基于KIVA的柴油机常规排放物变参数研究

发布时间：2018-01-16 04:14

本文关键词：基于KIVA的柴油机常规排放物变参数研究　出处：《河北工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着环境污染日益严重,排放法规越来越严格,如何能进一步降低柴油机排放成为现如今最重要的课题。柴油机以其高动力性和低燃油消耗率在动力装置方面得到广泛应用,柴油机的主要常规排放物有NOX,HC,CO和SOOT。由于计算科学的不断发展以及计算机运算能力的提高,数值模拟成为研究燃烧过程的重要手段。数值模拟耗时短,费用低,能获取大量试验无法得出的流场信息。本文以KIVA软件为研究工具,应用KIVA软件中的前处理器对4102柴油机的燃烧室进行了网格划分,并确定了计算的初始参数和边界条件,然后进行了数值模拟计算,模拟结果和实验结果较为吻合,说明建立的燃烧模型真实可行。计算分析了不同EGR对柴油机燃烧和排放性能的影响,为了确定CO2、H2O和N2这三种气体对柴油机燃烧与排放的影响差别,分别用它们来弥补氧气量的减少以维持进气量的总量不变,进行了EGR率为3%,6%,9%三个工况的九组模拟计算。结果表明三种气体对柴油机缸内燃烧及HC、NOX、CO和SOOT污染物排放的影响大致相同:都是随着EGR量增加,缸内最大爆发压力和最高燃烧温度呈下降的趋势,其峰值出现的位置越接近压缩上止点,且高温持续时间缩短,燃烧始点随着EGR率的增大而后移;HC最终排放量也逐渐升高;NOX最终排放量显著下降;CO最终排放量随着EGR率的增大而减小;SOOT最终排放量随着EGR率的增大而增大;但最终数值却不尽相同,发现在废气再循环中起主要作用的还是它的稀释效应,而化学效应和热效应起的作用较小。计算分析了不同负荷对柴油机燃烧和排放性能的影响,发现随负荷的增加,缸内平均压力和温度会逐渐增大,其最大爆发压力和最高燃烧温度也随之增大,曲线最大值所对应的曲轴转角向后推迟;最终的HC、NOX、CO和SOOT污染物排放量也是随之增大。计算分析了不同喷油提前角对柴油机燃烧和排放性能的影响,发现缸内最大爆发压力和最高燃烧温度随着喷油提前角的增大而增大,且其峰值出现的位置越接近于压缩上止点,燃烧始点随着供油提前角的前移而提前,高温持续时间增长;HC的最终排放量随喷油提前角的增大而减小;NOX生成量也随之增大;CO的最终排放量也随喷油提前角的增大而增大;但SOOT的排放量则是减少的趋势。
[Abstract]:With the increasingly serious environmental pollution, emission regulations are becoming more and more stringent. How to further reduce diesel engine emissions has become the most important issue nowadays. Diesel engine has been widely used in power plant because of its high power performance and low fuel consumption rate. The main conventional emissions of diesel engines are NOXCHCCO and SOOT.Because of the continuous development of computational science and the improvement of computer computing ability. Numerical simulation has become an important means to study combustion process. Numerical simulation takes short time, low cost, and can obtain a large amount of flow field information that can not be obtained by experiments. In this paper, KIVA software is used as a research tool. The combustion chamber of 4102 diesel engine was meshed with the preprocessor of KIVA software, and the initial parameters and boundary conditions were determined, and then the numerical simulation was carried out. The simulation results are in good agreement with the experimental results, which shows that the established combustion model is feasible. The effects of different EGR on the combustion and emission performance of diesel engine are calculated and analyzed in order to determine the CO2. The effect of H _ 2O and N _ 2 on combustion and emission of diesel engine is different. They are used to make up for the decrease of oxygen quantity to keep the total amount of air intake unchanged, and the EGR ratio is 3%. The results show that the effects of the three gases on the combustion in the cylinder and the emission of HCN NOXCO and SOOT pollutants in the diesel engine are approximately the same: both of them increase with the increase of the amount of EGR. The maximum burst pressure and the maximum combustion temperature in the cylinder showed a downward trend. The peak value was closer to the compression stop point, and the high temperature duration was shortened, and the combustion start point moved backward with the increase of EGR ratio. HC final emissions also increased gradually; The final emission of NOX decreased significantly; The final emission of CO decreases with the increase of EGR rate. The final emission of SOOT increases with the increase of EGR rate. But the final value is not the same, it is found that the main role in the exhaust gas recycling is its dilution effect. The influence of different load on combustion and emission performance of diesel engine is analyzed. It is found that the average pressure and temperature in cylinder will increase gradually with the increase of load. The maximum burst pressure and the maximum combustion temperature also increased, and the crankshaft rotation angle corresponding to the maximum curve was delayed. The final emissions of CO and SOOT also increased. The effect of different fuel injection advance angle on combustion and emission performance of diesel engine was calculated and analyzed. It is found that the maximum burst pressure and the maximum combustion temperature increase with the increase of the injection advance angle, and the position of the peak value is closer to the compression stop point, and the combustion start point advances with the advance angle of the fuel supply. The duration of high temperature increased; The final emission of HC decreases with the increase of fuel injection advance angle. The amount of NOX also increased. The final emission of CO also increases with the increase of fuel injection advance angle. But SOOT emissions are a decreasing trend.
【学位授予单位】：河北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK421;X701

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