Experimental investigation of fire behaviours and heat transfer in single cypress tree crown fires

Hanwen Guo; Yunji Gao; Ziqun Ye; Zhengyuan Yang; Yuchun Zhang; Zijian Lei; Ao Sun

doi:10.1071/WF24030

RESEARCH ARTICLE (Open Access)

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Experimental investigation of fire behaviours and heat transfer in single cypress tree crown fires

Hanwen Guo ^A ^B , Yunji Gao ^A ^* , Ziqun Ye ^A , Zhengyuan Yang ^A , Yuchun Zhang ^A , Zijian Lei ^A and Ao Sun ^A

+ Author Affiliations

- Author Affiliations

^A Department of Fire Protection Engineering, Southwest Jiaotong University, Chengdu, 610031, China.

^B College of Forestry, Northeast Forestry University, Harbin, 150040, China.

^* Correspondence to: gyj119@swjtu.edu.cn

International Journal of Wildland Fire 34, WF24030 https://doi.org/10.1071/WF24030

Submitted: 12 February 2024 Accepted: 21 January 2025 Published: 25 February 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background

Crown fires are among the most perilous and challenging types of forest fires to combat, posing a significant hazard to forest ecosystems and the wildland–urban interface.

Methods

Crown fire experiments were carried out using cypress trees with five different crown heights from 0.4 to 1.2 m to investigate the fire behaviours and heat transfer mechanisms.

Key results and conclusions

The characteristic values of flame height, mass loss rate and heat flux increased with crown height, whereas flame width increased with crown width. Empirical correlations of mass loss rates were established. Flame temperature varied with flame height and relationships between these were developed based on four dimensionless temperature zones. Flame emissivity was related to crown height and increased exponentially with the heat release rate. This study proposes a modified model to predict the radiation heat flux from crown fires, taking the variations of flame temperature and flame emissivity into account.

Implications

The findings of this work enhance understanding of fire behaviours and controlling mechanisms of crown fire under different crown heights, and also improve the accuracy of prediction of wildland fire development and spread in the wildland–urban interface.

Keywords: combustion, crown fire, fire behaviour, fire plume temperature, flame height, heat transfer, mass loss rate, radiation heat flux.

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