Combustion characteristics of ignition processes for lean premixed swirling combustor at ultralow equivalence ratios

To have good ignition performance of lean premixed swirling combustor (LPSC) at ultralow equivalence ratios, this paper researched experimentally the combustion characteristics of ignition processes for LPSC at the ultralow equivalence ratio conditions of 0.013~0.502 based on different conditions of ignition fuel ratio (F_n). The results indicate that, when F₂=10%, F₃=15% and F₄=20%, LPSC can ignite successfully at the equivalence ratio intervals of 0.063-0.251, 0.042-0.377 and 0.05-0.502 respectively, and the minimum values of equivalence ratio for ignition process are respectively 0.063, 0.039 and 0.011 by the fitting calculations of experimental results, but LPSC fails to ignite at F₁=5%. With decreasing equivalence ratio, the outlet temperature rise has a drop due to the increase of air massflow, which can lead to the rising of CH₄ and CO concentrations and the deceasing of combustion efficiency simultaneously. LPSC can ignite successfully at relatively low equivalence ratio for high F_n, but in which combustion efficiency deceases and pollutant emissions rise because of too much air massflow. Thus, keeping a certain massflow of ignition fuel is beneficial for high-efficiency and rapid startup of LPSC at ultralow equivalence ratio.