Experimental study on flame characteristics over diesel pool fires under the longitudinal ventilation in curved and inclined tunnels

Abstract

Compared to porous burners using gaseous alkanes or alcohols, the combustion characteristics of diesel pool fires more closely resemble actual tunnel fire scenarios. Diesel fires may exhibit more complex combustion behavior and higher flame burning rates under longitudinal ventilation, increasing the risk of fire spread within the tunnel. In a windy tunnel, the flame tilt angle and flame length are the two key parameters used to describe flame characteristics. This paper focuses on tunnels with steep gradients and small curvatures, establishing scaled models with varying curvatures and slopes to experimentally study the flame characteristics of diesel pool fires under the influence of longitudinal ventilation. The results show that a linear correlation between the logarithm of the mass loss rate and the logarithm of the measured fire source length in windless conditions. The square root of the ratio of longitudinal ventilation speed to the side length of the fire source is directly proportional to the fuel mass loss rate per unit area under longitudinal ventilation. Secondly, the flame title angle is linearly correlated with the tunnel slope in windless tunnel, and the flame tilt angle shows a slight increase as the curvature radius decreases. The flame title angle is linearly correlated with the longitudinal wind speed. Furthermore, Hu’s flame tilt angle model was refined for positive slope, low slope and negative slope tunnels under longitudinal ventilation. Finally, new flame length models for positive slope, low slope and negative slope tunnels under longitudinal ventilation were proposed based on theoretical analysis and experimental data.