Diesel particulate filters

[aceparts_com]

Silly question. Why don't manufacturers stick something like a Dyson on the end of a Diesel exhaust to collect all the soot?

[Pigeon]

They've got various things like that under development, but it doesn't work very well because the particles are too small. A workaround is to use an electrostatic agglomerator upstream of the cyclone to make the particles stick together and form large enough lumps for the cyclone to work, but that adds a fair bit of complexity.

The technique does work jolly well for cleaning the intake air though.

[anonymous-user]

The main problem is not trapping the particulates, but having to empty the filter in some way at regular intervals, easier on a heavy duty haulage application, but a bit of the pain on your personal car! Hence the introduction of DPF's that use a honeycomb matrix much like that of a conventional gasoline catalyst, but one that is porous to the particulates of soot. When it's full (detected either by a differential pressure sensor or by clever modeling logic) the ems comands special post combustion fuel injection pulses, that flush unburnt hydrocarbons into the DPF, allowing it to ignite catalytically and increase in temp (to approx 1000degC) to burn off the trapped particulates.

The complicated calibration of the system, and the additional costs involved have prevented most OEM's from implementing this on too many platforms (in conjunction with the advance in engine management control and common rail pressures, resulting in lower particulate level production to meet EU4 emissions without DPF's), Although the new PAG 2.2 diesel does offer a DPF as an "option" to owners green enough to want to spend the extra approx £300 on there new Freelander!