Investigation of swirl premixed dimethyl ether/methane flame stability and combustion characteristics in an industrial gas turbine combustor

Abstract

In this paper, a new scheme for DME/methane (CH4) blended fuel combustion in an industrial gas turbine is proposed and numerical calculations are conducted to reveal the swirl premixed flame stability and combustion characteristics. The results show that injecting recirculated flue gas into the inlet gas restrains the flashback induced by high DME blending ratios and achieves the fully substitution of CH4 by DME. The DME/CH4 flame stability boundary is strongly correlaterd with the laminar flame speed and the adiabatic flame temperature. Therefore, it is recommended to set up the operating conditions of DME/CH4 industrial gas turbines by maintaining a fixed value of the laminar flame speed or adiabatic flame temperature to guarantee burner safety. Additionally, the combustion characteristics of DME/CH4 flames were evaluated under different operating conditions. The results indicate that the two uniformity factors PF and γT are largely independent of the DME blending ratio. As the equivalence ratio increases, PF shows a slight overall rise but remains below 1 %. NO and CO emissions are both directly proportional to the DME blending ratio and the equivalence ratio. Notably, as the flame transitions from a stable state to combustion-induced vortex breakdown flashback, the growth rates of NO and CO emissions rise sharply. In this case, NO emissions increase by 136 %, while CO emissions rise by 126 %.