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On the Premixed Phase Combustion Behavior of JP-8 in a Military Relevant Single Cylinder Diesel Engine
Abstract:
Current U.S. Army ground vehicles predominately use commercial off-the-shelf or modified commercial diesel engines as the prime mover. Unique military engines are typically utilized when commercial products do not meet the mobility requirements of the particular ground vehicle in question. In either case, such engines traditionally have been calibrated using North American diesel fuel (DF-2) and Jet Propellant 8 (JP-8) compatibility wasn't given much consideration since any associated power loss due to the lower volumetric energy density was not an issue for most applications at then targeted climatic conditions. Furthermore, since the genesis of the ‘one fuel forward policy’ of using JP-8 as the single battlefield fuel there has been limited experience to truly assess fuel effects on diesel engine combustion systems until this decade. It is becoming more apparent that current and future commercial combustion system strategies will be adversely affected by use of JP-8 in comparison to commercial diesel fuel due to combustion affecting chemical and physical property differences of ‘out laying’ global JP-8 samples. (Additionally, the use of various fuel sensitive emission controls technologies on current and future commercial heavy-duty diesel engines is also a major challenge for JP-8 due to its high sulfur content.) One important example is ignition quality where the mean cetane index for JP-8 utilized by the U.S. Army during the last five years has been typically in the 43 to 44 range, but the variance has been relatively large depending on the particular supply source with worst case scenarios exhibiting values near 30. Similar variances have been observed with JP-8 distillation and viscosity. Any such potential combustion issues will be further amplified in specialty high output, low compression ratio military engines.
To date, there has been little research performed on assessing combustion characteristic differences between a mean physical and chemical property JP-8 and DF-2. The objective of this submission is to study and document JP-8 combustion characteristics under diesel engine-like thermodynamic conditions in order to provide information that might be useful in generating JP-8 ignition and combustion models.