基于GT-Power和KIVA-3V的柴油机性能及排放优化研究

发布时间：2018-01-28 07:48

  本文关键词： 柴油机 配气正时 数值模拟 KIVA-3V NOX Soot　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：配气正时直接影响着内燃机的换气过程优劣,尤其是充气效率、扫气效率和换气损失。换气过程的好坏决定了缸内燃烧品质,从而影响着发动机的动力性、经济性、排放水平及其可靠性。发动机处于高转速时,一般需要设置较大的气门重叠角及进气门迟闭角,减少缸内残余废气量和增加进入气缸的新鲜充量,提高输出功率;发动机处于低转速或怠速运转时,需要设置较小的气门重叠角及进气门迟闭角,以获得较好的怠速稳定性。考虑到要兼顾高低转速时发动机的性能,就要选择一种折衷的配气正时方案,使得发动机的整体性能水平发挥到最佳。本文利用GT-Power软件建立某9.5L增压中冷柴油机仿真模型,研究进排气门正时对发动机动力性能和燃油经济性的影响。计算并输出用于KIVA-3V计算的ESC工况缸内初始边界条件,运用KIVA-3V程序验证配气正时优化前后的排放水平。主要内容及结论如下:根据配气正时优化范围设计正交试验表格,利用已建立的9.5L柴油机仿真模型,确定对柴油机燃油消耗率影响的显著性因子为排气正时角EVT,并对其开展单因子7水平细化分析,最终确定最佳燃油消耗率下的配气正时组合为进气正时角228.5°CA;排气正时角127.2°CA。配气正时优化后,发动机工况区域(1100~1700rpm,40%~100%负荷)的燃油消耗率平均优化1.18%,即从191.34g/kWh降到189.07g/kWh;工况区域的扭矩平均提升1.2%,即从1157.52Nm提升到1171.22Nm。通过GT-Power仿真分析不同排气正时角对发动机动力性、燃油经济性和排放水平的影响。结果显示,随着排气正时角的推后,发动机的性能稳步提升,燃油经济性大幅改善。以1700rpm-100%负荷工况为例,排气正时角从111°CA调整到127.2°CA时,发动机扭矩从1401.14Nm提升到1527.23Nm,提升比例为9.0%;燃油消耗率从221.661 g/kWh下降到203.36 g/kWh,下降比例为8.1%。NOX排放随着排气正时角的推后而升高,Soot排放则随着排气正时角的推后而降低。鉴于将排气门正时从119.5°CA调整到127.2°CA时,NOX排放有所增加,本文随后利用燃烧排放模拟精度较高的KIVA-3V程序,进行了该发动机的燃烧排放研究。先利用发动机实验数据,进行了KIVA-3V程序中燃烧模型和排放模型的验证。随后进行了配气正时优化后发动机的燃烧和排放数值模拟及分析。模拟结果表明,配气正时优化前后发动机均达到了国四排放水平。这就使得本文的配气正时优化,不仅保证了排放水平,同时改善了发动机的动力性和燃油经济性。
[Abstract]:The timing of air distribution directly affects the quality of the internal combustion engine's air exchange process, especially the air filling efficiency, the scavenging efficiency and the air exchange loss. The quality of the in-cylinder combustion is determined by the quality of the air exchange process, which affects the engine's power performance. Economy, emission level and reliability. When the engine is at high speed, it is generally necessary to set a large valve overlap angle and intake valve late closing angle to reduce the residual exhaust gas in the cylinder and increase the fresh charge into the cylinder. Increasing output power; When the engine is running at low speed or idle speed, it is necessary to set small valve overlap angle and inlet valve late closing angle to obtain better idling stability. It is necessary to choose a compromise timing scheme to make the overall performance level of the engine to the best. A 9.5L turbocharged and intercooled diesel engine simulation model is established by using GT-Power software in this paper. The influence of intake valve timing on engine dynamic performance and fuel economy is studied. The initial boundary conditions in ESC operating conditions for KIVA-3V calculation are calculated and outputted. The emission level before and after timing optimization is verified by KIVA-3V program. The main contents and conclusions are as follows: the orthogonal test table is designed according to the optimal range of timing optimization. Using the established 9.5L diesel engine simulation model, the significant factor of the diesel fuel consumption rate is determined as the exhaust timing angle EVT, and the single factor 7 level refinement analysis is carried out. Finally, it is determined that the timing combination of gas distribution under the optimal fuel consumption rate is 228.5 掳CA. The exhaust timing angle is 127.2 掳CA.After the timing optimization, the average fuel consumption rate of the engine operating region is optimized by 1.18%. That is, from 191.34g / kWh to 189.07g / kWh; The average torque in the operating region is 1.2, that is, from 1157.52Nm to 1171.22Nm. The dynamic performance of the engine with different exhaust timing angles is analyzed by GT-Power simulation. The effect of fuel economy and emission level. The results show that the engine performance improves steadily with the delay of exhaust timing angle. The fuel economy was greatly improved. Taking 1700rpm-100% load condition as an example, the exhaust timing angle was adjusted from 111 掳CA to 127.2 掳CA. The engine torque was raised from 1401.14Nm to 1527.23Nm, and the lifting ratio was 9.0Nm. Fuel consumption decreased from 221.661 g / kWh to 203.36 g / kWh.Nox emissions increased with the delay of the timing angle of exhaust. The emission of Soot decreased with the delay of exhaust timing angle, whereas the emission of Soot increased when the timing of exhaust valve was adjusted from 119.5 掳CA to 127.2 掳CA. In this paper, the combustion emission of the engine is studied by using the KIVA-3V program with high accuracy of combustion emission simulation. First, the engine experimental data are used. The combustion model and emission model in the KIVA-3V program are verified. Then the combustion and emission numerical simulation and analysis of the engine after timing optimization are carried out. The simulation results show that. The engine before and after timing optimization has reached the level of four national emissions, which makes the timing optimization of this paper not only ensure the emission level, but also improve the engine power performance and fuel economy.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK421.5

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