study, the ignition process of thermally thick solid fuels is systematically investigated using a narrow-channel apparatus, with a specific focus on low-flow-velocity regimes. Within the tested parametric range, transient flame flashes are observed, the duration of which depends on the flow velocity, indicating a complex transport phenomenon driven by limited oxygen supply. Both the ignition delay time and the corresponding critical mass flux exhibit a non-monotonic dependence on flow velocity; that is, they decrease, reach minimum values at approximately 5 cm/s, and subsequently increase until ignition fails. This paper proposes an improved model for predicting the critical mass flux for ignition by explicitly accounting for the unique mass transport characteristics in low-flow-velocity environments. The model predictions demonstrate good agreement with both the present experimental results and existing literature data. Furthermore, by integrating this critical mass flux criterion with a comprehensive solid-phase degradation model, a one-dimensional transient ignition model is developed. By incorporating the additional heat feedback from the transient flashing flame at low velocities, this comprehensive model successfully reproduces the observed non-monotonic trend of the ignition delay time. The proposed modeling framework can also be extended to predict flame spread rates, thereby establishing a quantitative link between ignition and flame spread process.