Study on powder–gas “hybrid” combustion: Its mechanism to achieve variable burning velocities

This study investigates a low-carbon combustion method based on powder-gas “hybrid” flames, in which ultra-lean methane–air mixtures are assisted by biomass powder (Lycopodium spores) to achieve continuous “weak explosions”. This approach offers a solution to achieving stable combustion of low-calorific gaseous fuels with a small amount of combustible powder. In this hybrid fuel, both the powder concentration and the gas-phase equivalence ratio are below their respective flammability limits. A stagnation-point flame was employed, and the burning velocity was determined from particle image velocimetry (PIV) measurements. The results showed that an increase in powder loading rate leads to an increase in burning velocity. A qualitative analysis was conducted to assess the mechanisms controlling the burning velocity; namely, effects of pyrolysis-induced increases in the equivalence ratio and flame surface area, as well as the influence of radiative preheating on the burning velocity. This work offers a new pathway for the combustion of low-calorific gaseous fuels and biomass-based wastes, contributing to carbon neutrality through the utilization of renewable solid fuels. It may represent a promising direction for future developments in sustainable combustion technologies.