Abstract: Abstract: The influence of internal angle configuration on downward fire spread characteristics of polyurethane insulation material (FPU) is analyzed by small-scale experimental research, and the influence of different angle configurations on typical characteristic parameters of fire spread of FPU insulation material is studied and discussed, including flame shape, mass loss rate, near-field temperature and fire spread rate. The results show that, under the constraint condition of the side wall, the burning degree of the sample when the angle is 30° is obviously higher than that of 150°; For the confined space formed by the internal angle configuration, the burning degree of FPU sample under the small angle configuration is greater than that under the large angle configuration. Influenced by the limiting effect of the side wall, the mass loss rate and fire spreading rate of FPU both decrease at first and then increase with the increase of the included angle. Due to the stretching effect of stack effect, there are two temperature peaks, and the first temperature peak is higher than the second.

Key words: Key words: internal angle configuration, polyurethane insulation material, fire spread, stack effect