中文摘要：

在有点火源的条件下，对榆木在两种不同辐射方向下的热解和着火特性进行了研究，测定了不同外加热辐射强度、不同辐射方向下榆木的着火时间、表面温度、质量损失的变化规律。实验结果表明，榆木在水平方向下较垂直方向更容易着火，临界热流更小，着火表面温度更高，质量损失速率更小。

英文摘要：

The effect of radiation orientation on pyrolysis and piloted ignition of Elmwood under different heat flux has been experimentally investigated. Two orientations were selected, vertical or horizontal, according to the geometry of materials in the actual fire scene. Ignition time, surface tern- perature profiles, mass loss rate and critical heat flux were all measured in the experiments. Compared with the vertical orientation, the samples burned much easier and lower critical heat flux for pilot ignition, higher surface temperature and smaller mass loss rate were revealed for the horizontal orientation.