Autoignition Characteristics Of Low Cetane Number Jp-8 And Approaches For Improved Operation In Military Diesel Engines

2011 Ndia Ground Vehicle Systems Engineering And Technology Symposium
Power And Mobility (P&M) Mini-Symposium, August 9-11 Dearborn, Michigan
Autoignition Characteristics Of Low Cetane Number Jp-8 And Approaches For Improved Operation In Military Diesel Engines
Naeim Henein, PhD
Walter Bryzik, Ph.D.
Chandrasekharan Jayakumar
Department of Mechanical Engineering, Wayne State University, Detroit, MI
Eric R. Sattler
Nicholas C. Johnson
Nichole K. Hubble
U.S. Army RDECOM –TARDEC, Warren, MI
ABSTRACT
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.
INTRODUCTION [Excerpt]
The Single Fuel Policy requires military ground vehicles to operate on JP-8 fuel. Ideally, operating vehicles on JP-8 fuel occurs without loss in maximum power and fuel economy, without any increase in black smoke at heavy loads and transient modes, and without white smoke during cold start [1, 2, 3]. JP-8 has a wide range of CNs that can be as low as 25 or higher than 74 for FT SPK type fuel [1, 4, 5]. Low CN JP-8 blends have fairly long ignition delays (ID) that if used in diesel engines without adjustments, can cause power loss, an increase in fuel consumption, unsteady operation or even complete failure of certain engine parts. Such problems are not allowable in the field because they impact survivability and mission readiness. The goal of this paper is to analyze the autoignition characteristics of JP-8 and compare it with other fuels which may be used in military vehicles.
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