【作者】 国杰；

【导师】 张文平；

【作者基本信息】 哈尔滨工程大学 ， 轮机工程， 2013， 博士

【摘要】 当前，内燃机的低噪声设计更多的关注了活塞敲击噪声、燃烧噪声以及空气动力性噪声等，缺乏对配气机构振动和噪声的深入研究。随着相关法规和动力设备声学品质的要求的提高，配气机构振动和辐射噪声的研究成为重要课题。配气机构是内燃机重要的振动和噪声源，由其产生的结构振动和表面辐射噪声直接来源于各部件的接触力。建立一个基于激励源特性的配气机构振动和噪声的预测方法是内燃机低噪声设计的必然要求。预测配气机构的激励力需要建立一个合理的动力学模型。影响配气机构动力学规律的因素包括凸轮型线、转速、气阀间隙、润滑以及零件的刚度和质量等。合理的动力学模型应该能够恰当地考虑这些因素的影响，并能够通过数学变量来定性和定量描述。配气机构的各个部分可能采用不同的数学方法进行简化和建模。但是，其目的是一样的，就是使模型的计算结果尽可能地接近真实的动力学响应。本文采用离散体方法建立配气机构的集总参数动力学模型。模型中提出凸轮轴、挺杆、摇臂、气阀和气阀弹簧的新简化方法，即模态匹配法。考虑到这些零件的低阶模态对配气机构振动的贡献最大，依据配气机构振动和噪声的频率分析范围，要求凸轮轴、挺杆、摇臂、气阀和气阀弹簧的简化模型与各自的低阶模态匹配。根据这一建模思想研究集总质量参数、刚度参数和阻尼参数的确定方法。考虑到凸轮-挺柱的接触作用对配气机构的动力学特性的重要影响，建立凸轮-挺柱的接触模型。研究凸轮和挺柱的油膜润滑特性并推导摩擦力的计算公式。采用四阶龙格库塔方法求解动力学模型，并对计算结果进行详细分析。提出采用子系统法建立配气机构的连续体动力学模型，将凸轮轴、挺杆、摇臂、气阀弹簧和气阀杆考虑为连续体，通过零件之间的接触力将零件的刚体运动及其弹性振动耦合起来。由于零件的弹性振动方程为偏微分方程，同时零件之间有脱离接触的可能性，所以本文采用有限差分法求解配气机构的刚-柔耦合动力学方程组。为了避免边界条件的限制，使求解方法更具有通用性，本文结合接触约束方程建立差分边界条件。这种方法能够适应边界条件的实时变化，从而解决了因零件分离带来的求解困难。建立内燃机各部件的有限元模型，采用“耦合+接触”的方法建立各部件的组合结构模型，并通过与模态测试结果的对比验证振动预测模型的有效性；建立配气机构激励力的加载方法，包括凸轮与挺柱的接触力、挺杆与摇臂的接触力、摇臂与气阀杆的接触力、气阀弹簧力以及气阀与气阀座的接触力；在时域内采用分别加载激励力的方法计算了配气机构各激励力单独的和总的结构振动响应。在以上研究的基础上，采用边界元法建立配气机构辐射噪声的时域预测模型，以各激励力产生的结构表面振动响应为边界条件，计算不同激励力产生的结构表面辐射噪声。设计、搭建配气机构动力学、结构振动和辐射噪声测试系统，测量气阀运动的加速度、挺杆受力、气阀杆受力、结构表面的振动加速度和辐射声压.通过预测结果与实测结果的对比来验证本文预测方法和预测模型的正确性，为内燃机配气机构的振动噪声控制和低噪声设计提供理论指导。更多还原

【Abstract】 Nowdays the low noise design of internal combustion egine mainly focus on that thecombustion noise, the slap noise of piston and the aerodynamics nosie, neglecting of the deepresearch on the vibration and noise of valve train. With the development of requirement fromlegislations and acoustic quality of powers, the vibration and noise of valve train has becomean important research subject. Valve train is an important source of internal combustionengine noise, which is directly produced by the contact force between any two neighboringcomponents. Therefore, for low noise design of internal combustion engine, it is necessary todevelop a method for predictions of vibration and noise of valve train.The prediction of excitations in valve train needs an appropriate dynamic model. Thedynamics of valve train are influenced by cam profile, rotating speed, valve clearance,lubrication, stiffiness and mass of components and so on. All the fators shoud be taken intoconsideration correctly by dynamic model and described qualitatively and quantitativelythrough mathematical variables. Parts of valve train may be simplified and modeled bydifferent mathematical method, but the purposes are the same, that are to make results fromdynamic model even closer to the real dynamic responses of valve train.A lumped dynamic model of valve train is developed by lumped parameter method. Anew simplified method, namely mode matching method for camshaft, pushrod, rockarm,valve and valve spring is put forward in the model. The contribution made by pushrod,rockarm, valve and valve spring to the vibration of valve train should be in the low ordermodes, so the models of these components are required to match their low order modes withinthe considered frequency range of vibration and noise. Based on this idea, the computingmethod of lumped parameters such as mass, stiffness and damping is studied. The model ofcontact behaviors between cam and tappet is set up in view of its important influences ondynamic characteristics of valve train. The lubrication characteristics between cam and tappetare studied and the formula for the friction force is derived. The dynamic model is solvedusing a fourth-order Runge-Kutta method and the results are analyzed in detail.The continuous dynamic model of valve train is developed by son system method, inwhich the cam shaft, pushrod, rock arm, valve spring and valve stem are simplified ascontinuous bodies, and the rigid motions and flexible vibrations of components are coupledwith contact forces between each other. The rigid-flexible coupled dynamic equations aresolved by finite difference method, as the flexible equations are partial differential equations and the components are possible to lose contact with each other. The difference boundarycondition is developed in combination with contact constraint equations for the sake ofindependence of boundary condition and common use of the solution method. This methodcan act in submission to the variations of the boundaries at the right moment, thus the solutionproblem from separation of components is solved.The finite element models of the components of internal combustion engine aredeveloped; the composed structure model is set up by “coupled+contact” method, and all themodels for prediction of vibration are verified with the mode test results. The applied methodsof exicitation in valve train, including cam-tappet contact force, pushrod-rockarm contactforce, rockarm and valve stem contact force, valve spring force and valve-seat contact force,are developed. The vibration responses of structure exictated by every acting force and theircombination in time domain are computed.Based on the above studies, a model to predict noise of valve train in time domain isdeveloped by boundary element method, and exirior radiation noise is computed withboundary conditions from superficial vibration responses of structure exicited by every actingforce and their combination in time domain.Design and build an experimental system for dynamics, vibration and noise of valve train,test valve acceleration, pushrod force, valve stem force, superficial vibration acceleration andexirior radiation noise. The prediction method and model developed in this paper are verifiedby a comparison between the prediction results and the test results to provide directions forvibration and noise control of valve train and low noise design of internal combustion engine.更多还原