Influence of air gap ratio of the Chinese historical wooden window on the vertical flame spread performance

Abstract

The fire protection of historical buildings with wooden structures is a topic that has attracted much attention over the last few years. As one of the critical structures of ancient buildings, wooden windows have high fire hazards. This study aims to clarify the influences of air gap ratio on the fire propagation mechanism of wooden windows by experimental investigating flame characteristics such as mass loss rate (MLR), flame spread rate (FSR), total burning duration (TBD), and maximum flame length (MFL), and propose corresponding fire protection strategies. In the experiment, the typical wooden window structure in ancient buildings was selected as the research object. The wooden windows with different porosity were installed on the vertical sample rack to carry out the combustion experiment, and the area air gap ratio ranged from 32.9% to 64.2%. The experimental results show a clear relationship between MLR and the area air gap ratio. TBD, FSR and MFL are related to the vertical linear air gap ratio of the wooden window structure. FSR first increases and then decreases with the linear air gap ratio, and the peak value of FSR appears on the sample with a vertical linear air gap ratio of 69.6%.