Combustion and emission characteristics of a heavy duty engine fueled with two ternary blends of n-heptane/iso-octane and toluene or benzaldehyde

In this work, the influences of aromatics on combustion and emission characteristics from a heavy-duty diesel engine under various loads and exhaust gas recirculation (EGR) conditions are investigated. Tests were performed on a modified single-cylinder, constant-speed and direct-injection diesel engine. An engine exhaust particle sizer (EEPS) was used in the experiments to measure the size distribution of engine-exhaust particle emissions in the range from 5.6 to 560 nm. Two ternary blends of n-heptane, iso-octane with either toluene or benzaldehyde denoted as TRF and CRF, were tested, diesel was also tested as a reference. Test results showed that TRF has the longest ignition delay, thus providing the largest premixed fraction which is beneficial to reduce soot. However, as the load increases, higher incylinder pressure and temperature make all test fuels burn easily, leading to shorter ignition delays and more diffusion combustion. For each test fuel, the particulate number concentration in nucleation mode decreased with the increase of EGR rate, while more particles in accumulation mode were generated. Moreover, compared with TRF and CRF, diesel produces the most mass and number concentrations of particulate matter.