Control method of urea pump, urea pump and engine

Abstract

The invention relates to the technical field of engine tail gas treatment, in particular to a urea pump control method, a urea pump and an engine, and the urea pump control method comprises the steps that in the operation process of the engine, NOx values of the upstream and the downstream of an SCR device are detected; the first judgment condition is that the NOx value of the downstream of the SCR device is larger than a set threshold value and lasts for a first set time; according to the second judgment condition, the NOx value of the downstream of the SCR device is larger than the NOx value of the upstream of the SCR device and lasts for a second set time; if all the judgment conditions are met, the urea pump is closed, the first judgment condition is to avoid interference of a large ineffective numerical value generated during dew point detection of the NOx sensor, the second judgment condition is to prevent an engine from generating a large amount of NOx during high-power operation, and the urea pump is closed in time only when the SCR device is abnormal, so that the phenomenon that the SCR device is abnormal is avoided. Usage of a urea solution in the urea pump is saved, and the oxidation reaction time can be effectively shortened when the SCR device is abnormal.

Description

technical field [0001] The invention relates to the technical field of engine tail gas treatment, in particular to a control method of a urea pump, a urea pump and an engine. Background technique [0002] Selective Catalytic Reduction (SCR) is a technology that targets NO in diesel vehicle exhaust emissions. x A treatment process, that is, under the action of a catalyst, the reducing agent ammonia or urea is injected to remove the NO in the tail gas x It is reduced to nitrogen and water. The basic working principle of the system is: the exhaust gas comes out of the turbine and enters the exhaust mixing pipe. A urea pump is installed on the mixing pipe, and the urea aqueous solution is sprayed into the SCR device. The urea is hydrolyzed and heated at high temperature. NH is produced after the decomposition reaction 3 , using NH on the surface of the SCR device 3 Reduce NO X , exhaust nitrogen, excess NH 3 Also oxidized to nitrogen to prevent leakage. [0003] In the SCR...

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Problems solved by technology

[0005] The object of the present invention is to provide a control method of the urea pump, the urea pump and the engine, so as to solve the problems in the SCR box when the engine works abnormally in the prior art. The temperature rises rapidly, and the stored ammonia will be released together with NOx, resulting in ammonia leakage and excessive consumption of urea solution.

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