Micro-explosion enhanced combustion of Jatropha oil/2, 5-dimethylfuran (DMF) blended fuel droplets

Abstract

The present study investigated the micro-explosive combustion characteristics of Jatropha oil-2, 5-dimethylfuran (DMF) blended fuel droplets using fiber-support and high-speed backlit imaging technique. The flame temperature and soot optical thickness (KL) are measured by two-color pyrometry method. The results show that the combustion of Jatropha oil-DMF blended droplets containing four stages: ignition delay, first micro-explosive combustion, d2 law combustion and second micro-explosive combustion stage. The micro-explosion in second and fourth stage is caused by superheating of DMF and pyrolysis, respectively. The flames of DMF, diesel and Jatropha oil droplets belong to typical diffusion combustion. However, the micro-explosive flame of Jatropha oil-DMF blended droplets belongs to premixed combustion. When the DMF concentration reaches 50%vol, the ignition delay is equivalent to that of diesel. The average burning rate of Jatropha oil-DMF blended droplets increases nonlinearly with air velocity. When the DMF concentration is 75%vol, it reaches the peak, which is 66.4% higher than that of diesel. Furthermore, the effect of micro-explosion on droplet flame deformation is summarized into four modes: slight fluttering flame, local flame separation, large deformation flame, large deformation flame with local flame separation. When there is air flow in the horizontal direction, a “soot shell” forms around the droplets. This is due to the upward buoyancy interacts with the horizontal airflow force to form a rotating airflow force, which concentrates the soot particles around the droplets.