Initial Results With the Electrostatic Soot Separator on a Passenger-Car Diesel Engine

The electrostatic soot filter consists of an electrostatic field and a downstream cyclone. The usually very small soot particles are separated in the field and converted into considerably larger particles. In the cyclone, the soot is separated and the exhaust stream is divided into two streams, whereby the first, as a clean gas stream, should contain no soot particles and the other stream should contain all the soot particles. Whereas the clean gas stream can leave the vehicle by way of the exhaust pipe, the exhaust gas stream containing soot is recirculated into the intake manifold of the engine. The engine burns the soot with high conversion rates, so that particle emission improvements of 80% can be achieved in steady-state operation. In the CVS test the emission of particles is reduced by 50% with a first test sample.

Due to the continuous operation of the filter and the burning of the soot in the engine, the particularly critical problem of regeneration does not apply in this case. The danger of clogging can virtually be ruled out even if the filter is fitted at a considerable distance from the engine. This loss in pressure corresponds to that of a silencer. A drawback is the still comparatively large size (approximately 1 1/2 times the volume of a rear silencer).