Experimental and numerical investigations on fire development in a timber-based compartment with identification of characteristic events

Abstract

An experiment and numerical simulations were carried out to investigate the mechanism of the incipient and growth stages of a building fire. The building, constructed in the 1980s with wooden components, has one compartment and one opening. The average fire load density was 1495.3 MJ/m2, including the wooden columns, beams, furniture, etc. The evolution of indoor temperature, gas concentration, gas flow rate and burning behaviors were obtained and analyzed. To better understand the fire development process, we identified characteristic events, including pilot fire, incipient fire, pre-flashover fire spread, ceiling jet period, and flashover and spill plume. By defining dimensionless time (τ = ti/tflashover), it was found that the fire development process simulated by Fire Dynamic Simulator experienced the same characteristic events as the experiment. In this work, when flashover occurred, the neutral plane height decreased to about half the height of the opening, the velocity of hot smoke outflow was higher than 3 m/s, and the maximum thickness of the wood charred layer reached 1 cm. Two theoretical methods to estimate the heat release rate (HRR) in the fuel-controlled stage before flashover were proposed. The HRRs at the time of flashover with the two methods are at the same order of 5 MW, and the error between them was within 18.1%, which verifies the feasibility of the above methods to a certain extent. This study helps to learn the characteristics of early and growth stages of building fires with wooden components.