柴油车颗粒捕集器的理论分析与试验研究
发布时间：2019-03-12 18:34
【摘要】：柴油车与汽油车相比,具有功率大、低排放、动力性能好、可靠性高、使用寿命长等优点,因此从节约能源、降低燃料成本角度来讲,柴油车的推广使用具有重要意义。但柴油车有害颗粒物的排放却是汽油车的30～70倍,这种颗粒物严重地污染环境并危害人类健康,因此其净化技术一直是人们研究的热点。颗粒捕集器(Diesel Particulate Filter, DPF)是控制柴油车微粒排放最有效的后处理净化装置,随着我国排放法规的日益苛刻,后处理装置的排放限值越来越低,这就要求后处理技术的检测方法不断地进行改进和完善。因此深入开展柴油车DPF的研究是十分必要的。本文主要采用理论分析、数值计算、试验研究相结合的方法对DPF的性能指标进行检测研究。通过基于填充床捕集理论建立了微粒捕集过程的数学模型,并利用Matlab模拟计算分析了过滤体的微孔孔径、捕集微粒粒径、柴油车的排气流量和排气温度对颗粒捕集器三种捕集机理的影响。分析了壁流式颗粒捕集器的捕集过程,建立了空载和负载时DPF压降的数学模型,得出了排气流量随压降变化的曲线关系。同时运用计算流体力学的FLUENT软件对颗粒捕集器三维模型进行网格划分和边界条件的设定,从理论上进一步分析了DPF捕集颗粒物时内部流速、压力和温度的分布情况,以及内部气流的运动情况。根据试验室现有的仪器设备,并结合现阶段我国柴油车排放控制技术的特点和要求,以及国家在用标准GB17691-2005《车用压燃式、气体燃料点燃式发动机与汽车排气污染物排放限值及测量方法》和HJ451-2008《环境保护产品技术要求柴油车排气后处理装置》等相关内容,完成了柴油车可拆卸式DPF性能检测试验台架的搭建。通过颗粒捕集器的性能检测试验,验证了DPF捕集过程、空载、负载时压降数学模型以及理论分析的正确性。结果表明在整个微粒捕集过程中,布朗扩散起主导作用,减小排气流量和提高排气温度均能提高布朗扩散捕集系数和综合捕集系数,而排气流量和排气温度对直接拦截捕集机理的影响不大；随着柴油机排气流量的增加,空载和负载DPF的压降都近似呈线性增加,而负载DPF的压降值要比空载时高很多。最后得出,该样品的各项性能指标符合国家标准,同时也为研发高捕集效率的DPF奠定理论依据和试验基础。
[Abstract]:Compared with gasoline vehicle, diesel vehicle has many advantages, such as high power, low emission, good dynamic performance, high reliability, long service life, etc. Therefore, from the perspective of saving energy and reducing fuel cost, it is of great significance to popularize and use diesel vehicle. However, the emission of harmful particulate matter from diesel vehicles is 70 times higher than that of gasoline vehicles. This kind of particulate matter pollutes the environment seriously and endangers human health. Therefore, the purification technology of diesel vehicles has always been a hot spot of research. Particle trap (Diesel Particulate Filter, DPF) is the most effective post-treatment purification device for controlling particulate emission from diesel vehicles. With the increasingly stringent emission regulations in China, the emission limit of the post-treatment device becomes lower and lower. This requires the detection methods of post-processing technology to be continuously improved and perfected. Therefore, it is very necessary to carry out the research of diesel vehicle DPF. In this paper, a combination of theoretical analysis, numerical calculation and experimental research is used to detect the performance index of DPF. Based on the theory of packed bed trapping, a mathematical model of particle capture process was established. The micropore diameter and particle size of the filter were calculated and analyzed by Matlab simulation. The influence of exhaust flow rate and exhaust temperature of diesel vehicle on three kinds of trap mechanism. The capture process of wall-flow particle trap is analyzed, the mathematical model of DPF pressure drop under no-load and load is established, and the curve relation between exhaust flow rate and pressure drop is obtained. At the same time, the FLUENT software of computational fluid dynamics is used to mesh the three-dimensional model of particle trap and the boundary conditions are set, and the distribution of internal velocity, pressure and temperature of particulate matter captured by DPF is further analyzed theoretically. And the movement of the internal airflow. According to the existing instruments and equipment in the laboratory, and in the light of the characteristics and requirements of the emission control technology of diesel vehicles in China at the present stage, as well as the national standard GB17691-2005 < vehicle pressure ignition type in use, Gas fuel ignition engine and automobile exhaust emission limits and measurement methods > and HJ451-2008 < technical requirements for environmental protection products diesel vehicle exhaust aftertreatment device > and so on. Completed the diesel vehicle detachable DPF performance test bench. Through the performance test of particle trap, the correctness of DPF capture process, no-load, pressure drop mathematical model and theoretical analysis are verified. The results show that Brownian diffusion plays a dominant role in the whole process of particle trapping. Decreasing the exhaust flow rate and increasing the exhaust temperature can increase the Brownian diffusion trapping coefficient and the comprehensive trapping coefficient. However, the exhaust flow rate and exhaust temperature have little effect on the mechanism of direct interception and capture. With the increase of exhaust flow of diesel engine, the pressure drop of no-load and load DPF increases linearly, but the pressure drop of load DPF is much higher than that of no-load. Finally, it is concluded that the performance index of the sample accords with the national standard, and it also lays the theoretical basis and experimental foundation for the development of DPF with high capture efficiency.
【学位授予单位】：东北林业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.172
本文编号：2439049
[Abstract]:Compared with gasoline vehicle, diesel vehicle has many advantages, such as high power, low emission, good dynamic performance, high reliability, long service life, etc. Therefore, from the perspective of saving energy and reducing fuel cost, it is of great significance to popularize and use diesel vehicle. However, the emission of harmful particulate matter from diesel vehicles is 70 times higher than that of gasoline vehicles. This kind of particulate matter pollutes the environment seriously and endangers human health. Therefore, the purification technology of diesel vehicles has always been a hot spot of research. Particle trap (Diesel Particulate Filter, DPF) is the most effective post-treatment purification device for controlling particulate emission from diesel vehicles. With the increasingly stringent emission regulations in China, the emission limit of the post-treatment device becomes lower and lower. This requires the detection methods of post-processing technology to be continuously improved and perfected. Therefore, it is very necessary to carry out the research of diesel vehicle DPF. In this paper, a combination of theoretical analysis, numerical calculation and experimental research is used to detect the performance index of DPF. Based on the theory of packed bed trapping, a mathematical model of particle capture process was established. The micropore diameter and particle size of the filter were calculated and analyzed by Matlab simulation. The influence of exhaust flow rate and exhaust temperature of diesel vehicle on three kinds of trap mechanism. The capture process of wall-flow particle trap is analyzed, the mathematical model of DPF pressure drop under no-load and load is established, and the curve relation between exhaust flow rate and pressure drop is obtained. At the same time, the FLUENT software of computational fluid dynamics is used to mesh the three-dimensional model of particle trap and the boundary conditions are set, and the distribution of internal velocity, pressure and temperature of particulate matter captured by DPF is further analyzed theoretically. And the movement of the internal airflow. According to the existing instruments and equipment in the laboratory, and in the light of the characteristics and requirements of the emission control technology of diesel vehicles in China at the present stage, as well as the national standard GB17691-2005 < vehicle pressure ignition type in use, Gas fuel ignition engine and automobile exhaust emission limits and measurement methods > and HJ451-2008 < technical requirements for environmental protection products diesel vehicle exhaust aftertreatment device > and so on. Completed the diesel vehicle detachable DPF performance test bench. Through the performance test of particle trap, the correctness of DPF capture process, no-load, pressure drop mathematical model and theoretical analysis are verified. The results show that Brownian diffusion plays a dominant role in the whole process of particle trapping. Decreasing the exhaust flow rate and increasing the exhaust temperature can increase the Brownian diffusion trapping coefficient and the comprehensive trapping coefficient. However, the exhaust flow rate and exhaust temperature have little effect on the mechanism of direct interception and capture. With the increase of exhaust flow of diesel engine, the pressure drop of no-load and load DPF increases linearly, but the pressure drop of load DPF is much higher than that of no-load. Finally, it is concluded that the performance index of the sample accords with the national standard, and it also lays the theoretical basis and experimental foundation for the development of DPF with high capture efficiency.
【学位授予单位】：东北林业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：U464.172
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