| 摘要 |
PROBLEM TO BE SOLVED: To prevent the occurrence of error in a measured value and a controlled variable caused by fluctuation of sensitivity of a zirconia type NOx sensor when an operation state of a catalyst type denitrification device disposed in an exhaust gas passage of an engine is controlled by using the zirconia type NOx sensor.SOLUTION: NOx removal efficiency is acquired by using a first zirconia type NOx sensor capable of detecting a NOx concentration between an engine and a catalyst type denitrification device in an exhaust gas passage, and a second zirconia type NOx sensor capable of detecting a NOx concentration between the catalyst type denitrification device and an exhaust gas turbocharger on the basis of a formula (NOx inlet×α-NOx outlet×α)/NOx inlet×α, while eliminating α by reduction, where NOx inlet denotes a value detected by the first sensor, NOx outlet denotes a value detected by the second sensor, and α denotes a correction coefficent for correcting influence of a gas pressure in detection environment and SOx included in the exhaust gas on the values detected by the sensors. |
