Effects of n-Butanol Addition on the Combustion Characteristics of n-Heptane Counterflow Diffusion Flame at Elevated Pressure

Abstract

This study focused on the effects of n-butanol addition on the combustion characteristics of n-heptane counterflow diffusion flame under pressures of 1, 3, and 5 atm by a detailed kinetic simulation. The added n-butanol volume fraction ranged from 0 to 50%. The mass averaged velocity of fuel streams was selected to ensure momentum flux balance and was approximately constant for the investigated flames. Flame structures and mole fraction profiles impacted by n-butanol addition for major species, free radicals, and intermediate species were analyzed by concentrating on the formations of soot precursors and oxygenated air pollutants. The results showed that with the addition of n-butanol, the flame temperature decreased and the formation of the main soot precursors such as C2H2 and C6H6 was inhibited. This can be attributed to the reduced rate of production of these species. The flame temperature increased significantly, and the profile moved towards the fuel side with the increasing pressure. Moreover, the production of C2H2 and C6H6 was observably promoted as the pressure increased. The concentrations of free radical H, O, and OH decreased significantly as the pressure increased but slightly decreased with the increasing n-butanol addition, which might have been caused by the chemical effect of n-butanol.