Urea injection control method for SCR (selective catalytic reduction) system

Abstract

The invention discloses a urea injection control method for an SCR (Selective Catalytic Reduction) system. The urea injection control method has the conception that after a urea injection mechanism of the SCR system is started by a vehicle, if the current actual conversion efficiency is lower than the set target conversion efficiency, correction coefficient fac post-nitrogen oxygen is increased until regeneration operation is triggered, and the nitrogen and oxygen after the correction coefficient fac are forcibly reset; for example, the correction coefficient fac post-nitrogen oxygen can be reset initial value can be reset to an initial value 1 or other correction factors are adopted to correct the correction coefficient fac post-nitrogen oxygen, so that the fac post-nitrogen oxygen is set to be other set values, and the current urea injection amount is regulated and controlled in time; and therefore, the urea injection amount can be synchronously recovered to be a normal injection value after the efficiency of the SCR system is recovered to be normal through regeneration, and the problems of reduction of the reefficiency and crystallization of the SCR system caused by excessive injection of urea can be solved.

Description

technical field [0001] The invention relates to the technical field of selective reduction, in particular to a method for controlling urea injection in an SCR system. Background technique [0002] Selective Reduction Technology (SCR) is one of the important post-treatment technologies for reducing NOx emissions of National VI heavy-duty diesel vehicles. Its working principle is to inject a certain volume of urea solution into the exhaust pipe, and the urea solution is under the action of the mixer and exhaust Atomized hydrolysis generates ammonia gas, which is mixed with exhaust gas, and under the action of the reduction catalyst, nitrogen oxides are reduced to water and nitrogen gas, achieving the purpose of purifying exhaust gas. [0003] At present, the SCR system of National VI heavy-duty diesel vehicles includes urea pump, urea nozzle, urea connection pipeline, urea injection controller, SCR catalyst assembly, exhaust temperature, front and rear nitrogen oxide sensors, ...

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Problems solved by technology

[0006] In view of the above, the present invention aims to provide a method for controlling urea injection in an SCR system, which solves the problem of SCR HC poisoning and triggers regeneration. Failed to set the position in time, resulting in excessive spraying of urea and ammonia leakage, so that the SCR system will soon report the failure of low SCR efficiency and the problem of SCR crystallization

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