【作者】 欧阳林；

【导师】 李格升； 董健；

【作者基本信息】 武汉理工大学 ， 轮机工程， 2012， 硕士

【摘要】 本文采用仿真技术和模拟试验的方法对可变燃烧室(VCC:Variable Combustion Chamber)活塞的动力学特性进行了研究。提出了新的VCC活塞的技术方案,优化改进了VCC活塞的结构；通过扩充模型库进一步完善了VCC活塞动力学仿真分析平台；分析了影响VCC活塞动力学特性的关键控制参数及其它们之间的相互关系；采用VCC活塞的动力学仿真和发动机性能仿真的耦合迭代计算预测了VCC活塞的动态响应特性；分析了VCC活塞的温度场和热变形对机构预紧力的影响。新的VCC活塞的技术方案和优化设计主要包括有：提出了连杆小端复位凸轮的设计,保证VCC机构能在一个循环内及时复位；完成了支撑盘和限位盘的型线优化设计,进一步提高了VCC活塞的动态响应：改进了VCC机构的预紧方式,能够在不同预紧力的情况下保持预紧位置不变；此外,优化后的VCC活塞的质量减轻和结构更简单。进一步完善了VCC活塞的ADAMS动力学仿真分析平台,扩充了动力学仿真模型库。主要包括有：1)构建了新技术方案的动力学仿真模型；2)增加了连杆复位凸轮模块；3)增加了活塞整体运动模块；4)增加了连接螺栓结构细节仿真；5)提出和应用了VCC活塞动力学和VCC发动机工作过程相互之间的耦合仿真迭代计算方法。采用耦合仿真分析了影响VCC活塞动力学特性的控制参数及其它们之间的相互关系。主要的控制参数包括有：预紧力大小和预紧位置、材料参数、接触参数和结构参数等,通过对这些参数的仿真分析,确定这些参数的取值范围,有助于识别影响VCC活塞动力学特性的关键控制参数。同时还分析了活塞往复惯性力对VCC机构动态响应的影响。另外还采用热耦合有限元方法分析了VCC活塞温度场和热变形对VCC机构预紧力的影响。研究表明：1)所提出的VCC活塞技术方案能够基本满足汽车发动机各种工况对动态响应的要求；2)所提出的VCC活塞动力学和VCC发动机工作过程耦合仿真计算方法能够描述缸内压力和VCC机构位移的相互关系；3)动力学仿真模型库的扩充使仿真模型更加合理和更加完整；4)复位凸轮设计保证了VCC机构能够在一个循环内及时回复；5)支撑盘和限位盘的变角度设计使VCC机构具有更加快捷的动态响应；6)改进后的技术方案使VCC活塞的结构更加简单合理,质量进一步减轻,预紧位置更容易确定：7)VCC技术能够有效改善气缸压力循环波动,其压力波动范围约降低51%。更多还原

【Abstract】 Using dynamical simulation in combination with analogue test, the dynamical characteristics of VCC (Variable Combustion Chamber) piston are studied. A new design is put forward, based on which the structural improvements are performed and the software platform of dynamical simulation is improved by adding modules and extending the model library. The parameters affecting the dynamical characteristics and relationships among these parameters are analyzed. The dynamical characteristics of VCC piston are forecasted through dynamical simulation combined with engine performance simulation. The effect of thermal deformation of VCC piston on the pre-tightening force of VCC piston is analyzed.The new structural designs of VCC piston mainly contain the following: that the design of reset cam on the rod small end is put forward to ensure the VCC mechanism can reset in one working cycle, and that the profiles of support disc and limit disc are optimally designed to improve the response of the VCC piston, ant that the pre-tightening style is improved and then the pre-tightening position can keep the same under different pre-tightening forces, and besides, the optimal designed VCC piston is lighter and simpler.The software platform of dynamical simulation is improved by adding modules and extending the model library. The improvements mainly include that (1) the dynamical simulation model of new design is established, and (2) the reset cam module is added, and (3) the movement of piston is added. And (4) the joint bolts module are added and (5) coupling dynamical simulation of VCC piston with the engine performance are introduced.The parameters affecting the dynamical characteristics and the relationship among them are analyzed by means of coupling simulations. The parameters include the pre-tightening force and pre-tightening position, and material parameters, and contacting parameters and structural parameters etc. Their value ranges can be defined by simulation, by which the key parameters can be identified. Besides, the effect of piston reciprocating inertia force on the dynamical response of the VCC mechanism is analyzed. Moreover, the effect of thermal deformation of VCC piston on the pre-tightening force is analyzed by finite element method.Research shows that (1) the new design of VCC piston can meet the demands of automobile engines on the dynamical response under all loads, and (2) the correlation between in-cylinder pressure and VCC displacement can be described by coupling dynamical simulations of VCC piston with the engine performance simulation, and (3) the model of dynamical simulation becomes more reasonable by extending the modules, and (4) the design of reset cam ensures that the VCC mechanism can reset in one working cycle, and (5) the profile design of support disc and limit disc can improve the response of the VCC piston, and (6) the optimal designed VCC piston is lighter and simpler and the pre-tightening position is easy to define and (7) the VCC technology can decrease the cycle fluctuation of in-cylinder pressure by about51%.更多还原