Spray characteristics of fatty acid methyl ester(FAME)/diesel under common-rail injection condition were investigated,using the high speed photography and particle/droplet image analyses(PDIA),including penetration,spray angle and Sauter mean diameter(SMD). Experimental results show that both fuel sprays present the two-stage mode. The empirical correlation on injection pressure,ambient pressure and density was formulated for the spray tip penetration. Spray angle is increased with the increase of ambient p...