Sooting behaviors of n-butanol and n-dodecane blends

This work focuses on understanding the formation and oxidation of soot when adding nbutanol, as an oxygenated fuel, to n-dodecane. A two-stage burner is used to characterize the oxidation of soot from different n-butanol blends, 10%, 30%, and 60 mole%. The two-stage burner isolates the soot oxidation process from the formation process. Soot is formed in a first-stage premixed burner under fuel-rich conditions, while in a second stage, the soot is oxidized under slightly-rich conditions. A scanning mobility particle sizer (SMPS) was used to measure the soot particle size distributions in the flame at different height during oxidation. Results showed a decrease in particle concentration (g/cm³) as the fraction of n-butanol increased which indicates the capability of n-butanol to reduce soot particle mass and number formed in the surrogate fuel. On the other hand, the results demonstrated that when increasing n-butanol, the difference between initial mass of soot particles entering and final mass of soot particles leaving the second burner reduced. This result implies that increasing n-butanol decreases the rate of soot oxidation. Two different fuel quality indicators are used to quantify our observations. The first one, sooting tendency, is calculated to show how the amount of soot formed in the flame is affected by using different n-butanol percentages. The second one, a new fuel quality indicator, called sooting stability is proposed for quantifying the stability of soot particles against oxidation. The results demonstrated that by increasing n-butanol percentage, soot formation was suppressed. However, sooting stability increased with higher concentrations of n-butanol.