Regenerating DPFs

[ivymike]

(moved from other thread)

SomptingGuy (Automotive) 8 Aug 05 7:24
Does anyone know how low you have to go with a/f to kick off a DPF regeneration?


Rob45 (Automotive) 17 Aug 05 10:42
SomptingGuy:
My guess is you can't go low enough on A/F to kickoff regeneration of the diesel particulate filter since going low drops the exhaust temperature.
That's why Cat is using the fuel-added afterburner.

 

[ivymike]

Rob, that's interesting - is there an online article about that? How'd you hear about it (I assume those aren't on the road yet)?

Somtingguy- I think the answer will depend on how much platinum and other catalysts the DPF contains. I've heard that some are called "self regenerating" catalysts, and that they don't require any special operating conditions to oxidize PM.

 

[SomptingGuy]

So it's all about post-injection then? Send unburned fuel into a DOC to heat things up enough to fire up the DPF?

 

[SomptingGuy]

p.s. Thanks ivymike for the new thread. I should have done it myself!

 

[Rob45]

Ivy, Sompting:
Yes, fuel plus added fresh air (from the compressor) is introduced upstream of the DPF to kick-off regeneration.
This is done within a separate exhaust pipe leading to the DPF, for Caterpillar.
-----------
Don't know if there are any articles about this anywhere; I work at a heavy truck OEM, and that's what we're designing for Caterpillar engines.

And yes, it looks every bit the abortion it sounds.

Cummins have a much more sane approach; they simply add extra fuel upstream, and combustion occurs within the DPF.

 

[MikeHalloran]

I've installed two sets of 'self- regenerating' systems on yachts' gensets. According to the manufacturer, all you have to do to keep them clean is make sure the gensets stay above 80 pct load most of the time, e.g. by artificially loading the gensets.

Both sets were removed in six months or less. They worked for a while, but required mechanical cleaning at progressively shorter intervals, and when it became a daily maintenance item, the owners got fed up.

Systems that combine the artificial load with the catalyst in the same housing have a somewhat better reputation; I know of none that have actually been thrown overboard, the reported fate of mine. That may have been hyperbole, but the owners were clearly frustrated that they had spent large sums of money on socially responsible technology that quickly became a headache.

Given the performance of self-regenerating systems with a constant high load, I can't imagine how you could make them work in a truck. Maybe adding fuel, or air, or both, will make the difference, but my very limited experience is not encouraging.



Mike Halloran
Pembroke Pines, FL, USA