Autoignition Characteristics of Low Cetane Number JP-8 and Approaches for Improved Operation in Military Diesel Engines

摘要

Problems resulting from the use of low-Cetane Number (CN) JP-8 in military diesel engines are mainly caused by the poor autoignition quality of the fuel that requires a long period between the start of injection and the start of combustion. A detailed analysis of the processes which occur during the ignition delay period clearly shows that the start of combustion is preceded by a long period where the Low Temperature (LT) combustion chemistry (cool flame) prevails in which the rates of burning are very limited. Under certain operating conditions, the LT combustion regime is associated with the Negative Temperature Coefficient (NTC) regime, which adds to the length of the ignition delay period. The details of these regimes are examined by using computer simulation codes. In addition, the autoignition characteristics of JP-8 with a wide range of cetane numbers are investigated and compared with ULSD (Ultra Low Sulfur Diesel) and a Fischer-Tropsch Synthetic Paraffinic Kerosene (FT SPK) type fuel. The experimental investigations are carried out on a single-cylinder research diesel engine as well as on a heavy-duty diesel engine. The paper presents approaches for improved operation of military diesel engines on JP-8 with a wide range of cetane numbers.