Effect of preheating on combustion characteristics of a swirling flameless combustor.

Abstract

Flameless combustion is a state-of-the-art combustion technique that provides uniform temperature distribution while increasing efficiency and reducing emissions. An internally preheated swirling flameless burner (IPSFC) operating in flameless mode has been developed and tested to provide improved combustion characteristics and very low pollutant emissions. The IPSFC burner was operated at a heat input of 7 kW to 15 kW with a preheated combustion temperature. In the study, the effects of combustion air with and without preheating on gaseous fuel combustion characteristics are investigated for the six cases: SFR2, SFR4, SFR42, PSFR2, PSFR4 and PSFR42. The results show that the best configuration for a flameless burner is the SFR42 case, a vortex burner with four tangential air inlets, 12 axial air inlets, and 11 coaxial fuel inlets. The preheated air was found to increase the thermal efficiency of the process by about 10% compared to the process without preheating but at the cost of a small increase in NOx emissions. At an equivalence ratio of 0.8, the lowest NOx and CO emissions were found to be 3 ppm and 24 ppm, respectively. Temperature uniformity varied from 0.03 in SFR42 to 0.04 in SFR2 at different equivalence ratios.