【摘要】：柴油車與汽油車相比,具有功率大、低排放、動力性能好、可靠性高、使用壽命長等優(yōu)點,因此從節(jié)約能源、降低燃料成本角度來講,柴油車的推廣使用具有重要意義。但柴油車有害顆粒物的排放卻是汽油車的30～70倍,這種顆粒物嚴(yán)重地污染環(huán)境并危害人類健康,因此其凈化技術(shù)一直是人們研究的熱點。顆粒捕集器(Diesel Particulate Filter, DPF)是控制柴油車微粒排放最有效的后處理凈化裝置,隨著我國排放法規(guī)的日益苛刻,后處理裝置的排放限值越來越低,這就要求后處理技術(shù)的檢測方法不斷地進行改進和完善。因此深入開展柴油車DPF的研究是十分必要的。本文主要采用理論分析、數(shù)值計算、試驗研究相結(jié)合的方法對DPF的性能指標(biāo)進行檢測研究。通過基于填充床捕集理論建立了微粒捕集過程的數(shù)學(xué)模型,并利用Matlab模擬計算分析了過濾體的微孔孔徑、捕集微粒粒徑、柴油車的排氣流量和排氣溫度對顆粒捕集器三種捕集機理的影響。分析了壁流式顆粒捕集器的捕集過程,建立了空載和負(fù)載時DPF壓降的數(shù)學(xué)模型,得出了排氣流量隨壓降變化的曲線關(guān)系。同時運用計算流體力學(xué)的FLUENT軟件對顆粒捕集器三維模型進行網(wǎng)格劃分和邊界條件的設(shè)定,從理論上進一步分析了DPF捕集顆粒物時內(nèi)部流速、壓力和溫度的分布情況,以及內(nèi)部氣流的運動情況。根據(jù)試驗室現(xiàn)有的儀器設(shè)備,并結(jié)合現(xiàn)階段我國柴油車排放控制技術(shù)的特點和要求,以及國家在用標(biāo)準(zhǔn)GB17691-2005《車用壓燃式、氣體燃料點燃式發(fā)動機與汽車排氣污染物排放限值及測量方法》和HJ451-2008《環(huán)境保護產(chǎn)品技術(shù)要求柴油車排氣后處理裝置》等相關(guān)內(nèi)容,完成了柴油車可拆卸式DPF性能檢測試驗臺架的搭建。通過顆粒捕集器的性能檢測試驗,驗證了DPF捕集過程、空載、負(fù)載時壓降數(shù)學(xué)模型以及理論分析的正確性。結(jié)果表明在整個微粒捕集過程中,布朗擴散起主導(dǎo)作用,減小排氣流量和提高排氣溫度均能提高布朗擴散捕集系數(shù)和綜合捕集系數(shù),而排氣流量和排氣溫度對直接攔截捕集機理的影響不大；隨著柴油機排氣流量的增加,空載和負(fù)載DPF的壓降都近似呈線性增加,而負(fù)載DPF的壓降值要比空載時高很多。最后得出,該樣品的各項性能指標(biāo)符合國家標(biāo)準(zhǔn),同時也為研發(fā)高捕集效率的DPF奠定理論依據(jù)和試驗基礎(chǔ)。
[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.
【學(xué)位授予單位】：東北林業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：U464.172

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