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Featured Application: Particle number measurements directly from the tailpipe of heavy-duty engines are possible for type approval regulatory purposes. The type approval of heavy-duty engines requires measurement of particulates downstream of a proportional to the exhaust flow partial flow dilution system. However, for particle number systems, which measure in real time, this is not necessary and a fixed dilution could be used. In order to assess this dilution possibility, an inter-laboratory exercise was conducted, where a "Golden" system measuring directly from the tailpipe with "hot" (150 °C) fixed dilution was compared with the laboratory regulated systems. Additional "Golden" counters were measuring from 10 nm, below the current cut-off size of 23 nm defined in the regulation, in order to collect data below 23 nm and to confirm that the direct sampling is also possible for smaller sizes. Seven diesel engines and two CNG (compressed naturals gas) engines were used in six laboratories. The results of the "Golden" instruments were within 25% in most cases, reaching 40% in two laboratories for both >23 nm and >10 nm. The repeatability of the measurements (10% to 40%) remained the same for both systems with both cut-off sizes. One test with regeneration showed clear difference between the 10 nm systems, indicating that the thermal pre-treatment only with evaporation tube might not be adequate. Another system measuring from the tailpipe with a fixed "cold" (at ambient temperature) dilution gave differences of up to 50% in most cases (on average +26%). Dedicated tests with this system showed that the differences were the same with fixed or proportional dilution, indicating that it is not the concept that resulted in the overestimation, but the calibration of the system. The main conclusion of this study is that direct sampling with fixed dilution from the tailpipe can be introduced in the future regulation. [ABSTRACT FROM AUTHOR]

The type approval of heavy-duty engines requires measurement of particulates downstream of a proportional to the exhaust flow partial flow dilution system. However, for particle number systems, which measure in real time, this is not necessary and a fixed dilution could be used. In order to assess this dilution possibility, an inter-laboratory exercise was conducted, where a “Golden” system measuring directly from the tailpipe with “hot” (150 °C) fixed dilution was compared with the laboratory regulated systems. Additional “Golden” counters were measuring from 10 nm, below the current cut-off size of 23 nm defined in the regulation, in order to collect data below 23 nm and to confirm that the direct sampling is also possible for smaller sizes. Seven diesel engines and two CNG (compressed naturals gas) engines were used in six laboratories. The results of the “Golden” instruments were within 25% in most cases, reaching 40% in two laboratories for both >23 nm and >10 nm. The repeatability of the measurements (10% to 40%) remained the same for both systems with both cut-off sizes. One test with regeneration showed clear difference between the 10 nm systems, indicating that the thermal pre-treatment only with evaporation tube might not be adequate. Another system measuring from the tailpipe with a fixed “cold” (at ambient temperature) dilution gave differences of up to 50% in most cases (on average +26%). Dedicated tests with this system showed that the differences were the same with fixed or proportional dilution, indicating that it is not the concept that resulted in the overestimation, but the calibration of the system. The main conclusion of this study is that direct sampling with fixed dilution from the tailpipe can be introduced in the future regulation.

In this study, the crankcase gas temperature, flow rate, gaseous emissions (NOx, CO and HC) and particle emissions (particle size distribution, number and mass concentration, geometric mean diameter) compared with tailpipe are investigated in a light-duty common rail diesel engine. It is shown that the emissions from the crankcase are mainly affected by the second in-cylinder pressure peak. The crankcase gas temperature varies between 52 °C and 68 °C, and the crankcase gas flow rate slightly increases with load and speed but does not vary much with injection timing. The CO emission from crankcase is about 2%−5% of that from tailpipe, the NOx emissions are only about 1% and the HC emissions are more than 10%. The blow-by gas percentage is 10−8 order and reduces with heavier engine load and faster engine speed. The blow-by HC emission percentage varies from 5% to 35%. As engine load is increased and engine speed is decreased, the nuclei mode particles of crankcase reduce and the accumulation mode particles increase. Furthermore, the particle total number concentration increases with load but decreases with speed and retarding injection timing. The total mass concentration increases with load but rises and falls with speed and injection timing. The crankcase particle geometric mean diameter based on mass is nearly twice larger than that of tailpipe, while the ones based on number are rarely different except the higher load. [ABSTRACT FROM AUTHOR]

Abstract: We monitored two Seattle school buses to quantify the buses’ self pollution using the dual tracers (DT), lead vehicle (LV), and chemical mass balance (CMB) methods. Each bus drove along a residential route simulating stops, with windows closed or open. Particulate matter (PM) and its constituents were monitored in the bus and from a LV. We collected source samples from the tailpipe and crankcase emissions using an on-board dilution tunnel. Concentrations of PM1, ultrafine particle counts, elemental and organic carbon (EC/OC) were higher on the bus than the LV. The DT method estimated that the tailpipe and the crankcase emissions contributed 1.1 and 6.8 μg m−3 of PM2.5 inside the bus, respectively, with significantly higher crankcase self pollution (SP) when windows were closed. Approximately two-thirds of in-cabin PM2.5 originated from background sources. Using the LV approach, SP estimates from the EC and the active personal DataRAM (pDR) measurements correlated well with the DT estimates for tailpipe and crankcase emissions, respectively, although both measurements need further calibration for accurate quantification. CMB results overestimated SP from the DT method but confirmed crankcase emissions as the major SP source. We confirmed buses’ SP using three independent methods and quantified crankcase emissions as the dominant contributor. [Copyright &y& Elsevier]

In China particulate matter (PM) is the leading environmental risk factor to morbidity and mortality, with transport being the main source of PM pollution in cities. China VI emission limit standards, which are one of the most stringent worldwide, have only recently been introduced and there is lack of studies assessing the PM emissions of new engines. In Europe, there are discussions ongoing to permit sampling directly from the tailpipe with fixed dilution for determining the solid particle number (SPN) emissions during type approval of heavy duty engines; something that is practically allowed for on-road testing. In this study the particulate emissions of seven engines were measured. Three of them were fulfilling the China VI limits, two China V, while two of them were China III engines retrofitted with diesel particulate filters (DPFs). One system with evaporation tube was installed at the full dilution tunnel, as prescribed in the regulation, and another one with catalytic stripper was sampling from the tailpipe, both measuring >23 nm and >10 nm particles. The results showed a wide range of particulate emission levels depending on the engine, the existence of a DPF, the connection point of the crankcase ventilation, and the occurrence of active or passive regeneration. The system at the tailpipe measured on average 20% lower than the system at the dilution tunnel. The system at the dilution tunnel measured much higher during one regeneration due to re-nucleation of volatiles downstream of the evaporation tube. For one engine, the emissions of the evaporation tube system were more than double when the crankcase ventilation was connected downstream of the aftertreatment devices. The main message from this study is that a catalytic stripper is necessary for sub-23 nm measurements and tailpipe sampling with fixed dilution is a plausible option. • China III to VI engine particulate matter (PM) mass and particle number (PN) emissions. • Filtration efficiency of retrofitted diesel particulate filters. • Comparison of PN systems measuring from the tailpipe and the full dilution tunnel. • Contribution of crankcase ventilation to engine emissions. • Passive and active regeneration emissions. [ABSTRACT FROM AUTHOR]