液体燃料在毛细管出口扩散火焰燃烧特性

为了解微尺度扩散火焰燃烧特性，选用液体燃料，进行燃烧实验，并利用理论模型对层流火焰高度进行了预估。结果表明:毛细管层流扩散火焰尺寸随燃料流量的增加而增大，水平方向当流量大于50μL/min时，由于燃料蒸发不完全，会有液滴喷出，火焰尺寸增长速度变小；竖直方向受浮力影响，火焰高度被拉长，远大于水平方向。火焰尺寸越大，振荡越剧烈，表现为振荡周期随流量的增加而减小，且竖直方向小于水平方向。燃料含碳量影响火焰特性，含碳量越多，火焰尺寸越大，火焰越明亮，振荡越剧烈。流量较大时，含碳量较多的煤油会向管口周围喷射燃料，形成剧烈振荡的不稳定火焰。竖直方向火焰高度与管口处燃料蒸汽雷诺数成正比，Roper模型预估结果与实验结果相近，可用于计算液体烃类燃料在竖直方向的层流扩散火焰高度。 

Combustion characteristics of liquid fuel diffusion flame at capillary oulet

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.