【作者】 李沛然；

【导师】 邓兆祥；

【作者基本信息】 重庆大学 ， 车辆工程， 2011， 博士

【摘要】 安装排气消声器是控制汽车排气噪声的主要手段。迄今为止,排气消声器性能的精确分析预测和精准设计仍是一个难题,消声器的设计开发需要高度依赖于经验知识,使得其设计工作变得难以把握,令许多设计人员倍感困惑。因此,在国内企业尚未掌握消声器的自主研发核心技术的情况下,突破和掌握汽车排气消声器研发的关键技术,研究和开发消声器设计专家系统,对加快消声器设计技术向产业的转移和推广,具有很大价值和现实意义。首先,将试验与仿真分析结合,研究隔板缝隙对消声性能的影响,反流插入管消声器压力损失的规律。研究结果表明:批量生产的消声器隔板形成的缝隙对共振式消声器消声性能有巨大影响;进口管离后壁的距离对压力损失的影响远胜于出口管,即当进口管短于出口管时,可以获得更低的压力损失;进口管离后壁的距离对反流插入管消声器的压力损失影响存在一个临界距离(称为临界壁面距离),如果离后壁的距离小于这个距离会造成压力损失急剧升高,离后壁的距离大于这个距离后压力损失变化很,临界壁面距离与进口管管径相关。这些客观规律的发现,有助于设计时合理地选择参数;同时为消声器设计专家系统储备设计规则和知识。其次,针对当前排气消声器性能的综合评价主要停留在基于个人经验和定性评价上的现状,以消声器特性为出发点,建立一系列针对汽车排气噪声、气流特点相适应的量化的性能指标,并通过层次分析法结合专家打分作为各指标加权依据,进行消声器消声性能的定量评价。通过对现有排气消声器传声损失试验结果进行横向比较、验证,表明该评价方法正确可行。然后研究消声器设计推理技术,围绕“消声器设计案例知识表达”、“消声器设计案例推理方法”、“消声器设计调整策略”提出了解决方法。特别是提出了一种实现汽车排气消声器内部结构表达的方法和判断消声器内部结构拓扑关系的算法,并提出了消声器设计案例推理结果案例相似度综合评判方法。解决了案例推理和规则推理在消声器设计中的应用难题。然后研究基于特征参数化建模技术的排气消声器快速建模方法,并在对商用声学有限元软件二次开发的基础上实现消声器消声性能的自动分析,拓展消声器专家系统应用。最后,基于上述研究,开发了集合专家系统、设计工具、分析工具等主要功能,包含排气消声器设计案例、设计知识、评价方法的数据库的汽车排气消声器设计专家系统——“ES2”。应用该系统在两款汽车消声器改进和设计中,其推理得到的消声器通过装车试验表明该系统具有很强的实用价值,设计出的消声器满足工程实际要求。上述研究跨车辆工程、人工智能、图形图像处理、管理科学等领域。将综合评价应用于消声器评价,使得消声器设计及其评价更具科学性;将专家系统与消声器设计结合,提高了消声器设计成功率;将参数化设计和自动分析技术融入消声器设计,提高了设计效率。汽车排气消声器设计专家系统在汽车零部件企业的应用,对迅速提高企业消声器设计水平,具有较大的促进作用。更多还原

【Abstract】 Using exhaust muffler is the main way to control automotive engine exhaust noise.To this day, exhaust muffler performance precision prediction and accurate design is still a problem. Its design is still highly dependent on the experience. As a result, the design work of exhaust muffler is harder to grasp and many designers feel so confused. In the case of the domestic enterprises have yet to master the muffler core R&D technique, the development muffler design expert system has a great value to speed up the muffler design technique to transfer and promotion of industrial.First of all, by the approach of combination with the experiment and simulation analysis, it develops studies on the effect of a baffle seam on reactive muffler acoustics and the effect of the distance between inlet-tube and back wall in reverse flow extended-tube chamber muffler on pressure drop. It results three key conclusions:①The baffle seam has undermined sound attenuation of resonant muffler or moves its resonant frequency.②In the reverse flow extended-tube chamber muffler, the distance between inlet tube and back wall has a greater impact than the outlet on pressure loss. In other words, if the inlet tube is shorter than the outlet tube, it can get a lower pressure loss.③There exists a critical distance between inlet tube and back wall in the reverse flow extended-tube chamber muffler. Less than this distance can cause pressure drop sharply rise. The critical distance is related to inlet-tube inner diameter. The discovery of objective laws is helpful for designers to choose parameters reasonably, and also reserves design rules and knowledge of the expert system for muffler design.Secondly, the performance evaluation of automotive exhaust muffler is still no unified approach and remains in the qualitative evaluation based on personal experience. This leads to the evaluation results arbitrary large and cannot be quantified. According to the present situation, it builds an evaluation system for multi-performance of automotive exhaust mufflers by establishing a series of indexes for each performance of mufflers and finds index’s weighting base on Analytic Hierarchy Process (AHP). It shows that the evaluation system is suitable and feasible for multi-performance comparison by using the evaluation system to evaluate the measured results of 5 passenger car mufflers. This evaluation system can be used in comparing different mufflers quantitatively.Thirdly, by developing the reasoning technique of muffler design, its proposed solutions for case representation, case reasoning and case revise on muffler design. In particular, it presents a representation method of the internal structure of exhaust muffler, an algorithm for determining of structure topology relations and a means of judging reasoning results similarity. With those studies, it achieves case-based reasoning and rule-based reasoning in muffler design.Fourthly, aiming to expand the scope of reasoning in muffler design, it also developed rapid prototyping methods of exhaust muffler by feature-based parametric modeling technique and achieves automatic computing by secondary development of commercial FEM software.Finlay, it’s built an expert system for automotive exhaust muffler design which names‘ES2’. The system integrates a collection of functions such as reasoning, design, analysis. And a database with design cases, design knowledge and evaluation methods for muffler design is also included. Using the system for developing two cars’muffler, the measured results show that the system has a strong practical value and the designed muffler meets the practical requirements of engineering.The above studies cross vehicle engineering, artificial intelligence, image processing, management science and other fields. Comprehensive evaluation of the application of the muffler evaluation makes the design and evaluation more scientifically. The application of expert system in muffler design improves the design success rate. The techniques of automatic analysis and parametric modeling in the blend of the muffler design make the design more efficient. The Implement of the expert system for muffler design in automobile parts enterprises has practical significance to improve their muffler design level.更多还原