Application of JP-8 in a heavy duty diesel engine Jinwoo Lee, Choongsik Bae ⇑ Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon, Republic of Korea article info Article history: Received 8 June 2010 Received in revised form 8 December 2010 Accepted 20 January 2011 Available online 4 February 2011 Keywords: JP-8 Diesel fuel Macroscopic fuel spray Direct imaging abstract 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 com- mon-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 macro- scopic spray images obtained by the Mie-scattering method. The combustion and emission characteris- tics 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 char- acteristics. 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. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The idea of using a single military fuel was conceived after the Second World War in order to simplify the logistic supply chain for petroleum products in the NATO nations [1,2]. This idea has been called the Single Fuel Concept (SFC). JP-8, which had been used as an aviation fuel, was selected for the SFC. This movement re- sulted in many studies on the effect of JP-8 when diesel fuel was fully substituted by JP-8 in diesel engines [3–6]. Most engines equipped with the conventional fuel injection system, such as a mechanical rotary pump or unit injector, operated successfully with JP-8 [4,5], while penalties in torque and fuel economy due to the lower density of JP-8 were reported [7]. With regard to ex- haust emissions, using JP-8 was reported to have the potential to reduce smoke emission compared to diesel fuel [7]. From previous researches, it can be confirmed that JP-8, as a full substitution for diesel fuel, showed no critical limitation. Nevertheless, it is obvious that differences in engine performance, combustion phasing, and emissions exist. Therefore, it is crucial to determine the causes of these differences because they may be fatal in wartime. However, most studies performed until now have focused on emission measurements, which give little information about physical reasons for the observed differences. Differences in the fuel properties of JP-8 and diesel fuel can lead to different spray development, fuel mixing and combustion char- acteristics. The fuel–air mixing process affects the combustion and exhaust emission in a direct injection diesel engine. Therefore, comparative investigation concerning spray and combustion char- acteristics for both fuels is indispensable for the better understand- ing of JP-8 application in a diesel engine. In this study, the spray characteristics of JP-8 and diesel fuel are compared by using macroscopic spray visualization in terms of spray tip penetration and spray angle. Combustion analysis and emission measurement enabled investigation on the different behaviors of JP-8 and diesel fuel, in additions to the spray experi- ment. Visualization by direct imaging was also used to characterize pollutant formations. 2. Experimental setup 2.1. Macroscopic spray visualization A schematic diagram of the optical diagnostic system for non- evaporating macroscopic spray visualization is shown in Fig. 1. The spray images were taken by direct photography using Mie-scattering. Optical access to the pressure chamber was avail- able through three window glasses of 80 mm in diameter. The chamber was pressurized with nitrogen at room temperature. For 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.01.032 ⇑ Corresponding author. Address: Dept. Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong-Dong, Yuseong-Gu, Daejeon, Daejeon 305-701, Republic of Korea. Tel.: +82 42 350 3044; fax: +82 42 350 5023. E-mail addresses: csbae@kaist.ac.kr, csbae@kaist.edu (C. Bae). Fuel 90 (2011) 1762–1770 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel