【作者】 武起立；

【导师】 段树林；

【作者基本信息】 大连海事大学 ， 轮机工程， 2012， 博士

【摘要】 船舶柴油机是船舶的主要推进动力装置,其曲轴飞轮输出端连接中间轴、艉轴和螺旋桨,构成船舶的推进轴系,将主机所产生的机械功传递给螺旋桨,推动船舶前进。船舶柴油机推进轴系由若干滑动轴承共同支承,包括曲轴主轴承、支承中间轴的中间轴承和内置在艉轴管内支承艉轴的前、后艉轴承。推进系统结构和受力复杂,深入分析船舶推进轴系各摩擦副的润滑性能及其影响因素,对于提高船舶动力装置经济性及可靠性、优化轴系设计有重要的现实意义。目前大型低速二冲程船舶柴油机推进轴系各轴承润滑特性的分析和预测还难于开展有效的实验研究。本文建立了船舶柴油机推进轴系的多体动力学分析模型,依据弹性流体动压润滑理论,开展了各轴承润滑特性的计算分析,对各滑动轴承的润滑特性及其影响因素进行了深入研究。以MAN B&W6S50MC-C二冲程船舶柴油机作推进动力的39000载重吨油轮推进轴系为研究对象,建立了弹性曲轴、中间轴、艉轴以及柴油机各主轴承座、中间轴承座和艉轴承座的三维实体有限元模型。考虑各弹性体间的动力学耦合作用以及弹性体和润滑油膜间的流固耦合作用,采用模态缩减子结构法将有限元模型进行动态缩减,继而用缩减得到的模型信息文件构建推进轴系轴承润滑的多体动力学分析模型。在单纯考虑柴油机本身曲轴、活塞连杆机构,未考虑中间轴系、螺旋桨等部件的影响下,对额定工况下的MAN B&W6S50MC-C柴油机主轴承润滑特性进行仿真研究。计算结果表明：各主轴承载荷数值各不相同,润滑状况存在较大差异,其中MB2轴承的工作状态相对较差。轴承各种参数和运行工况等对主轴承润滑特性的影响程度各不相同。单缸熄火时,柴油机需要降速降负荷运行,由于惯性力的影响,各轴承载荷变化并不相同；由于装配等因素导致轴承座上下偏移,载荷会发生变化,润滑状态也相应改变；在轴承座倾斜情况下,载荷变化不大,但润滑状况急剧恶化,高油压区偏布于轴承边缘。在上述柴油机多体动力学分析模型的基础上,计入传动轴系和螺旋桨等的影响,将曲轴、中间轴、艉轴和螺旋桨等包含进来,通过完整的全轴系轴承润滑计算模型来分析中间轴承和艉轴承的润滑状况及其主轴承润滑状态的变化情况。边界条件更趋于实际情况,可以得出更趋合理和更准确的主轴承、中间轴承和艉轴承的润滑特性参数。计算结果表明：远离柴油机功率输出端的主轴承工作状态变化不大,距离输出端越近,主轴承工作状态变化越明显,最后一道主轴承变化情况甚为显著。对用作船舶主推进动力装置的柴油机曲轴主轴承进行准确的润滑分析,必须考虑后端轴系的影响作用。中间轴承沿轴向受力均匀,润滑状况良好,工作较为平稳；由于螺旋桨重力的影响,后艉轴承载荷的边缘效应十分明显,高油压区分布在靠近螺旋桨侧的艉轴承边缘；随着螺旋桨运行转速的增大,轴系的横向振动也增大,轴系滑动轴承的载荷幅值也随之变化；由于陀螺效应的影响,艉轴的倾斜角度逐渐减小,艉轴承润滑状况也随之趋于好转。综上所述,本文建立船舶柴油机推进轴系多体动力学计算模型,对滑动轴承润滑特性参数进行了数值分析。该多体动力学分析模型和耦合仿真分析方法为船舶推进轴系轴承润滑特性的分析和预测提供了一种有效的研究方法,实现轴系滑动轴承快速和高效的优化设计。更多还原

【Abstract】 Marine propulsion shaftings, composed of crankshaft, intermediate shaftings, stern shaftings and propeller, transmit power generated by marine diesel engine to propel vessel forward. Marine propulsion shaftings are supported by sliding bearings such as main bearings, intermediate bearings, fore and aft sterntube bearings built-in stern tube. Marine propulsion system has particular structure and complicated loads. In-depth analysis of the lubrication characteristics for friction pairs of marine propulsion shaftings and its influencing factors has important practical value for improving the economy and reliability of marine power plant and optimizing the shafting design. Currently, it is difficult to develop effective experimental study for the analysis and prediction of bearing lubrication characteristics for large low-speed two-stroke marine diesel engine propulsion shafting. In this paper, the multi-body dynamics model of marine diesel engine propulsion shafting was established, based on elastohydrodynamic lubrication theory, the lubrication characteristics of all bearings and its influencing factors were analyzed thoroughly.The propulsion system of a39000deadweight tonnage oil tanker propelled by a MAN B&W6S50MC-C diesel engine was taken as study objective, and the three dimensional solid finite element models of flexible crankshaft, intermediate shaft, and stern shaft, main bearings of diesel engine, intermediate bearing and sterntube bearings were established. Considering dynamic interaction behaviors of all flexible bodies and the fluid-solid interaction behavior between flexible bodies and elastohydrodynamic lubrication oil film, Modal Reduced-Substructuring method was employed for dynamic reduction of finite element models, the resulting files generated from reduced FE models were employed to create multi-body dynamics model of propulsion system.Considering purely the engine pistons, connecting rods, crankshaft and main bearings, but ignoring intermediate shafting, stern shaft and propeller, the simulation study on lubrication characteristics of MAN B&W6S50MC-C main bearings was carried out at rated working conditions. Simulation results show that:the loads and lubrication conditions of main bearings were quite different to each other, and the lubrication conditions of No.2main bearing was poor. The influences of bearings structure parameters and operating conditions to the lubrication characteristics of main bearings were quite different. Once one cylinder misfire, engine load should decrease, and the load on each bearing varied differently due to the influence of inertia forces. Supposing the bearing offset owing to mis-assembly probably, the bearing lubrication changed. In the case of bearing tilting, the bearing load changed very small, but the bearing lubrication deteriorated sharply, and high oil pressure zone deviated to bearing edges.Based on the above multi-body dynamics model, considering the influence of driving shafting and propeller, full shafting model for lubrication simulation of large low-speed two-stroke marine diesel engine propulsion system was created. The boundary conditions exerting on this model were closer to actual situation, and the lubrication characteristics of main bearings, intermediate bearing and sterntube bearings were more reasonable and more accurate. Simulation results show that:The lubrication characteristics of the main bearings close to engine output end changed significantly, but small change appeared on the main bearings close to engine free end. The load distributed uniformly on the intermediate bearing in axial direction, and the intermediate bearing lubricated well and worked smoothly. As the impact of the propeller gravity, the edge effect of the aft sterntube bearing load was very obvious, and high oil pressure zone located at the aft edge of aft sterntube bearing. With the increasing running speed of propeller shaft, the lateral vibration of shafting strengthened, and the bearing loads increased accordingly. As the impact of gyroscopic effects, the tilting angle of stern shaft decreased, and the sterntube bearing lubrication improved accordingly.In summary, the multi-body dynamics model of marine diesel engine propulsion shafting was established and the lubrication characteristics of sliding bearings were simulated in this paper. The multi-body dynamics model and interaction simulation method provides an effective research method to the analysis and prediction of bearing lubrication characteristics for marine propulsion shafting, and fast and effective optimization design of sliding bearings were achieved.更多还原