Urea supply injection system with two-stage injection function

Abstract

The invention discloses a urea supply injection device with a two-stage injection function. The urea supply injection device aims to realize quantitative injection and metering of two paths of urea nozzles. According to the the technical scheme, the urea supply injection device with the two-stage injection function is characterized in that two paths of urea injection can achieve respective accurate metering and output through unique structural design, the post-treatment double-path urea injection demand of the China VII vehicle emission standards is met, high-pressure air is adopted for assisting urea injection, the high-pressure air is introduced into two mixing cavities through pipeline design to be mixed with urea, and the total urea injection amount is controlled by controlling the rotating speed of a motor of a urea pressure building mechanism and combining with a pressure sensor, the urea injection amount of the second path is the difference value between the total urea injection amount and the urea injection amount of the first path, so that the urea injection amount of the second path is indirectly and accurately controlled in real time, the high-pressure gas can purge the mixing cavities and the nozzles, and urea crystallization in the injection device and at the nozzles can be effectively prevented.

Description

technical field [0001] The invention relates to the field of diesel engine tail gas treatment, in particular to a urea supply injection system with a dual-stage injection function. Background technique [0002] With the increasingly stringent emission regulations, it is expected that the National VII emission regulations will further reduce the emission limits of NOx, PM, and PN on the basis of the National VI emission regulations. The current National VI emission regulations for heavy vehicles use WHSC and WHTC cycles for bench emission tests, and the NOx emission limits are 0.4g / kWh and 0.46g / kWh respectively. The WHTC cycle is divided into a cold cycle and a hot cycle, and their weights account for 14% and 86% respectively. It is expected that the NOx emission limit in the National VII emission regulations will be further tightened to 0.12g / kWh, which is about 70% lower than the national VI emission limit. [0003] At present, the Chinese patent with the publication num...

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Problems solved by technology

[0004] Although this SCR exhaust gas treatment system for the engine can control the urea injection amount of the engine under different operating conditions by controlling the metering device, the urea injection system sprays the atomized solution evenly into the engine exhaust to improve the catalytic performance of the catalyst. conversion efficiency; the SCR exhaust gas treatment system can make the nitrogen oxides undergo a sufficient catalytic reaction with the urea solution on the surface of the SCR catalyst, convert the nitrogen oxides into harmless nitrogen and water and discharge the engine with the exhaust pipe, but it uses The first-stage injection cannot fully treat the exhaust gas better

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