| 摘要 |
An embodiment of the invention provides a method to estimate NO2concentration in exhaust gas flowing through an exhaust pipe 30 of an internal combustion engine, wherein the exhaust pipe 30 has a first section 30A and a second section 30B, 30C and is equipped with an aftertreatinent device 31, 32 such as an SCR type catalyst located between the first 30A and the second section 30B, 30C and wherein the method comprises the steps of: determining a parameter related to a NO2concentration of exhaust gas flowing in the first section 30A determining an oxidization index indicative of a rate of NO contained in the exhaust gas which oxidizes into NO2inside the after-treatment device 31, 32 and a reduction index indicative of a rate of NO2contained in the exhaust gas which is re-duced into NO inside the aftertreatment device 31, 32 calculating a parameter related to a NO2concentration in the second section 30B, 30C as a function of the parameter related to a NO2concentration in the fist section 30A, the oxidization index and the reduction index. The estimate of NO2allows for fine control of the amount of urea supplied to the exhaust gas for use in the SCR. Also disclosed is an associated computer program for carrying out the method and an internal combustion engine having an electronic control unit (ECU) which uses program.
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