Influence of woodgrain orientation on the upward flame spread over discrete wood chips

Abstract

To have a deep understanding of influence of woodgrain orientation on the upward flame spread performance, a series of tests were conducted to obtain the profile of mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD), and the maximum flame characteristic length (MFL) by using a traditional flame spreading measurement facility. The woodgrain orientation of samples tested in the current work are horizontal (H), vertical (V), and slanting (S). During the tests, a series of six 2 cm-long 10 cm-wide wood chips were uniformly installed on a vertical sample holder. The distance of air-gap differed from 1.0 cm to 3.0 cm and the thickness of wood chips varied from 1 mm to 4 mm. It is found that flame spread over discrete solid fuels depends on the generation rate of pyrolysis gas and direction of gas-flow, which is highly differed by the woodgrain orientation with respect to the wooden chips. The charring rate of samples imposed a strong effect on the flame spread performance. The a-MLR of three kinds of woodgrain are ranked as V > S > H. The FSR are ranked in general as H > V > S. The thickness of the samples imposed a larger effect on the TBD comparing with wood grains orientation. The TBD are ranked as S > V > H. The results of MFL indicate that as the thickness of the sample increases, MFL of samples performed with the H woodgrain is reduced greatly. However, both S and V woodgrain show a small effect on the MFL. It hopes to provide a deep understanding of flame spreading performance over wooden structures.

Keywords

• Wooden structures
• Traditional wood
• Discrete fuels
• Air-gap
• Flame spread rate
• Woodgrain orientation