【作者】 李民；

【导师】 舒歌群；

【作者基本信息】 天津大学 ， 动力机械及工程， 2009， 博士

【摘要】 本文通过虚拟设计和实验研究的方法,围绕内燃机结构声学特性及其优化这一主题,就内燃机低噪声结构优化设计方法、结构辐射噪声虚拟预测方法、组合体振动和声辐射特性、机械激励力的仿真等方面展开了研究。使用离散法对齿轮室盖声辐射特性进行了实验研究。研究了齿轮室盖壁厚、加强筋、约束条件、激励点位置等因素对齿轮室盖声辐射系数的影响。以试验研究和软件模拟为基础,结合现代优化设计理论,研究了进行内燃机整机进行声学结构优化的方法。针对油底壳、齿轮室盖、气缸盖罩等具体零件的特点,制定了不同的优化策略,采用HYPERWORKS/OPTISTRUCT软件,使用形状优化、形貌优化、拓扑优化等现代优化设计方法,完成以减低薄壁件结构辐射噪声为目的优化设计,并利用软件模拟的方法预测了优化设计的降噪效果。对YN4100QB柴油机机体,采用形状优化技术,选机体侧板、曲轴箱隔板厚度等12个设计变量,以机体的应变能、节点的水平位移、机体的重量为约束函数,以和裙部振型相关的模态频率的加权和为目标函数,完成了以提高机体裙部刚度为目标的优化设计,同时也进行了设计变量对响应变量的灵敏度分析。为了降低4100柴油机的噪声辐射,在机体下部使用了加强框,用发动机整机动力响应结果分析了加强框对机体裙部的减振效果,用有限元和边界元结合的方法预测了加强框对发动机整机的降噪效果。用实验研究的方法对缸盖-机体组合件的动态特性和声辐射特性进行了研究。通过模态实验和声辐射系数实验,研究了螺栓连接方式(贯穿螺栓连接和普通螺栓连接)及预紧力矩大小对缸盖-缸体组合件固有频率、结构阻尼,传递函数等动态特性和声辐射效率的影响规律。从解决发动机虚拟仿真结果和台架试验结果一致性问题出发,采用多体动力学仿真的方法,研究了多体动力学建模各环节对发动机主轴承载荷计算的影响。在ADAMS中建立刚柔混合的4100QB柴油机多体动力学模型,其柔性体部件包括:机体、缸盖、安装支架、连接法兰、曲轴、飞轮等,其它零件则为刚性体。通过比较不同模型间主轴承载荷的差异,探讨了发动机曲轴和机体的柔性、发动机的安装方式、悬置刚度、连接法兰、联轴节弹性等多体动力学建模因素对主轴承载荷计算的影响;利用实测的气缸体表面节点振动数据验证了多体动力学计算结果的有效性。更多还原

【Abstract】 Centering on key theme of structural acoustic characteristics and optimization for internal combustion engine, the study on the low noise structure design, noise radio virtual prediction, assemblies’vibration behavior and acoustic characteristics wereperformed by using virtual design and experiment method.The acoustic characteristics of gear-cover were investigated by using the Discrete Calculation Method (DCM). The influence of the thickness of the part, rib, constraint condition and the position of exciting force on the radiation efficiency wasalso explained.Based on the analysis of the result from experiment and simulation, by application of modern optimal design methods, the design for reducing radiated noisefrom the structure of internal combustion engine was accomplished. According to the structure characteristic of the oil pan, gear cover, cylinder head cover, different optimal strategies were made based on HYPERWORKS/OPTISTRUCT software. By the method of shape optimization, topology optimization, topography optimization, the optimized design to lower the radiated noise of the surface were accomplished, and the radiated noise of the optimization was also evaluated by software simulation.Shape optimization was performed on a cylinder block of 4100QB diesel engine.The maximum of nature frequency related with the shirt of the cylinder block was obtained by optimizing twelve structure dimensions of the cylinder block with constrains of flexibility of the cylinder block, the point displacement, the weight of the cylinder block, meanwhile the sensitivity analysis of the block was carried out to illustrate the variables’effect on the response of the structure, and their contribution to the optimization was also discussed. Aim to reduce the radiated noise from engine, ladder frame was used on 4100QB diesel engine, the improvement of vibration was evaluated by the result of frequency response by MSC/NASTRAN software, and the radiated noise was also predicted by using SYSNOISE software.The vibration behavior and acoustic characteristics of the assemblies wereinvestigated by experiments. The effect of the assembling method, with Tap-Bolts or with Through-Bolts, and the value of the tightening torque were explained by the parameters, such as nature frequency, damping ration, frequency response function and sound radiated efficiency. To validate the results of software simulation,bench scale test was necessary. A research on the influence of multi-body dynamics modeling method on the bearing force simulation of an engine, including bench installation conditions, were presented. 4100QB diesel flexible multi-body dynamics model was built by employing the modal synthesis technique in the software Adams, the flexible engine cylinder blockcomponent include cylinder block, cylinder head, gear chamber, wheelhouse, and engine bracket, the flexible shaft component include the crankshaft, the flywheel and the connecting flange, and the other parts were treated as rigid bodies. By comparing the simulation results of different models, the effects of flexibility of cylinder block and crankshaft, installing method of engine, coupling flange, mounting stiffness and the elasticity of shaft coupling were discussed, and the simulation result was validated by the measuring engine block vibration acceleration.更多还原