Experimental Investigations on Non-premixed Methane-air Flames in Radial Microchannels with a Controlled Temperature Profile

ABSTRACT

Experimental investigations were made on the stabilization and dynamics of non-premixed methane-air flame in a series of radial microchannels with a diameter of 60 mm and widths of 2.0, 2.5 and 3.0 mm with a controlled wall temperature profile. Various flame modes, termed periodically rotating flame, stable flame, broken and cellular flames, single broken flame, and periodically splitting flame were observed with high-speed imaging. Regime diagrams of all these stable and unstable flame modes were then drawn for the three channel gap widths. In addition, some critical flame characteristics, such as the mean radii of the stable flames, and the rotating frequencies of the periodically rotating flames were quantitatively assessed. Effects of the fuel/oxidizer inflow rates and the nominal equivalence ratios on these parameters were studied. Furthermore, numerical studies on the flow field were performed, revealing the inner mechanism of various flame modes to a certain extent. Disturbance of the fuel/oxidizer mixing layer for various flow conditions was considered to be greatly responsible for the formation of some flame patterns.

KEYWORDS:

• Micro-combustion
• non-premixed combustion
• diffusion flame
• rotating frequency
• mean flame radius

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was funded by the National Natural Science Foundation of China [Grant Number 51806158] and the Fundamental Research Funds for the Central Universities [WUT: 2019IVB029].