Performance, Durability, and Stability of a Power Generator Fueled with ULSD, S-8, JP-8, and Biodiesel 2010-01-0636

The feasibility of using ultra low sulfur diesel (ULSD), synthetic paraffinic kerosene (S-8), military grade jet fuel (JP-8) and commercial B20 blend (20% v biodiesel in ULSD) in a power generator equipped with a compression ignition (CI) engine was investigated according to the MIL-STD-705C military specifications for engine-driven generator sets. Several properties of these fuels such as cetane number, lubricity, viscosity, cold flow properties, heat of combustion, distillation temperatures, and flash point, were evaluated. All fuels were tested for 240 hours at a stationary load of 30 kW (60% of full load) with no alteration to the engine calibrations. The brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), frequency, and power of the generator using S-8, JP-8 and B20 were compared with the baseline fuel ULSD. At a stationary load of 30 kW, S-8 produced the lowest BSFC of 0.267 ± 0.019 kg/kW-hr and the highest BTE of 0.309 ± 0.005 compared to 0.308 ± 0.001 BSFC and 0.287 ± 0.002 BTE for ULSD. The BTE of B20 was comparable to that of ULSD. Both ULSD and B20 showed the highest stability in the generator in terms of frequency and power. Out of the two aviation fuels tested, S-8 had the most unstable generator frequency and power due to its lower viscosity, while JP-8 had acceptable stability. These instabilities increased with increasing engine load. B20 tends to form a density gradient (phase separation) at low temperatures in which unsaturated FAMEs such as C16:0 and C18:0 crystallized and deposited at the bottom of the fuel tank. This crystallization process was completely reversible at elevated temperatures during the testing period, and conditions did not show any adverse effects on engine performance, such as fuel filter plugging. Analysis of lubricating oil after 240 hours of each fuel usage did not show any indication of wear in engine parts.