Experimental Studies on the Effects of Spacing on Upward Flame Spread over Thin PMMA

Abstract

Experiments were carried out to study the effect of spacing between wall and thin fuels on upward flame spread. The front flame height, back flame height, pyrolysis height, burnout length, and pyrolysis spread rate were measured by video image analysis with spacings of 2 mm, 7 mm, 13 mm, 19 mm, and 25 mm. Experiments were performed on uniform PMMA (polymethyl-methacrylate) samples with 200 mm height, 50 mm width, and 1 mm thickness. The results are as follows: (1) As the spacing increased, the front flame height, back flame height, pyrolysis height, and burnout length showed the same trajectory, first increased and then decreased. The maximum trajectory was observed at a spacing of 6.5% of the wall height. (2) At an infinite length of PMMA, the pyrolysis zone and pyrolysis spread rate would reach an asymptotic steady state, and the pyrolysis and burnout spread rates will be asymptotically equal. (3) Of particular interest is the maximum mass-loss rate for a wall spacing/sample height ratio (0.065) due to enhanced the radiation fluxes. In this study, the effects of spacing between wall and fuels on upward flame spread was investigated for the first time using 1 mm thick PMMA sheets, including two-face burning case.

Effects of Overlap Length on Flammability and Fire Hazard of Vertical Polymethyl Methacrylate (PMMA) Plate Array

“…where h is the PMMA plate length. Substituting Equations (4), (5), 7, and 9into Equation 8, Equation 10is obtained.…”

“…Most of previous works focused on combustion and flame spread over continuous materials, either solid materials or liquid materials [4][5][6][7][8][9][10][11][12]. Moreover, scholars have conducted extensive research on the flame spread and combustion characteristics of continuous PMMA plate.…”

“…Moreover, scholars have conducted extensive research on the flame spread and combustion characteristics of continuous PMMA plate. Zhu et al [5] experimentally studied the effect of spacing between the wall and the PMMA plate (1 mm thick) on the upward flame spread behavior. Their experiment results indicated that, as the spacing increases, the flame height, pyrolysis height, and burning-out length exhibit the same rule, that is, they first increase and then decrease.…”

Thermodynamic and Kinetic Characteristics of Combustion of Discrete Polymethyl Methacrylate Plates with Different Spacings in Concave Building Facades

“…Therefore, PMMA is a relatively important material in building thermal engineering. However, PMMA without flame retardant is flammable, releasing a lot of toxic gas and resulting in rapid flame spread, which enhances building fire hazards [ 4 , 5 ]. The fire hazard of PMMA is significantly affected with distribution of materials and structures of building facade.…”

Effects of equivalent diameter on vertical PMMA combustion in natural convection environment

“…Understanding combustion characteristics of solid fuels is important for fire safety and combustion applications. It is of practical significance to study the combustion of polymethyl methacrylate (PMMA) because it is a commonly used material in ordinary life for its exceptional transparency, shape adaptability, and high strength 1 . In addition, PMMA is one of the most widely used experimental materials in fire and combustion research area because of its many good performances, such as easy to ignite, no charring, and stable combustion.…”