Urea injection system controlled by common rail-type valve group and control method thereof

Abstract

The invention discloses a urea injection system controlled by a common rail-type valve group and a control method thereof. The urea injection system comprises a urea tank, a plurality of urea nozzles,a cooling water pipeline, a compressed air pipeline, a urea pipeline, an air bleed pipeline, a plurality of blowing pipelines, and a valve group injection unit, wherein the valve group injection unitcomprises a cooling water solenoid valve, a first air solenoid valve, a plurality of second air solenoid valves and a plurality of injection pressure sensors, a plurality of blowing solenoid valves,a plurality of injection solenoid valves, a pressure sensor, an air bleed solenoid valve and a temperature sensor. The entire system provides power to each branch of the urea pipeline by air compression and carries out measurement by each solenoid valve, and the temperature sensor and pressure sensor performs feedback control on the degree of opening of the solenoid valves to complete the processof common rail-type urea injection with low cost and high precision. Special blowing pipelines and blowing solenoid valves are provided to enable respective blowing on the front and rear sides of theinjection solenoid valves on the urea pipeline, so that the entire urea pipeline remains no urea after parking.

Description

technical field [0001] The invention relates to aftertreatment of exhaust gas, in particular to a urea injection system controlled by a common rail 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. The single-channel, single-nozzle SCR system can only inject urea at one location, and the second is that the injection volume of a single nozzle is limited, which makes it difficult to meet the requirements of large-displacement engines and lower emission requirements. Therefore, a multi-stage parallel SCR system has emerged (also known as common rail SCR), leading to multiple noz...

AI Technical Summary

Problems solved by technology

The single-channel, single-nozzle SCR system can only inject urea at one location, and the second is that the injection volume of a single nozzle is limited, which makes it difficult to meet the requirements of large-displacement engines and lower emission requirements. Therefore, a multi-stage parallel SCR system has emerged (also known as common rail SCR), leading to multiple nozzles through multi-stage parallel intake passages and parallel urea pipes

[0003] At present, the common control method of urea injection system is to apply high pressure in the urea tank, and use the compressed gas in the urea tank to pump the urea into the exhaust pipe, which cannot be purged and is easy to crystallize. Patents CN201610083835.7 and CN201610084047. There is a purge solenoid valve on the air pipeline to the nozzle, 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 Residual urea cannot be purged, so there is still residual liquid in the urea pipeline

Moreover, the above patents are all aimed at single-rail urea injection control, which is difficult to apply to multi-stage parallel SCR systems

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