In order to study the characteristics of micro scale diffusion flame

liquid fuels were chosen for combustion experiment

and the theoretical models were used to estimate the height of the laminar flame. The following results were obtained. The flame size increased with the increase of the volume flow; in the horizontal direction

when the fuel volume flow was more than 50μL/min

a droplet injection occurred because of the incomplete fuel evaporation

and the flame size changed a little; when the capillary was placed vertically

because of the greater influence of buoyancy

the flame height was elongated. Flame oscillation period decreased with the increase of volume flow

and the bigger flame size meant the stronger flame oscillation. Flame oscillation period in vertical direction was smaller than in horizontal direction. With the increase of carbon content

the flame size became larger

and the oscillation was stronger. Kerosene with more carbon content injected fuel around the nozzle

resulting in unstable flame. The flame height was proportional to the Reynolds number of the fuel vapor at nozzle in the vertical direction

Roper model predicted the experimental result best

helping to calculate the laminar diffusion flame height of liquid hydrocarbon fuels in the vertical direction.