High concentrations of tropospheric ozone remain a concern, and strategies to reduce the precursors of ozone, volatile organic compounds (VOCs) and nitrogen oxides, have been established in many countries. In this study, chassis dynamometer experiments were conducted for 25 late model gasoline passenger vehicles in the Japanese market to evaluate VOC emission trends. Tailpipe emissions were collected and analyzed using gas chromatography mass spectrometer and flame ionization detector, and liquid chromatography–mass spectrometry (LC-MS). Results showed that tailpipe VOC emissions increased linearly with vehicle mileage due to deterioration of the three-way catalysis converter used to purify the toxic components in vehicle emissions. Distance normalized total VOC emissions showed that port injection mini-sized vehicles were effective in decreasing tailpipe VOC emissions because of their low vehicle weight. The VOC composition of tailpipe emissions was dependent on the fuel type (regular or premium gasoline). VOC emissions from hybrid vehicles were similar to those of other vehicles because cooling of the three-way catalysis converter during battery operations sometimes tended to reduce catalyst effectiveness during engine operations. However, it can also be assumed that each manufacturer is aware of this phenomenon and is taking action. Further monitoring of hybrid vehicles is warranted to ensure that these vehicles remain an effective means of mitigating air pollution.
Abstract. A portable emission measurement system (PEMS) was used to
measure the real-world driving emissions pertaining to a Japanese
middle-sized heavy-duty vehicle. The testing was performed with the vehicle
being driven in the metropolitan area of Tokyo in four seasons (January,
June, August, and November) to analyze the seasonal dependence of NOx
and CO2 emissions. The experimental results indicated that the amount
of NOx emissions was particularly high in the cold season owing to the
slow starting of the NOx after-treatment systems, which is to say the exhaust
gas recirculation and urea-selective-catalytic-reduction systems, under low-ambient-temperature conditions. In real-world driving, a high
acceleration pattern was observed in the low-speed region which is not
considered in the world harmonized vehicle cycle, which is the worldwide
official driving mode in the chassis dynamometer experiment. Finally, the
transient emission tables for NOx and CO2 were constructed based
on the PEMS measurement results and the classical mechanic theory. The
constructed tables replicated well the experimental results in all the
considered conditions involving different ambient temperatures and
locations. The proposed approach can be used to evaluate emission
inventories in the future.
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