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Tenneco developing new gasoline particulate filter (GPF) technology ahead of Euro 6c emissions regulation

Tenneco is leveraging its expertise in diesel particulate filter (DPF) technology to develop gasoline particulate filters for 2017 model year light vehicles. These filters are designed for gasoline direct injection (GDI) engines to reduce particulate emissions in compliance with the Euro 6c emissions regulation (particulate number of no more than 6 x 1011particles/km), which takes effect on 1 September 2017.

GDI engines help improve fuel economy and therefore reduce CO2 emissions; however, they can have higher particulate emissions due to shorter fuel/air mixing times in the cylinder compared to multiport fuel injection engines. Advanced fuel injection strategies are currently used to control gasoline particulate emissions in-cylinder but they are designed for a particular emission test cycle and may be less effective under real driving conditions.

Gasoline particulate filters effectively control particulate emissions under all operating conditions. Tenneco has been working on GPF technology for several years, exploring concepts including coated and uncoated filters.

Diesel particulate filters for original equipment applications remove particulate matter from engine exhaust gases in a closed system. When gases carrying particulate matter flow through the filter’s substrate walls, particulate matter is trapped and collected in the filter. A regeneration process, triggered by the engine management system, then burns off the soot using either a fuel borne additive or a catalytic filter coating.

Gasoline particulate filters use the same type of wall-flow substrates as diesel particulate filters and can be included in the exhaust system in addition to the series three-way catalyst or the catalyst coating can be directly applied to the filter substrate to form a four-way catalyst.

However, there are substantial differences between gasoline and diesel exhaust; the engine-out particulate emissions are roughly 10-30 times lower compared to a modern light-duty diesel. This difference drives different choices for optimal filter technologies. In addition, in a 2011 report from the European Commission’s Joint Research Centre exploring the feasibility of GPFs, the authors noted that:

  • Gasoline engine exhaust temperatures are relatively higher than diesel; engine-out temperatures range between 300 and 500°C under urban driving conditions, but can reach 700°C at high speed (motorway) driving. Although these temperatures are high enough to sustain passive regeneration of a GPF, there is generally a shortage of oxygen in the exhaust of GDIs running stoichiometrically. Accordingly, regeneration generally occurs during vehicle deceleration were the fuel is cut-off and oxygen becomes available in the exhaust. Catalyzed GPF systems with oxygen storage capabilities may also allow short periods of lean operation to initiate passive or active regeneration. Installation in lean-burn engines is more straightforward as there exist generally a surplus of oxygen in the exhaust and the exhaust temperatures are similar to those of their stoichiometric counterparts.

  • In addition to the lower particle concentrations, the soot emitted from GDI vehicles oxidizes much faster than diesel soot; studies have measured burnout rates 2.5 times higher than those of diesel soot. This all points to insignificant soot storage in the GPF, even after prolonged operation under real world driving conditions. As a result, no extreme heat release due to soot oxidation is expected so thermal durability is not considered an issue.

  • The low soot loading also allows for the use of more compact—and less expensive—filters from diesel applications due to the lower volume and in the case of catalyzed GPFs the lower precious metal content. While in diesel vehicles, the volume of the filter is typically 1.5 to 2.5 times the engine displacement, the envisaged GPF systems have much smaller size, equal or smaller to the engine swept volume.

Improvements in the acoustic function of the gasoline particulate filter make it possible to reduce muffler volume, helping to reduce backpressure, increase performance, reduce weight and save cost.

Tenneco produces more than 2 million DPFs annually at its clean air manufacturing facilities in Edenkoben, Zwickau and Saarlouis, Germany; Rybnik, Poland; Hodkovice, the Czech Republic; Tredegar, the UK and Port Elizabeth, South Africa.

At Tenneco we understand the functional requirements for gasoline particulate filters based on our experience as one of the first global suppliers to offer diesel particulate filter technologies in serial production. With our design, engineering, systems integration and advanced manufacturing capabilities, we provide customers flexible solutions for any powertrain to meet future emissions regulations without compromising vehicle performance or durability.

—Josep Fornos, Executive Vice President, Clean Air, Tenneco



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