Engine emission control method and device

Abstract

The invention provides an engine emission control method and device, and the method comprises the steps: determining a first emission amount of nitrogen oxide corresponding to a target working condition according to a first corresponding relation between a working condition when an exhaust gas recirculation function is started in a steady state and the emission amount of nitrogen oxide; according to a second corresponding relation between the working condition when the exhaust gas recirculation function is closed in a steady state and the emission amount of the nitric oxide, the second emission amount of the nitric oxide corresponding to the target working condition is determined, and according to the set exhaust gas recirculation rate and the actual exhaust gas recirculation rate of the engine, a target deviation correction coefficient is determined; by means of the difference value of the first emission amount and the second emission amount and the target deviation correction coefficient, the correction value of the emission amount of the nitric oxide is determined, the correction value related to the actual working condition can be used for correcting the first emission amount, the accurate target emission amount is obtained, and therefore the appropriate urea injection amount can be determined in the transient state.

Description

technical field [0001] The present invention relates to the field of vehicles, and in particular, to a method and device for controlling engine emission. Background technique [0002] Nitrogen oxides (NOx) are one of the key emission pollutants of diesel engines. Exhaust Gas Recirculation (EGR) is one of the key technologies for engine emission control, which can reintroduce the exhaust gas from the engine into the intake pipe and fresh gas. After mixing, it enters the combustion chamber for combustion. Because the exhaust gas can effectively reduce the peak temperature and oxygen content of combustion, EGR can effectively suppress the formation of NOx, which can effectively reduce the emission of NOx from the engine. The EGR system is composed of components such as EGR valve and flow meter, which adaptively adjusts the amount of exhaust gas (EGR rate) entering the engine through the adjustment of the opening of the EGR valve. [0003] The NOx emitted by the engine is proce...

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Problems solved by technology

[0004] At present, most of the NOx models are relatively simple, without or only with a simple EGR correction function, resulting in poor accuracy of the NOx value calculated by the model, resulting in extensive post-treatment urea injection, causing excessive emissions or even crystallization, etc. These problems lead to engine thermal efficiency. decline

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