Soot measurements for diesel and biodiesel spray combustion under high temperature highly diluted ambient conditions

• Published in: Fuel (Guildford) Vol. 135; pp. 340 - 351
• Main Authors: Zhang, Ji, Jing, Wei, Roberts, William L., Fang, Tiegang
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2014; Elsevier
• Subjects: Applied sciences; Biodiesel; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fuels; High temperature highly diluted combustion; Soot; Spray combustion; Two-color thermometry; High temperature highly diluted combustion; Spray combustion; Two-color thermometry; Biodiesel; Soot; Measurement; combustion; Diesel fuel; High temperature highly diluted; Color; Biofuel; High temperature
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2014.06.071

•Simultaneous transient quantitative measurement of soot temperature and concentration.•Spray combustion under LTC, conventional, and high temperature highly diluted combustion modes.•Soot temperature is lower for biodiesel than diesel for the three regimes.•Soot concentration shows complicated variation trend for different regimes. This paper presents the soot temperature and KL factor for biodiesel, namely fatty acid methyl ester (FAME) and diesel fuel combustion in a constant volume chamber using a two-color technique. The KL factor is a parameter for soot concentration, where K is an absorption coefficient and proportional to the number density of soot particles, L is the geometric thickness of the flame along the optical detection axis, and KL factor is proportional to soot volume fraction. The main objective is to explore a combustion regime called high-temperature and highly-diluted combustion (HTHDC) and compare it with the conventional and low-temperature combustion (LTC) modes. The three different combustion regimes are implemented under different ambient temperatures (800K, 1000K, and 1400K) and ambient oxygen concentrations (10%, 15%, and 21%). Results are presented in terms of soot temperature and KL factor images, time-resolved pixel-averaged soot temperature, KL factor, and spatially integrated KL factor over the soot area. The time-averaged results for these three regimes are compared for both diesel and biodiesel fuels. Results show complex combined effects of the ambient temperature and oxygen concentration, and that two-color temperature for the HTHDC mode at the 10% oxygen level can actually be lower than the conventional mode. Increasing ambient oxygen and temperature increases soot temperature. Diesel fuel results in higher soot temperature than biodiesel for all three regimes. Results also show that diesel and biodiesel fuels have very different burning and sooting behavior under the three different combustion regimes. For diesel fuel, the HTHDC regime offers better results in terms of lower soot than the conventional and LTC regimes, and the 10% O2, 1400K ambient condition shows the lowest soot concentration while maintaining a moderate two-color temperature. For biodiesel, the 15% O2, 800K ambient condition shows some advantages in terms of reducing soot concentration. Based on these results, the practical implementation of this combustion mode is outlined and a feasible option is proposed.