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Research Bulletin by Russian Maritime Register of Shipping

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No 76 (2024)
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SEAWORTHINESS

4-15 31
Abstract

Navigation in old ice channels filled with broken (or brash) ice is a frequent operational scenario for ice-going ships, and at the same time insufficiently studied. The purpose of the present work is to study the change of ship propulsion performance in brash ice as compared with open-water conditions taking Yury Topchev, one of the ice-going ships currently in service, as a case study. Two related tasks to the propulsion performance study have been performed in the paper: 1) the brash ice resistance assessment of ship moving in the channel, and 2) analytical assessment of the change in propeller in thrust and power demand, in brash ice conditions as compared with open water. Numerical simulations have shown that a brash ice layer with the thickness equal to 0,2 propeller diameter reduces propeller efficiency by up to 20 %. Propulsion performance calculations for Yury Topchev, including the assessment of both hull resistance and propeller hydrodynamics have shown that in brash ice with the thicknesses of 1 and 3 m (0,125 and 0,375 draft) the maximum speed of this ship might drop as low as by 25 % and 40 % respectively. The results of this study may be used in planning of long ship voyages in ice conditions, when the changes in propulsion performance due to brash ice become especially relevant.

16-21 38
Abstract

Due to the active development of probabilistic approaches to stability normalization, there is a need to study and adapt them to existing practice. The article provides an overview of probabilistic methods of stability assessment and various schemes for constructing probabilistic stability criteria. The review of various physical models of behavior of a vessel exposed to various external effects during operation is carried out. The objective of the review was to determine the most optimal method of probabilistic stability assessment for rationing purposes. From the review, it can be seen that the probabilistic method of stability assessment should take into account many random factors, such as loading, ship speed, heading angle, sea state, the presence or absence of additional heeling effects, such as the impact from the jerk of the tow rope, cargo breakage during lifting operations, etc. It is also necessary to take into account the specific operating modes which are actual for certain types of ships. In conclusion, it is noted that it is possible to build stability standards based on probabilistic methods and the need to take into account the time spent in various operating conditions is noted.

22-37 69
Abstract

In the process of designing ice-going ships and icebreakers, one of the key tasks is to determine the parameters of their ice-going capabilities, i.e. the ability to overcome ice of maximum thickness at a steady speed of 2—3 kt when the power plant is operating at maximum power. Ice-going capabilities depend on a whole range of factors, the most important of which are ice resistance, thrust of the propulsion system and the power of the power plant.
This work is the first part of a study focused on the development of recommendations for the selection of existing computational methods for determining the ice resistance to ship movement in level ice. Despite the extensive accumulated experience and the development of a number of calculation methods, their application is limited. The reason for these limitations lies in the imperfection of the developed mathematical models of the interaction of the ship's hull with the ice cover, as well as in the inconsistency of the applied empirical coefficients with modern ship designs. At the same time, it should be noted that different methods have different calculation results in terms of accuracy for ships of different classes and sizes. This is also due to the specifics of the mathematical models used and the number of factors considered.
The paper analyzes and systematizes scenarios of interaction between the hull of a vessel of various types with a level ice. Next, the existing computational methods for determining ice resistance are considered and their SWOT analysis is provided. In the second part of the study, it is proposed to provide data on the verification of the considered methods by experimental research data. Based on the results obtained, recommendations will be formed on the choice of calculation methods depending on ice conditions, the type of vessel and the shape of its hull. Research aimed at solving the problem of improving the accuracy of forecasting ice resistance values at the preliminary stages of design is relevant and can significantly reduce the financial and labor costs of design organizations.

STRENGTH OF SHIPS AND FLOATING FACILITIES

38-51 34
Abstract

Active development of the ocean by developed countries dictates the need for intensive deep-sea operations without direct human control by means of autonomous underwater vehicles (AUVs). Recently, the installation of manipulators on AUVs has become of particular relevance. A variant of hybrid submersibles classification is presented. The basic stages of vehicle design are considered: calculation of strong hulls using computer-aided design systems, determination of main characteristics and dimensions. A variant of the self-equilibrated manipulator complex layout is presented.

52-62 33
Abstract

The article discusses the main provisions of the methodology for determining permissible speeds of a ship, based on a new model of dynamic ice destruction. Calculated dependences for determining ice load parameters of the new model do not allow us to explicitly identify the values associated with the speed of movement of a ship, with ice thickness and hull shape parameters. In this regard, the inverse problem of determining the permissible ship speed and ice thickness for a given structural strength presents significant mathematical difficulties. The proposed method for solving the inverse problem is based on the use of the approximation apparatus of the experimental planning method to construct regression dependencies for ice load parameters and the mathematical programming apparatus to establish a connection between construction and ice strength.

DESIGN OF SHIPS AND FLOATING FACILITIES

63-73 14
Abstract

In the present work, a multi-criteria task of choosing types of offshore technical structures at the stage of conceptual design was undertaken. Criteria that allow evaluate and compare the offshore technical structures types were defined. Features of defining the criteria for marine structures have been established; at the same time, the indicators, including calculation assessments and regulated by normative documentation (the Register Rules), were not considered as criteria. The marine technical structures type for a given range of depths is determined with a minimum amount of initial data as a result of the researches at the conceptual design stage. An assessment of the consistency of opinions of the expert group was carried out.
The aim of the work was to determine the possibility of applying the methods of rank correlation in the design of marine technical structures at the conceptual design stage (that is, at the initial stage with a minimum amount of input data) and the applicability limits of various offshore technical structures for the shelf development. To solve the problem, the principle of unity was used, when the system (the offshore technical structure) was considered both as a whole and as a set of elements (criteria). Based on the method of expert assessments, the choice of the structure type was made at the initial stage of design, in conditions when the input data is practically absent. The Delphi method was chosen for the expert survey procedure. The experts presented their judgment assessed by ranking of the proposed options on the 10-point assessment scale. The ranking of criteria was determined using the hierarchies’ analysis method. The consistency degree of the expert group was evaluated using the Spearman's rank correlation coefficient.

74-86 28
Abstract

The article examines foreign norms for determining the number and carrying capacity of harbour tugs in various ports. The purpose of the study is the analysis of different approaches as well as parameters of tugs for towing operations in confined operation areas based on the size of transport vessels. The result of study is the identification of the interrelation between the size of transport vessels and the operational characteristics of harbour tugs for their processing. Options were determined for the number and capacity of harbour tugs in relation to transport vessels of the required standard sizes in accordance with foreign rules of different ports. This will potentially help to understand in which ports these requirements are closest to the requirements of mandatory regulations of the Russian Federation seaport captains. The research also allowed to conclude that a more convenient criterion for selection of a towing connection required for tugging and towing of transport vessels is not the mechanical power of its main engines, but the tractive force on the hook developed at headway movement.

MECHANICAL INSTALLATIONS AND PROPULSION

87-95 39
Abstract

The paper examines the existing international and domestic regulatory framework for the control of the carbon footprint of sea transport. The aim of the study was to assess the impact of the type of marine fuel used on the carbon footprint of the transport service, determined through the energy efficiency coefficient of the transport vessel. The materials and methods used were generalized and analyzed research materials of domestic and foreign scientists, as well as relevant guidance documents. The article presents the results of calculating the carbon footprint of transport vessels of various types with ice reinforcements of class Arc7 on sections of the Northen Sea Route using various types of marine fuels. The use of the presented methodology for estimating the carbon footprint made it possible to quantify the impact of the type of marine fuel used on the carbon footprint of a transport service, determined through the energy efficiency coefficient of a transport vessel. The calculations presented in the study allow us to draw several important conclusions: the use of alternative fuels can significantly reduce the amount of greenhouse gases emitted into the atmosphere, the best results were demonstrated by methanol and ammonia — the amount of CO2 equivalent emitted decreased by 57 % and 96 %, respectively.

96-105 50
Abstract

The influence patterns of the intake valve shape on the characteristics of the air vortex in the cylinder of a marine engine are studied. The literature review showed that the scientific side of the issue of improving the design of intake valves is studied by scientists and engineers from leading universities and technology companies around the world. Unresolved scientific issues hinder the large-scale use of valves with screens and spiral guides in marine diesel engines. Therefore, further research in this area is an urgent task. The article presents the results of a study of the influence of the wrap angle of the screen and spiral guides on the intake valve on the filling factor, swirl number, average and pulsation velocities of the air vortex in the cylinder of the 16D49 marine diesel engine. The mathematical model of the working process of the marine engine was based on three-dimensional equations of unsteady transfer. The k-ω SST turbulence model was used to determine the turbulence characteristics. It was found that the use of valves with guide inserts contributes to the formation of an organized orderly air movement around the engine cylinder axis; reduction of the filling factor by 1 — 4 %; increase of the swirl number by 2.7 times; reduction of the pulsation velocity by 3.9 times and increase of the average flow velocity by 3.6 times. It is shown that the use of valves with guide inserts can be a relevant solution for organizing the vortex movement of air in the cylinder of a marine engine.

106-118 44
Abstract

The article analyses the experience of application of different types of power plants on Aframax class ships. Features, advantages and disadvantages of steam turbine, gas turbine, electric, conventional diesel and combined units are considered. Special attention is paid to the introduction of multi-fuel solutions, integration of heat utilisation and electric propulsion technologies. The comparison of promising concepts of power plants based on a set of criteria of energy efficiency, environmental friendliness and flexibility is carried out. Optimal configurations of EPS for the main types of Aframax class ships are proposed. Priority areas in the context of fleet decarbonisation trends are framed.

119-128 29
Abstract

Two new energy efficiency indicators of different types of marine fuel are proposed: the coefficient of carbon intensity of the fuel CEFCO2 and the relative coefficient of carbon intensity of the fuel KOET. A method is proposed for assessing the effect of the fuel used on the ship on the operational carbon intensity index of the CII vessel using the proposed carbon energy intensity coefficients. According to the methodology for assessing changes in CII when transferring ships from heavy fuel to diesel (motor) fuel, it provides an improvement in the energy efficiency of the CII vessel by approximately 5 — 7 %. The results of the assessment were compared with data on the operation of Atlantic-333 type ships using two types of fuel, which showed a good match.
The data on the change in fuel and oil consumption when using heavy fuel compared to distillate fuel after the conversion of the main engines of the 6M20 type of the company MAK to heavy fuel on ships of the Atlantic-333 type are presented. Based on these data, an assessment of heavy fuel losses associated with leaks and fuel preparation costs for marine consumers is carried out. It also provides data on changes in the life of various engine parts and an increase in maintenance work on the ship.
In connection with the introduction of the MARPOL Convention ban on the use of heavy fuel in polar waters and the introduction of energy efficiency requirements, it is concluded that there is a trend towards wider use of distillate diesel fuel on ships flying the Russian flag.

129-136 31
Abstract

The crankshaft is considered as the main part of a marine internal combustion engine. As the object of research, the crankshaft of the 6CHN 31.8/33 diesel engine used on ships as the main marine engine is chosen. The reasons leading to the violation of the geometry of the longitudinal axis of the crankshaft are determined. The cases of crankshaft deflections exceeding the permissible values are systematized. A maximum deflection of 4.10 mm is recorded with an acceptable value of 0.03 mm. The fourth frame neck is marked, which accounts for the largest number of curvatures of the longitudinal axis of the crankshaft. The dependence of the deflection value on the number of the frame neck and the repair size is determined. The thermal correction with heating by an oxygen-gas flame of the crankshaft approved and used at repair enterprises of JSC Russian Railways is considered. It is noted that the neck heating temperature during thermal correction is significantly higher than the temperature at which structural changes occur in the shaft material, and spot heating can lead to stresses exceeding the tensile strength of the shaft material. A thermomechanical correction of crankshafts based on the phenomena of creep and stress relaxation is proposed. It is proposed to calculate the force with which we act on the shaft according to the formulas of the resistance of materials, and to control the magnitude of the stress by calculating the deflection arrow. The necessity of continuing research in the field of operational reliability of crankshafts of marine internal combustion engines after their restoration by thermomechanical correction based on the phenomenon of creep and stress relaxation is confirmed.

137-147 137
Abstract

The object of this paper is to present the main results of a Walk to Work system conceptual design.
The main purpose of a Walk to Work system is offshore people transfer to various technological means of ocean development, such as oil/gas platforms, wind turbines and, potentially, other objects: unmanned vessels, fish farms etc. The main elements of a Walk to Work system are a telescopic gangway and a compensating system which minimizes the effect of vessel rolling, pitching and heaving on people crossing the gangway to an offshore structure or a vessel. The main particularity of the designed system is its capability of operating in all of Russia’s offshore areas where expected to be necessary.
The relevancy of this work is defined by Russia’s import independence policy as such systems are currently not produced in the country. The fact that the leading positions in the Walk to Work sphere are taken by the ‘unfriendly states’ leads to severe limitations in technological interaction and therefore, a need for Russia’s own systems of such type.
The pre-design stage included creation of a database concerning the specifications of existing Walk to Work systems and vessels, research of weather and climate conditions in the expected regions of operation as well as other theoretical data collection. This was done with the aid of manufacturers’ official websites, register records of ship classification societies, official reference sources as well as various media materials as additional sources of information. The further determination of the system’s main characteristics was based on strength, stiffness and deflection calculations.
The design is based primarily on the Code for Offshore Personnel Transfer Systems by Lloyd’s Register as this Code contains the most precise and detailed guidelines on offshore gangway systems. However, the requirements of Rules for the Cargo Handling Gear of Sea-Going Ships by the Russian Maritime Register of Shipping as well as of DNV-ST-0358 ‘Offshore Gangways’ by Det Norske Veritas are also met.
The data collected during the design process shall be of a significant aid during further development of the described conceptual design as well as creation of new types of Walk to Work systems and development of projects for re-equipment of vessels. It can also be important for preparation of amendments to the Rules of the Classification Society.
The integration of Walk to Work systems into the offshore industry shall contribute to safety, efficiency and comfort during personnel transfer operations to marine installations in the seas of Russia.



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ISSN 2223-7097 (Print)