Effects of six different fuels on low temperature premixed compression ignition (PCI) combustion were experimentally investigated in this paper with a light-duty HSDI engine. The PCI combustion concept reduces NOx and smoke emissions simultaneously by low temperature and premixed combustion, respectively. To achieve low temperature and premixed combustion, the ignition delay is prolonged and the injection duration is shortened.
Six fuels were chosen to examine the influence of cetane number (CN) and other fuel properties on low temperature PCI combustion. The fuel selection also included a pure Gas- to-Liquid (GTL) fuel and a blend of base diesel and 20% soy based biodiesel (B20). Fuel effects were studied over a matrix of seven part load points in the low temperature combustion mode. The seven part load points were specified by engine speed (RPM) and brake mean effective pressure (BMEP). Engine parameters such as pilot and main injection timing, pilot quantity, rail pressure, boost pressure and exhaust gas re-circulation (EGR) rate were kept the same and were not optimized for each fuel. Only the main injection quantity was adjusted to achieve the same BMEP at the respective engine speed for each fuel. Each fuel underwent a detailed thermodynamic analysis.
The main purpose of this paper is to provide the fuels and engine development community more insight into the influence of fuel properties on engine out emissions and performance with low temperature PCI combustion.