柴油机结构振-声特性的多物理场耦合有限体积方法研究

Diesel engine is the main source of the ship vibration and noise. Research on vibro-acoustic characteristics of the diesel engine is helpful for the low noise design. The transfer process of vibration and noise in the diesel engine is influenced by multi-physics coupling among displacement field, sound field, flow field and temperature field. The influence of temperature field is mainly due to the temperature nonlinearity caused by large temperature gradient and the additional stiffness caused by thermal stresses. At present, researches focus on structural vibration and noise radiation without considering the effect of temperature nonlinearity, while influences of fluid-structure coupling and thermal-structure coupling are not clear. Lack of a simple and reliable numerical method for the multi-physics problem is one of the reasons. The aim of the project is to study the numerical solution of the multi-physics problem with temperature nonlinearity and heterogeneous materials. The fluid-structure coupling numerical model will be developed based on the cell-centered finite volume method (CC-FVM) and the acoustic-structure coupling numerical model will be developed based on the cell-vertex finite volume method (CV-FVM). According to the thermal-structure coupling mode, a unified numerical framework will be constructed to combine the two methods based on the same grid model. Finally, a unified finite volume method (FVM) for the multi-physics analysis of vibro-acoustic characteristics of the diesel engine will be proposed. Simulate and analyze influences of temperature nonlinearity and thermal-fluid-structure-acoustic coupling on transmission characteristics of combustion noise via cylinder head and cylinder cover. The achievements can provide a numerical predictive tool for vibro-acoustic characteristics and some advice for the low noise design of the diesel engine.

柴油机是船舶振动噪声的主要来源，研究其振-声特性有利于柴油机低噪声设计。柴油机结构振-声特性受位移场、声场、流场、温度场等多物理场耦合作用的影响，其中温度场的影响主要体现在大温度梯度引起的温度非线性及热应力造成的附加刚度。目前柴油机结构振-声特性研究主要是围绕结构振动声辐射展开的，未考虑温度非线性的影响，流固耦合、热固耦合的影响规律尚不明确，原因之一是缺乏简便、可靠的多物理场耦合数值模拟方法。本课题旨在通过研究温度非线性、非均质多物理场耦合问题的数值求解方法，建立流固耦合格心型有限体积法和声固耦合格点型有限体积法；基于热固耦合模式，构建统一的数值框架，在同一套网格的基础上融合两种方法，最终发展一套适用于柴油机结构振-声特性研究的多物理场耦合有限体积法。采用该方法研究温度非线性、热-流-固-声多场耦合对燃烧噪声经缸盖/缸盖罩传递过程的影响规律。成果可为柴油机低噪声设计提供模拟方法和理论参考。

柴油机是船舶振动噪声的主要来源，研究其振-声特性有利于柴油机低噪声设计。柴油机结构振-声特性受位移场、声场、流场、温度场等多物理场耦合作用的影响，其中温度场的影响主要体现在大温度梯度引起的温度非线性及热应力造成的附加刚度。目前柴油机结构振-声特性研究主要是围绕结构振动声辐射展开的，未考虑温度非线性的影响，流固耦合、热固耦合的影响规律尚不明确，原因之一是缺乏简便、可靠的多物理场耦合数值模拟方法。本课题旨在基于同一套网格建立多物理场耦合有限体积法（FVM），并用于研究温度非线性、热-流-固-声多场耦合对燃烧噪声经由缸盖/缸盖罩传递特性的影响规律。首先，基于格心型有限体积法（CC-FVM）提出温度非线性流固耦合问题数值求解方法，建立温度非线性/非均质双向流固耦合CC-FVM数值模拟方法并验证。其次，采用交错网格技术处理非均质问题，建立考虑温度影响的非均质双向声固耦合格点型有限体积（CV-FVM）数值模拟方法并验证。然后，借鉴交错网格的思想，构建统一的FVM数值框架，融合流固耦合CC-FVM数值模型与声固耦合CV-FVM数值模型，形成统一的多物理场耦合FVM数值模型并验证。最后，建立柴油机结构振-声计算模型并验证计算方法的正确性。利用建立的数值方法，研究多物理场耦合因素对燃烧噪声经由缸盖/缸盖罩传递特性的影响。