Development of a multiple opposing jets' burner for premixed flames

摘要

A burner was developed to accommodate multiple opposing premixed flames, where the turbulence stimulated by impingement was found to extend the stability limits of methane/air mixtures. The opposing jets established closed loop flow currents in a number of sectors, which is twice that of the jets thus providing more eddies within a stronger turbulent flame structure. The stagnation zone for four opposing jets was testified to be larger than that for two jets such that it was able to sustain higher reactive jet velocities up to 14.2 m/s at larger flow shearing rates. Increasing the number of opposing jets and decreasing their separation distance provided higher rates of heat/mass transfer into the ports. As the flow deceleration zone was enlarged, the correspondingly higher burning capacities were correlated to the port diameter, the separation distance, the number of jets, Reynolds number, and the strain rate. Strain rates of growing magnitudes up to 13,080 s~(-1) were sustained at jet velocities as high as 21.8m/s. At such velocities and upon increasing the ratio of the jet diameter to the separation distance, the turbulent kinetic energy was found to exhibit one local peak, as the strain rate due to impingement became enriched by the jet radial shearing effects. A lean blowout equivalence ratio of 0.59 was pronounced as a basis for acquiring low NO_x emissions. The burner serves as a potential prototype for increasing the power-to-weight ratio of the combustion chambers like those utilized in furnaces, boilers, gas turbines, as well as jet-propelled vehicles with effectively minimized emissions of pollutants.