Estimation of urea crystallization amount, judgment of crystallization state and method of crystallization elimination

Abstract

The invention provides a urea crystallization amount estimation, crystalline state judging and crystal eliminating method. Based on the engine running working conditions, influences of the urea crystallization speed and the SCR conversion efficiency on urea crystallization are estimated under the current working condition. When the urea crystallization amount is too much, the engine running state is adjusted, crystals are removed in time, and the stone forming phenomenon is prevented.

Description

technical field

[0001] The invention relates to the field of engines, in particular to the technical field of SCR exhaust gas post-treatment. Background technique

[0002] Urea selective catalytic reduction (selective catalytic reducton, SCR) technology is one of the most commonly used technical means to control diesel engine nitrogen oxide (NOx) emissions. However, in the process of actual use, due to the problem of urea crystallization, for example, when the urea injection amount is not appropriate or the mixer structure is too simple, the urea distribution uniformity is too poor, which will lead to lumps on the SCR box or the urea nozzle. Or powdery urea nodules have an adverse effect on the SCR control of nitrogen oxides, resulting in incomplete tail gas reaction, resulting in excessive emissions. The prior art is based on the design of mixer hardware to prevent crystallization. However, after the design of the mixer is finalized, it is impossible to prevent and elimin...

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