Brake Wear Particle Emissions of a Passenger Car Measured on a Chassis Dynamometer

Brake wear emissions with a special focus on particle number (PN) concentrations were investigated during a chassis dynamometer measurement campaign. A recently developed, well-characterized, measurement approach was applied to measure brake particles in a semi-closed vehicle setup. Implementation of multiple particle measurement devices allowed for simultaneous measurement of volatile and solid particles. Estimated PN emission factors for volatile and solid particles differed by up to three orders of magnitude with an estimated average solid particle emission factor of 3∙109 # km−1 brake−1 over a representative on-road brake cycle. Unrealistic high brake temperatures may occur and need to be ruled out by comparison with on-road temperature measurements. PN emissions are strongly temperature dependent and this may lead to its overestimation. A high variability for PN emissions was found when volatile particles were not removed. Volatiles were observed under high temperature conditions only which are not representative of normal driving conditions. The coefficient of variation for PN emissions was 1.3 without catalytic stripper and 0.11 with catalytic stripper. Investigation of non-braking sections confirmed that particles may be generated at the brake even if no brakes are applied. These "off-brake-event" emissions contribute up to about 30% to the total brake PM10 emission

EU project UPGRADE (No 724036) - measurements of a Jeep Renegade prototype vehicle by JRC

Within Work Package 5 of the H2020 project UPGRADE (High efficient Particulate free Gasoline Engines) http://www.upgrade-project.eu/, JRC tested a demonstrator vehicle specifically developed by Centro Ricerche Fiat (CRF) in WLTP conditions. The results showed that: 1. All pollutants were below the EURO 6 limits. 2. Particle number emissions were two orders of magnitude below the limit of 6*10^11/km. PN10 were in average 13% higher than PN23. 3. CO2 emissions were on average 165.3 g/km.JRC.C.4-Sustainable Transpor

Regulating particle number measurements from the tailpipe of light-duty vehicles: the next step?

Light-duty vehicle emission regulation in the European Union requires the dilution of the whole exhaust in a dilution tunnel with constant volume sampling prior to emission measurements. This methodology avoids measurement uncertainties associated with direct raw exhaust emission measurements from the tailpipe, such as exhaust flow determination, exhaust flow pressure pulsations, differences in the response time between exhaust flow and instrument signals, or their misalignment. Transfer tubes connecting the tailpipe to the dilution tunnel of different lengths and mixing of the exhaust gas with the dilution air in the dilution tunnel may increase differences in measurements performed at different facilities. Recently, the light-duty vehicle regulation was complemented by on-road measurements with Portable Emissions Measurement Systems (PEMS). PEMS measurements are conducted from the vehicle tailpipe. Differences between tailpipe and full dilution tunnel measurements have not been adequately addressed so far. In this study we compare particle number emissions measured at the full dilution tunnel or directly at the tailpipe. The measurements covered solid particles with diameter larger than 23 nm, as required by the current regulation, but also solid particles larger than 10 nm, as recommended for future regulations. The studied vehicle technologies were diesel, gasoline, and compressed natural gas. The differences between tailpipe and dilution tunnel particle number emissions were found to be small (<15%) for both size ranges, with the exception of engine cold start (up to 35% in some cases). Theoretical estimates showed that agglomeration in the transfer line from the vehicle to the dilution tunnel might reduce particle concentrations by up to 17%. Exhaust flow rate determination and time misalignment of exhaust flow and particle concentration signals can introduce uncertainties of ±10% and ±5%, respectively, to the tailpipe measurements. The results suggest that tailpipe sampling is not only possible, but it can additionally give more representative (“real”) emissions of the vehicle and should be considered in post Euro 6 regulations.JRC.C.4-Sustainable Transpor

Brake wear particle emissions of a passenger car measured on a chassis dynamometer

Brake wear emissions with a special focus on particle number (PN) concentrations were investigated during a chassis dynamometer measurement campaign. A recently developed, well-characterized, measurement approach was applied to measure brake particles in a semi-closed vehicle setup. Implementation of multiple particle measurement devices allowed for simultaneous measurement of volatile and solid particles. Estimated PN emission factors for volatile and solid particles differed by up to three orders of magnitude with an estimated average solid particle emission factor of 3∙109 # km−1 brake−1 over a representative on-road brake cycle. Unrealistic high brake temperatures may occur and need to be ruled out by comparison with on-road temperature measurements. PN emissions are strongly temperature dependent and this may lead to its overestimation. A high variability for PN emissions was found when volatile particles were not removed. Volatiles were observed under high temperature conditions only which are not representative of normal driving conditions. The coefficient of variation for PN emissions was 1.3 without catalytic stripper and 0.11 with catalytic stripper. Investigation of non-braking sections confirmed that particles may be generated at the brake even if no brakes are applied. These “off-brake-event” emissions contribute up to about 30% to the total brake PM10 emission.JRC.C.4-Sustainable Transpor

Comparisons of Laboratory and On-Road Type-Approval Cycles with Idling Emissions. Implications for Periodical Technical Inspection (PTI) Sensors

For the type approval of compression ignition (diesel) and gasoline direct injection vehicles a Particle Number (PN) limit of 6 × 10^11 p/km is applicable. Diesel vehicles in circulation need to pass a periodical technical inspection test, typically every two years, after the first four years of circulation. However, often the applicable smoke tests or On-Board Diagnostic (OBD) fault checks cannot identify malfunctions of the Diesel Particulate Filters (DPFs). There are also serious concerns that a few high emitters are responsible for the majority of the emissions. For these reasons, a new periodical technical inspection procedure at idle run with PN systems is under investigation. The correlations between type approval cycles and idle emissions are limited, especially for positive (spark) ignition vehicles. In this study the type approval PN emissions of 32 compression ignition and 56 spark ignition vehicles were compared to their idle PN concentrations from laboratory and on-road tests. The results confirmed that the idle test is applicable for diesel vehicles. The scatter for the spark ignition vehicles was much larger. Nevertheless, the proposed limit for diesel vehicles was also shown to be applicable for these vehicles. The technical specifications of the PTI sensors based on these findings were also discussed.JRC.C.4-Sustainable Transpor

Identification and Quantification of Uncertainty Components in Gaseous and Particle Emission Measurements of a Moped

The recent Euro 4 and 5 environmental steps for L-category vehicles (e.g., mopeds, motorcycles) were mainly designed to reduce the emissions of particulate matter and ozone precursors, such as nitrogen oxides and hydrocarbons. However, the corresponding engine, combustion, and aftertreatment improvements will not necessarily reduce the solid particle number (SPN) emissions, suggesting that a SPN regulation may be necessary in the future. At the same time, there are concerns whether the current SPN regulations of passenger cars can be transferred to L-category vehicles. In this study we quantified the errors and uncertainties in emission measurements, focusing on SPN. We summarized the sources of uncertainty related to emission measurements and experimentally quantified the contribution of each uncertainty component to the final results. For this reason, gas analyzers and SPN instruments with lower cut-off sizes of 4 nm, 10 nm, and 23 nm were sampling both from the tailpipe, and from the dilution tunnel having the transfer tube in closed or open configuration (i.e., open at the tailpipe side). The results showed that extracting from the tailpipe 23–28% of the mean total exhaust flow (bleed off) resulted in a 24–31% (for CO2) and 19–73% (for SPN) underestimation of the emissions measured at the dilution tunnel. Erroneous determination of the exhaust flow rate, especially at cold start, resulted in 2% (for CO2) and 69–149% (for SPN) underestimation of the tailpipe emissions. Additionally, for SPN, particle losses in the transfer tube with the closed configuration decreased the SPN concentrations around 30%, mainly due to agglomeration at cold start. The main conclusion of this study is that the open configuration (or mixing tee) without any instruments measuring from the tailpipe is associated with better accuracy for mopeds, especially related to SPN measurements. In addition, we demonstrated that for this moped the particle emissions below 23 nm, the lower size currently prescribed in the passenger cars regulation, were as high as those above 23 nm; thus, a lower cut-off size is more appropriate.JRC.C.4-Sustainable Transpor

Assessment of 10-nm Particle Number (PN) Portable Emissions Measurement Systems (PEMS) for Future Regulations

The particle number (PN) emissions of vehicles equipped with particulate filters are low. However, there are technologies that can have high PN levels, especially below the currently lower regulated particle size of 23 nm. Sub-23-nm particles are also considered at least as dangerous as the larger ultrafine particles. For this reason, the European Union (EU) is planning to regulate particles down to 10 nm. In this study we compared prototype portable emission measurement systems (PEMS) and reference laboratory systems measuring from 10 nm. The tests included cycles and constant speeds, using vehicles fuelled with diesel, gasoline or liquefied petroleum gas (LPG). The results showed that the PEMS were within ±40% of the reference systems connected to the tailpipe and the dilution tunnel. Based on the positive findings and the detection efficiencies of the prototype instruments, a proposal for the technical specifications for the future regulation was drafted.JRC.C.4-Sustainable Transpor

Laboratory and on-road evaluation of a GPF-equipped gasoline vehicle

The introduction of a solid particle number limit for vehicles with gasoline direct injection (GDI) engines resulted in a lot of research and improvements in this field in the last decade. The requirement to also fulfil the limit in the recently introduced real-driving emissions (RDE) regulation led to the introduction of gasoline particulate filters (GPFs) in European vehicle models. As the pre-standardisation research was based on engines, retrofitted vehicles and prototype vehicles, there is a need to better characterise the actual emissions of GPF-equipped GDI vehicles. In the present study we investigate one of the first mass production vehicles with GPF available in the European market. Regulated and non-regulated pollutants were measured over different test cycles and ambient temperatures (23 °C and −7 °C) in the laboratory and different on-road routes driven normally or dynamically and up to 1100 m altitude. The results showed that the vehicle respected all applicable limits. However, under certain conditions high emissions of some pollutants were measured (total hydrocarbons emissions at −7 °C, high CO during dynamic RDE tests and high NOx emissions in one dynamic RDE test). The particle number emissions, even including those below 23 nm, were lower than 6 × 1010 particles/km under all laboratory test cycles and on-road routes, which are <10% of the current laboratory limit (6 × 1011 particles/km).JRC.C.4-Sustainable Transpor

Emissions of a Euro 6b Diesel Passenger Car Retrofitted with a Solid Ammonia Reduction System

Nitrogen oxides (NOx) emissions from diesel vehicles are a serious environmental concern. Prior to the introduction of on-road tests at type approval, vehicle on-road NOx emissions were found many times higher than the applicable limits. Retrofitting an existing vehicle is a short/mid-term solution. We evaluated a NOx reduction retrofit system installed on a Euro 6b diesel passenger car both in the laboratory and on the road. The retrofit consisted of an under-floor SCR (Selective Catalytic Reduction) for NOx catalyst in combination with a solid ammonia based dosing system as the NOx reductant. The retrofit reduced NOx emissions from 25% (50 mg/km) to 82% (725 mg/km) both in the laboratory and on the road. The minimum reduction was achieved at cold start cycles and the maximum at hot start cycles. The retrofit had small effect on CO2 (fuel consumption). No ammonia emissions were detected and the N2O increase was negligible at cold start cycles, but up to 17 mg/km at hot start cycles. The results showed that the retrofit technology could be beneficial even for high emitting Euro 6b diesel vehicles.JRC.C.4-Sustainable Transpor

The comparison of particle oxidation and surface structure of diesel soot particles between fossil fuel and novel renewable diesel fuel

Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel. (C) 2010 Elsevier Ltd. All rights reserved