Combustion instability of lean premixed swirl flame

An experimental study was conducted on combustion instability in a lean-premixed swirl-stabilized combustor at atmospheric pressure and temperature. The primary objectives were to study the influence of equivalence ratios, swirl number, geometry of premixed sector on combustion instability. The result also revified the influence of equivalence ratios on combustion instability, demonstrating that the combustion process consisted of stable, pause oscillation, instable steps with little variation of frequency and great expansion of peak value of oscillation pressure, finally achieving limit cycle. With the rise of swirl number, the pulsation of oscillation pressure increased signally while the lowest equivalence ratio of combustion instability decreased gradually. Compared with the open geometry of premixed section, the polyporous structure of premixed section could reduce the oscillation pressure in combustor and premixed section.