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Conference report: 4th BOSMAL Emissions Symposium

30 May 2014

The 4th International Exhaust Emissions Symposium organized by BOSMAL Automotive Research & Development Institute was held on May 22-23, 2014 at the BOSMAL facilities in Bielsko-Biała, Poland. The conference program included 25 presentations and a number of posters on current developments in emission regulations and new European measurement procedures, emissions health effects, emission control technologies, as well as fuel and lubricant development.

Regulatory Trends. A number of speakers discussed the two major changes coming to the European emission regulations for light-duty vehicles: (1) Real Driving Emissions (RDE) limits and (2) the new Worldwide harmonized Light vehicles Test Procedure (WLTP) for laboratory, chassis dynamometer testing. It’s been long acknowledged that the current NEDC test is not representative of European driving conditions, with one of the central issues being NOx emissions from in-use diesel cars that in some cases can significantly exceed the NEDC limits. The NEDC also underestimates CO2 emissions—according to some estimates, real world CO2 emissions are 30% higher than the NEDC values [V. Franco, ICCT]. Hence, the NEDC cycle is to be replaced by the WLTP and RDE testing—a combination of procedures intended to ensure that vehicle emissions in real driving do not exceed the respective regulatory approval limits. While the procedures are not yet finalized, the new tests and associated limits are expected to become effective from around 2017.

The RDE regulation will add PEMS (portable emission measurement systems) field testing requirements and emission limits to Euro 6 type approvals and in-use conformity testing. In the case of diesel cars, this will require the introduction of SCR technology on more vehicle models and will likely cause increased urea (AdBlue) consumption. These changes would render diesel cars—especially small diesel cars—less cost effective, potentially leading to a reduction in their market share in Europe. In gasoline engines, the RDE and WLTP testing requirements will likely ensure that gasoline particulate filters (GPF) are used to control particle number (PN) emissions from directly injected gasoline engines.

The WLTP driving cycle was discussed and compared with the NEDC by Alessandro Marotta [European Commission Joint Research Council]. The new cycle—based on driving patterns from the EU, Japan, India, Korea and the USA—has been designed to harmonize the regional differences. The urban-rural-motorway approach was abandoned. Instead, the WLTP includes four speed phases representing low, medium, high, and extra-high speed driving.

The WLTP will eventually replace the NEDC for all types of tests, including pollutant emissions as well as CO2 testing. Compared to NEDC, higher mass vehicles—especially gasoline vehicles—show a CO2 benefit over the WLTP, while smaller vehicles seem to be penalized. Hybrids also appear to show less CO2 benefit when tested over WLTP, which may impact future manufacturers’ strategies.

In addition to the new driving cycle, the WLTP testing procedure includes a number of other changes [K. Engeljehringer, AVL], including new definition of vehicle preparation, conditioning before and during the test (temperature, battery charging), more accurate definition of the test temperature (23°C ± 5°C), and a better definition of road load determination. The new test procedure will be defined by the Global Technical Regulation GTR 15.

WLTP testing is expected to become mandatory from the Euro 6.2 stage (2017.09 for new type approvals), but the implementation schedule still remains uncertain. One scenario considered by the European Commission involves a gradual phase-in of the WLTP (for example, beginning with new vehicle fuel consumption labels), while NEDC testing would continue for other tests (e.g., pollutant emissions). Such phase-in period with dual test cycle requirements could necessitate a major expansion of emission testing resources—more test hours and additional test cells—by vehicle manufacturers.

Regardless of the implementation schedule, the coming regulatory changes will require an expansion of testing capabilities. It is expected that mandatory testing and reporting requirements will be added for a number of additional emissions [L. Hill, Horiba]. These would include nitrogen dioxide, nitrous oxide and ammonia. Furthermore, emissions of ethanol, acetaldehyde and formaldehyde would be measured from vehicles fueled with ethanol blends.

Emissions & Health Effects. From a public health perspective, future regulatory directions and emission standards should be based on proper understanding of the health effects of air pollution. In the recent years, the World Health Organization (WHO) has increasingly associated air pollution with high numbers of deaths from heart disease and stroke, as well as respiratory illnesses and cancer. At the same time, it still remains uncertain which components of air pollution are most harmful—the list of suspects includes compounds ranging from ultra-fine solid particles to secondary organic aerosols (SOA). A keynote speech on the current scientific understanding of health effects from traffic-derived emissions was given by Flemming Cassee [National Institute for Public Health and the Environment, The Netherlands]. Ambient exposures of PM10 and PM2.5, regulated by air quality standards worldwide, have many sources—not limited to traffic—and variable composition. Based on the mechanisms of particle deposition in the lungs and their translocation to other body organs, as well as other evidence, ultra-fine particles (UFP, below 100 nm) seem to be more hazardous than larger particles. Professor Cassee, who is also a WHO expert, emphasized that particulate filters avoid diesel exhaust health effects even if they increase NO2 emissions. The health effects of NO2 are not well known and the WHO has developed exposure standards using NO2 as an indicator in the gas mixture, not necessarily responsible for the health effects. As NO2 is strongly indicative of traffic emissions, one could even speculate that the health effects that correlate with NO2 exposures could be actually caused by UFP emissions. However, increased atmospheric concentrations of NO2 are linked to increased ozone levels.

Very clean vehicles, such as those with DPFs, still emit particles—noted Flemming Cassee—with the particle sources including tires and brakes. Recent health studies indicate that tire wear particles have little adverse health effect. Brake particles, on the other hand, may have very high toxicity and appear to be more potent than diesel exhaust particles.

The overwhelming majority of studies that attempted to quantify the health effects of air pollution relied on particle mass measurements, often PM2.5. The results have shown a strong correlation between PM2.5 exposures and health, but provide little insight on the role of ultra-fine particles and particle number exposures. Andreas Mayer [VERT] retrospectively analyzed a number of studies and attempted to calculate the particle number exposures corresponding to the published particle mass data using generic mass-number correlations used in aerosol science. His results suggest a strong correlation between solid particle number exposures and adverse health effects.

Concerns with the potential health effects from UFP emissions led to the adoption of particle number limits in the European emission standards for light- (Euro 5) and heavy-duty (Euro VI) vehicles. There is also some initial interest in the control of UFP emissions from mobile sources in the United States. Some of the first regulatory programs to control PN/UFP emissions were adopted in Switzerland [G. D'Urbano, Swiss Federal Office of the Environment]. DPF requirements were first introduced for tunnel construction in 2000, in connection with the construction of the Gotthard tunnel, and then extended onto other construction projects. Following the 2006 incident of air inversion that produced severe particle pollution in many areas of Switzerland, a PN emission limit of 1×1012 kWh-1 was adopted for new nonroad engines. Alternatively, machines can be retrofitted with DPF systems with a PN reduction efficiency of 97% for particles of 20-300 nm. The Swiss PN limit of 1×1012 kWh-1 is considered for adoption in the coming EU Stage V nonroad emission standards. If adopted, it would force DPF application on all affected nonroad engines.

The efficiency of particulate filters installed under the Swiss requirements must be monitored using PN instruments. TSI [L. Bustin] unveiled their newest Model 3795 nanoparticle emission tester designed for this application. The instrument will be officially launched in June at the ETH Conference in Zürich.

A wealth of data on gaseous emissions from diesel and gasoline vehicles under real world and laboratory testing conditions was presented by Gordon Andrews [University of Leeds]. Field measurements conducted in Leeds and other cities show that significantly increased emissions can be observed in congested urban traffic. Due to urban congestion, the improvement of urban air quality has been slower than the progressive stringency of the Euro 1...5 emission standards, even though newer generation vehicles are cleaner. A number of unregulated emissions were also measured, which are emitted almost exclusively at cold start, including benzene, methane, or nitrous oxide. One unregulated emission, ammonia, increased in Euro 4 gasoline engine exhaust over the entire duration of the test, not only at cold start. The NH3 emissions are generated during enrichment events over the three-way catalyst. Ammonia emissions from gasoline engines, also discussed by other speakers [P. Bielaczyc, BOSMAL], may become a new emission concern in the European Union and elsewhere.

Emission Control Technologies. The session on emission reduction technologies was opened by Tim Johnson [Corning] with his overview of emerging trends in engine, fuels, and aftertreatment technology. The main focus area in diesel aftertreatment remains the efficiency and durability improvement of SCR technology. Cycle-averaged SCR NOx conversion efficiency has improved from 94% in 2012 to 96% today, and is projected to reach 98% in 2016. Another development area is SCR-on-filter (SCRF) technology. It is already commercial in light-duty applications (e.g., the 2L EA288 engine by VW), where the SCRF saves space while providing NOx conversions comparable to standalone SCR at most test points.

In particulate filter technology, the focus areas include the development of high porosity substrates for SCRF devices, to provide the necessary high washcoat capacity while ensuring the required PN emission performance. Another development area is the adaptation of particulate filters to spark-ignited engines, with first commercial GPFs being launched this year. Several studies have reported on high metal oxide emissions from natural gas engines, suggesting another possible area of application for particulate filters.

Perhaps the most important driver for engine and vehicle technology are CO2 emissions and fuel economy regulations in Europe and in the United States that, in light-duty vehicles, require a 25-30% emission reduction from today by 2020. And yet, further refinements in current GDI and diesel vehicle technologies show a diminishing rate of return, with additional emission reductions becoming increasingly costly. This threatens the market viability of future, more fuel efficient cars. Unless new, highly efficient engine technologies are commercialized—such as gasoline direct-injection compression ignition (GDCI) or 2-stroke opposed piston engines—meeting the regulated fuel efficiency targets may present a major challenge.

A highly efficient SCR system, dubbed HiSCR, was developed by FPT Industrial for Stage IV/Tier 4 nonroad applications [M. Lavana, CNH Industrial]. Utilizing model-based SCR control with NOx and NH3 sensors, the system exceeds 97% NOx reduction efficiency. The engine meets Tier 4 emission standards without EGR and without a DPF, while achieving a 46% brake thermal efficiency (FPT is targeting a 55% BTE in heavy-duty engines by 2020). The same HiSCR based engines are available for Euro VI applications. The onroad version, however, is fitted with a DPF in order to meet the applicable particle number emission limit.

Sumitomo [A. Narewski, Sumika Ceramics] talked about their aluminum titanate ‘Sumipure’ DPF substrates with hexagonal cell structure—a novel cell configuration that can provide not only high ash storage capacity, but also certain desirable soot accumulation and regeneration dynamics, resulting in a low pressure drop characteristics. Sumika Ceramics acquired the DPF manufacturing plant built in Wrocław, Poland by Bosch and Denso, after their DPF joint-venture was dissolved.

A critically important component in modern engines is the electronic control unit (ECU) [E. Martini, Continental]. State-of-the-art ECUs exhibit impressive characteristics: start-up times below 100 ms, an operating temperature range of -40 to +125°C, vibration tolerance of over 20 g, durability of over 7,500 h for cars and 40,000 h for trucks, as well as an impressively low failure rate of less than 100 ppm. Model based control as well as calibration have been adopted to cope with the increased system complexity. Model-based approach has been also used in the design of experiments (DoE) in engine development [A. Rainer, AVL]. Through the optimization of input-output distances in the DoE process using the AVL algorithm, the number of measurements and the test time can be reduced by up to 15%.

Fuels and Lubricants. The fuels session was opened by Thomas Wallner [Argonne National Lab] who talked about the US fuel trends for light-duty vehicles. The presentation covered the increased US oil production, the trends in fuel consumption and imports, and the US alternative fuel program. Under the Renewable Fuels Standard (RFS2), 29% of the automotive fuel volume is to be ultimately replaced by renewables. But the large majority of the RFS2 obligation is fulfilled by blending corn-ethanol into gasoline—a practice that hit the “blending wall” with practically all gasoline in the US market containing 10% ethanol (E10). E15 blends are legal, but not commercially available (and opposed by fuel manufacturers, distributors and consumers alike), while flex fuel vehicles (E85 capable) are routinely fueled with regular gasoline rather than with the more costly E85 blend. Contrary to some early expectations, the RFS2 program has not succeeded in promoting commercial production of cellulosic ethanol or other technically and commercially viable renewable fuel options and the future RFS2 mandates appear not feasible. With growing criticism pointing out that the RFS2 program is merely a form of agricultural subsidy and that the production and use of corn-ethanol as automotive fuel is both environmentally harmful and counterproductive economically, there is increasing likelihood that the US renewable fuels scheme—just like its EU counterpart—will be classified a failed project.

Most of the remaining presentations focused on fuel and lube oil additives. Statoil [K. Skardalsmo] reported on the laboratory and field evaluation of gasoline deposit control and friction control additive package that preceded a market introduction of a new gasoline formulation. Italy’s Eni [G. Gioco] talked about their CFD tool to characterize diesel engine behavior in the presence of injector deposits, while Lubrizol [B. Sword] and BASF [M. Walter] discussed solutions to fuel injector deposits in diesel and gasoline engines, respectively.

After the technical program, the delegates could participate in a tour of the BOSMAL testing facilities, which include vehicle and engine emission test cells, as well as an array of state-of-the-art equipment and instruments for testing of vehicles and vehicle components, materials, electronic tests and metrology measurements.

Next BOSMAL Emissions Symposium is planned for May 2016.

Conference website