Abstract: Using 45 cm tall, 5.0 cm wide and 2.0 mm thick advertising canvas，the effects of limited distance with the range of 3.0~9.0 cm between wall and fuel surface on flame length, spread rate and ignition time are quantitatively analyzed. The major conclusions are summarized as follows: When the limited distance is 3.0~8.0 cm，the flame length on limited side is larger than that on unlimited side, whereas when limited distance is beyond 8.0 cm, the flame lengths on both sides are basically the same. Both the flame length and spread rate first increase and then decrease with limited distance, and finally reach a constant value, while the ignition time decreases first and then rises with limited distance, and ultimately achieves a stable value. The relationship between the heat flux received by virgin surface and ignition time is established. Moreover, the variation trend of the heat flux received by virgin surface with the limited distance is analyzed, which can be used to explain the cause of the non-monotonic trend in spread rate.

Key words: limited distance, upward flame spread, advertising canvas, flame spread rate, heat transfer