Fundamental Spray Combustion Characteristics of Rapeseed Biodiesel, Diesel and Blend

The spray combustion characteristics of rapeseed methyl esters (RME) and 50% RME/diesel blend were investigated and compared with conventional diesel fuel using a swirl flame burner. The main swirling air flow was preheated to elevated temperature of 350°C prior to coaxially enveloping an airblast-atomized liquid fuel spray at atmospheric pressure. The reacting spray droplets were characterised using a phase Doppler anemometry (PDA). Flame imaging was employed to investigate the flame reaction and post-reaction zones. Droplets located around the centreline region of the flame were relatively small, while larger droplets were found at the spray boundary with lesser direct influence from the flame reaction zone. RME exhibits spray characteristics similar to diesel but with significantly higher droplet concentration and volume flux, indicating a longer droplet evaporation timescale. RME presented a different flame reaction zone with an extended core reaction due to delayed droplet vaporisation, and a post-reaction with no soot formation, unlike the case of diesel and 50% RME/diesel blend