Testing and evaluation of cold-start emissions in a real driving emissions test

Du, Baocheng; Zhang, Li; Geng, Yangtao; Zhang, Yun; Xu, Hualong; Xiang, Gan

doi:10.1016/j.trd.2020.102447

Cited by 39 publications

(10 citation statements)

References 20 publications

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“…The SPN 23 emissions at 23 • C were low (10 9 -10 10 #/km, reaching 10 11 for the cold start US06), and are comparable with those in the literature [6,22,25,30,56]. What was rather surprising was that the vehicle was emitting a very high amount of sub-23 nm particles, exceeding the current limit for GDIs and reaching up to 10 13 #/km, even though a high filtration efficiency GPF was used.…”

Section: Discussionsupporting

confidence: 86%

Challenging Conditions for Gasoline Particulate Filters (GPFs)

et al. 2022

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The emission limit of non-volatile particles (i.e., particles that do not evaporate at 350 °C) with size >23 nm, in combination with the real driving emissions (RDE) regulation in 2017, resulted in the introduction of gasoline particulate filters (GPFs) in all light-duty vehicles with gasoline direct injection engines in Europe. Even though there are studies that have examined the particulate emissions at or beyond the current RDE boundary conditions, there is a lack of studies combining most or all worst cases (i.e., conditions that increase the emissions). In this study, we challenged a fresh (i.e., no accumulation of soot or ash) “advanced” prototype GPF at different temperatures (down to −9 °C), aggressive drive cycles and hard accelerations (beyond the RDE limits), high payload (up to 90%), use of all auxiliaries (air conditioning, heating of the seats and the rear window), and cold starts independently or simultaneously. Under hot engine conditions, the increase of the particulate emissions due to higher payload and lower ambient temperature was 30–90%. The cold start at low ambient temperature, however, had an effect on the emissions of up to a factor of 20 for particles >23 nm or 300 when considering particles <23 nm. We proposed that the reason for these high emissions was the incomplete combustion and the low efficiency of the three-way oxidation catalyst. This resulted in a high concentration of species that were in the gaseous phase at the high temperature of the close-coupled GPF and thus could not be filtered by the GPF. As the exhaust gas cooled down, these precursor species formed particles that could not be evaporated at 350 °C (the temperature of the particle number system). These results highlight the importance of the proper calibration of the engine out emissions at all conditions, even when a GPF is installed.

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Section: Discussionsupporting

confidence: 86%

Challenging Conditions for Gasoline Particulate Filters (GPFs)

et al. 2022

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“…For NO x , the contribution was lower in most RDE short tests. Other studies have also found a high contribution from cold start for CO (>70%), but this is smaller for NO x (40-60%) for turbo-charged GDI vehicles [53][54][55]; however, lower percentages have also been reported for RDE trips [32,56]. The cold start contribution was around 50% for NH 3 .…”

Section: Cold Startmentioning

confidence: 88%

“…When the rear part of the catalyst is not yet reduced, it oxidizes NH 3 back to NO x [78]. Another study showed that the instantaneous peaks of v × a had a clear one-to-one correspondence with the peaks of instantaneous NO x emissions [53]. For the same route, higher v × a results in higher emissions [23,79] but, when different routes are compared, this is not necessarily true [41] because v × a does not take into account slope or additional weight.…”

Section: Dynamic Drivingmentioning

confidence: 99%

Effect of Extreme Temperatures and Driving Conditions on Gaseous Pollutants of a Euro 6d-Temp Gasoline Vehicle

et al. 2021

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Gaseous emissions of modern Euro 6d vehicles, when tested within real driving emissions (RDE) boundaries, are, in most cases, at low levels. There are concerns, though, about their emission performance when tested at or above the boundaries of ambient and driving conditions requirements of RDE regulations. In this study, a Euro 6d-Temp gasoline direct injection (GDI) vehicle with three-way catalyst and gasoline particulate filter was tested on the road and in a laboratory at temperatures ranging between −30 °C and 50 °C, with cycles simulating urban congested traffic, uphill driving while towing a trailer at 85% of the vehicle’s maximum payload, and dynamic driving. The vehicle respected the Euro 6 emission limits, even though they were not applicable to the specific cycles, which were outside of the RDE environmental and trip boundary conditions. Most of the emissions were produced during cold starts and at low ambient temperatures. Heavy traffic, dynamic driving, and high payload were found to increase emissions depending on the pollutant. Even though this car was one of the lowest emitting cars found in the literature, the proposed future Euro 7 limits will require a further decrease in cold start emissions in order to ensure low emission levels under most ambient and driving conditions, particularly in urban environments. Nevertheless, motorway emissions will also have to be controlled well.

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“…27 It was consistent with the conclusions of the reference 28 which addressed unregulated emissions as well. Du et al 29 researched the RDE under cold-start conditions, revealing that the cold-start period accounted for a significant proportion of the total urban driving emissions; meantime, the cold-start emissions were very sensitive to driving behaviors; additionally, the correlations between coldstart emissions and ambient temperature were addressed. The impacts of cold-start emissions by driving behaviors were also discussed in Gao et al's study.…”

Section: Introductionmentioning

confidence: 99%