| 摘要 |
The invention relates to an exhaust post-treatment system (2) for a combustion engine (4) which produces an exhaust flow (6), which system (2) comprises at least one diesel oxidation catalyst (DOC) and/or at least one diesel particle filter (DPF), and at least one selective reduction catalyst (SCR catalyst). The system further comprises a reducing agent device (8) adapted to supplying a reducing agent (10) to the exhaust flow (6) upstream of said SCR catalyst, a first NOx sensor (12) situated upstream of said DOC and/or DPF and adapted to measuring the content of nitrogen oxide compounds (NOx) in the exhaust flow and to producing on the basis thereof a first NOx output signal (NOX1), a second NOx sensor (14) situated downstream of said SCR catalyst and adapted to measuring the content of nitrogen oxide compounds (NOx) in the exhaust flow and to producing on the basis thereof a second NOx output signal (NOX2), and at least one temperature sensor (16) adapted to monitoring the temperature of the exhaust flow and to producing on the basis thereof at least a first temperature signal (T1). The exhaust post- treatment system (2) comprises a calculation unit (18) to which said first and second NOx output signals (NOXl, NOX2) and said first temperature signal (T1) are arranged to be conveyed, said first and second NOx sensors (12, 14) are adapted to measuring the content of nitrogen oxide compounds NOX1 upstream of said DOC and/or DPF and to measuring at substantially the same time the content of nitrogen oxide compounds NOX2 downstream of the SCR catalyst when no reducing agent (10) is being supplied to the exhaust flow (6) from the reducing agent device (8), and said temperature sensor (16) is adapted to measuring the temperature T when the measurements of NOXl and NOX2 are taking place, which calculation unit (18) is adapted to comparing NOX2 with a detection criterion, which preferably comprises comparing with a predetermined threshold value NOXtr related to the measured temperature, and to generating on the basis of the comparison an indicating signal (20). |
