Wyniki wyszukiwania - BazTech

1

Transfer function for a controllable pitch propeller with added water mass

Leshchev Volodimir, Maslov Igor, Palagin Oleksandr, Naydyonov Andrii

Polish Maritime Research

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2023

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nr 4

74--80

EN

The relevance of this study lies in the fact that it presents a mathematical model of the dynamics of the propulsion system of a ship that takes into consideration the mass of water added to it. The influence of this phenomenon on the resonant frequencies of the propeller shaft is examined, and a transfer function for a controllable-pitch propeller is obtained for various operating modes. The purpose of the study is to improve the calculation of the dynamic operating modes of a controllable-pitch propeller by examining the features of a visual models. The VisSim software package is used in the study. A visual model is developed that considers the influence of the rotational speed on the value of the rotational inertia attached to the variable-pitch screw of the mass of water, and a special transfer function is proposed. The study shows that a transfer function of this type has a loop enabling negative feedback. An analysis of the operation of the propeller shaft at its resonant frequency is conducted based on the application of frequency characteristics using the transfer functions obtained. We show that in the low-frequency region, a consideration of the added rotational inertia using the proposed transfer function leads to a significant difference compared to the result obtained with the existing calculation method.

2

Analiza oddziaływań dynamicznych na linię wałów okrętów transportowo-minowych

Grządziela A., Szymak P.

Przegląd Mechaniczny

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2017

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nr 9

32--37

PL

W artykule przedstawiono analizę oddziaływań dynamicznych na okrętową linię wałów z uwzględnieniem specyfiki działania okrętów transportowo- minowych, potocznie zwanych desantowymi – ODs. W pracy scharakteryzowano strukturę elementów transmisji mocy, przedstawiono model dynamiczny wału śrubowego oraz dokonano analizy wpływu oddziaływań silnika i pędnika na użytkowanie linii wałów w warunkach przybrzeżnych. Zdefiniowano potencjalne zagrożenia eksploatacyjne wynikające z problemów zejścia z mielizny brzegowej okrętu desantowego. Zaproponowano model oddziaływań zapiaszczonej wody dla obliczeń obciążeń dynamicznych wału śrubowego na płyciznach piaskowych i piaskowo-żwirowych.

EN

The paper presents shaftline analysis of dynamics impacts landing vessel, taking into account the specificity of the operation during hull contact with the sea bed. The structure of the power transmission components was characterized in the work, the dynamic model of the propeller shaft was presented. The main goal of the paper is analysis of influence of the engine and propeller effects on the use of the shaft lines in the coastal environment. Operational hazards resulting from the problem of descent from sea bed shifting of a landing ship have been identified. An interaction model of sandy water was proposed for calculating the dynamic loads of the propeller shaft on sand and gravel sand.

3

Analysis methods of crankshaft's stiffness characteristics

Murawski L., Charchalis A.

Journal of KONES

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2013

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Vol. 20, No. 1

219--226

EN

Development of on-line diagnostic (monitoring) method of marine propulsion system working parameters is the authors' target. Crankshaft springing characteristics are one of the most important from the ships' main engines reliability point of view. Planned monitoring system will be able to verify crankshaft springing characteristics by continuous measurements of the crankshaft free-end's axial deformations. Development of the analysis methods of crankshaft's stiffness characteristics is the first step of planned SHM system. The main purpose of research is method developing of the springing analysis for the marine crankshafts in the high-power engines. Crankshaft modeling method, by Finite Element Method, has been discussed. Short overview of the crankshaft boundary conditions is presented. Bearings' oil film stiffness characteristics, ship hull stiffness characteristics and temperature deformation of the ship hull and main engine body are taking into account. Influence of the crankshaft's foundation stiffness on springing values is analysed. During the analyses it was proved that flexibility of engine foundation has a big influence upon the value of crankshaft springing. The authors' method of cylindrical mass and gas forces decompositions has been presented. Analysis of modeling precision of piston-crank system's forces has been performed. Results of calculations are well compatible in the terms of quality with the measurements data.

4

Analysis Of Ship Shaft Line Coupling Bolts Failure

Dymarski C., Narewski M.

Journal of Polish CIMAC

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2009

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Vol. 4, no 2

33-40

EN

The ship propulsion shaft line is one of the most critical ship components having big influence on a ship safety. Because of that, there is well known need for proper shaft line survey either by ship crew, ship owner technical services as well as by classification society surveyors. One of the most dangerous and frequent kind of shaft line failures, especially on old ships, is a fatigue break of the collar coupling bolts. It usually causes the loss of the possibility to use the main propulsion system. In case of the bad weather and severe sea conditions it can lead even to the ship loss. The paper presents some data on failure statistics that was observed to shaft lines and propulsion system machinery. Furthermore, analyses of causes and generation mechanism of the mentioned fatigue breaks of the collar coupling bolts is presented.

5

Dynamic analyses of ships shafts lines

Grządziela A.

Systems Science

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2008

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Vol. 34, no 3

45-50

EN

Ship propulsion plant usually works in a hard environment caused by static forces and permanent dynamic loads. Exceeding tolerable values of shaft alignments causes damage to radial and thrust bearings in a relatively short time. The modeling of dynamical reactions could bring information for the designer to recognize the level of hazard to a propulsion system. The paper presents a proposal of identification of the degree of hazard to ship shaft line due to forces of shaft misalignment. A theoretical analysis was made of the influence of changes in co-axiality of shafts resulting from the elastic deformations of a hull structure in the vicinity of the shaft bearing foundations. The main problem concerning naval vessels is the lack of dynamical requirements as regards the stiffness of the hull. The modelled signals were recognized within sensitive symptoms of two sub-models: a model of propulsion system and a model of shafts misalignment. Both sub-models allow testing forces and their responses in vibration spectrum using SIMULINK software.

6

Metodyka obliczeń numerycznych ułożenia okrętowych linii wałów

Murawski L., Ostachowicz W., Krawczuk M., Żak A.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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1998

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z. 6

255-260

PL

W pracy przedstawiono nową metodę obliczeń optymalnego układania okrętowych linii wałów.; Zaprezentowano specjalistyczne programy komputerowe do wyznaczania linii ugięcia oraz obciążeń wału korbowego i linii wałów oraz do wyznaczania sztywnościowo-tłumieniowych charakterystyk dynamicznych łożysk okrętowych. Przeprowadzono analizę wpływu sposobów modelowania elementów układu napędowego na wyniki obliczeń parametrów pracy układu przeniesienia mocy.

EN

In the paper a new original method of marine shaft line alignment analysis is presented. Specialised numerical algorithms are used to determined shaft line deflection and crankshaft loading and also to determined stiff-dumping dynamic characteristics of the marine bearings. Modelling methods of the power transmission system and its involving on analysis results are discussed.