Experimental Study of Influence of Fuel Ratio on Combustion Characteristics of Diesel-Wetted Wood Powder

In this study, experiments were conducted to examine the influence of the fuel ratio (i.e., the ratio of diesel mass to wood powder mass) on the combustion characteristics of diesel-wetted wood powder, in which 0# diesel and poplar wood powder were used and well mixed. The fuel ratios were set to 0, 0.5, 1.0, 1.5, and 2.0. Fire behaviors, temperature distributions, mass loss rates, and CO concentrations were measured and analyzed. The results showed that because of the coupled effect of evaporation and the capillary force, the ignition point of diesel-wetted wood powder (less than 3°C) dropped dramatically as compared with that of pure wood powder (higher than 280°C) and pure diesel (higher than 107°C). At the early stage of combustion, diesel is lifted upwards by the capillary force, increasing both the concentration of diesel vapor and the temperature at the surface. When the surface temperature reaches that of the pyrolysis of wood powder, considerable pyrolysis gas emerges and combusts. As the flammable gas is consumed gradually, carbon combusts prominently when plenty of oxygen diffuses to its surface. Regarding the influence of the fuel ratio, the results showed that in cases with lower fuel ratios, the combustion was not self-sustainable. When the fuel ratio was relatively high, the temperature at the flame center was lower owing to incomplete combustion. More CO could be found in cases with higher fuel ratios in the early and late stages of combustion. The results could help to improve knowledge regarding combustion of fuel-wetted wood powder.