共查询到19条相似文献,搜索用时 265 毫秒
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汽车排放的污染物主要是一氧化碳(CO)、碳氢化合物(HC)、氮氧化合物(NOx)及炭烟等。在相同工况下汽油机排放的CO、HC和NOx的排放量比柴油机大,因此目前国家标准中对汽油机主要限制CO、HC和NOx的排放量。而柴油机由于其燃烧时混合气形成的时间非常短,在空气不足或混合气不均匀的情况下主要是产生炭烟污染,因此排放标准中主要限制柴油机排气的烟度。 相似文献
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CNG缸内直喷发动机稀薄燃烧火焰传播过程影响因素的研究 总被引:1,自引:0,他引:1
在试验用单缸光学发动机上,采用可视化技术研究缸内CNG直喷稀薄燃烧过程中喷射方式和点火方式对火焰传播过程的影响,同时采用双喷油器、双火花塞,分析研究喷射时刻、喷射位置和点火时刻等参数对稀薄燃烧特性和NOx排放特性的影响。结果表明,在稀薄燃烧过程中,火花塞附近的混合气浓度梯度对火焰传播和燃烧稳定性影响很大;混合气浓度梯度越大,循环变动越小,燃烧更稳定,但NOx排放量也增加。可见,控制稀薄燃烧过程的关键是控制火花塞附近的混合气浓度梯度,而它又直接影响NOx的生成。 相似文献
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基于局部线性模型树的高压共轨柴油机排放模型 总被引:3,自引:0,他引:3
为研究面向闭环控制的柴油机在线排放模型,以1台高压共轨、涡轮增压中冷柴油机的转速、扭矩、空燃比、燃烧始点、燃烧重心、燃烧终点、最高燃烧温度、最大缸内压力等运转和燃烧的各项参数为基础,运用局部线性模型树对排放物HC,CO,CO2,NOx和烟度进行了仿真研究。研究结果表明,以转速、扭矩、空燃比为输入时,CO,CO2,NOx的仿真结果与试验值具有较好的一致性,以转速、扭矩、空燃比、燃烧重心为输入时,HC、烟度的仿真结果与试验值具有较好的一致性。各排放的期望响应与仿真输出的平均误差在10%以内,线性回归相关系数达到0.96以上。各个排放物的仿真过程单独进行时,可以得到较好的仿真效果。因此,局部线性模型树模型适用于高压共轨柴油机排放物的仿真。 相似文献
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Numerous research has been devoted to finding a method to simultaneously reduce NOx and soot emissions from diesel engines. In-cylinder EGR stratification is a technique that simultaneously reduces NOx and soot using a nonuniform EGR distribution in the combustion chamber. To study the potential of in-cylinder EGR stratification, a new combustion model is required that considers the non-uniform EGR distribution and the chemical kinetics. In this study, a new combustion model, the Flamelet for Stratified EGR (FSE) model, was developed to consider the non-uniform in-cylinder gas distribution based on chemical kinetics. The concept of the FSE model is based on using multiple flamelets with the multizone concept. To describe the non-uniform gas distribution, the combustion chamber is divided into several zones by oxygen concentration at the start of injection. Then, the flamelet equations are solved at the boundary of each zone. The final species mass fraction of each cell is calculated using linear interpolation between two results from the boundaries. In this paper, the FSE model was validated under in-cylinder EGR stratification conditions, and then, the potential of in-cylinder EGR stratification was studied by using the FSE model. The effect of in-cylinder EGR stratification was verified under various injection timing, engine speed, and road conditions with optimized engine geometries. The results shows simultaneous NOx and soot reductions under the stratified EGR condition. 相似文献
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U. B. Azimov K. S. Kim D. S. Jeong Y. G. Lee 《International Journal of Automotive Technology》2009,10(3):265-276
The concept of Low Temperature Combustion (LTC) has been advancing rapidly because it may reduce emissions of NOx and soot
simultaneously. Various LTC regimes that yield specific emissions have been investigated by a great number of experiments.
To accelerate the evaluation of the spray combustion characteristics of LTC, to identify the soot formation threshold in LTC,
and to implement the LTC concept in real diesel engines, LTC is modeled and simulated. However, since the physics of LTC is
rather complex, it has been a challenge to precisely compute LTC regimes by applying the available diesel combustion models
and considering all spatial and temporal characteristics as well as local properties of LTC. In this paper, LTC regimes in
a constant-volume chamber with n-Heptane fuel were simulated using the ECFM3Z model implemented in a commercial STAR-CD code.
The simulations were performed for different ambient gas O2 concentrations, ambient gas temperatures and injection pressures. The simulation results showed very good agreement with
available experimental data, including similar trends in autoignition and flame evolution. In the selected range of ambient
temperatures and O2 concentrations, soot and NOx emissions were simultaneously reduced. 相似文献
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以点燃式汽油转子发动机为研究对象,建立了相应的湍流和燃烧模型,实现了发动机工作过程的三维动态模拟,并利用试验结果进行对比验证。在此模型基础上,模拟计算和分析了4种不同点火位置对缸内压力、温度、火焰传播及NO_x生成的影响。结果表明:点火位置选择在燃烧室中轴线上,与转子凹坑中心位置重合,能优化燃烧,获取较大的功率;在燃烧室后部点火时,燃烧初期火焰传播速度快,压力升高率大,但是受限于燃烧室后部燃料少,压力峰值不高,且NO_x的生成量偏高;在燃烧室前部点火时,在补燃期阶段燃烧速度最快,但是点燃后压力升高阶段的燃烧效率一般;点火位置位于燃烧中轴线两侧错位排布时,燃烧效率低下导致压力峰值最低,同时NO_x的生成量稍高;一定工况下,双点火位置的坐标分别为(10 mm,-56 mm,-37.2 mm)和(-10 mm,-56 mm,-37.2mm)时,该发动机能获得最大的功率且NO_x生成量较少。 相似文献
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U. B. Azimov E. A. Roziboyev K. S. Kim D. S. Jeong Y. G. Lee J. E. Yun 《International Journal of Automotive Technology》2008,9(5):523-534
In this study, a visual investigation of sprays and flames is performed, and soot formation in Diesel-GTL fuel blends is studied
in a specially designed quiescent constant-volume chamber under various ambient gas temperatures and O2 concentrations. Similar to the case of soot formation during diesel fuel combustion, the sooting zone during the mixing-controlled
combustion of Diesel-GTL blends is located in the leading portion of the jet boundaries. Auto-ignition delay and soot concentration
decrease with an increase of GTL content in the fuel blend. Soot also decreases with lower O2 concentration, higher injection pressure, and lower ambient gas temperature. The lack of soot formation at lower O2 concentrations and lower temperatures suggests that Diesel-GTL fuel blends can be successfully utilized in low-temperature
diesel combustion technologies that are currently being developed. Furthermore, this mixing controlled combustion method with
Diesel-GTL blends can be used to modulate various engine operation parameters, and therefore to simultaneously reduce the
formation of soot and NOx within a wide range of diesel engine loads. 相似文献
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以降低瞬态过程烟度和NO_x排放为目标,在一台高压共轨电控重型柴油机上进行了EGR对柴油机恒转速增扭矩5s典型瞬态过程燃烧和排放性能影响的优化研究。结果表明:瞬态过程中固定EGR阀开度造成EGR率"超调"、烟度剧增;与"全程轨压"策略相比,"分段轨压"有利于改善小负荷工况的燃烧热氛围,提高瞬态起始负荷并耦合"分段轨压"可以有效降低瞬态过程烟度峰值;EGR阀的开闭对瞬态性能影响最大,瞬态过程1.5s关阀、4s开阀的策略可以实现较好的烟度和NO_x排放折中,消光烟度峰值为9.2%,NO_x峰值稍有增加但增幅不大。 相似文献
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针对预混合氢气的柴油机,在AVL Fire软件上建立了计算模型,并与试验结果进行对比,验证模型的准确性。在此基础上改变了喷射策略,对发动机缸内工作过程及相应的燃烧和排放性能进行数值模拟和分析。研究结果表明:随着预混合氢气质量分数的增加,缸内压力和温度升高,NOx 排放恶化,Soot排放改善;随着预喷射油量和预喷间隔角的增加,NOx 质量分数升高,Soot质量分数降低;随着后喷射喷油量的增加,缸内压力和放热率稍微减小,NOx 和Soot质量分数降低;随着后喷间隔角的增加,缸内压力、放热率、NOx 和Soot排放均未发生明显变化。 相似文献