【作者】 刘孟祥；

【导师】 龚金科； 钟志华；

【作者基本信息】 湖南大学 ， 车辆工程， 2008， 博士

【摘要】 针对三效催化转化器转化效率低、起燃温度较高、工作寿命较短以及工作过程排放控制效率较低等现实存在的问题,将机理建模、数值模拟、多学科设计优化以及人工智能等理论应用于三效催化转化器的研发以及工作环境优化匹配过程中,以期探索一种更为有效、合理的高效长寿低排放三效催化转化器优化设计理论及方法,使三效催化转化器转化效率高、起燃温度较低、工作寿命较长以及工作过程排放控制效率高等性能,这对于提高汽车三效催化转化器的排放控制水平,探索新的三效催化转化器研发方法和技术都具有重要的理论意义和现实意义。本文以湖南大学“985”二期——汽车先进设计制造技术科技创新平台(动力排放与电控子项目)(教重函[2004]1号)及湖南省科技攻关重点项目“车用三效催化转化器理论方法、关键技术及应用”(湘科计[2002]87号)为依托,以成功研发转化效率高、起燃温度较低、工作寿命较长以及工作过程排放控制效率高的三效催化转化器为目的,采取理论分析与实验研究相结合的方法,创新研究一种高效长寿低排放三效催化转化器优化设计理论及方法,论文的主要工作及创新点如下:(1)建立了包括流动与传热、化学反应等子模型在内的多形状三效催化转化器性能数学模型,提出了用于流动与传热守恒方程组计算的控制容积逐面叠加法以及湍流流动压力场数值解法,以椭圆截面为代表的非圆柱形载体进行数值模拟,并分析了椭圆率、载体长度与载体截面积耦合、载体孔密度与孔壁厚耦合对三效催化转化器性能的影响,为多形状三效催化转化器性能研究提供了坚实的理论基础。(2)基于汽车三效催化转化器中气相和固相(载体表面)的质量平衡和能量平衡原理,建立了包括多基元催化反应机理、催化剂表面覆盖度变化、Ce储放氧的化学反应等子模型的多基元反应的三效催化转化器转化特性数学模型,模拟结果表明,转化效率模拟结果、气体组分分布与催化剂表面覆盖度变化模拟结果、三效催化转化器冷起动模拟结果以及助催化剂的储放氧能力模拟结果均与试验结果相吻合。(3)从烧结速率以及反应速率建立了包含劣化过程的三效催化转化器的劣化特性模型,对三效催化转化器老化特性进行数值仿真,结果表明:在老化过程中,Pt颗粒平均直径迅速增大,而失活因子在老化后迅速减小,催化剂的活性下降最大。在三效催化转化器100000km老化后, HC、CO、NOx三种气体的转化效率都降低20%以上。为此,从催化剂及其分布等方面提出了三效催化转化器的抗劣化措施,为三效催化转化器结构优化和性能改进提供了一定的依据。(4)首次提出了高效长寿三效催化转化器多学科优化设计方法,即以三效催化转化器转化效率、压力损失、质量以及抗热冲击性能为目标函数建立了多学科设计优化模型,系统研究基于多形状、多工况等几何、结构以及状态约束下高效长寿三效催化转化器的整体优化,采用高效长寿三效催化转化器多学科优化设计方法后,结果表明,三效催化转化器转化效率η提高了5.42%,压力损失Δp下降了6.99%,质量M减少了11.68%,位移变形Δε减少了20.91%,整体性能U提高了8.40%。这为高效长寿低污染三效催化转化器的优化设计提供了有力的理论指导。(5)采用最小二乘法和最小二乘支持向量机建立汽油机空气质量流量测量动态模型,基于椭圆齿轮油耗测量传感器测量原理建立了汽油质量流量测量模型,应用小波分析提取或者去除信号中的白噪声,分别采用剔除跳变信号算法及递推平均滤波算法剔除测量信号所出现的跳动性和波动性,并对去噪声处理后数据的进行函数链神经网络拟合,有效地消除采集数据时各种干扰的存在。并针对三效催化转化器工作环境参数信号特点,设计了模糊神经网络控制器和采用串行编程与ODBC技术相结合成功地开发了三效催化转化器工作环境热工状况监测系统,为确保三效催化转化器工作环境优化匹配提供有力的技术支持。汽油机三效催化转化器台架实验结果表明,本文研发的三效催化转化器的起燃温度大约在255℃左右。将三效催化转化器在国家汽车检测中心(襄樊)进行整车匹配后的排放检测实验,结果表明:本文研发的三效催化转化器对三种废气的转化效率均在92%以上,各项性能指标均满足欧IV排放标准限值。汽油机三效催化转化器与整车配套使用结果表明,本文研发的三效催化转化器与整车装车使用寿命长达120000km以上。更多还原

【Abstract】 In this dissertation, in view of real problems, such as low conversion efficiency, high light-off temperature, a shorter working life as well as Inefficient control of emissions in the working process in Three-Way catalytic Converter(TWC), the theory including mechanism modeling, numerical simulation, and multi-disciplinary design optimization and artificial intelligence, etc. is applied to TWC for exploring a design optimization theories and methods of effective, rational, efficient , longevous and low- emission TWC, Which improve the TWC characteristics of high efficiency, low light-off temperature, a longer working life, as well as efficient emissions control performance in the working process. It is of great theoretical and practical significance to explore new TWC development methods and techniques, which improve the level of emission control of the automotive TWC.In this paper, based on Hunan University"985" the second phase project, " Scientific and technological innovation platform for advanced automotive design and manufacture technology " (electronic control and power emission subproject) (key project of the Ministry of Education [2004] 1), and focusing scientific and technological project in Hunan Province, " research and development on automotive TWC "( Hunan Science and technology research project [2002] 87) , a design optimization theory and methods of highly efficient, longevous and low-emission TWC is studied through the combination method of theoretical analysis with experimental study for the purpose of the successful research and development on TWC with characteristic of higher conversion efficiency, lower light-off temperature, a longer working life, as well as highly efficient emission control process. The main work and innovation of the paper are as follows:A mathematical model of multi-shape TWC performance including sub-models, such as the flow and heat transfer, chemical reactions is established, and side-by-stacking method of the volume control for the conservation of flow and heat transfer equations calculating, as well as the numerical solution in turbulent flow pressure field is put forward. Non-cylindrical monolith represented by elliptical cross section carries out numerical simulation and the effect of ellipticity, the length of monolith coupled with cross-sectional area, the monolith hole density coupled with the hole wall thickness on the TWC performance is analyzed, Which provides a solid theoretical foundation for the study of multi-shape TWC performance.Based on principle of the mass and energy balance of the gas and solid phase (monolith surface) in the automobile TWC, the multi-element response and conversion features mathematical model in the TWC is established including sub-models, such as a multi-million-catalytic reaction mechanism, the catalyst surface coverage changes, Ce storage of oxygen chemical reaction. The simulation of conversion efficiency, the gas composition and distribution, the catalyst surface coverage changes, the cold-start of the TWC as well as the catalyst oxygen storage capacity coincides with the test results very well.The TWC deterioration characteristics model is established from the sintering rate and the response rate including the deterioration process, the TWC aging characteristic is simulated numerically, the results show that in the aging process, an average diameter of Pt particles increases rapidly, and the inactivation factor in the aging rapidly decreases, the activity of the catalyst declines largest. After 100,000 km aging of the TWC, HC, CO, NOx conversion efficiency reduces by 20 percent or more. To this end, TWC anti-aging measures are proposed from catalyst and its distribution, which provides a basis for the structure optimization and performance improvement of TWC.For the first time, multidisciplinary design optimization method is put forward for highly efficient, longevous and low-emission TWC which objective function includes conversion efficiency, pressure loss, mass and thermal shock resistance of TWC, in which based on more shape and working condition, such as geometry, structure and state bound, the overall optimization of highly efficient, longevous TWC is systematically studied. Through the method, the results show that the TWC conversion efficiencyηincreases by 5.42 percent, pressure lossΔp decreases by 6.99 percent, the mass M reduces by 11.68 percent, displacement deformationΔεreduces by 20.91 percent, and overall performance improves up to 8.40 percent. The method provides optimization design for highly efficient, longevous and low-emission TWC with strong theoretical guidance.Using the least square method and least squares support vector machines, the gasoline engine air mass flow measurement dynamic model is built,and Based on oval gear sensor fuel consumption measuring principle,gas mass flow measurement model is established. With the signal of white noise extracted or removed using wavelet analysis , and measurement signal beating and volatility removed by respectively using eliminating hopping signal algorithm and average recursive filter algorithm, and with function chain neural network fitting for the noise data processing, the interference of the various data collection is effectively eliminate. To provide strong technical support for the working environment optimization match in TWC, a fuzzy neural network controller is designed according to the TWC work environment characteristics of the parameters signal,and thermal situation of the working environment monitoring system of TWC is successfully developed by combining Serial Programming with ODBC technology.Gasoline engine TWC bench test results show that, the light-off temperature of the TWC developed in this paper is about 255℃, emissions testing of the TWC matched with the vehicle tested in the National Automotive Test Center (Xiangfan)show that, the exhaust gas conversion efficiency of the TWC developed is more than 92 percent, the performance indicators meets the European IV emission standards limit, the useful time of TWC with Vehicle loaded is up to more than 120,000 km.更多还原