液体燃料碳原子数对微尺度扩散火焰特性的影响

Effects of Number of Carbon Atoms in Molecule of Liquid Fuels on Characteristic of Micro-Scale Jet Flames

关键词:  微尺度  烷烃  燃烧尺度极限  火焰高度  管壁温度

Key words:  Micro-scale  Alkane  Combustion limit  Flame height  Tube wall-temperature

摘要:

为了解微尺度扩散火焰燃烧特性，选用正戊烷、正庚烷、正辛烷、正癸烷、正十二烷五种不同液体烷烃，进行燃烧实验。结果表明:火焰在不同流量下会呈现球型、椭球型、细长型、聚积型以及喷射型；燃料含碳越多，其火焰燃烧极限越小。对于每种烷烃，火焰高度H与Re都呈线性正相关，燃料含碳量越多，火焰高度H随Re变化越小；Roper火焰长度预估模型对于液体烷烃同样适用，实验所得数值与模型的误差在25%以内。火焰管壁温度随流量增大而降低，火焰温度随流量增大而升高，火焰温度与火焰形态有关；不同燃料的管壁温度和火焰温度都随含碳量增大而降低。

Abstract:

In order to get characteristics of the micro-scale diffusion flame of liquid fuels， n-pentane， n-heptane， n-octane， n-decane， n-dodecane were studied experimentally. The following results are obtained. (1) The diffusion flame shapes are different， including spherical shape， ellipsoidal shape， slender shape， agminated shape and explosive shape depending on the flow rate; the more carbon contained in the fuel， the smaller the combustion limit is. (2) The flame height is proportional to Reynolds number， and the fuel containing more carbon has smaller ratio of flame height and Reynolds number. Roper’s model for estimating diffusion flame height applies to liquid alkane as well. The error between the experiment value and the model is within 25%. (3) The temperature of tube wall decreases as the flow rate increase， and the temperature of flame increases instead. The flame temperature depends on the shapes of these flame. The temperature of tube wall and flame temperature of different fuel decrease with the increase of carbon content.