A Fault Diagnosis Method of Nitrogen Oxide Input Sensor in Scr System of Diesel Engine

Abstract

The invention discloses a fault diagnosis method of a nitric oxide input sensor of a diesel SCR system, and belongs to the technical field of mechanical failure diagnosis. The fault diagnosis method comprises the following steps: according to SCR system parameters, a NOx input concentration threshold and a time threshold are set; then a NOx input concentration actual value measured by a NOx input sensor is transmitted to a NOx sensor fault diagnosis module, a NOx input concentration estimation module estimates a NOx input concentration estimation value and transmits a signal of the NOx input concentration estimation value to the NOx sensor fault diagnosis module, and the NOx sensor fault diagnosis module calculates a NOx input concentration residual error Delta delta according to the received signal; and the NOx input concentration residual error Delta delta is compared with the NOx input concentration threshold and the time threshold, a working state of the NOx input sensor is determined, and a final NOx input concentration value is given. A calculation procedure is simple, a response speed is high, the fault diagnosis can be carried out on an SCR system sensor online in real time, and the fault diagnosis method has higher diagnosis precision and can be widely applied to diesel SCR system sensor fault diagnosis.

Description

technical field [0001] The invention relates to a fault diagnosis method, which is especially suitable for fault diagnosis of an input NOx sensor in an SCR system for aftertreatment of exhaust gas of a medium-heavy diesel engine. Background technique [0002] The SCR system is widely used in diesel engines to reduce NOx (x=1,2) emissions, and is considered to be the most promising exhaust aftertreatment technology for removing nitrogen oxides. SCR (Selective Catalytic Reduction) is mainly a selective catalytic reduction technology. It sprays urea at the inlet of the system, and uses the ammonia gas hydrolyzed to reduce NOx to nitrogen and water that are not polluting to the atmosphere under the action of a catalyst. [0003] In the SCR system, the injection of urea is the only input control of the system, and the concentration of NOx is considered to be an important state parameter in the control of SCR urea injection, so the input concentration of NOx is very important to t...

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Problems solved by technology

In addition, the diesel engine will produce strong vibration when it is working, and the sensor is also extremely prone to failure in such a harsh working environment.

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