基于流固耦合传热的内燃机活塞内冷油腔多目标优化设计

The cooling gallery has a great impact on the temperature distribution, the structural strength and the rigidity of the piston, while solving the increasingly serious thermal load problem of the piston. With the development of the internal combustion engine, multiple control requirements such as the local temperature, structural strength, and stiffness of the piston are increasing. The traditional single-objective optimization design method has been failed to take into account the multiple needs for piston development of the modern internal combustion engine. This study uses a common rail diesel engine as the research object. Combining with the heat transfer test of the cooling gallery physical model, the formation of gas-liquid two-phase flow, the cooling oil distribution and the oscillation motion regulation inside cooling galleries are further studied. Moreover, the heat transfer intensity and heat transfer mode of cooling galleries are studied. The constraint relationship between the geometry of cooling galleries and the space of the piston head are analyzed. A three-dimensional parametric model of the cooling gallery and the piston geometry are established. Based on the relative displacement method, a fluid-solid coupling heat transfer simulation model of the cooling gallery and the piston is established. In the oscillating heat transfer processes inside the cooling gallery, the changes of transient temperature and thermal stress field of the piston are investigated. During the optimization design process, the influence of the constraints and optimization goals on the optimized results are analyzed. The mathematical model of multi-objective design of the cooling gallery is established to obtain the optimized solutions by using a multi-objective optimization algorithm. By means of real machine test of the trial production, the multi-objective optimized design of the cooling gallery is realized.

内冷油腔在解决活塞日益严重的热负荷问题的同时，还影响着活塞的温度、结构强度与刚度。随着内燃机不断发展，活塞局部温度、结构强度及刚度等多重控制需求日益增加，单目标优化设计法已不能兼顾现代内燃机活塞开发的多重需要。以强化程度较高的柴油机铝合金活塞为研究对象，结合内冷油腔振荡传热模型试验，进一步研究内冷油腔内气液两相流的形成、分布、受振荡运动的调制等规律，及其对振荡传热强度与传热模式的影响。分析内冷油腔几何结构与活塞头部空间的约束关系，搭建内冷油腔与活塞几何结构的三维参数化模型，结合相对位移法，建立内冷油腔与活塞的流固耦合传热数值仿真模型。深入研究内冷油腔振荡传热过程中，活塞瞬态温度场和热应力场的变化规律。分析优化设计过程中的约束与优化目标的处理对优化结果的影响，建立内冷油腔多目标优化设计数学模型，采用多目标优化算法获得内冷油腔的最优设计解集，通过样品试制与实机验证，实现内冷油腔多目标优化设计。

内冷油腔在解决活塞日益严重的热负荷问题的同时，还影响着活塞的温度、结构强度与刚度。随着内燃机不断发展，活塞局部温度、结构强度及刚度等多重控制需求日益增加，单目标优化设计法已不能兼顾现代内燃机活塞开发的多重需要。以强化程度较高的柴油机铝合金活塞为研究对象，改造原有的振荡流动与传热试验台，采用高速摄影的方式开展了振荡流动与传热模型试验。结合内冷油腔振荡传热模型试验，研究了往复空间角度、壁面局部结构、液相物理性质等对内冷油腔内气液两相流的形成、分布、受振荡运动的调制等规律，及其对振荡传热强度与传热模式的影响。提出一种柔性截面设计方法以探索更丰富的内冷油腔截面形状，分析内冷油腔几何结构与活塞头部空间的约束关系，搭建内冷油腔与活塞几何结构的三维参数化模型，结合相对位移法，开发出一套活塞与内冷油腔耦合传热的多目标优化仿真流程，建立内冷油腔与活塞的流固耦合传热数值仿真模型。提出一种可控热状态内冷油腔多目标优化设计方法，深入研究内冷油腔振荡传热过程中活塞瞬态温度场和热应力场的变化规律，分析优化设计过程中的约束与优化目标的处理对优化结果的影响，建立内冷油腔多目标优化设计数学模型，采用多目标优化算法获得内冷油腔的最优设计解集，探索研究了活塞变截面内冷油腔的设计思路，最终实现内冷油腔多目标优化设计。.本项目执行期公开发表期刊论文12篇，其中JCR分区一区的SCI Top期刊论文3篇，其他SCI检索2篇，中文核心2篇，国际国内学术会议交流论文5篇；授权国家发明专利1件，发明专利转让3件，参与制定团体标准1项，培养毕业硕士研究生2人。完成项目拟定的研究目标和预期成果。