Abstract:

The combustion characteristics of premixed C₁-C₄ alkane jet flames were studied experimentally with a slit burner between two parallel walls. The effects of wall temperature, the distance between two walls, equivalence ratio and fuel type on flame pattern and stability were investigated. The flame images were captured by using a high-speed charge-coupled device camera. The results indicated that the flames experienced three states with the decrease of the distance between the walls, i.e., stable flame, pulsating flame and flame extinction. It was found that the pulsating flames only existed in a very narrow range before reaching the extinction distance. The flame pulsation frequency increased monotonically with the wall temperature. For the same fuel, the frequency was independent to the distance between two walls at a fixed wall temperature and equivalence ratio. Meanwhile, the flame pulsation frequency and the range of the pulsation zone were related to the type of fuel for premixed C₁-C₄ alkane flames. Generally, the methane flame showed the lowest pulsation frequency and narrowest pulsation zone, while these characteristics were almost the same for C₂-C₄ alkane flames.

Key words: microscale, alkane, fuel, combustion characteristic, flame stability, pulsating flame

摘要：

对平行平板狭缝间C₁~C₄烷烃预混射流火焰进行了实验研究，考察了壁面温度、狭缝间距、当量比、燃料种类等对火焰形态和稳定性的影响，并利用高速相机获得了狭缝间的火焰图像。结果表明，随着狭缝间距的减小，火焰经历了稳定、脉动和熄火3个阶段。其中，火焰脉动发生在大于熄火间距的狭小范围内，其脉动频率随着壁面温度的升高而增加。对同一种燃料，当预混气当量比和壁面温度保持恒定时，火焰的脉动频率在脉动发生的区域内保持不变。对比C₁~C₄烷烃预混火焰的脉动频率及脉动火焰持续距离范围，发现甲烷预混火焰的均最小，而其他3种燃料则比较接近。

关键词: 微尺度, 烷烃, 燃料, 燃烧特性, 火焰稳定性, 脉动火焰