Experimental Study of Ignition Delay of Homogeneous Supercritical Fuel Sprays of Dieseline Blend in Constant Volume Combustion Chamber

Abstract

In present experimental work, supercritical (SC) fuel spray combustion technology is studied under diesel engine-like operating conditions inside a constant volume combustion chamber. Ignition delay (ID) of SC sprays is measured, analyzed, and compared with conventional diesel sprays under similar operating conditions. It is found that ID of SC sprays is significantly smaller than liquid diesel sprays at all operating conditions. At typical normal diesel engine operating conditions of 300 bar injection pressure (IP) and 40 bar cylinder air pressure (CP), substantial percentage reduction in ID of SC sprays occurs, which is above 55%. It is further found that SC spray combustion mainly occurs as homogeneous hot air combustion rather than hot surface combustion/ignition. Significant reduction in ID of SC spray as compared to diesel spray would cause a drastic reduction in NOx and homogeneous single-phase combustion of SC spray would consequently result in a substantial reduction in particulate matter (PM) formation. The best combination of experimental conditions in the present study at which maximum percentage reduction in ID occurs (nearly 85.83%) is found to be HST = 673 K, CP = 20 bar, IP = 300 bar. SC spray combustion is a single-phase homogeneous, faster, and cleaner combustion technology for next-generation diesel engines.