The alternative fuel jet propellant 8 (JP-8, NATO F-34) can be used as an auto-ignition source instead of diesel. Because it has a higher volatility than diesel, it provides a better air-fuel premixing condition than a conventional diesel engine, which can be attributed to a reduction in particulate matter (PM). In homogeneous charged compression ignition (HCCI) or dual-fuel premixed charge compression ignition (PCCI) combustion or reactivity controlled compression ignition (RCCI), nitrogen oxides (NOx) can also be reduced by supplying external exhaust gas recirculation (EGR). In this research, the diesel and JP-8 injection strategies under conventional condition and dual-fuel PCCI combustion with and without external EGR was conducted.
Two tests of dual-fuel (JP-8 and propane) PCCI were conducted at a low engine speed and load (1,500 rpm/IMEP 0.55 MPa). The first test was performed by advancing the main injection timing from BTDC 5 to 35 CA to obtain the emissions characteristics. A fuel ratio of JP-8 to propane of approximately 30:70 was established based on the low heating value of each fuel without the addition of external EGR. The second test investigated the optimal point for low emissions and indicated mean effective pressure (IMEP) with a small amount of external EGR and a post-injection strategy.
NOx emissions showed a ‘bump’ curve with an advancement of the main injection timing. The PM emissions were maintained below 0.63 mg/m3, which reveals almost zero PM emissions. The optimized test results showed appropriate NOx and PM emissions.