不确定性参数条件下舰船推进系统摩擦诱导振动机理研究

The presence of friction-induced vibrations in marine propulsion systems as induced by large water-lubricated stern-tube bearings friction is highly detrimental to the reliability and acoustic stealth performance of ships, which is very sensitive to the uncertainties admitted in construction processes and working conditions. Existing research on this topic is generally conducted based on the assumption of ideal system, which is not always sufficient for a complete analysis of random phenomenon encountered in the abnormal vibrations, and is difficult to meet the real needs of accurate predictions of dynamic behaviors. Therefore, it becomes necessary to take into account uncertainties in order to ensure the robustness of the analysis and the prediction of self friction-induced vibrations. Concerning friction-induced vibrations in multi-span marine propulsion systems, a spatial distribution model of random friction is first built by involving vibrations and initial prestressed configurations of systems to explore interaction between bearing-elevation and system vibrations. A probabilistic model of friction-induced vibrations with consideration of system-parameter uncertainties and bench tests are then conducted to reveal the influence of the uncertainties of the bearing-elevation and the friction coefficient, and to clarify the basic excitation mechanism leading to the statistical characteristics of abnormal vibrations. The research work completed through this project would be meaningful in the effective assessment, prevention and control of abnormal friction-induced vibrations in marine propulsion systems.

大尺寸水润滑橡胶艉轴承摩擦诱导的舰船推进系统振动是制约舰船可靠性和声隐身性能的重要因素，而且推进系统建造工艺、工作状况等具有不确定性的复杂因素对其影响显著。然而现有基于确定性参数假设的研究，无法充分解释具有随机性的摩擦异常振动现象，难以满足摩擦振动准确预报的现实需求，因而迫切需要从参数不确定性的角度寻求突破，以实现对摩擦振动演化规律的精确模拟和分析。. 本项目针对多支承复杂舰船推进系统摩擦异常振动问题，从基于系统振动状态和初始变形的艉轴承空间分布摩擦力随机模型构建、不确定性参数条件下推进系统摩擦振动理论建模及概率特性分析、台架模拟试验三方面开展深入研究，探讨轴承摩擦力与转轴和轴承振动、轴承标高等的内在关联，揭示轴承标高和摩擦系数的不确定性对系统时频响应统计特性的影响规律，阐明摩擦异常振动的不确定性特征及其发生机制。研究成果对有效地评估、预防及控制推进系统摩擦异常振动具有重要指导意义。

项目针对多支承复杂舰船推进系统摩擦异常振动问题，面向其振动评估、预防或控制的技术瓶颈，研究艉轴承摩擦振动理论与方法，揭示摩擦异常振动的演化规律及其发生机制。项目从界面摩擦与推进系统整体动力学耦合的角度出发，将现有基于理想参数假设下的确定性研究拓展为不确定性分析，可实现推进系统摩擦振动演变规律更为精确的模拟和分析，以更准确、合理地解释具有随机性的摩擦异常振动和噪声现象。首先，建立了大长径比水润滑橡胶艉轴承空间分布摩擦力模型、复杂支撑螺旋桨推进轴系动力学模型等，可以更接近真实情形地刻画轴承载荷的空间分布非均匀性、界面摩擦与系统振动耦合所诱使的摩擦力时变性、参数变异导致的接触摩擦随机性等特征。其次，发展了不确定性参数条件下推进系统摩擦诱导振动的理论模型和快速计算方法，建立了基于复模态分析、部件模态综合和广义随机多项式展开的摩擦振动非侵入式随机分析方法。第三，探讨了推进系统摩擦异常振动的随机响应特征及其影响机制，揭示了转轴-轴承反向涡动失稳和粘-滑自振两种失稳机制，前者成因是摩擦力在接触点处的交叉耦合效应，后者成因是混合润滑状态下摩擦力的Stribeck效应。最后，开展艉轴承摩擦诱导轴系振动测试，基于测试信号的时、频特征分析进一步阐明了不同转频和轴承标高等工况下艉轴承摩擦诱导轴系振动规律，并验证了理论模型的合理性。项目所开展的推进系统摩擦振动不确定性研究是舰船科学技术领域的前瞻性研究内容，有望成为未来船舶推进系统可靠性和隐蔽性设计中需考虑的重要方面。项目所揭示的推进系统摩擦诱导振动机理可为低噪声推进系统的中高频异常振动、噪音溯源和振动抑制等提供理论依据。

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