超大型船舶推进轴系

近年来,随着新一代巨型超级油船VLCC和超大型油船ULCC出现,轴系的刚性增加,船体的柔性增大,使得轴系的校中非常困难,传统的轴系校中方法难以适应轴系校中的要求,因此,有必要研究适用于超大型船舶轴系校中的计算方法、测量手段和安装检验准则。作者在查阅国内大量文献资料的基础上,提出了超大型船舶推进轴系弹性校中的概念,对其理论进行了系统深入地研究,建立了轴系弹性校中计算模型,在国内率先开发了具有自主知识产权的弹性校中计算软件,通过在实际中的应用,能满足超大型船舶轴系校中的需要。 论文对超大型船舶推进轴系弹性校中计算理论进行了系统深入地研究。①根据超大型船舶推进轴系设计、安装检验的需要,提出了推进轴系弹性校中的概念,系统地研究了弹性校中计算的有限元法、传递矩阵法和三弯矩方程法等,通过改进使三种方法均能适用于超大型船舶推进轴系弹性校中计算的需要。同时,提出了弹性校中计算是多因素综合计算的结果,对超大型船舶推进轴系校中衡准应以弹性校中计算的结果为基础。在系统研究弹性校中计算理论的基础上,基于Visual Basic.Net面向对象的编程工具,开发了具有自主知识产权的超大型船舶轴系弹性校中计算软件。软件具有界面友好,操作简便,通用性强,便于二次开发等特点,能满足弹性校中计算的需要。②根据流体润滑动力学理论以及国内外学者所给出的近似计算公式,结合轴系弹性校中计算有限元模型,提出了一种确定轴系在实际运转过程中艉管轴承支承点位置以及轴心空间位置的计算方法,有利于准确地确定轴系在实际工作过程中轴系中心线的位置和轴承支反力:该方法简单易行,也可用于其它轴承支承位置的确定。针对大型船舶尾管轴承工作特点,基于流体润滑动力学理论,建立了艉管轴承的非线性模型。讨论了轴承油膜刚度的数值计算方法,建立了艉管轴承的动力润滑模型,给出了求解油膜压力分布的有限元方法,导出了油膜主要特征参数的计算公式。③根据螺旋桨水动力计算的传统方法一拟定常理论,同时结合螺旋桨设计计算理论,应用面元法对螺旋桨进行水动力计算,其计算结果与实验结果更接近,计算精度高,计算方便,能够较好的运用于弹性校中计算中水动力的计算。④分析研究了弹性校中计算最优化方法,建立了弹性校中优化计算模型,并将遗传算法应用于弹性校中优化计算,根据弹性校中计算的特点,对标准遗传算法进行了改进,将优选技术、非线性排名选择机制与基于实数编码的遗传算法相结合,建立了遗传算法优化模型。与标准遗传算法相比,改进后的优化算法具有
电加热器
The alignment of the propulsion shaft is the vital part of the design and installation of the shafting. A misalignment of the shaft is highly harmful since it may affect the vibration behavior and the strength of the shafting, or even more destroy the main engine and the gearbox. Early in the 1960’s, the foreign scholars did some researches on the theory and the testing analysis of the shaft alignment and got some achievements, which can meet the need of the design of the ship at that time. But with the appearance of the newly Very Large Crude Carrier (VLCC) and Ultra-Large Crude Carrier (ULCC), the hull becomes relatively more flexible when compared with the rigidity of the shafting, it made the alignment highly difficult and complex. This the traditional alignment method can’t meet the requirement of the shafting alignment any more. As a result, the new calculation method, testing measure and installation checking criterion of the shafting alignment are worth studying now.After studying lots of the literatures about the design, manufacture, installation of the propulsion shaft home and abroad, comprehensively considering the hull deflection, propeller dynamic force, bearing rigidity, oil film rigidity, environment temperature, crankshaft model of the main engine and so on, the elastic alignment calculation model of the shafting of the huge ship is established. Meanwhile, the relative calculation methods, such as the finite elements method (FEM), the transition matrix method and the three bending moment method of the elastic alignment are discussed in detail. At last, a general shaft alignment calculation software, which satisfies all the needs of the huge ship’s shaft alignment is developed.The main factors that effect the calculation model of the elastic alignment have been further discussed in this paper. ①Considering the feature of the stern-tube bearing of the huge ship, and on the base of the hydrodynamic theory of lubrication, a non-linear model of the stern-tube bearing is built, then an FEM approach of computing the pressure distribution of the oil film and the relationship of the main oil-film characteristic parameters are presented. ②According to the traditional calculation method of propeller’s dynamic force, the surface element method is applied to calculate the propeller’s dynamic force, associating with the calculationmethod of the aviation and space-flight propeller. The numerical result is closer to the experimental result. So it is more precise, convenient and can be used in the dynamic force calculation of the elastic alignment.(3)The optimum method of the elastic alignment is analyzed, then the calculation model of elastic alignment is established and the genetic optimum arithmetic is used in the elastic alignment. According to the calculating characteristic of elastic alignment, the genetic arithmetic and the optimum genetic model are improved, considering best choose technology, non-linearity rank choose mechanism and real number coding method. Compared with the standard genetic arithmetic, the improved optimum calculation is better in quality and efficiency.?According to the feature of the main propulsion shafting of the huge ship, an simplified calculation model, namely the equivalent shaft of crankshaft alignment calculation of the large low-speed main engine, is proposed firstly. Then the numerical result is gained by using this model and compared with the finite element numerical calculation result, the error is in the allowable range, which proves the correctness and feasibility of the approach. It meets the requirement of the elastic alignment and can be used expediently.(§)Compared all the checking methods used in the shaft installation, the advantages of strain-gage method are described. It can be used to check the shaft state constantly with the change of the rigidities. On the basis of the measured strain and the Riccati matrix method, the strain of the shaft and the bearing reaction can be checked, so as to satisfy the requirement of the shaft alignment by the iterative method.(6)Based on the previous studies, the elastic alignment software is developed. Then the elastic alignment calculation of one actual VLCC is carried out by using the software. At last some tentative checking rules of the elastic alignment are proposed in this paper.