Active control method for urea crystallization risk of Urea-SCR system

Abstract

The invention discloses an active control method for the urea crystallization risk of a Urea-SCR system. The active control method comprises the following steps that (1) data such as the engine rotating speed, the torque, the exhaust mass flow, the SCR inlet NOx concentration, the SCR inlet temperature and the urea injection amount in an ECU are collected in real time; (2) a current crystallization risk grade of the system is calculated and obtained by using a crystallization risk online diagnosis module; (3) a driver is prompted and induced through a voice prompt system and an instrument when the risk level is low; (4) when the risk level is in a medium crystallization risk level, once working conditions are met, the EGR rate, the post-injection fuel injection quantity, the fuel injection advance angle, an exhaust TV valve, an electric heating unit, a urea injection control strategy and the like are correspondingly controlled by actively triggering a standard crystallization elimination mode; and (5) when the risk level is high, the driver is required to start a strong crystallization elimination mode under the parking condition as soon as possible so as to eliminate the urea crystallization risk as soon as possible.

Description

technical field [0001] The invention relates to an active control method for the risk of urea crystallization in a Urea-SCR system, belonging to the technical field of motor vehicle emission control. Background technique [0002] Engine exhaust contains harmful substances called nitrogen oxides (NO x ), whose main components are NO and NO 2 . NO x is the N in the air sucked into the cylinder by the engine 2 and O 2 Reaction product at high temperature. Engine emission regulations for NO x The amount of emissions is limited, and different levels of limit values ​​are stipulated, requiring vehicles that exceed the corresponding limit values ​​to produce necessary and differentiated responses to achieve control of NO x purpose of discharge. [0003] Urea selective catalytic reduction technology (referred to as Urea-SCR technology) is an engine control NO x The main technology of emission, the most common form of this technology is: using urea aqueous solution to decomp...

AI Technical Summary

Problems solved by technology

[0005] The urea crystallization problem of the existing SCR system is mainly caused by unreasonable design of the mixing system, excessive injection of urea solution, and low exhaust gas temperature.

The accumulation of urea crystals (also known as urea deposits) will cause the exhaust back pressure to increase, the efficiency of the catalyst will decrease, and the engine economy and emission characteristics will deteriorate. In severe cases, the exhaust pipe will even be blocked, causing the engine to fail to work normally

[0006] There is no corresponding sensor or detection device on the current vehicle to monitor the occurrence of urea crystallization. It is often necessary to wait until the degree of urea crystallization is serious enough to affect the vehicle's dynamic performance or emission characteristics before the problem of urea crystallization is discovered. At this time, the engine and The exhaust aftertreatment system has been operating for a long time in a state of poor economy and emission, which has caused great pollution to the environment

At the same time, even if the driver discovers the problem of urea crystallization in time, it is difficult for him to take effective measures to eliminate urea crystallization during the use of the vehicle due to the fact that he does not have the corresponding professional background. The processing system is removed for maintenance, which seriously affects the normal performance of the vehicle

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