Air-assisted hybrid gas drive urea injection system and method

Abstract

The invention discloses an air-assisted mixing type air-drive urea injection system and method. The air-assisted mixing type air-drive urea injection system comprises a urea tank, a support, an air inlet pressure building pipe, a urea liquid outlet pipe, an air-assisted air pipe, an air-assisted mixing cavity, a urea injection pipe, a mechanical nozzle, an exhaust pressure relief pipe, an electromagnetic valve switch device and a controller, wherein the electromagnetic valve switch device comprises a urea solution metering valve and a triple electromagnetic valve assembly, and the triple electromagnetic valve assembly comprises an air inlet pressure building valve, an exhaust pressure relief valve and a pressure reduction switch valve. According to the air-assisted mixing type air-drive urea injection system, the urea injection and atomization effects of an air-drive selective catalytic reduction (SCR) system can be improved, the NOx conversion efficiency is improved, the risk that crystallization and freezing are caused due to the fact that urea is left in the urea injection pipe after injection is completed is avoided, and the problems that a valve body breaks down due to crystallization of the urea, and consequentially pressure building and pressure relief of the urea tank fail are solved, and the reliability of the system is greatly improved. According to the overall structure, all parts of the air-assisted mixing type air-drive urea injection system are designed in an integrated mode, installation is simplified, and maintenance in the later stage is facilitated.

Description

technical field [0001] The invention relates to an air-assisted hybrid gas-driven urea injection system and method. Background technique [0002] Selective Catalytic Reduction (SCR) technology is a technology to reduce NOx in diesel vehicle exhaust emissions, that is, under the action of a catalyst, the reducing agent ammonia or urea is injected into the exhaust pipe to reduce NOx in the exhaust gas to N2 and H2O to achieve the purpose of eliminating NOx. [0003] The urea nozzle of the existing air-driven SCR system is an integrated metering direct injection nozzle, and its spray atomization effect is not good. Usually, the spray particle size exceeds 100um, and the spray angle of the nozzle is relatively large (the spray angle is defined as the direction of the middle line of the urea spray angle and The angle between the center line of the exhaust pipe), urea is easily sprayed onto the inner wall of the exhaust pipe, resulting in crystallization, which can seriously caus...

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Problems solved by technology

[0003] The urea nozzle of the existing air-driven SCR system is an integrated metering direct injection nozzle, and its spray atomization effect is not good. Usually, the spray particle size exceeds 100um, and the spray angle of the nozzle is relatively large (the spray angle is defined as the direction of the middle line of the urea spray angle and Angle between the center line of the exhaust pipe), urea is easily sprayed onto the inner wall of the exhaust pipe, resulting in crystallization, which can seriously cause pipeline blockage

At the same time, the failure rate of the integrated metering direct injection nozzle is relatively high. After a failure occurs, it is often necessary to replace the nozzle as a whole, which is very costly.

At the same time, after the vehicle is powered off, the urea in the urea injection pipe is not emptied, and the urea remains in the urea injection pipe and the nozzle, which causes the urea in the urea injection pipe to freeze easily at low temperature and is not easy to be thawed, affecting the system work

Moreover, the integrated metering direct injection nozzle is easily affected by the long-term residual urea corrosion, shortening the service life

The existing gas-driven SCR system uses a double-connected solenoid valve assembly with a direct-acting piston structure. Urea crystals are prone to occur at the pressure relief port in the exhaust valve, resulting in lax valve body closure and pressure build-up and pressure relief failures; at the same time, urea crystallization will Corrosion of the spring of the actuator, resulting in failure of the action

Finally, the components of the existing gas drive SCR system are relatively scattered, the integration level is not high, and the installation and post-maintenance are inconvenient

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