本文選題：壓燃式發(fā)動(dòng)機(jī)　切入點(diǎn)：汽油/柴油混合燃料　出處：《吉林大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著環(huán)境污染越來越嚴(yán)重， PM2.5、霾逐漸成為社會(huì)的關(guān)注點(diǎn)。而內(nèi)燃機(jī)排放作為城市大氣的重要污染來源也越來越受到重視。相比于汽油機(jī)，柴油機(jī)的微粒排放是其的幾十倍以上，因此，我國乃至全世界范圍內(nèi)都對(duì)柴油機(jī)排放微粒進(jìn)行了嚴(yán)格要求。隨著排放法規(guī)的日益嚴(yán)格，近幾年來，新的燃燒理論也逐漸發(fā)展。由于汽油燃料揮發(fā)性較好，，能很好的解決預(yù)混合化的問題，目前已有研究學(xué)者對(duì)汽油/柴油混合燃料對(duì)發(fā)動(dòng)機(jī)燃燒與排放的影響進(jìn)行了研究。而柴油機(jī)微粒捕集器（DPF）作為柴油機(jī)減少微粒排放的重要手段之一，研究其對(duì)使用混合燃料的微粒排放的捕集特性具有重要意義。 本文主要采用模擬計(jì)算與試驗(yàn)的手段針對(duì)DPF對(duì)柴油機(jī)超細(xì)微粒的捕集特性開展研究工作。對(duì)DPF內(nèi)部的兩相流運(yùn)動(dòng)進(jìn)行了模擬仿真分析，探討了邊界條件以及微粒捕集器結(jié)構(gòu)參數(shù)對(duì)氣流均勻性的影響。同時(shí)試驗(yàn)研究了柴油機(jī)在不同工況、不同邊界條件以及使用不同汽油添加比例的汽油/柴油燃料時(shí)，DPF對(duì)不同模態(tài)的微粒的捕集效率。研究結(jié)果表明： 1）通過使用ANSYS FLUENT軟件對(duì)DPF內(nèi)部進(jìn)行模擬分析，本文主要研究了0.1m及0.3m粒徑的微粒在DPF內(nèi)部的濃度分布。從結(jié)果可以看出，隨著微粒直徑的減小，微粒的慣性相應(yīng)減小，當(dāng)微粒足夠小時(shí)將沿布朗運(yùn)動(dòng)軌跡進(jìn)行運(yùn)動(dòng)，因此整個(gè)DPF內(nèi)的微粒濃度分布的均勻性很好。 2）研究了不同壁面滲透率、不同過濾孔道寬度、不同入口進(jìn)氣速度、不同擴(kuò)張角對(duì)DPF內(nèi)部氣流運(yùn)動(dòng)均勻性的影響。壁面滲透率與過濾孔道寬度的大小并不影響氣相流場分布的均勻性，只影響速度值的大小。減小入口進(jìn)氣速度能提高DPF內(nèi)流速分布的均勻性，但入口進(jìn)氣速度受到柴油機(jī)工況的制約，不能隨意的改變。減小擴(kuò)張角可以迅速的提高流速分布及微粒濃度分布的均勻性。同時(shí)采用離散相模型對(duì)過濾孔道內(nèi)的微粒運(yùn)動(dòng)軌跡進(jìn)行了研究，隨著DPF軸向位置的增加，氣流速度在進(jìn)氣孔道內(nèi)減小，在排氣孔道內(nèi)增大,在出口處達(dá)到最大；而壁面滲流速度也逐漸增大。 3）DPF對(duì)不同模態(tài)微粒的都具有很高的捕集效率。其中，DPF存在核態(tài)和積聚態(tài)兩個(gè)穿透窗口，而當(dāng)發(fā)動(dòng)機(jī)排放微粒在此穿透窗口處存在較多微粒時(shí)，會(huì)影響DPF對(duì)此粒徑微粒的捕集，導(dǎo)致DPF后此粒徑微粒比例增多。 4）對(duì)相同粒徑微粒，DPF的捕集效率與發(fā)動(dòng)機(jī)工況有關(guān)。存在最優(yōu)工況點(diǎn)。中等轉(zhuǎn)速、中等負(fù)荷時(shí)，DPF的捕集效率最大。與負(fù)荷相比，轉(zhuǎn)速的變化對(duì)DPF的捕集效率影響更大。隨著發(fā)動(dòng)機(jī)主噴定時(shí)提前，DPF前后核態(tài)微粒比例及超細(xì)微粒比例均升高。 5)對(duì)于不同汽油添加比例的燃料，相比與純柴油燃料，使用汽油添加比例為30%的燃料時(shí)，DPF前50nm以下的核態(tài)微粒比例有所降低，但DPF后核態(tài)微粒比例升高，由此可以說明，使用汽油/柴油混合燃料可以有效降低核態(tài)微粒的比例，但此時(shí)，有大部分核態(tài)微粒粒徑處于捕集器的核態(tài)穿透窗口處，導(dǎo)致DPF后核態(tài)微粒比例增多。對(duì)于超細(xì)微粒，DPF后微粒比例相比于使用純柴油燃料時(shí)在中高負(fù)荷時(shí)降低顯著，微粒數(shù)量最多降低了90%。因此，DPF可以有效控制使用汽柴油混合燃料的柴油機(jī)的超細(xì)微粒排放。
[Abstract]:With more and more serious environmental pollution, PM2.5, haze has gradually become a social concern. As an important source of pollution emissions and combustion atmosphere of the city is attracting more and more attention. Compared to the gasoline engine, the diesel particulate emission is dozens of times, therefore, China and the world within the scope of diesel engine emissions the particles of a strict requirement. With the increasingly stringent emission regulations, in recent years, the new combustion theory has gradually developed. Because of the gasoline fuel volatility is good, can be a good solution to the problem of pre mixing, at present scholars of gasoline / diesel fuel blends on engine combustion and emissions were studied. While the diesel particulate filter (DPF) is one of the important means to reduce the diesel particulate emissions, it is important to study the particulate emission of hybrid capture characteristics.
This paper mainly uses the simulation calculation and test means for DPF capture characteristics of diesel ultrafine particles to carry out research work. The movement of the DPF internal two-phase flow simulation analysis, discusses the boundary conditions and the DPF structural parameters on the flow uniformity influence. At the same time were studied in different diesel engine conditions, different boundary conditions and different proportion of the gasoline gasoline / diesel fuel, DPF of particles of different modes of trapping efficiency. The results show that:
1) by using ANSYS FLUENT software to simulate and analyze the internal DPF, this paper mainly studies 0.1M and 0.3m particle size particle concentration within the DPF distribution. From the results we can see that, with the decrease of particle diameter, particle inertia decreases, when the particle is small enough along the Brown motion trajectory, so uniformity the particle concentration distribution in the DPF is very good.
2) of different wall permeability, different filter channel width, different entrance velocity, different expansion angle of uniform airflow movement. The influence of DPF internal wall permeability and filtration pore width size does not affect the gas flow uniformity, only affect the speed value of the reduced intake speed can improve the entrance. The velocity distribution within the DPF uniformity, but the entrance inlet velocity is restricted by the operating condition of the diesel engine, can not arbitrarily change. Reduce the divergentangle can quickly improve the velocity distribution and particle concentration distribution. At the same time were studied by the particle trajectory, discrete phase model of the filtration pore, with the increase of DPF axial position air velocity in the intake, reduce the pore increases in the exhaust channel, reaches the maximum at the outlet; and the wall seepage velocity increases gradually.
3) DPF of different modal particles have high trapping efficiency. Among them, the existence of DPF nucleation and accumulation mode two through the window, and when there are many particles in the particle emission of the engine through the window at the time, this will affect the capture DPF particles, DPF particles lead to the proportion of increased.
4) on the same particles, the collection efficiency of DPF is related with the operating condition of the engine. The existence of the optimal operating point. Medium speed and medium load, the collection efficiency of DPF. The maximum load and speed compared to the change of DPF trapping efficiency greater impact. With the engine main injection timing, DPF and nuclear the proportion of state particles and ultrafine particles were increased.
5) for different proportion of added gasoline fuel, compared with pure diesel fuel, gasoline mixed with 30% fuel, the proportion of nucleation particles before DPF below 50nm decreased, but DPF increased the proportion of nucleation particles, which can show the use of gasoline / diesel blended fuel can effectively reduce the nucleation particles the proportion, but this time, most of the particle size in the nucleate nucleate collector through the window, resulting in DPF after nucleation particles increased. For ultrafine particles, compared the proportion of particles at DPF after using pure diesel fuel in high load decreased significantly, the largest number of particles reduces 90%. so DPF ultrafine particle emission in diesel engine to effectively control the use of gasoline and diesel fuel.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TK421.5

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