Visualization of OH Chemiluminescence and Natural Luminosity of Biodiesel and Diesel Spray Combustion

Diesel and biodiesel spray combustion in a high temperature and high pressure environment was investigated in a constant volume combustion chamber. The effects of ambient gas temperature and ambient oxygen concentration on the combustion process were studied. The ambient temperatures varied from 800 K to 1200K, while the ambient oxygen concentrations varied from 21% to 9%. The results indicate that a higher ambient temperature increases natural luminosity level and decreases the lift-off length for both fuels. At the quasi-steady stage, biodiesel shows a shorter lift-off length at low ambient temperature compared to diesel, while the lift-off lengths at higher ambient temperature for both fuels are comparable. The upstream air/fuel entrainment analysis agrees with the experimental results. Results show lower flame natural luminosity of biodiesel fuel than regular diesel. Under low ambient oxygen concentration and low ambient gas temperature, ultra-low natural luminosity was observed for both fuels. Furthermore, the simultaneous measurement of OH chemiluminescence and natural luminosity has been applied to a special case. The preliminary results have shown the validity to identify the reaction regions and can help better interpret the natural luminosity signals. * Corresponding author, [email protected] ILASS Americas, 23 Annual Conference on Liquid Atomization and Spray Systems, Ventura, CA., May 201