Development of an Industrial Burner Accommodating Methane-Air Triple Flames

ABSTRACT

Concentric fuel-rich and fuel-lean mixtures of methane and air were fed in the form of multiple pairs of circumferentially oriented opposing jets that are normal to an air cross flow inside a cylindrical burner to achieve the maximum firing capacity. As two premixed flames developed per each set of concentric jets (while the excess fuel and air diffused into a non-premixed flame wing), combustion via triple flames was thus sustained by a duplicated stagnation impact and a vortical flow field with intense heat recirculation. Setting equivalence ratios of 1.35 and 0.80 for six pairs of opposing jets increased the firing intensity to 100.4 MW/m³ which corresponded to jet flow velocities of 74.5 m/s. While the maximum blow-out velocity corresponded to a combined equivalence ratio of one, the minimum flame length and the peak combustion efficiency were reached at a combined equivalence ratio of 0.6. Switching from normal to inverse triple flames increased the blowout velocity limit from 74.5 to 82.2 m/s but increased the maximum value of the visible flame length/burner diameter ratio from 1.52 to 1.64.

KEYWORDS:

• Burner
• methane-air
• triple flames

Additional information

Funding

This work was supported by the STDFERAFRICA project.