极端海况下多因素影响的大型船舶轴系振动耦合方法研究

The hull of large/super-large ships can be deformed easily by the wave loads during the navigation in the extreme sea conditions. The hull deformations would affect the shaft by the bearings greatly, especially with the effects of main engine efforts and the propeller excitations. When the vibration of the shaft exceeds its allowable amplitude, it will impact the reliability of the power plant operation and threaten the safety of the ship navigation. Therefore, this research project takes the marine shaft system in the large scaled ship as the object of study, simplifies the ship hull-main engine-shaft as the mechanical model to establish the kinematical equations of the coupled system. According to the technical difficulties to solve the equations with the asymmetric stiffness matrix and asymmetric damping matrix in the coupled system, a general frequency-domain response estimation method is proposed to study the shaft vibration coupling relationship with the effects of hull deformations, main engine efforts and propeller excitations for the coupled system in the extreme sea conditions. As a result, the coupling effect and operating characteristics of the shaft can be revealed, the performance of shaft can be improved in the complex ocean environment and the theory of the ship for the large scaled ship can be perfected to provide theoretical and technical supports for the optimization design of the large/ super-large ships and the shaft vibrations.

大型/超大型船舶在极端海洋环境中航行时，易受到波浪载荷引起船体变形。而船体变形会通过轴承作用于轴系，配合主机作用及螺旋桨激励等因素的影响，轴系会产生各种形式的振动，当振动超过允许的幅值，会严重影响动力装置运行可靠性，威胁船舶航行安全。本项目以大型/超大型船舶轴系为研究对象，以船体-主机-轴系为简化力学模型，建立起船体-主机-轴系耦合系统运动学方程，并且针对模型中含有非对称刚度、阻尼矩阵耦合振动方程解耦的技术难点，提出一种高效的通用频响函数算法。以此来分析船体-主机-轴系耦合模型在极端海况中船体变形、主机作用、螺旋桨激励等多因素耦合作用下船舶轴系振动响应关系，揭示轴系耦合效应及其运行特性，得到轴系在复杂海洋环境中性能提升方法，完善船舶大型化后的船舶理论，为大型/超大型船舶的优化设计和轴系振动问题提供理论和技术支持。

随着船舶大型化的发展，船体作为柔性结构受波浪载荷等环境因素影响产生形变，作用于船舶推进系统，造成结构的振动和失中，因此，在船舶推进系统振动理论研究中，需要纳入船体变形带来的激励影响来完善相应的理论。项目组以大型船舶为研究对象，开展了大型/超大型船舶船体-推进系统的耦合建模理论研究，通过对船体-推进系统结构模型的简化，建立船体-轴承、轴承-轴系、轴系-螺旋桨等等子结构的理论分析模型，利用各子系统之间的耦合关系和边界条件，对船体-推进系统进行整体建模。针对理论模型存在着非对称的刚度矩阵及阻尼矩阵的解耦问题，提出了非对称刚度、阻尼矩阵的耦合振动方程解耦方法，将控制方程转变为Laplace域下，基于复指数分解的方法，得到系统的传递函数，从进行多因素载荷作用下的结构动力响应分析，为极端海况下多因素激励的轴系振动理论分析提供可靠的技术处理手段。最后结合数值计算与试验分析验证了耦合模型各子系统之间的关系，探究了轴系耦合振动之间的相互影响。