Abstract
AbstractAutomobile emissions are significantly dependent on the after‐treatment system performance, which is partly determined by exhaust temperature. Regarding diesel passenger cars, after‐treatment systems generally include diesel oxidation catalyst (DOC), diesel particulate filter (DPF), and selective catalytic reduction (SCR). The layouts affect their temperature variations because of the heat loss and thermal capacity of tailpipes and after‐treatment systems. As for the original layout of DOC+DPF+SCR, nitrogen oxides (NOx) emissions are the main concerns of diesel vehicle emissions, especially under cold‐start conditions. Ammonia Creation and Conversion Technology (ACCT) system shows excellent performance of reducing cold‐start NOx emissions; additionally, the damage costs of individual exhaust emissions are different greatly, which may change the priority of emission reductions when considering monetary penalty. In this article, the impacts of the after‐treatment system layouts on the exhaust emission reductions were investigated based on a diesel passenger car; additionally, SCR and ACCT systems as the De‐NOx devices were adopted individually in corresponding scenarios; the after‐treatment system layouts were assessed from the viewpoints of both emission factors and monetary penalty. The results indicated that the ACCT system presented much better NOx reduction effectiveness than SCR system over different layouts. NOx reduction efficiency was very sensitive to vehicle operation conditions over the upstream layouts of NOx reduction devices. The layout‐1 of DOC+ACCT+DPF showed the lowest global emission factors from the diesel passenger car. DPF was much easier to achieve regeneration under the original layout conditions due to its shortest distance to the engine. The layout‐2 of ACCT+DOC+DPF had the minimum monetary penalty factor of exhaust emissions from this diesel passenger car.
Highlights
With the increase of the amounts of automobiles, the problems caused by exhaust emissions are becoming more and more prominent.1-3 As indicated by the report,[4] carbon dioxide (CO2) emission from transportations account for 29% of the total CO2 emission, being the largest proportion, followed by electricity, industry
In order to investigate the impacts of after-treatment system layouts on exhaust emissions and corresponding monetary penalty factors, a diesel passenger car was simulated over Worldwide harmonized Light vehicles Test Cycles (WLTC); the effect of De-Nitrogen oxides (NOx) systems (SCR and ACCT systems) on the exhaust emissions and monetary penalty factors were discussed
For selective catalytic reduction (SCR) and ACCT scenarios, NOx emission distributions presented similar patterns over various layouts; ACCT scenarios showed a lower proportion over high emission rate regions
Summary
With the increase of the amounts of automobiles, the problems caused by exhaust emissions are becoming more and more prominent.1-3 As indicated by the report,[4] carbon dioxide (CO2) emission from transportations account for 29% of the total CO2 emission, being the largest proportion, followed by electricity, industry. Nitrogen oxides (NOx), particulate matter (PM2.5), and volatile organic compounds (VOCs) from automobiles contribute to large proportions of total hazardous emissions, being approximately 35%, 5%, and 20%, respectively, indicated by Minnesota Pollution Control Agency.[5] Emission regulations aiming to drop automobile emissions are becoming more and more stringent[6]; real driving emissions (RDE) test procedure is introduced.[7] Compared with standard driving cycles such as Worldwide harmonized Light vehicles Test Cycles (WLTC),[8] the real driving conditions are more complicated and variable, which leads to higher emission factors over real driving than WLTC.[9,10]. It was demonstrated that Euro 6b diesel cars emitted emit 5-16 times of NOx in the real world than certification tests[11]; meantime, CO2 emission was 1.4-1.8 times of the certificated values. CO2 emission of a Euro 6 gasoline passenger car was approximately 194 g/km under real-
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