The objective of this work is to analyze the fuel spray injection characteristics and macroscopic behaviors of the dimethyl ether (DME) blended methyl ester derived from soybean oil at different blending ratios. The injection characteristics of the blended fuels such as injection delay, injection rate, and effective velocity in the nozzle flow passage were investigated under the various DME and its blended fuels. In comparison with the injection delay of blended fuels, the lower blending ratio of DME blended fuel with biodiesel showed a shorter injection delay than the higher blending ratio of the blended fuel. At the same energizing period and injection pressure, the DME fuel with a higher blending ratio showed a longer injection duration than that of the lower blending ratio. The higher DME blended with biodiesel also showed a low peak value of injection rate compared to the lower DME blended fuel at the same injection time. As the blending ratio of DME fuel was increased, the effective initial velocity of neat biodiesel and lower DME blended with biodiesel increased compared to the higher DME blended fuel. In comparison of spray penetration of blended fuel, biodiesel and blended fuel have a similar spray length at the same condition except the neat DME fuel. (C) 2009 Elsevier Ltd. All rights reserved.