Active Increase of Exhaust Temperature by Throttling
VERT® - Throttle - Project 2014/15
Globally, an increasing number of transport companies are retrofitting particle filters.
Their fleets mostly are of less stringent emission standards and are often deployed in dense city traffic at low cycle speeds. The attained exhaust gas temperatures are not always sufficient to ensure reliable regeneration of the particle filter. Several supplementary methods have been previously investigated to increase exhaust gas temperatures. One such method is throttling to directly increase exhaust gas temperatures by decreasing the air surplus (lower λ).
The Figure above shows the computed and experimentally engine verified increase in exhaust gas temperatures by regulating to a constant λ-value. There are 2 retrofitting challenges: Intervention in the engine management is usually impossible. And a simple on-off throttle can only be located in the exhaust gas system.
The objective was to develop and test such a throttling system using commercially available components. The VERT Association entrusted the task to the Institute for Commercial Vehicular Research and Exhaust Gas Analysis (BELICON), Chief Executive Prof. Dr.-Ing. Ralph Pütz, at the University of Applied Sciences Landshut Germany. The tests were done during a few days in September and October 2014. The Landshut municipality made available a bus driver and a city bus of type Mercedes-Benz O 405. The test stretch was bus route 3 that connects two suburbs via the city center. The route is almost flat and all bus stops were driven at average speeds of 12 to 18 km/h. BELICON supplied the mobile instrumentation for emission measurements. The prototype for a modular exhaust-gas throttling concept used an inexpensive pneumatic actuated exhaust gas throttle from IVECO.
The throttling inadequately increased the temperature when it was only closed during idling or coasting. Hence throttling was also done in low load operation, i.e. up to speeds of 20 or 25 km/h selectively, which diminished acceleration response.
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