Guiding device and guiding method for diesel engine selective catalytic reduction (SCR) system for automobile

Abstract

The invention relates to a guiding device and a guiding method for a diesel engine selective catalytic reduction (SCR) system for an automobile. The guiding device comprises an expansion pipe and at least two guiding plates arranged in a mutually embedding mode. The end where gas flows to the expansion pipe is a gas inlet end and the end where the gas flows out of the expansion pipe is a gas output end. The guiding plates at fixedly arranged on the gas inlet end of the expansion pipe and each guiding plate is in a trumpet shape without a front end face and a rear end face. A fluid channel is formed among the guiding plates. The guiding device is simple in structure, low in manufacturing cost and easy to install. According to the guiding device and the guiding method, due to backflow generated in the portion of an elbow pipe, exhaust of the automobile and urea sprayed from a nozzle can mix well so that generation of crystal on a wall is reduced. Due to the guiding device in the expansion pipe portion, mixed gas is converted from turbulent flow to laminar flow so that velocity distribution is even, radial pressure difference and temperature difference inside a catalytic agent are reduced, conversion efficiency of nitric oxides is improved, through capacity of a catalytic agent carrier is improved and service life of a catalyst is prolonged.

Description

technical field [0001] The patent of the present invention relates to the field of exhaust systems of diesel engines for vehicles, and more specifically relates to a flow guide device and method for SCR systems of diesel engines for vehicles. Background technique [0002] Diesel engine is famous for its fuel economy, power, reliability and CO 2 Low emissions are favored by people, but there is a big problem with diesel engines, which is the emission problem, which brings a lot of NOX and PM emissions and causes serious environmental pollution. With the increasingly stringent emission regulations, the emission control of diesel engines is still one of the key challenges in diesel engine applications. [0003] There are two different routes for exhaust after-treatment technology for diesel engines to meet the requirements of my country's upcoming National IV emission regulations: one is the exhaust gas recirculation + particulate filter route represented by the United States;...

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Problems solved by technology

[0004] SCR technology is being promoted and applied all over the world, but to achieve the best purification effect, several shortcomings need to be overcome: after the air flow enters the expansion tube, flow separation occurs along the wall surface, forming a large stagnation area; the catalytic converter The gas flow rate in the interior is uneven, and the air flow is mainly concentrated in the central area of ​​the carrier, which causes the catalyst in the central area to age at high temperature, while the edge area is not fully utilized, which affects the service life of the catalyst; at the same time, the uneven flow rate will also cause the catalyst carrier radial direction Excessive temperature and pressure gradients will cause large thermal fatigue damage and affect the power and economy of diesel engines

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