The combustion processes involved in the lean premixed combustor are studied with help of coaxial burner using bluff body flame holder. The lean stability and emission analysis are investigated in details for two flame holder locations, H/Dcore = 0.61 and 5.0. The lean flame stability limits are measured for a wide range core velocity of 4-20 m/s. The lean stability limits for coflow air stream are improved for H/Dcore = 5. 0 due to the improved mixing of coflow with core flow streams. But there is an increase of the NO emission for H/Dcore = 5.0, which may be due to higher combustion gas temperature. On the contrary, the CO emission level is reduced considerably, which may be attributed to the presence of excess coflow air. In order to reduce the emission level, the partially premixed fuel-air mixture is injected in the coflow stream instead of air. The stability limit is improved marginally for H/Dcore = 5.0 when the premixed mixture is used in the coflow stream. Interestingly, this partially premixed fuel injection in the coflow stream although reduces the NO emission level, but produces little more CO emission. It is believed that these findings will be helpful in designing and developing lean premixed flame based combustor in future.
Dr. R. Kannan and Mishra, D., “An Experimental Study of Lean Premixed Combustor”, International Journal of Turbo and Jet Engines, vol. 20, pp. 245-253, 2003.