Urea injection system controlled by valve group and control method thereof

Abstract

The invention discloses a urea injection system controlled by a valve group and a control method thereof. The urea injection system comprises: a urea tank, a urea nozzle, a cooling water pipeline, a compressed air pipeline, a urea pipeline, an air release pipeline, a purging pipeline, and a valve group Injection unit; the valve group injection unit includes a controller, a cooling water solenoid valve, a first air solenoid valve, a second air solenoid valve and a pressure regulating device, a purge solenoid valve, an injection solenoid valve, a pressure sensor, and a deflation solenoid valve ,Temperature Sensor. The whole system is powered by compressed air and measured by various solenoid valves. There are also temperature sensors and pressure sensors for feedback control of the opening of the solenoid valves to complete the urea injection process with low cost and high precision; set up special purge pipes and The purge solenoid valve can purge the front and rear sections of the urea pipeline respectively, so that there is no urea residue in the whole urea pipeline after parking.

Description

technical field [0001] The invention relates to aftertreatment of exhaust gas, in particular to a urea injection system controlled by a valve group and a control method thereof. Background technique [0002] At present, Urea-SCR technology is considered to be the most effective way to reduce NOX emissions from vehicle diesel engines. After spraying urea aqueous solution with a mass fraction of 32.5% into the exhaust pipe through the urea injection system, it needs to go through collision, evaporation, hydrolysis, pyrolysis, etc. The process converts to NH3, which then reacts with NOx. [0003] The current urea injection system has two working modes: 1) The motor urea pump pumps and measures the urea solution into the exhaust pipe. This kind of urea injection system driven by a motor will have poor measurement accuracy due to fluctuations in urea pressure. ; 2) High pressure is applied in the urea tank, and the compressed gas in the urea tank is used to pump the urea into th...

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Problems solved by technology

[0003] The current urea injection system has two working modes: 1) The motor urea pump pumps and measures the urea solution into the exhaust pipe. This kind of urea injection system driven by a motor will have poor measurement accuracy due to fluctuations in urea pressure. ; 2) High pressure is applied in the urea tank, and the compressed gas in the urea tank is used to pump the urea into the exhaust pipe, which cannot be purged and is easy to crystallize. In patents CN201610083835.7 and CN201610084047.X, the air pipe to the nozzle There is a purge solenoid valve on the road, which can solve the residual urea on the urea pipeline from the connection with the air pipeline to the nozzle after parking, but the residual urea on the urea pipeline from the urea tank to the connection with the air pipeline cannot be purged Therefore, there is still residual liquid in the urea pipeline

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