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Conference report: CTI Conference Exhaust Systems

27 January 2015

The 13th International CTI Conference Exhaust Systems was held on 19-21 January 2015 in Stuttgart, Germany. The three-day program started with an introductory seminar on engine and emission technologies [S. Carstens, EngineSens]. Presentations during the following two days covered topics ranging from emission testing through aftertreatment technologies, sensors and OBD in diesel and gasoline engines. The Conference program also included a tour of the TÜV SÜD exhaust emissions testing facilities.

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Real Driving Emissions. Pollutant emissions and fuel consumption from European vehicles during real onroad operation have been higher than emissions over the NEDC test procedure used for EU type approvals. UK’s Emissions Analytics [J. Thomas] has tested over 800 vehicles in real world operation since 2011 using PEMS equipment. According to their data, the average gap between real world fuel economy and NEDC results is about 22%, and growing at about 2% per year. Vehicles powered by small, downsized engines—a common technology for meeting European regulatory CO2 emission targets—are the worst offenders with the highest difference between real world and NEDC results. This higher sensitivity to the test conditions of vehicles with downsized engines is apparently caused by the relatively small area of high efficiency in their engine map, which is more often exceeded in real driving compared to vehicles with larger, conventional engines. PEMS measurement results of pollutant emissions were also presented that showed the already well publicized high NOx emissions from diesel cars with no NOx aftertreatment (pre-Euro 6), as well as some interesting insights into the effects of cold start and DPF regenerations.

SCR Technology. Most presentations on emission control technologies focused on various aspects of the SCR technology, from low temperature operability to the integration with particulate filters in the SCR-on-filter approach. Tue Johannessen [Amminex] presented an update on the AdAmmine gaseous ammonia delivery system. A retrofit AdAmmine system has been developed to replace the urea system on urban buses with SCR aftertreatment. The system utilizes the pre-existing SCR catalyst. Bus fleet demonstrations have been conducted in Copenhagen and in London. Using gaseous ammonia, the reductant injection can start at temperatures as low as 150°C, significantly improving SCR performance at low temperatures, such as those typical for urban bus operation. In the Amminex bus fleet demonstration, NOx conversion increased to 80-90%, compared to about 33% measured with the original urea systems. The Amminex technology utilizes replaceable and rechargeable cartridges, where ammonia is stored in the form of a solid, strontium chloride compound. Existing Amminex production capacity is 200,000 cartridges per year. The current cartridge recharging capacity can service applications throughout Scandinavia.

OBD and Sensors. Onboard diagnostics (OBD) is arguably the most dynamically evolving area of vehicle technology. Matthias Weber [Continental] presented an overview of OBD systems for commercial vehicles, from types of OBD architecture to hardware definitions. Cloud based diagnostics and other new types of functionality are expected to drive future change in OBD systems. Cloud diagnostics, for example, may be used as an analysis tool during vehicle service and repair, reducing or eliminating the need for test equipment at the repair shop. Fourier analysis of sensor signals may enable new diagnostics algorithms, such as using amplitude and frequency signatures for engine control and for diagnostic detection. Cloud technologies also carry significant privacy risks—they can reveal information ranging from the maximum speed to the history of vehicle location to the police force, governments and cyber cryminals. A special interest group, OBD4HDD, has been formed by developers of automotive electronics for heavy-duty applications to guide the development of these new technologies.

Other Topics. Challenges and options for future diesel EGR systems were discussed by Ford [D. Styles]. High pressure loop (HP) EGR systems have cooling limitations due to the fouling of EGR cooler—a phenomenon that increases NOx emissions over time. The fouling is especially severe when post injection of fuel is used during cold start and warm up, due to the high HC concentrations. Colder intake manifold temperatures are also in conflict with aftertreatment warm-up strategies. The low pressure loop (LP) EGR, on the other hand, can result in feeding acidic concentrates into the engine (if the EGR stream is drawn from upstream of NOx aftertreatment). Condensation in the charge air cooler with LP EGR is another problem that can result in compressor wheel damage. A compromise solution is the dual loop EGR, where LP EGR is usually combined with uncooled HP EGR. A welcome innovation to simplify the EGR system and reduce costs would be a device to combine the functions of the LP throttle and the LP EGR valve.

HJS [D. Lamotte] reported on the development of a three-way catalyst emission system for a heavy-duty Euro VI gas engine. Due to packaging limitations, the system was split into a close coupled pre-catalyst and a main catalyst. Development and validation testing of the emission performance and the mechanical design of the system was performed on a gas burner test rig, followed by a 2000 hr engine test.

Conference website: exhaustsystems-forum.com