Experimental study on the combustion characteristics of typical surface vegetation in power transmission corridors

In recent years, global climate change and intensified human activities have significantly increased surface fire risk in power transmission corridors spanning mountainous and forested areas, posing a serious threat to the safe and stable operation of modern power grids. Surface vegetation serves as the primary fuel for ground fires and wildfires, directly influencing the flame spread velocity, fire development stages, and combustion intensity. Therefore, investigating the combustion characteristics of surface vegetation is crucial for improving wildfire prevention systems, enhancing the accuracy of fire behavior predictions, and ensuring the operational reliability of transmission infrastructures. However, current research on the combustibility and fire behavior of various surface fuels in transmission corridors remains insufficient, particularly in terms of comparative analyses across different vegetation types and accumulation thicknesses. There is a pressing need for systematic experimental studies to reveal the heat release mechanisms, fire growth, and gas emission characteristics of these vegetation types.

This study aimed to experimentally explore the combustion characteristics of typical surface vegetation in transmission corridors under varying accumulation thicknesses, compare differences in fire behavior among vegetation types, and identify key parameters, including flame spread patterns, mass loss rate evolution, temperature distributions, and gas volume fraction dynamics. The combustion characteristics of different types of surface vegetation in transmission corridors were investigated through small-scale experiments. A self-designed 1m² small-scale combustion platform was constructed and equipped with cameras, a thermocouple array, a high-precision electronic balance, and gas sensors to collect key combustion data, including flame behavior, temperature distribution, mass loss, and gas volume fractions, during the tests. Three typical vegetation types—shrubs, coniferous litter (pine needles), and broadleaf litter (maple leaves)—were selected as the research objects. For each vegetation type, three accumulation thicknesses (10, 15, and 20cm) were specified. Under an ambient wind speed of 1 m/s, key parameters, including flame morphology, flame height, mass loss rate, temperature distributions, and smoke gas volume fraction, were recorded and analyzed to reveal the spatiotemporal evolution of their combustion characteristics.

The results showed that the combustion process of typical surface vegetation in transmission corridors could be divided into four stages: initial, development, peak, and extinguishment. Flame propagation exhibited an arc-shaped outward expansion pattern. As the accumulation thickness increased, the flame height, mass loss rate, and peak temperature also increased. The CO₂ volume fraction followed a "sharp rise-gradual decline" trend, whereas the volume fraction of CO exhibited a phased characteristic of concentrated release in the initial and extinguishing stages. The volume fractions of both CO and CO₂ increased with increasing accumulation thickness. At the same accumulation thickness, flame heights ranked from highest to lowest as coniferous litter, shrubs, and broadleaf litter. Among them, coniferous litter exhibited the highest combustion intensity, greatest flame height, maximum mass loss rate, and most pronounced multipeak fluctuation behavior.

This study reveals the combustion characteristics of typical surface vegetation in transmission corridors under varying accumulation thicknesses. This study also systematically analyzes the differences in flame spread characteristics, thermal behavior, and gas emissions across vegetation types. The findings provide a robust experimental basis for assessing surface fire risk, modeling fire behavior, and developing wildfire warning strategies for power transmission corridors.