The fuel injection rate profile and spray characteristics of both the highly dispersed spray nozzle and the conventional nozzle have been studied through experiments. The experimental results indicate that the highly-dispersed nozzle has a higher fuel injection rate, shorter injection duration, shorter spray tip penetration, fatter spray cone angle, smaller spray projected area and larger spray volume than the conventional nozzle. According to the original experimental results and the fluid collision and breakup theories, the SMD of the highly-dispersed nozzle is smaller than that of the conventional nozzle. Additionally, the combustion and emission characteristics of a heavy-duty diesel engine when equipped with the highly-dispersed nozzle and the conventional nozzle respectively have been studied through experiments. The experimental results indicate the tested engine equipped with highly-dispersed nozzles has a lower emission level and better BSFC performance than that equipped with conventional nozzles. All these validate that compared with the conventional nozzle, the highly-dispersed nozzle can shorten the fuel injection duration to save time for the fuel-air mixing, promote the fuel-air mixing and improve the fuel atomization, which are beneficial to the formation of homogeneous mixture. (C) 2012 Elsevier Ltd. All rights reserved.