A Study on the Combustion and Emission Characteristics of JP-8 Jet Fuel in a CI Engine

Abstract

Many recent studies aim to reduce pollutant emissions and improve efficiencies in CI engines by adopting the state of art combustion strategies to meet the more stringent regulations as years go by. Among the noble combustion strategies, homogeneous charge compression ignition (HCCI) uses well mixed fuel-air mixture to reduce NOx and PM simultaneously. Diesel-gasoline blending fuel was also studied for NOx and PM simultaneous reduction by prolonging ignition delay of diesel fuel. However, those studies have critical defects. Therefore, JP-8 combustion in a CI engine was investigated as one of the methods to forming homogeneous fuel-air mixture. Since JP-8 jet fuel has lower Cetane Number than that of diesel fuel, ignition delay is extended despite higher volatility and low viscosity of the fuel. Although JP-8 has already been used at both military aircrafts and ground vehicles by NATO nations as a part of Single Fuel Concept (SFC) through sufficient studies, further studies are needed to understand combustion process of the fuel. In this study, JP-8 and diesel fuel were combusted in a CI engine with four cylinders and two pilot injection. And the effect of boost pressure, injection pressure, main injection timing, and EGR rates under the same torque condition on combustion and emissions were investigated to determine combustion optimization. Results show that JP-8 has similar combustion characteristics to diesel fuel except for longer ignition delay caused by higher Cetane Number. Therefore, PM emission is considerably decreased without noticeable NOx increase and efficiency losses. Moreover, simultaneous reduction in NOx and PM would be achieved by increasing EGR rate.