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

Methodology of propeller strength calculations in settled and emerging work conditions

Murawski L.

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

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2018

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no. 2

37--44

EN

In the paper, the methodology of propeller strength analyses is presented. Numerical calculations based on the finite element method were used during the analyses. Analyses methodology is based on solid state mechanics with loadings determined by fluid mechanics calculations. Several propulsion working conditions (including steady-state and transient fluid flow) were taken into account. In order to determine the optimal modelling method of the propeller, several different numerical models were compared, including a free model of the whole propeller and single blade with boundary conditions placed in the foot. The propeller optimisation was the main target of the analyses. After numerical calculations, the propeller mass saving (in comparison to classification societies’ empirical formulas) was achieved.

PL

W pracy przedstawiono metodologię analiz wytrzymałościowych okrętowych śrub napędowych. Obliczenia numeryczne zostały oparte o metodę elementów skończonych. Metodologia analiz bazuje na mechanice ciała stałego z obciążeniami wyznaczanymi na podstawie mechaniki płynów. Szereg warunków pracy układu napędowego (włącznie z ustalonymi i nieustalonymi przepływami płynów) zostało wziętych pod uwagę podczas analiz. W celu wyznaczenia optymalnej metodologii obliczeń, zostały porównane różne modele śruby napędowej włącznie ze swobodnym modelem całej śruby napędowej oraz z pojedynczym skrzydłem śruby z warunkami brzegowymi umieszczonymi na jej stopie. Głównym celem analiz była optymalizacja masy śruby napędowej. W wyniku obliczeń numerycznych osiągnięto znaczną oszczędność masy śruby napędowej w porównaniu do śruby zaprojektowanej zgodnie ze wzorami empirycznymi towarzystw klasyfikacyjnych.

3

Some aspects of torsional vibration analysis methods of marine power transmission systems

Murawski L.

Journal of Polish CIMAC

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2012

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Vol. 7, no 1

175-182

EN

In the paper, the torsional vibrations of marine power transmission system's nonlinear method have been presented. Short presentation of marine propulsion system evolution (and its influence on ship's vibration level) in the last 30 years was included in the introduction. Some aspects of the modeling method of the elements of propulsion system have been shown. Comparison between one-degree model and 3-D Finite Element Method model was discussed. Short description of advantages and disadvantages of the undercritical and overcritical propulsion system was presented. Modeling method of propeller's mass characteristics and damping recalculation method have been shown as an example. Specialised software, for the marine power transmission system torsional vibration’s analysis, made by the author, has been performed as an iterative process. Also example of torsional vibration analysis, for tanker ship, was presented in the paper. A discussion about calculation results was included in the final part of the paper. Overcritical power transmission system is better for typical ship (with slow-speed main engine and directly driven propeller).