| 摘要 |
<P>PROBLEM TO BE SOLVED: To measure the NOx reduction rate of an exhaust emission control device with good accuracy. <P>SOLUTION: Urea water U is injected from an addition nozzle 7 toward the upstream side of NOx reducing catalyst 6 incorporated in an exhaust passage 5 of a diesel engine 1, and in the case of reducing and purifying NOx contained in exhaust gas G, both a measured value of an NOx concentration sensor 9 on the upstream side of the addition nozzle 7 and a measured value of an NOx concentration sensor 12 on the downstream side of the NOx reducing catalyst 6 are corrected using the primary response model depending on the flow rate and exhaust temperature of exhaust gas G, and then NOx reduction rate is obtained on the basis of these NOx concentration correction values, thereby correcting an error due to a time lag of a measured value of the downstream NOx concentration sensor 12 to the measured value of the upstream NOx concentration sensor 9 when the flow of the exhaust gas G is small and lowering of reducing processing speed of NOx when the exhaust temperature is low. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
