Diesel engine SCR control system temperature sensor fault-tolerant control method and device

Abstract

The invention discloses a diesel engine SCR control system temperature sensor fault-tolerant control method. The diesel engine SCR control system temperature sensor fault-tolerant control method comprises the following steps that working condition information of the engine is acquired, and upstream and downstream temperature measured values of a SCR catalyst are acquired; an upstream NOx emissionestimated value of the SCR catalyst and an engine exhaust mass flow rate estimated value are calculated according to the working condition information of the engine, and a downstream exhaust temperature estimated value of the SCR catalyst is calculated; when it is detected that a temperature sensor breaks down, the downstream exhaust temperature estimated value of the SCR catalyst is used for replacing the downstream temperature measured value of the SCR catalyst to serve as the input quantity of the SCR system state estimation and control, and the ammonia coverage rate is calculated accordingto the downstream exhaust temperature estimated value of the SCR catalyst so as to control the urea injection amount. According to the provided diesel engine SCR control system temperature sensor fault-tolerant control method, when the temperature sensor breaks down, fault-tolerant control is performed on the system, so that the negative influence of the sensor fault on the SCR control system isreduced.

Description

technical field [0001] The invention relates to the technical field of engine emission control, in particular to a method and device for fault-tolerant control of a temperature sensor in a diesel engine SCR control system. Background technique [0002] Due to its high thermal efficiency, power, economy and durability, diesel engines are widely used in transportation, construction machinery, agricultural machinery, power generation and other fields, but the exhaust emissions of diesel engines also have a great impact on the atmospheric environment. Diesel engines The main emissions include: nitrogen oxides (NOx), hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM). Compared with gasoline engines, the emissions of hydrocarbons (HC) and carbon monoxide (CO) of diesel engines are relatively low, but due to the high air-fuel ratio and combustion temperature of diesel engines, the emissions of nitrogen oxides (NOx) and particulate matter (PM) are much higher than t...

AI Technical Summary

Problems solved by technology

The Urea_SCR control system is mainly divided into two types: open-loop and closed-loop. In the National IV emission standard for diesel engines, the open-loop control strategy can still meet the requirements of the regulations, and its NOx conversion efficiency can reach 60%-80%. With the proposal and implementation of six emission standards, the emission limit of NOx has been further reduced, and the original open-loop control strategy cannot achieve the ideal control effect

The Urea_SCR closed-loop control strategy is mainly divided into closed-loop control based on ammonia coverage, closed-loop control based on NOx sensor and NH-based 3 The closed-loop control of sensors, in which many sensors are used, such as temperature sensors, NOx sensors, NH 3 Sensors, etc. The signal accuracy of the sensors determines the performance of the control strategy to a large extent. Since the Urea_SCR emission after-treatment system works in harsh environments such as high temperature, high dust, and high vibration for a long time, its key components are prone to failure or damage, resulting in Deviations in the control system affect the emission control effect; taking the downstream temperature sensor as an example, when it fails, its output signal is abnormal, which will cause the control system to misjudge the current system state, and the control command does not match the current system requirements. As a result, the control accuracy is reduced, and the NOx emission and ammonia leakage exceed the standard.

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