Investigation of particle number measurement and combustion and emissions from alternative fuels in diesel engines

The popular usage of diesel engine and diesel fuels in recent decades leads to enormous reliance on fossil derived fuels and environment pollution. Alternative fuels for diesel engine can be a solution. However, considering the production limitation of those alternative fuels, finding an effective and environmental way to apply alternative fuels to diesel engines is an important research topic. The hydrotreated vegetable oil (HVO) and gas to liquid (GTL) fuels can be directly used on diesel engines with any desirable blending ratio to diesel fuel. In addition, the HVO and GTL fuels consist of straight chains and no aromatics compounds, indicating the potential to reduce total hydrocarbon (THC) and particle number (PN) emissions.
The PN emissions from a diesel engine is always critical and the accurate PN measurement is very challenging. Because the PN is very sensitive to sampling conditions and types of PN measurement instruments. This research presents the comparison of PN (Particle Number) measurement results from five PN instruments (two HORIBA SPCSs, one DMS 500, one SMPS, and one AVL 438) with different sampling frequency and various dilution settings. The correlation factors among the tested instruments were obtained and the lower detection limit of the DMS 500 was found to be 2×104 (#/cm3).
In addition to by the PN research, HVO and GTL fuels were blended with diesel fuels at 30%, 50%, 70%, and 100%. Their combustion and emission performances were tested on a IVECO made 3-litre direct injection diesel engine equipped with EGR and intercooler. The engine is EURO 5 compliant. The combustion performance was measured with a pressure transducer installed at the top dead centre (TDC) of one combustion cylinder. The particle number size distribution and gaseous emissions were measured using DMS 500 and HORIBA MEXA 7100. The results showed that HVO, GTL, and their blends can significantly reduce the particle number (PN) and THC emissions, and the reduction increased with the increasing of blend ratio. At the engine outlet, the peak values of accumulation mode particles reduced with the increasing of blending ratio. The PN emissions measured at the downstream of the aftertreatment system was below the DMS lower detection limits. The pure GTL and HVO fuels did show similar NOx emissions with diesel fuel, however, the blended fuels all showed NOx reduction from 20% to 35%. The combustion performances of all fuels were similar in general, especially when the engine power reached 27 KW. The ignition delay became shorter with the increasing of blending ratio.