A selective catalytic reduction control method and system suitable for mixed fuels

Abstract

The invention relates to a selective catalytic reduction control method and system suitable for mixed fuels. The method includes: acquiring the type of mixed fuel, and selecting an engine exhaust temperature gauge and engine NO according to the type of mixed fuel. X Emission table; get the correction value of the target ammonia storage, get the basic target ammonia storage, add the basic target ammonia storage and the correction value of the target ammonia storage considering the time delay to get the target ammonia storage; calculate the existing ammonia storage, Calculate the ammonia injection correction amount according to the target ammonia storage amount and the existing ammonia storage amount; obtain the basic ammonia injection amount, add the ammonia injection correction amount and the basic ammonia injection amount to obtain the actual ammonia injection amount; perform selective catalysis based on the actual ammonia injection amount Restore control. Compared with the existing technology, it optimizes the NO when the engine operating condition changes suddenly X Conversion efficiency and ammonia leakage, and improve the control accuracy of the selective catalytic reduction system.

Description

technical field [0001] The invention relates to the field of engine emission control, in particular to a selective catalytic reduction control method and system suitable for mixed fuels. Background technique [0002] Engine exhaust contains a large amount of nitrogen oxides, referred to as NO X , whose main components are nitric oxide NO and nitrogen dioxide NO 2 . Since nitrogen oxides have varying degrees of toxicity, emission regulations have clear limit requirements for their emissions. On the current vehicle engine, for NO X Emission control mainly uses selective catalytic reduction technology, that is, SCR technology. The most common form of this technology is: using urea aqueous solution to decompose to produce ammonia gas, which is mixed with engine exhaust gas and enters the SCR catalyst. Under the action of the catalyst, ammonia gas and NO X A selective catalytic reduction reaction occurs, and nitrogen and water are generated and discharged into the atmosphere...

AI Technical Summary

Problems solved by technology

However, the existing SCR control strategy is mainly based on the imported NO X with export NO X with NH 3 The PID control of emission has a better effect in steady state conditions, but when the engine operating condition is switched, due to the sudden change of emission, the NO X Emissions will increase or decrease rapidly, resulting in too little or too much urea injection, causing NO X Low emission conversion rate, or excessive ammonia slip

In order to solve this problem, the current common method is to establish an ammonia storage model. However, when a diesel engine uses mixed fuels, the emission map (table) of the engine will change accordingly with the change of fuel, which makes the ammonia storage model deviate, causing The amount of ammonia injection does not match the actual demand, which affects the overall conversion efficiency and ammonia leakage

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