Valve-group-controlling urea spraying system and control method thereof

Abstract

The invention discloses a valve-group-controlling urea spraying system and a control method thereof. The urea spraying system comprises a urea tank, a urea spray nozzle, a cooling water pipeline, a compressed air pipeline, a urea pipeline, a blow-off pipeline, a purging pipeline and a valve group spraying unit. The valve group spraying unit comprises a controller, a cooling water electromagnetic valve, a first air electromagnetic valve, a second air electromagnetic valve, a pressure regulating device, a purging electromagnetic valve, a spraying electromagnetic valve, a pressure sensor, a blow-off electromagnetic valve and a temperature sensor. Motive power is provided for the whole system through compressed air, metering is carried out through all the electromagnetic valves, feedback control over the opening degrees of the electromagnetic valves is performed through the temperature sensor and the pressure sensor, the urea spraying process is finished with low cost and high accuracy; and by means of the special purging pipeline and the special purging electromagnetic valve, purging can be performed on an upper section and a rear section of the urea pipeline, and thus the whole ureapipeline is free of residual urea after a car stops.

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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