Experimental Study of the Burning Characteristics of Wood Grilles with Different Porosities

Abstract

ABSTRACT This paper investigates the effect of porosity on the burning and flame spread characteristics of the wood grille. Five pore side lengths (1–9 cm, 5 porosities φ, 38.25%−85%) of the grilles are studied and compared, which are widely used in Chinese historical buildings. The results show that both peak mass loss rate and peak heat release rate decrease with increasing porosity, while the grille with 65% porosity is the first to experience significant mass loss. The flame height and pyrolysis height have a clear power-law relationship. When the side length is less than 5 cm (φ ≤75.5%), the flames are merged and this relationship is similar to continuous fuels. While for the side length higher than 5 cm (φ > 75.5%), the main part of the flame mostly stays on the vertical strips in a discrete state, rather than continuous fuels. This phenomenon can be explained that the flow rate of the gas flowing through the pores increases with the increase of the porosity, which effectively enhances convective heat transfer. As the porosity increases further, the effective heating length on the wood samples is reduced, resulting in a smaller total heat input and a slower burning process.