Study On The Effects Of Gasoline Properties On Vehicle Particulate Emissions And The Corresponding Predictive Model

The surge of the automobile population has caused the vehicular emissions become a major source of urban atmospheric fine particulate matter(PM_2.5)in China.The vehicular emission control is now a major sector of atmospheric pollution prevention in megacities.As one of the key elements in the control system of“vehicle-fuel-road”,fuel properties significantly affect the vehicular emission characteristics.Therefore,it is necessary to conduct the relevant research in order to formulate policies of gasoline and vehicle emissions suiting to Chinese conditions.This thesis mainly focuses on the impacts of gasoline properties containing olefin content,aromatic content,T50?defined as the50%v distillation temperature?,T90?defined as the 90%v distillation temperature?and ethanol content on tailpipe and evaporative emissions from nine typical gasoline vehicles with nine test fuels designed based on the difference between China and foreign standards.This work summarized as follows:?1?Olefin content,aromatic content,T50,T90 and ethanol content were selected for the study,and nine test fuels were designed using the single factor method.Firstly,impacts of particle number counter instrument,driving cycle,start-up mode,vehicle load and technology on particle emissions from nine typical vehicles were investigated.Secondly,the influence rules of olefin,aromatic,T50,T90 and ethnaol on particle emissions considering the effects of environmental temperature based on both GDI and PFI vehicles were studied.Finally,a prediction model of“gasoline properties-particle emissions”was constructed based on theoretical derivation and experimental studies.?2?Compared with olefins,aromatics had more significant impacts on particulate emissions from both tested gasoline vehicles.It is necessary to decline the threshold value of aromatic content in the next regulation of vehicle gasoline.14%decrement in olefin content had no obvious impacts on particulate emission factors,but could reduce the particulate emissions under some high driving conditions.15%decrement in aromatic content resulted in 67?70%and 29?63%reduction of the PM?particulate mass?and PN?particulate number?emissions,and the impacts mainly occurred under the cold-start moment,extra-high running and dramatically driving conditions.Additionally,BC?Black Carbon?emissions could also be controlled effectively with decreasing the aromatic content.Overall,olefin and aromatic contents in gasoline had some impacts on regulated gaseous emissions,but there were no consistent variation trends.?3?Compared with T50,T90 had more significant impacts on particulate emissions from gasoline vehicles,especially during the cold-start moment.It is recommend to decrease the threshold of T90 in the next regulation of vehicle gasoline.40?C increment of T50 had non-linear impacts on regulated gaseous emissions,and slightly decreased the PN emissions,but the impacts on PM lacked consistentcy variation tendency.20?C increment of T90 significantly resulted in 40.4?239.2%and41.4?233.8%increasement of PM and PN emissions from two gasoline vehicles,but had no significant impacts on regulated gaseous emissions.?4?With the decline of ambient temperature,particulate emissions from gasoline vehicle deteriorated seriously,especially during the cold-start moment.Compared with traditional gasoline,ethanol gasoline could effectively decrease the vehicle particuate emissions,but the advantage of E10in restricting the particulate emissions would become smaller at low ambient temperature.Compared with the PFI?port fuel injection?vehicle,the GDI?gasoline direct injection?vehicle could restrain the generation of particulate matters caused by the ambient temperature decrease.At 30?C,PM,PN and BC emissions from the GDI vehicle were higher than those from the PFI vehicle.However,the particulate emission factors of the PFI vehicle were comparable to or even higher than those of the GDI vhielce at-7?C.?5?The experiment proved that contents of olefin,aromatic and ethanol were closely related to evaporative emissions from gasoline vehicle.However,the emission levels could be controlled with the adjustment of the physicochemical indexes of gasoline,and the OFP?Ozone formation Potential?could also be reduced.The gasoline with higher content of olefin and aromatic would promote the evaporative emissions and the corresponding OFP.Overall,the evaporative emissions with E10 had no significant increase compared with traditional gasoline in this study.?6?A new gasoline index?Particle Index?PI?was designed based on theoretical derivation.The gasoline PI and PN emission factors of two tested vehicles had positive correlations.Coefficient of fitting optimization?R²?between gasoline PI and PN emissions from both GDI and PFI vehicles could be up to 0.90,while values of R² for PM emission factors were very small,especially for the PFI vehicle.Finally,the model was verified with commercial gasoline and the result showed that this model could predict the particulate number emissions very well.However,the model can not predicte particulate emissions accurately with E10,because the“oxygen premixing effect”of ethanol gasoline was not considerred in the model construction.