| 摘要 |
A method of controlling a desulphation process of a Lean NOx Trap (LNT) comprises wobbling of combustion between lean 500 and rich phases. At least one of the rich combustion phases is a stepped phase comprising a rich combustion phase 510 and a very rich combustion phase 520. The step of the stepped phase is realised either: by a first air/fuel ratio (AFR) being followed by a second AFR, the first AFR being lower, i.e. richer, than the second; or, alternatively, by a first exhaust temperature being followed by a second exhaust temperature, the first exhaust temperature being higher than the second. Preferably, there is instantaneous transition 530 from the lean combustion phase to the very rich combustion phase and ramped transition 540,550 from the very rich combustion phase to the rich combustion phase and from the rich combustion phase back to the lean combustion phase. Ideally, the very rich combustion phase is at 700°C with an AFR of 0.9 and the rich combustion phase is at 650°C with an AFR of 0.95. The method is particularly suited to optimising desulphation of a LNT in an exhaust system of an internal combustion engine running under urban driving conditions. |
