Strategies to Gain the Loss in Power in a Military Diesel Engine Using JP-8 Instead of ULSD

The Department of Defense (DOD) has adopted the use of JP-8 under the “single battlefield fuel” policy. Fuel properties of JP-8 which are different from ULSD include cetane number, density, heating value and compressibility (Bulk modulus). While JP8 has advantages compared to ULSD, related to storage, combustion and lower soot emissions, its use cause a drop in the peak power in some military diesel engines. The engines that has loss in power use the Hydraulically actuated Electronic Unit Injection (HEUI) fuel system. The paper explains in details the operation of HEUI including fuel delivery into the injector and its compression to the high injection pressure before its delivery in the combustion chamber. The effect of fuel compressibility on the volume of the fuel that is injected into the combustion chamber is explained in details. A fuel such as JP-8 which has a lower Bulk modulus is compressed to a smaller volume than ULSD which has a higher Bulk modulus before its delivery in the combustion chamber, and this is the main reason for the drop in power explained earlier. Experiments conducted on a CAT C7 engine demonstrated the loss in peak power associated with JP-8 over the whole speed range. Different approaches in the injection process have been discussed to gain the loss in peak power.