Model-based urea emitting amount control method and aftertreatment control system

Abstract

The invention relates to a model-based urea emitting amount control method. The method includes the following steps that S1, according to the actual urea emitting amount, based on an SCRF model, a first ammonia storage value in an SCRF is calculated; S2, based on an SCR model, a second ammonia storage value in an SCR is calculated; S3, the first ammonia storage value obtained in the step S1 and the second ammonia storage value obtained in the step S2 are subject to weighted treatment to obtain an actual ammonia storage value; S4, a difference is obtained from the actual ammonia storage value obtained in the step S3 and an actual storage setting value, and a closed-cycle correction ammonia nitrogen ratio is obtained through a PID controller; and S5, the sum of the closed-cycle correction ammonia nitrogen ratio obtained in the step S4 and a feedforward ammonia nitrogen ratio is obtained to be finally converted into the needed urea emitting amount. According to the model-based urea emitting amount control method, a model-based closed-cycle control strategy is adopted, accurate control over urea emitting can be achieved, the engine emission requirements can be met, standardization work can be reduced, and the problem about crystallization can be solved.

Description

technical field [0001] The invention relates to the field of engines, in particular to the field of gas emission purification. Background technique [0002] With the increasingly stringent automobile emission regulations, after-treatment systems with SCR (Selective Catalyst Reduction, Selective Catalyst Reduction) have become the mainstream technology for reducing emission pollution. The method of reducing emission pollution by the post-treatment system with SCR is to spray urea into the SCR tank to reduce nitrogen oxides, thereby reducing emissions and meeting the requirements of emission regulations. [0003] On the basis of SCR, SCRF technology is further developed. SCRF refers to coating SCR catalyst on DPF (particulate matter trap), also known as SCR on Filter, SDPF, etc. Using SCRF technology can not only reduce the aftertreatment volume, but also have better light-off characteristics, which can improve the conversion efficiency of SCR. SCRF technology also faces the...

AI Technical Summary

Problems solved by technology

[0004] In the prior art, the method of controlling urea injection volume is to use SCR and DPF to control calibration separately. In this case, the NH in SCR 3 Shared with DPF passive regeneration and competes to consume NO 2 Case

Therefore, the existing technology has poor adaptability in the SCRF system, and the calibration accuracy is difficult to meet the requirements

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