An experimental investigation is conducted to evaluate the performance, combustion, and emission characteristics of a diesel engine using cerium oxide (CeO2) nanoparticles as diesel fuel additives. Using cetyl trimethyl ammonium bromide (CTAB) as the cationic surfactant and with ultrasonic vibration, CeO2 nanoparticles at dosing levels of 50 and 100 mg/L can be stably and uniformly dispersed in diesel. Physically, the mixing of fuel blends with air is enhanced by microexplosion events because of the large surface-volume ratio and intensified thermal transmissibility of nanoparticles. Moreover, chemically, CeO2 in diesel fuel plays a positive role in the dehydrogenation reaction at a high temperature because of its excellent redox ability. As a result, the addition of nano-CeO2 to neat diesel (50 and 100 mg/L) leads to a gradual increase in the cylinder pressure compared with the reference neat diesel. Meanwhile, the ignition of fuel blends with a high dosing level of nano-CeO2 occurs earlier by ...

Electric field has the potential to influence the combustion characteristics of hydrocarbon fuel. In this paper, the atomization and combustion characteristics of the droplets of biodiesel and biodiesel–ethanol blend in a uniform direct-current electric field were investigated using photography. It was revealed that a certain electric field strength could induce droplet deformations and cone jets. For the droplet blended with 10 vol. % ethanol, the sizes of the secondary droplets from bubble breakups decreased with the increase in electric field strength, possibly due to the Coulomb repulsion in the ligament. The high breakup intensity of the droplet blended with 30 vol. % and 50 vol. % ethanol covered up the effect of electric field on the sizes of secondary droplets from bubble breakups. During the entire range of electric field strength, cone jets generated smaller secondary droplets in comparison with bubble breakups. Moreover, the electric field distorted the flame morphology, especially the flame width increased at the electric field strength of 50 kV/m. The maximum droplet temperature decreased with the electric field strength, in addition to the biodiesel droplet. Overall, the electric field ameliorates fuel droplets' atomization and combustion characteristics.

The effects of two pilot injections on combustion and emissions were evaluated in a single−cylinder turbocharged diesel engine, which operated in premixed charge compression ignition (PCCI) modes with multiple injections and heavy exhaust gas recirculation under the low load by experiments and simulation. It was revealed that with the delay of the start of the first pilot injection (SOI−P1) or the advance of the start of second pilot injection (SOI−P2), respectively, the pressure, heat release rate (HRR), and temperature peak were all increased. Analysis of the combustion process indicates that, during the two pilot injection periods, the ignition timing was mainly determined by the SOI−P2 while the first released heat peak was influenced by SOI−P1. With the delay of SOI−P1 or the advance of SOI−P2, nitrogen oxide (NOx) generation increased significantly while soot generation varied a little. In addition, increasing Q1 and decreasing the second pilot injection quantity (Q2) can manipulate the NOx and soot at a low level. The advance in SOI−P2 of 5 °CA couple with increasing Q1 and reducing Q2 was proposed, which can mitigate the compromise between emissions and thermal efficiency under the low load in the present PCCI mode.