An experimental study was carried out to investigate the combustion and emission of JP-8 and diesel fuel in an optically-accessible single-cylinder heavy duty diesel engine equipped with a high pressure common-rail injection system in order to evaluate the feasibility of JP-8 application in diesel engine. The basic spray characteristics, including spray tip penetration and spray angle, were investigated with macroscopic spray images obtained by the Mie-scattering method. The combustion and emission characteristics were analyzed on the basis of the results obtained from the spray experiments. Visualization by direct imaging was used to characterize the combustion process. It was found that JP-8 had a shorter spray tip penetration and wider spray angle than diesel fuel mainly due to the faster vaporization characteristic of JP-8. The peak heat release rate was higher and the pre-mixed burn portion was larger with JP-8 due to its superior mixing rate through faster vaporization characteristics. Furthermore, ignition delay with JP-8 was longer than that with diesel fuel due to the lower cetane number of JP-8. In terms of emission, JP-8 showed a benefit in smoke reduction while it produced larger amounts of HC and NO(x). Longer ignition delay and accelerated oxidation in the late stage of JP-8 combustion were verified by direct imaging. (C) 2011 Elsevier Ltd. All rights reserved.