Ship Shaft Research Articles

A study on the influences of journal axial vibration on ship shaft stern bearing dynamic characteristics

PurposeThis paper aim to take the ship shaft stern bearing as the research object, and studies the influence of journal axial vibration on bearing dynamic characteristics under different misaligned angles and rotation speeds.Design/methodology/approachComputational fluid dynamics (CFD) and harmonic excitation method were used to build bearing unstable lubrication model, and the dynamic mesh technology was used in calculation.FindingsThe results indicate that journal axial vibration has a significant effect on bearing dynamic characteristics, like maximum oil film pressure, bearing stiffness and damping coefficients, and the effect is positively correlated with journal misaligned angle. The effect of shaft rotation speed and journal axial vibration on bearing dynamics characteristics are independent; they have no coupling. Bearing axial stiffness is mainly affected by the journal axial displacement, bearing axial damping is mainly affected by journal axial velocity and they are positively correlated with the misaligned angle. The influence of rotational speed on bearing axial stiffness and axial damping is not obvious.Originality/valueThis paper establishes the bearing dynamic model by CFD and harmonic excitation method with consideration of cavitation effect and analyzing the influence of journal axial vibration on the dynamic characteristics. The results are benefit to the design of ship propulsion shaft and the selection of stern bearing. Also, they are of great significance to improve the operation stability of the shaft bearing system and the vitality of the ship.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-11-2022-0337/

Design of a Brushless Doubly Fed Generator With Simplified Three-Phase Wound Rotor

The brushless doubly fed generator (BDFG) shows great potential for the variable speed constant frequency ship shaft power generation applications due to its high reliability and low system costs. The rotor topology, which directly couples two stator magnetomotive forces (MMFs) with different pole pairs, is essential for the BDFG. However, existing rotor topologies cannot have both strong magnetic field coupling ability and simple structure. To address this problem, this paper proposes a simplified three-phase wound rotor that can produce two MMFs with different pole pairs simultaneously. Useless harmonics are also eliminated to achieve strong magnetic field coupling ability. The complete design method of a novel integral-slot single-layer winding acting as a basic unit of the compound wound rotor is presented. Two sets of basic winding units are merged into one according to the principle of Ampere-conductor wave, whose approaches are also thoroughly developed with the design example. The maximum number of winding layers and the coil types are reduced to simplify the winding layout. Steady-state performances of a prototype generator are analyzed by both finite element simulations and experimental tests, which verify proposed design methods and schemes.

Machine learning performance comparison for main propulsive shafting systems alignment

The ship shaft alignment is crucial to achieve a high-performance propulsion system. This alignment is carried out, still in drydock, by adjusting the bearings' offsets. However, there are numerous available combinations sets of vertical offsets which results in good alignment final condition. Defining an optimum set of vertical displacements is costing shipyards a valuable time. Therefore, this work proposes the use of machine learning algorithms to predict if a given set of offsets, following the mandatory rules in force, should be implemented or not. In this manner, this paper presents a case study where a finite element model of an Anchor Handling Tug Supply (AHTS) vessel’ shaft line was assembled in order to obtain the bearings reactions, shaft line deflections, shear forces, bending moments and, finally, the influence coefficients matrix (ICM). Those data were used to feed machine learning (ML) models based on four different algorithms, namely, K-Nearest-Neighbors, Extremely Randomized Trees, Random Forest and Gradient Boosting in order to solve multiclass classification problems concerning the offset's set to be applied in the alignment of the shaft line. Results showed that the Gradient Boosting and Random Forest algorithms presented the best results, achieving up to 98.1% of precision in one of the 36 scenarios tested, and an average precision above 96.0%. Such results corroborated with the authors' proposal to implement ML techniques as a way to speed up the currently very time-consuming shaft alignment process.

Estimating the effect of biofouling on ship shaft power based on sensor measurements

ABSTRACT Marine biofouling on a ship's hull and propeller increases the resistance of the ship moving through water and reduces the propulsion efficiency of the ship. Estimating the effect of fouling is difficult, as the biomass is rarely measured. In this paper, we present a new data-driven model for the total shaft power use of a large containership, in order to estimate the unobserved effect of fouling. Due to the limitations of both physical models and machine learning models, we develop a Bayesian generalized additive model for our purpose. We discuss issues of representative training data for the model. Further, we subset and subsample the data to a representative sample. Models are compared by out-of-sample predictive quality, physical appropriateness, and through autocorrelation of residuals. The Bayesian generalized additive model combined with computational inference using integrated nested Laplace approximations gives a robust estimate of the biofouling effect over time. It also allows a decomposition of the total shaft power use into effects of speed, weather, and other conditions. This model can be used to understand the effectiveness and timing of different hull and propeller treatments.

Совершенствование системы регулирования выходного напряжения комплекса «валогенератор – преобразователь частоты»

The article focuses on operation of the ship shaft generator on the joint buses of the main switchboard through a frequency converter that consists of an uncontrolled rectifier and a self-excited inverter with pulse width modulation. The most common schemes of using shaft generators on ships are given, their advantages and disad-vantages are analyzed. There has been illustrated a flowchart and given a detailed description of the operation 
 of a ship electric power plant with power take-off from the main engine. A control system regulating the constant flow interlinkage in the “frequency converter - shaft generator” complex, which ensures stable output voltage, has been developed. It has been stated that a random change in the rotational speed or in a torque fluctuation of the shaft generator rotor have little impact on the quality of generated electricity. Simulation modeling of the complex is given in the MATLAB/Simulink software package. The developed controller of a self-excited inverter supports continuous flow interlinkage by vector control. There has been demonstrated the composition and operation principle of the control system of output voltage of a shaft generator by using vector regulation method. Modeling has proved the availability of the self-excited inverter control system. The oscillograms of modeling the input and output current and voltage values have been obtained. The modeling results justified that changing the input voltage and frequency of the generator provided the high quality output voltage indicators. Harmonic distortion coefficients and static deviations have been analyzed. The expediency of using combined filters of higher harmonics to eliminate interharmonics and higher harmonics in the ship network has been proved. Practical recommendations are given to improve the quality of operation of the ship electrical complex with a shaft generator.

Ship Shaft Frequency Extraction Based on Improved Stacked Sparse Denoising Auto-Encoder Network

The modulation spectrum of ship radiated noise contains information on shaft frequency, which is an important feature used to identify ships and a key parameter involved in calculating the number of propeller blades. To improve the shaft frequency extraction accuracy, a ship shaft frequency extraction method based on an improved stacked sparse denoising auto-encoder network (SSDAE) is proposed. Firstly, the mathematical model of the ship radiated noise modulation spectrum is built and data simulation is carried out based on this model, combined with the actual ship parameters. Secondly, we trained the SSDAE model using the simulation data and made slight adjustments to this model by using both simulation and measured data to improve it. Finally, the experimental ship modulation spectrum information was input to the SSDAE model for denoising, enhancement, and regression estimation. Accordingly, the shaft frequency was extracted. The simulation and experimental results show that the shaft frequency extraction method based on the improved SSDAE model has high accuracy and good robustness, especially under the conditions of both missing line spectra and noise interference.

Анализ работоспособности силиконовых демпферов крутильных колебаний судовых двигателей внутреннего сгорания на основе результатов испытательного центра Marine Technology Service

The article presents the analysis results of changes in the operability of silicone dampers of torsional vibrations of marine diesel engines on the basis of practical measurements carried out by the Testing Center Marine Technology Service under the Astrakhan State Technical University (TC MTS). TC MTS is accredited by the Russian classification society - the Russian Maritime Register of Shipping (RMRS) in the field of calculation and measurement of torsional vibrations. During its functioning (2001 – to date) the TC MTS has conducted torsiographing procedures of the machine-propulsion systems (MPS) of more than 200 vessels. The large amount of data obtained makes it possible to assess the dynamics of changes in the parameters of torsional vibrations, including amplitude and frequency, according to the results of periodic torsiographing the ship MPS. A change in the technical condition of the torsional vibration damper (a decrease in the efficiency of its operation) and the lack of its constant monitoring lead to the increasing stresses in the ship shaft line and, as a result, to a growing risk of its breakdown, which confirms the urgency of the study. There are given the images as real examples of ship operation failure: Aratere ship shaft fracture, damper mass wedging due to silicone fluid leakage, silicone fluid viscosity increasing to suspension state due to wear products, wear of silicone damper flyweight surfaces, silicone damper body wear. The Hasse & Wrede damper cap fastening with bolts is illustrated.

Способ повышения надежности дейдвудных подшипников валопроводов судов

The paper gives the analysis of the ship power plant its elements: a shaft line and deadwood bearings. The deadwood bearings are said to serve as supports for the ship shaft line. The operating conditions, the effect of loads and the occurrence of possible defects that reduce the life of deadwood bearings and the shaft line are described. The actual operation life of ships without repair depends on the technical condition of the deadwood unit and on the size of clearance between the propeller shaft and deadwood bearings which increases because of wear of the bearings. Structural and technological ways of increasing the reliability of deadwood bearings are described. It is stated that the resource loss of deadwood bearings is caused by the irreversible physical processes occurring on the surface and inside the bearings at the structural level under continuous cyclic stresses, which results in the extreme condition and wear unacceptable for further operation. There are considered the methods of improving the structures of the deadwood unit, as well as new solutions for the design or repair of ship deadwood bearings. There is proposed a new design of a deadwood bearing based on the requirements and rules of regulatory documents. A sketch and a picture of the proposed deadwood bearing are presented, which is a metal housing with segments made of two materials: ZX-100K (Zedex) and rubber. The proposed design of the deadwood bearing will increase the reliability of the ship deadwood device, eliminate non-working sections of segments and increase the support area of the propeller shaft on the bushings. It has been inferred that there is a possibility to reduce the contact static and dynamic specific loads and amortize the shock loads.

Analysis of underwater explosion shock on ship shaft stern bearing lubrication characteristics under different bearing working conditions

Warship always face the threat of underwater explosion shock, which may affect the ship stern tube bearing lubrication performance when the propeller shaft is bending. This paper builds the coupling model of shaft longitudinal vibration and bearing lubrication with consideration of shaft axial shock and misalignment. The performance of stern bearing under the influence of explosion shock was analyzed by solving the generalized Reynolds equation, shaft longitudinal vibration equation and explosion shock equation. The result shows that: the effect of underwater explosion shock on bearing lubrication performance is transient, and the effect will be more obvious when the bearing works at close quarter, larger misaligned angle, eccentricity and rotation speed. Moreover, the edge effect which caused by shaft bending will increase with the decrease of explosion distance and the increase of eccentricity.

CFRP 소재의 선박용 축계 적용을 위한 비틀림강도 특성

The Carbon Fiber Reinforced Plastic (CFRP) material is recently widely used in the composite industry with excellent rigidity and lightweight properties. A ship shaft system requires high standards of safety on torsional strength capacity. The purpose of this study is to verify the applicability of a CFRP shaft system to take the place of metal shaft systems for ships from a viewpoint of torsional strength. Selection of materials and manufacturing method are executed then two geometrically scaled CFRP shaft system models were designed and manufactured with three-layer patterns. The models were used for a series of torsion tests under single and repeated torsional loading conditions. Detailed design and manufacturing methods for a CFRP ship shaft system are documented and the torsion test results are listed in this paper. The results of this study could be useful guidelines on the development of CFRP ship shaft systems and a test method.

Оценка эффективности методов прогнозирования технического состояния в системах судового валопровода

The article considers an approach to assessing the effectiveness of the most common methods of predicting the technical conditions and failure with reference to the ship shafting. There have been analyzed the main factors in operation of the ship shaft line, which cause the change in its technical state. It has been found that a special feature of some loads acting on the propeller shaft is their stochastic or changing nature over time, which hampers predicting the technical state of the shafting and its units. The features of stochastic and extrapolation forecasting methods have been analyzed. The possibility of using statistical methods in conditions of mass standard production of shafting units with a relatively short regulated service life is estimated. An extrapolation method is proposed for predicting the maximum permissible clearance of stern tube bearings. The case of accumulating samples of measuring results of the propeller shaft sagging in the given time intervals is considered, the approximating functions are constructed. The criteria for the reliability of the results of extrapolation methods for predicting the wear of stern tube bearings are determined. There have been developed the proposals for adapting the causal method as an alternative to the extrapolation method. A schematic diagram of a system for the ship shafting failure predicting has been developed using the registration and analysis of vibration parameters, which serves as the basis for constructing a regression model of damage accumulation. The proposed forecasting system allows studying the actual operating conditions of the shafting, defining the actual external loads and the regularities of their occurrence, measuring deformations and stresses, and determining quantitative indicators of the reliability of the shafting during normal operation and special operating modes, for example, with vibration resonance. The theoretical basis of the algorithm for calculating and registering loads affecting the service life of shafts is proposed.

Control of mobile equipment for the processing of marine shaft lines

The purpose of the research is to develop solutions for mobile equipment control in the processing of marine shaft lines; to solve the issues of geometric accuracy of processing; to create a corrective program to address the issues of accuracy of the geometric parameters processing; to give reasons for the application of linear electrohydraulic step drive (LEHSD) in mobile equipment control. The analysis of schemes and mathematical dependencies for calculating the trajectory of the tool movement of a mobile machine when processing shaft lines is carried out; the choice of the optimal zone for finishing the shaft line, taking into account the beats. The object of the study is a ship shaft line. The paper presents an original scheme of rotation of the shaft line section, as well as schemes for changing the position of the shaft line during processing; justifies the possibility of using a linear electrohydraulic step drive (LEHSD) with a corrective program for processing taking into account automatic measurements and a specified error.

Анализ причин повреждений и отказов судовых валопроводов

The paper highlights the problem of a ship shaft line failure, which entails significant economic losses, because most vessels of the Russian fleet are equipped with a shaft line. A large number of domestic and foreign works are devoted to studying the causes of damage and failures of ship shafting. The complexity of collecting, systematizing and analyzing statistical data on breakdowns and damages of shafting lies in the fact that the data refer to different periods of time, different periods of operation and types of ships, and are also contained in various sources. There has been considered the approach to systematization of modern statistical data on damages and failures of ship shafting elements collected on the basis of defect-technological lists of the Astrakhan shipyards and from other sources. Information on breakdowns of ships, their elements and ship shaft lines within 2010 - 2019 provided by the Russian River Register of Shipping is given. The analysis of accidents on ships of the class of the Russian Maritime Register of Shipping. The places of occurrence and the nature of the propeller shaft cracks have been established, which makes it possible to assess the nature and magnitude of the destructive loads, as well as the real safety margins. The general classification of the location of the propeller shaft cracks in the order of the frequency of their occurrence is given. There have been shown the results of the analysis of defect-technological lists, which make it possible to establish the causes of ship shafting failures, which led to emergency repair, and the most common defects identified during the scheduled dock repair of ships. The influence of the diameter of propeller shafts on the nature and size of defects, as well as the frequency of their manifestation, is estimated. Based on the results of the analysis, certain measures have been proposed to reduce the number of accidents in shafting of projected vessels, and the most promising directions for improving the already developed structures of shafting in operation are outlined. The results of the analysis are in addition to the ongoing research and development work to improve the reliability of ship power systems.

Анализ влияния упругих свойств дейдвудных подшипников на рабочее состояние судового валопровода

The paper considers the ship shafting and its design. Depending on the constructive features, operating conditions, effects of continuous, dynamic, variable and random loads the operation of the shaft line is accompanied by wear of the shafting structure and auxiliary parts. The formulas for calculating the maximum permissible clearances during operation in stern bearings of propeller shafts are given, according to the norms and technical and operational requirements. A graph of the maximum permissible clearances in metal stern bearings is presented. There has been carried out a dynamic design of the shaft line in order to define the influence of rigid characteristics of the stern bearings on eigen frequency of transverse vibrations. It is noted that the service life of the shaft line depends on the material of bushings or liners of the bearings (bakout, babbit, textolite, caprolon, bronze, polyurethanes, rubber) and their wear degree. The design scheme of the ship shaft line on elastic supports with a coefficient of rigidity is presented. To assess the influence of the elastic properties of deadwood bearings, the method of initial parameters was used. According to the researchers’ opinion, the greater the wear, the lower their stiffness coefficient. At a certain wear degree of deadwood bearings, there occurs resonance at the lowest operating frequencies. It has been proved that the greater the deflection at the attachment point of the propeller, the lower the eigen frequency of transverse vibrations of the shaft line. It has been pointed out that the calculations should include the separation of the shaft line from the deadwood bearing, since it contributes to a decrease in eigen frequency and causes a resonance during transverse vibrations.

РАЗРАБОТКА БЛОКА ОБРАБОТКИ ИНФОРМАЦИИ ДЛЯ ПРОГРАММНО-АППАРАТНОГО КОМПЛЕКСА СИСТЕМЫ МОНИТОРИНГА КРУТИЛЬНЫХ КОЛЕБАНИЙ СУДОВОГО ВАЛОПРОВОДА

The article considers torsional vibrations in combination with other technical factors, which remain a cause of damages and breakdowns of the ship's propeller shafts, intermediate shafts and crankshafts. Torsional vibrations inevitably occur in the ship plants. It can be explained by the uneven torque of the engine and the torque on the propeller (exposure of the propeller, uneven movement of the water flow, stormy weather, etc.), which leads to alternating twisting of the shaft. To reduce torsional vibrations, dampers are used, which require periodic performance testing by using the torsiography procedure. In contrast to the existing monitoring systems of the technical condition of the damper, it is planned to install an information processing unit for the software and hardware complex for monitoring torsional vibrations of the ship's shaft line and the parameters associated with them (vibration and temperature changes of the flexible elements of the connecting couplings). The unit under development will allow to constantly monitor the level of torsional vibrations and, if they increase, to signal the ship's mechanic to switch to another operational mode of the main engine, which will increase the reliability and automation of the ship power plants, the safety of navigation, and reduce the economic costs of ship operating

Application of adaptive line enhancer based on NLMS algorithm in shaft-rate electric field signal detection

There is lots of useful signal feature in ship’s shaft-rate electric field. Extracting the signal feature is vital in underwater target recognition. In order to extract the feature of the shaft-rate electric field, the shaft-rate electric field is processed by ALE based on NLMS. The improved NLMS algorithm is proposed to construct an adaptive line-spectrum enhancer, and then the measured data of shaft-rate electric field is processed by ALE. The results show that the algorithm can effectively separate the weak shaft frequency electric field signal from the broadband background noise at low SNR. Compared with the ordinary ALE, the algorithm has more significant effect in improving SNR, faster convergence speed and smaller steady-state error, which greatly improves the detection ability of ship shaft frequency electric field.

A recent approach to the research on axial oscillation of shaft system on ships

In the design of ship propulsion system, the study of oscillation is a great importance because they play a decisive role in the operating ability of the shaft system. Among ship shaft oscillations, axial oscillation has been only a particular interest after applying on ships for diesel engines with ratio of piston stroke and its diameter 3-4,4. In this paper, the special features of the computational model are presented when studying the axial oscillations on the ship shaft system. It should be emphasized that the system of differential equations in describing the free and forced oscillations can be obtained directly from the analogous equations of the torsion oscillation. However, unlike the torsional oscillation, the axial oscillation of the ship shaft system directly affects the hull through the thrust bearing. In order to solve with the problem of determining the forced and resonant axial oscillations based on the Runge-Kutta numerical method is done by directly integrating the system of 2nd order differential equations in describing the oscillations. Therefore, the paper presents the research results in proposing a procedure to reduce the order of 2nd order differential equations and providing an algorithm to solve the system of differential equations in describing axial oscillations. From that, it will be considered that the mechanism under which forces of variable value are applied to it, axial oscillation occurs. The accuracy in calculating of the axial oscillation depends not only on the accepted method of determining the free and forced oscillation, but also the proper in giving the parameters of the discrete model. If the masses are easy to calculate, the evaluation of the axial deformation of the crankshaft is not univariate because there are many formulas given on the basis of idealizing the crankshaft under the structure of bar. Hence, it is proposed to build a 3D model and determine the deformation of the engine crankshaft components by the finite element method.

Design of Power and Energy System for a Small Garbage Cleaning Ship

Port garbage and dirty oil will cause pollution to the marine environment, and the sea area of port is narrow and not easy to clean, which limits the use of conventional cleaning ships. There is a need for an environmentally friendly and flexible small garbage cleaning ship. This study introduces the composition and principle of the ship propulsion system, analyzes and calculates the characteristics of the motor and the power of the ship shaft, determines the type of the motor and the composition of the energy system, and further analyzes and calculates the solar power generation system. The results show that the mode of using lithium battery as main energy and solar energy as auxiliary energy can meet the power needs of the small cleaning ship and meet the relevant environmental protection requirements.

Automatic Test Method for Dynamic Load of Ship Shaft-belt Power Generation System

Zheng, H., 2020. Automatic test method for dynamic load of ship shaft-belt power generation system. In: Bai, X. and Zhou, H. (eds.), Advances in Water Resources, Environmental Protection, and Sustainable Development. Journal of Coastal Research, Special Issue No. 115, pp. 110-112. Coconut Creek (Florida), ISSN 0749-0208.Ship shaft generator is a power supply device widely deployed on large ships, which is driven by ship main shaft. Some automatic testing methods for power dynamic load of ship shaft-belt power generation systems have the problems of low testing accuracy and long testing time. Some large ship loads account for a large proportion of the ship's total load capacity. When this part of the load starts or stops, it will have a great impact on the ship's power grid. The traditional shaft generator system has many disadvantages, such as large loss, noise pollution, inconvenience in maintenance and inability to be coupled with the entire marine power grid. For the ship, the dynamic load test is the basis of the planning and control of the shaft power generation system. The accuracy of the test directly affects the stability of the shaft power generation system and the economy of the ship navigation. This paper analyzes the automatic test method of the power dynamic load of the marine shaft generator system, in order to meet the control demand of the marine power grid for the generator and realize the independent and stable operation of the marine diesel generator set.

Методика определения гидродинамических изгибающих моментов, действующих на судовой валопровод

The paper considers the problem of engineering systems design in modern shipbuilding, which is based on using the computer-aided design systems. In today’s environment, not all engineering calculations can be implemented in the form of an algorithm for a specific design procedure. One of these calculations is determining the resonant frequency of transverse vibrations of a ship shaft line. Analyzing the parameters of such a dynamic system is a serious task even at the stage of preliminary design. The urgent task in the design and strength calculations of the shaft line is to calculate the hydrodynamic bending moments resulting from the operation of the propeller in an uneven velocity field. There has been presented a software implementation of the semi-empirical methodology for determining the hydrodynamic bending moments acting on ship shaft lines. The main principles of the methodology, the initial data on the vessel hull, and the quantities characterizing the operating mode of the propeller are described. There is proposed a sequence and software implementation of the method for determining hydrodynamic bending moments in the environment of Maple computer algebra. The problem of representing empirical data in the form of bilinear interpolation and interpolation polynomial is solved. The results of a numerical experiment to determine the constant and amplitude values of the hydrodynamic bending moments for shaft shafts of full-scale vessels are presented. The software implementation of the technique proposed made it possible to automate the process of determining external forces in the calculations of the cyclic strength of the propeller shaft at the early stages of the design of the vessel. The research results are in addition to existing automation tools.