This paper introduces a spatial model of a riser and describes its application for determining the movement of a base (platform or vessel) in order to implement a planned path for the lower end of a riser. This scheme takes into consideration the fact that the lower end of the riser must bypass obstacles on the seabed despite the action of the marine environment (sea currents, hydrodynamic resistance, buoyancy forces, mass of added water). The task of determining the movement of the base is formulated as a dynamic optimisation process. As a result of this optimisation procedure, parameters are selected to characterise the functions describing the movement of the base at certain time points. These functions are then approximated by third-degree spline functions. A series of computer simulations is carried out for a riser with lower marine riser package and blowout preventer attached to its lower end. The riser is discretised by means of the lumped mass method. The proposed method is verified and validated, and can be used to determine the movement of a vessel when transporting a riser to a new position.
This article describes a study of a tubular–annular combustion chamber in a 25 MW gas turbine operating on a hydrogen–ammonia mixture, with the aim of determining its energy and environmental characteristics. A novel approach was developed for modelling the combustion processes of this mixture under conditions where the gaseous fuel was premixed with an oxidiser in the channels of radial–axial swirlers within flame tubes. A detailed kinetic scheme for mixture combustion within the eddy dissipation concept framework was used in three-dimensional calculations of the combustion chamber. It was found that the range of stable operation, without the formation of a flame flashback zone in the radial–axial swirler channels, was defined by an ammonia content exceeding 50% (by volume) in the mixture. The main features of the working process in the combustion chamber with different compositions of the hydrogen–ammonia mixture were analysed. The results will be useful for the design of advanced gas turbine engine combustion chambers as part of decarbonised energy systems.
Gas turbines are widely used as prime movers in marine power systems due to their high power density and thermal efficiency. With the increasing application of high-power gas turbine systems in the maritime industry, the modelling and dynamic characteristic analysis of medium-voltage gas turbine power systems have become increasingly important. This paper presents a nonlinear dynamic simulation model of a marine gas turbine medium-voltage AC power system, which was created in the MATLAB/Simulink platform using a modular approach. Load variation and multi-condition simulations were performed, and key indicators such as the generator terminal voltage, rotor speed, and grid frequency were analysed to reveal the dynamic behaviour of the system. The results show that the proposed model can reflect the dynamic operating process of a marine gas turbine power system. The control strategy adopted here can suppress the adverse effects of load fluctuations and external disturbances on the performance of the shipboard power grid, thereby improving the quality of operation. This work provides a basis for simulation and a theoretical reference for the design of marine gas turbine medium-voltage power systems.
The aim of this study was to explore the potential of using digital twins to enhance the accuracy and reliability of additive manufacturing under marine operating conditions. A comprehensive theoretical and analytical framework was developed for creating a digital twin for wire arc additive manufacturing (WAAM) in marine engineering, in which external destabilising factors were taken into account. It was found that without digital control, under conditions involving vibrations (0.2–3 Hz), temperature differentials of up to 500°C and platform instability, the risk of defect formation was increased. The numerical values reported here were derived from modelling results, a review of the literature, and analytical generalisation of published WAAM and digital twin data, rather than from new full-scale offshore experiments. The use of digital twins can enable real-time monitoring of parameters such as the wire feed speed (2–10 mm/s), arc power (300–1200 W), and feed angle (20–45°), thus allowing the heat transfer to be optimised and residual stresses to be reduced. Modelling-based synthesis and analytical generalisation of published data show that the implementation of this framework reduces the number of defective zones from 18 to four per component, decreases the energy consumption per part from 6.2 to 4.1 kWh, and improves the dimensional repeatability from ±0.9 to ±0.25 mm. Digital twins also allow the printing trajectory to be adapted to current conditions through integrated sensors and deformation modelling, thereby ensuring operational reliability on offshore platforms. The use of digital twins is therefore critically important for improving the accuracy, energy efficiency, and operational reliability of WAAM in marine environments.
Corrosion degradation of cargo and ballast tanks in marine structures strongly affects the operational lifetime and safety of floating units. Welded regions, including the weld metal and adjacent heat-affected zone, are particularly susceptible to localised corrosion due to microstructural heterogeneity and electrochemical differences. This paper describes a comparative laboratory investigation of the corrosion processes in welded and non-welded hull steel using acoustic emission monitoring supported by metallographic analysis. Accelerated corrosion tests were conducted using a KE-2 corrosion tester and a controlled corrosive solution to simulate an aggressive tank environment. Acoustic signals were continuously recorded using a Vallen AMSY-5 system equipped with VS-75 and VS-150 RIC sensors, and metallographic examination using optical microscopy was performed to characterise the corrosion pit morphology. The acoustic results confirmed the detectability of corrosion-related activity in both configurations, with clear separation of corrosion signals from background noise. However, despite the similar overall character of the acoustic responses in both cases, metallographic analysis revealed significantly different corrosion morphologies: numerous shallow pits were distributed across the surface of the non-welded specimen, whereas the welded specimen showed localised intensification with deeper pitting near the weld interface. This indicates that although acoustic emission is effective for real-time detection of active corrosion processes, it has a limited capability to distinguish the spatial characteristics and morphology of corrosion damage without complementary analysis. This study highlights both the potential and the limitations of acoustic emission monitoring in the assessment of corrosion processes in welded marine structures.
