Particulate emission characteristics of a light duty diesel engine under transient operation conditions

This research work focused on evaluations of improving the acceleration, cold start transient performances and emissions in a common rail direct injection (CRDI) turbocharged diesel engine. The temperature impacts on the engine emissions were investigated at ambient temperatures ranging between -7 and 20°C. The results show that the highest specific gaseous and particulate emissions are produced at the earlier stage of the NEDC. The particulates emitted at extremely high AFR conditions are more dominant compared to those that are caused by the turbo-lag problem over the NEDC. Both the fuel and engine oil contribute as main carbon sources to produce the SVOC particulate emissions from the engine combustion. A controlled intake air thermal heating system was implemented to improve the engine performances at cold ambient conditions. By using the thermal heating system, the engine efficiency during the first UDC can be improved by up to 1.46. By using high blending biodiesel fuels, the transient emission spikes can be significantly eliminated. The cumulative PN and THC emissions of biodiesel can be reduced by up to 75% and 50% respectively. An incremental transient EGR strategy was evaluated to improve the instantaneous particulate emission performance during acceleration conditions. With the improvement of the turbocharger performance and boosted intake fresh air mass flow, the novel strategy resulted in a reduced fuel injection quantity and improved combustion

Chemical Vapor Deposition of High-Quality Large-Sized MoS2 Crystals on Silicon Dioxide Substrates

Large???sized MoS2 crystals can be grown on SiO2/Si substrates via a two???stage chemical vapor deposition method. The maximum size of MoS2 crystals can be up to about 305 ??m. The growth method can be used to grow other transition metal dichalcogenide crystals and lateral heterojunctions. The electron mobility of the MoS2 crystals can reach ???30 cm2 V???1 s???1, which is comparable to those of exfoliated flakes.ope