Theoretical assessment of the stress-strain state of the cylinder sleeve of a marine diesel engine from the effects of variable moving gas loads

Цилиндровые втулки относятся к наиболее нагруженным деталям судовых дизелей. Оценка их напряженно-деформированного состояния показывает, что последовательное форсирование дизелей по среднему эффективному давлению требует существенного пересмотра некоторых положений конструирования этих деталей. Это касается конструктивного оформления наружных поверхностей втулок, а также их закрепления в блоке цилиндров. В статье рассматривается влияние условий закрепления верхнего торца втулки и промежуточных опор-уплотнителей на деформирование цилиндровой втулки газовыми нагрузками. Показано, что для выбора оптимального места установки кольца-уплотнителя по длине втулки целесообразно исходить из минимизации воздействий на него со стороны подвижных газовых нагрузок. Предлагается расчётная методика, которая позволяет определить то место установки промежуточной опоры, где она практически не влияет на параметры напряженно-деформированного состояния цилиндровой втулки судового дизеля с учётом особенностей закрепления её верхнего торца в цилиндровом блоке. Применение данной методики позволяет с учётом особенностей конкретного двигателя обоснованно решить вопрос размещения дополнительных опор-уплотнителей. Cylinder bushings are among the most loaded parts of marine diesel engines. Evaluation of their stress-strain state shows that the sequential forcing of diesel engines according to the average effective pressure requires a significant revision of some provisions for the design of these parts. This applies to the design of the outer surfaces of the bushings, as well as their fastening in the cylinder block. The article examines the influence of the conditions for fixing the upper end of the sleeve and intermediate support-seals on the deformation of the cylinder sleeve by gas loads. It is shown that in order to select the optimal place for installing the seal ring along the length of the sleeve, it is advisable to proceed from the minimization of the effects on it from the movable gas loads. A calculation method is proposed that allows you to determine the place of installation of the intermediate support, where it practically does not affect the parameters of the stress-strain state of the cylinder liner of a marine diesel engine, taking into account the peculiarities of fixing its upper end in the cylinder block. The use of this technique allows, taking into account the characteristics of a particular engine, to reasonably solve the issue of placing additional support-seals.

CALCULATION OF INTERMEDIATE SUPPORTING PARTS OF INSEPARABLE PERFORATED BEAMS IN THE SOFTWARE COMPLEX «LIRA»

Due to the simplicity of design and manufacture, as well as reliability during operation, beams are one of the most common elements used in industrial, civil and public construction. The most rational cross-section of metal beams are rolled I-beams with inclined or parallel inner faces of the shelves, the predominant use of which is due to the value of the core distance, which is twice as much the same value for a rectangular section and almost three times for a round section. This figure is even higher for perforated profiles obtained from conventional rolling beams, which allow you to compose sections with increased values of moments of inertia and moments of resistance without increasing material consumptions. For inseparable beams, an additional significant factor influencing on their bearing capacity, is the structural design of the intermediate support part. The aim of these researches is to study the stress-strain state of inseparable perforated beams of I-beam profile of different heights in areas near the intermediate support, the design of which is made without a transverse stiffening rib placed on the axis of the support, and with unwelded holes to the left and right of the support under the action of evenly distributed load in the software complex "Lira". The objectives of the study are to establish the actual values of stresses and strains in the characteristic cross sections of the inseparable perforated I-beam, which occur on the intermediate support, and perform a comparative analysis of numerical studies obtained in the software complex "Lira" for intermediate support node beams of different heights for actions of different magnitudes of loads. The analysis of the obtained diagrams of normal stresses was carried out, which showed that for the proposed design of the support part of the beam, the cross-sections with holes directly to the left and right of the support are calculated. The conclusion about necessity of carrying out further experimental-theoretical researches of various types of support parts of beams for the purpose of development of a complex technique of their calculation and recommendations on definition of rational scope of application of each of them is formulated.

Study on Design Approach for Tall Pressure Vessels With Intermediate Support in Consideration of Bottom Structure Flexibility

The skirt and shell thicknesses of vertical tall pressure vessels are sometimes much increased in FPSO (Floating Production, Storage and Offloading) due to ship motion acceleration. In that case, intermediate support is used as an additional support from steel structure surrounding the vessels. By theoretical calculation, Nanjo et.al. introduced dimensionless parameter N that can represent stiffness of pressure vessel and acceleration load with the assumption of structure drift at intermediate support [1]. The authors proposed N-chart to investigate the necessity and effective elevation of intermediate support by using the parameter N. The flexibility of steel structure on the bottom affects the function of intermediate support (e.g. increasing reaction force at intermediate support, effect on bottom skirt calculation); however, the flexibility is not included in the parameter N. In this paper, an additional factor for the flexibility was studied and introduced by structural analysis. A model with flexibility of structure supporting the bottom skirt was used for the analysis. The variable flexibility of steel structure was applied to the bottom of the model to study the impact of bottom structure flexibility on the pressure vessel design. The analysis result was compared with the bottom fixed model without structure flexibility to study an additional factor. Finally, appropriate design approach for tall pressure vessels with intermediate supports was proposed.

Effects of intermediate support stiffness on nonlinear dynamic response of transmission system

This study is aimed at investigating the effects of intermediate support stiffness on nonlinear vibration response of transmission system. A coupled bending–torsional–lateral dynamic model with 14 degrees of freedom of transmission system is proposed comprehensively considering rubber dynamic stiffness, time-varying stiffness, static transmission error, and backlash. Meanwhile, a model of intermediate support with rubber nonlinear properties is developed to improve the accuracy of analysis. On the basis of the nonlinear differential equations derived by the lumped-parameter method, the dynamic responses of the key parts in the transmission system are obtained using the Runge–Kutta method and the effects of intermediate support stiffness on the dynamic characteristics are analyzed. Numerical results show that complicated interaction occurs and intermediate support stiffness has a great influence on the vibration of the coupled system. With the increase in the intermediate support stiffness, the vibration displacements in the three directions of the gear are progressively reduced and the nature frequencies are changed. The influence of the radial stiffness is greater than that of the axial stiffness. An experiment is performed subsequently to validate the effect of intermediate support stiffness on system, and the experimental results are consistent with numerical ones.