Research On Theory And Method Of Purification Of Diesel Exhaust Particulates

In recent years,many cities in China have been shrouded in haze.Environmental problems have become increasingly serious.And people's attention to environmental governance methods has also been increasing.As one of the vehicles that people use for daily travel and transportation,diesel vehicles are widely used in daily life.However,exhaust particulate in diesel vehicle emissions is one of the major sources of haze,causing significant damage to the human body and the environment.In order to effectively reduce the emissions of diesel exhaust particulates,this paper starts from the point of view of reducing the emission of solid particles in diesel exhaust gas.The theoretical analysis,numerical simulation and experimental verification are used to study the purification of diesel particulates.The main research contents of this article are as follows:Firstly,the microscopic appearance of diesel exhaust particulates is observed by optical microscope and scanning electron microscope,respectively.The microscopic morphology and particle size range of diesel exhaust particulates are determined.It lays the foundation for the study of the separation of particulate matter from gases in the exhaust gas and the establishment of mathematical models.Second,the gas-solid two-phase flow theory is introduced.The gas phase is considered as a continuous medium and the solid phase is considered as discrete particles.A spiral separation model and a particle-droplet separation model are established.The analysis of the movement of the particles in the exhaust gas in the spiral tube and the movement of the particles after their adsorption by the droplets are performed.The optimization effects of spiral separation method and droplet adsorption method on the separation efficiency of gas-solid two-phase flow in exhaust gas are studied.Again,based on the spiral separation theory model and the particle-droplet separation model,a design idea for a new type of diesel exhaust gas purification device is proposed.The factors that affect the performance of the purification device are analyzed.Using Fluent,the gas flow field and particles in the spiral tube of the new purification device are simulated and analyzed by CFD simulation,and the distribution characteristics of particle and gas flow fields in the spiral tube are obtained.According to the results of CFD simulation,the effects of parameters such as pipe diameter,helix angle and pitch on the gas-solid separation efficiency and pressure drop at the inlet and outlet of the pipe is discussed respectively.The structural parameters of the spiral pipe that are favorable for gas-solid separation are obtained.Finally,a diesel exhaust particulate purification device is designed and manufactured.The device mainly uses the spiral separation method and the droplet adsorption method to separate and collect the particulate matter in the exhaust gas.The feasibility of the device is verified by the diesel engine bench test.The experimental results show that the device has a certain purifying effect on the diesel exhaust particulate matter and can reduce the emissions of diesel exhaust particulate matter.