SCR system control device

Abstract

The invention relates to a SCR system control device. The device comprises a signal module, a feedforward control module, a feedback module, an urea jet control module and an actuator control module; the signal module is responsible for processing and detecting the signals from vehicles, engines, the SCR system sensor and external diagnostic apparatus; according to an upstream NOx concentration value, venting mass flow rate, SCR temperature and catalyst temperature efficiency MAP, the feedforward control module obtains the jetting amount of feedforward urea; the feedback module carries out PID control in real time based on the amount of NH3 leakage and figures out the jetting amount of feedforward urea; the urea jet control module obtains the total jetting quantity demand of urea based on the total jetting amount both of the feedforward urea and the feedback urea, and then outputs the amount of urea eventually required for the urea pump; the actuator control module drive the urea pump and the nozzle to eject urea. The device has the advantages that the precision of SCR control system is improved and the emission control of NOx from the national six emission regulations is met.

Description

technical field [0001] The invention relates to an SCR system control device, which belongs to the technical field of diesel engine aftertreatment system control. Background technique [0002] SCR post-treatment technology is a diesel engine to reduce NO in the exhaust x The main technical means, the basic principle is that the ammonia gas formed by spraying urea hydrolysis and atomization in the catalytic converter and the NO in the exhaust x Oxidation-reduction reactions occur to produce harmless nitrogen gas. [0003] With the gradual tightening of national emission regulations, starting from the National IV emission regulations, SCR systems have been applied to diesel vehicles in batches. The SCR system generally consists of a control system, a urea injection system, related sensors, and a urea heating device. The control system is the brain of the SCR system. into the SCR catalytic converter to reduce NO x emission value. [0004] At present, the SCR control strate...

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Problems solved by technology

due to NO x The sensor cannot differentiate between NO x and NH 3 Two gases, will mistake NH 3 gas as NO x , resulting in a large deviation in the closed-loop control

[0007] 2. All signal input depends on the measured value of the sensor, and it is impossible to judge whether the current sensor measured value is reasonable and accurate

If someone deliberately places the exhaust temperature sensor upstream of the SCR in an area with a lower exhaust temperature, it will result in reduced or no injection of urea

[0008] 3. Based on the measurement error and corresponding time delay of the sensor, it is easy to cause a large deviation between the urea injection amount and the actual demand injection amount

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