DOC Temperature Control for Low Temperature Operating Ranges with Post and Main Injection Actuation

Format:

Conference/Event

Author/Creator:

Stadlbauer, Stadlbauer, author.

Contributor:

Del Re, Luigi

Schilling, Alexander

Waschl, Harald

Conference Name:

SAE 2013 World Congress & Exhibition (2013-04-16 : Detroit, Michigan, United States)

Language:

English

Physical Description:

1 online resource

Place of Publication:

Warrendale, PA SAE International 2013

Summary:

In a typical diesel engine exhaust aftertreatment systemconsisting of a diesel oxidation catalyst (DOC), a dieselparticulate filter (DPF) and a selective catalytic reduction (SCR)system the main purpose of the DOC, besides the oxidation of CO toCO₂, is the oxidation of NO to NO₂. The NO to NO₂ conversion is anessential contribution for the downstream SCR system because thefast SCR reaction which provides the highest conversion rates ofNOx to H₂O and N₂ works well only under roughly equalconcentrations of NO and NO₂.The typical amount of NO to NOx ratio produced by theengine is about 0.95, hence the DOC is necessary to decrease thiscoefficient close to 0.50. Due to the temperature dependency of theDOC reaction mechanism the oxidation of NO to NO₂ takes only placesufficiently if the temperature of the DOC is higher than 200°C,which, however, cannot be reached during low engine speed and lowload situations. As a consequence, under these circumstances thewhole reduction system is ineffective and, moreover, thepotentially high raw NOx emissions in this operatingrange may cause significant tailpipe emission values.Against this background this paper presents a strategy to raisethe DOC temperature during lower temperature operating ranges inits most effective way by acting on the post or the main injection.The final temperature control approach is designed with respect tothe additionally required fuel amount and the effect of thedifferent injections on the total NOx emissions.Finally the control strategy was implemented on a test bench toevaluate the benefit of the DOC temperature increase andconsequently the gain in SCR conversion efficiency against the fuelpenalty. Of course, the additional consumption must be traded offagainst other system modifications, especially in theaftertreatment case

Notes:

Vendor supplied data

Publisher Number:

2013-01-1580

Access Restriction:

Restricted for use by site license