The ignition and subsequent transition to steady-state flame spread behaviors over a vertical solid fuel in normal gravity and static environment were numerically studied in this work. Unlike the general approach based on the NS equation for buoyancy flow, the lattice Boltzmann method (LBM) was employed to solve the velocity field in the gas phase. Elliptic equations of temperature and concentration in gas and solid phases were solved by the finite difference method (FDM). An LBM-FDM coupling model for investigating the downward flame spread over solid fuel was developed. The ignition and the flame propagation behavior can be predicted quantitatively. The results show that a point flame with the shape of a disk appears first at the sheet surface when the vertical solid fuel is ignited. The instantaneous temperature response of ignition lags behind the chemical reaction. The point flame gradually develops into an asymmetric arch-shaped flame with two flame fronts near the sample surface. And then, the flame in the downstream zone is separated from the upstream flame source under the effect of the induced buoyant flow, and eventually disappears at the downstream boundary. Finally, the flame on the upstream gradually develops into a steady downward flame spread. The developed model in this work is validated by comparing the gas-phase temperature and flame spread rate between the predicted results and previous experimental data. This paper provides another method to predict the development of solid flame spread.

在这项工作中，数值研究了在正常重力和静态环境下垂直固体燃料上的点火和随后向稳态火焰蔓延行为的转变。与基于浮力流的 NS 方程的一般方法不同，采用格子玻尔兹曼方法 (LBM) 来求解气相中的速度场。通过有限差分法（FDM）求解了温度和气相和固相浓度的椭圆方程。开发了一个 LBM-FDM 耦合模型，用于研究固体燃料上的向下火焰蔓延。可以定量预测点火和火焰传播行为。结果表明，垂直固体燃料点燃时，片材表面首先出现圆盘状点状火焰。点火的瞬时温度响应滞后于化学反应。点火焰逐渐发展成不对称的拱形火焰，在样品表面附近有两个火焰锋。然后，下游区域的火焰在诱导浮力流的作用下与上游火焰源分离，最终在下游边界处消失。最后，上游的火焰逐渐发展为稳定的向下火焰蔓延。通过比较预测结果和先前实验数据之间的气相温度和火焰蔓延速率，验证了这项工作中开发的模型。本文提供了另一种预测固体火焰蔓延发展的方法。点火焰逐渐发展成不对称的拱形火焰，在样品表面附近有两个火焰锋。然后，下游区域的火焰在诱导浮力流的作用下与上游火焰源分离，最终在下游边界处消失。最后，上游的火焰逐渐发展为稳定的向下火焰蔓延。通过比较预测结果和先前实验数据之间的气相温度和火焰蔓延速率，验证了这项工作中开发的模型。本文提供了另一种预测固体火焰蔓延发展的方法。点火焰逐渐发展成不对称的拱形火焰，在样品表面附近有两个火焰锋。然后，下游区域的火焰在诱导浮力流的作用下与上游火焰源分离，最终在下游边界处消失。最后，上游的火焰逐渐发展为稳定的向下火焰蔓延。通过比较预测结果和先前实验数据之间的气相温度和火焰蔓延速率，验证了这项工作中开发的模型。本文提供了另一种预测固体火焰蔓延发展的方法。最后，上游的火焰逐渐发展为稳定的向下火焰蔓延。通过比较预测结果和先前实验数据之间的气相温度和火焰蔓延速率，验证了这项工作中开发的模型。本文提供了另一种预测固体火焰蔓延发展的方法。最后，上游的火焰逐渐发展为稳定的向下火焰蔓延。通过比较预测结果和先前实验数据之间的气相温度和火焰蔓延速率，验证了这项工作中开发的模型。本文提供了另一种预测固体火焰蔓延发展的方法。