液体乙醇小尺度扩散火焰的稳燃极限

Stable Combustion Limit of Small Diffusion Flame Using Liquid Ethanol as Fuel

研究了燃烧器喷管的材料及尺寸、针形电场和水平磁场等因素对乙醇小尺度扩散火焰稳燃极限的影响.结果表明:不同内径的陶瓷喷管,当内径从0.4,mm增大到1.0,mm,其燃烧下限由0.6,mL/h减小到0.5,mL/h,燃烧上限由1.05,mL/h增大到1.6,mL/h,内径相同的燃烧器喷管,不锈钢管燃烧上限为1.85,mL/h,石英玻璃管的为1.65,mL/h,即采用内径较大,材料导热系数较大的燃烧器喷管,火焰的稳燃范围较宽;45°针形电场作用下,当电极距为4,cm,电压大于5,kV时,针形电场产生的离子风能吹熄低流量时的火焰,此时火焰的燃烧下限急剧增大,直到增大到与火焰燃烧上限相同时,火焰没有稳燃区间;水平磁场作用下,当磁场强度从0 mT增大到52.5,mT,磁场中乙醇的扩散系数随之增大,进而增大了乙醇的燃烧速度,火焰的燃烧上限也随之增大.

How these factors including burner nozzle, needle-shaped electric field and horizontal magnetic field influence small diffusion flame stability limits was studied experimentally using liquid ethanol as fuel. The results show that as the inner diameter of the ceramic nozzle increases from 0.4 mm to 1.0 mm, its lower flame stability limit decreases from 0.6 mL/h to 0.5 mL/h while its upper flame stability limit increases from 1.05 mL/h to 1.6 mL/h. When the burner of the same inner diameter is used, the upper flame stability limit of stainless steel tube is 1.85 mL/h, and that of quartz glass tube is 1.65 mL/h, which indicates that the larger the inner diameter is and the higher the thermal conductivity of burner nozzle is, the wider the range of stationary combustion flame will be. Under the influence of 45~ needle-shaped electric field, when the electrode distance is 4 cm and the voltage is greater than 5 kV, the needle electric field produced by the ion wind will blow out the low flow of flame, and the flame has no stable combustion interval. Under the action of horizontal magnetic field, as the magnetic field strength increases from 0 mT to 52.5 mT, the diffusion coefficient of the ethanol in the magnetic field increase, thus increasing the flame burning velocity of ethanol and its upper flame stability limit.