Polish Maritime Research

Analysis of Model-Scale Open-Water Test Uncertainty

2023-01-19T09:19:49+01:00

Within the frame of CTO’s standard procedure, a propeller open-water test is preceded by a reference measurement, which is taken for a reference propeller model (P356). The results of these measurements are assembled to conduct an open-water test uncertainty analysis. Additional material was gathered from open-water tests that were conducted throughout several research projects on the CP469 model, which is a model of the Nawigator XXI propeller. The latter is a controllable pitch propeller; its pitch was reset before each test repetition. Known procedures for the determination of the open-water test uncertainty do not allow one to extract the manufacture impact directly, without building many models. This factor was addressed with the use of lifting surface calculations. Under certain additional assumptions, these calculations were performed for 100 generic versions of each propeller’s geometry, which were generated by random deviations from the theoretical data within the limits of allowed tolerances. The results of the conducted analyses made it possible to extract separate factors, which were connected to the test’s repeatability, measurement bias and geometry tolerance.

Simulation of Turning Manoeuvre of Planing Craft Taking Into Account the Running Attitude Change in a Simplified Manner

2023-01-19T09:41:25+01:00

The modelling and simulation of planing craft manoeuvres requires coupled six degrees of freedom (6 DOF) motion equations. A coupled 6 DOF motion equation needs hundreds of manoeuvring hydrodynamic coefficients (MHCs) that are mostly determined using the planar motion mechanism (PMM) test. The number of test runs is too high, unless a kind of simplification is imposed to the motion equations. This study modifies 6 DOF motion equations to 4+2 DOF motion equations in which heave and pitch equations are replaced by dynamic draught and trim (so-called running attitude), respectively. The method is applicable for a manoeuvre that commences in the planing regime and ends in the same regime. On that basis, the PMM test is conducted and the model is restrained in the vertical plane at a certain running attitude, determined by a resistance test. The 4+2 DOF method, together with MHCs from the PMM test, are employed for the simulation of turning manoeuvres of a 25° prismatic planing hull. The results of the simulation indicate that the 4+2 DOF method reasonably predicts the path of the craft during the turning manoeuvre and cuts the number of PMM tests required at the same time. The PMM test results show that MHCs are highly related to forward speed and wetted surfaces. The turning manoeuvre simulation shows that the non-linear terms of MHCs cannot be ignored. The STD/L (Steady Turning Diameter divided by Length of the craft) for a planing craft is very large, compared to ships.

Review of the Container Ship Loading Model – Cause Analysis of Cargo Damage and/or Loss

2023-01-19T11:40:57+01:00

As the maritime transport of containers continues to grow and container ships change in terms of design and construction, it is important to ensure the appropriate level of safety for this type of transport. Over the decades, the size and cargo capacity of container ships have been changing, and so have their manoeuvring restrictions and required stability criteria. It seems that changes in the regulations, technological development and increased stability requirements are not yielding satisfactory results – the causes of container ship accidents continue to show similar patterns. The present article refers to the problem of ensuring safety in sea container transport, with a particular focus on cargo processes. Its purpose is to determine cause-and-effect relations leading to the loss of containers at sea, and to develop a model of loading that could significantly raise the level of safety of container transport.The article provides a general description of threats to ships related to weather conditions, loading methods or stability limitations. A statistical analysis of the occurrence of damage and/or loss of cargo from container ships was carried out and the risk of cargo loss was assessed on the basis of data from 2015‒2019. A Pareto diagram was used for this purpose. The authors present the concept of the container ship loading model, which may contribute to increasing the safety of shipping in the future.

THREE-DIMENSIONAL PATH-FOLLOWING CONTROL OF AN AUTONOMOUS UNDERWATER VEHICLE BASED ON DEEP REINFORCEMENT LEARNING

2023-01-19T11:45:49+01:00

In this article, a deep reinforcement learning based three-dimensional path following control approach is proposed for an underactuated autonomous underwater vehicle (AUV). To be specific, kinematic control laws are employed by using the three-dimensional line-of-sight guidance and dynamic control laws are employed by using the twin delayed deep deterministic policy gradient algorithm (TD3), contributing to the surge velocity, pitch angle and heading angle control of an underactuated AUV. In order to solve the chattering of controllers, the action filter and the punishment function are built respectively, which can make control signals stable. Simulations are carried out to evaluate the performance of the proposed control approach. And results show that the AUV can complete the control mission successfully.

AUTONOMOUS CONTROL OF THE UNDERWATER REMOTELY OPERATED VEHICLE IN COLLISION SITUATION WITH STATIONARY OBSTACLE

2023-01-19T11:50:59+01:00

The article considers the problem of autonomous control of the underwater remotely operated vehicle mini Remotely Operated Vehicle (ROV) in a collision situation with a stationary obstacle. The control of the collision avoidance process is presented as a synthesis of fuzzy proportional-differential controllers for the control of distance and orientation concerning the detected stationary obstacle. The control of the submergence depth of the underwater vehicle has been adopted as a separate control flow. A method to obtain the main motion parameters of the underwater vehicle relative to the detected stationary obstacle using a Laser-based Vision System (LVS) and a pressure sensor coupled to an Inertial Measurement Unit (IMU) is described and discussed. The result of computer implementation of the designed fuzzy controllers for collision avoidance is demonstrated in simulation tests and experiments carried out with the mini ROV in the test pool.

IMPACT OF PROPELLER EMERGENCE ON HULL, PROPELLER, ENGINE, AND FUEL CONSUMPTION PERFORMANCE IN REGULAR HEAD WAVES

2023-01-19T11:55:02+01:00

In this study, the impact of propeller emergence on the performance of a ship (speed), propeller (thrust, torque, and RPM), a diesel engine (torque and RPM) and fuel consumption are analysed under severe sea conditions. The goal is to describe the variation in the system variables and fuel consumption rather than analysing the motion of the ship or the phenomenon of propeller ventilation in itself. A mathematical model of the hull, propeller, and engine interactions is developed in which the propeller emergence is included. The system parameters are set using model experiments, empirical formulae, and available data for the engine. The dynamic response of the system is examined in regular head waves under submerged and emerged conditions of the propeller. The pulsatility and the extent of variation of 20 selected variables for the coupled system of hull, propeller, and engine are elaborated using quantitative and qualitative terms and absolute and relative scales. The simulation begins with a ship moving on a straight path, in calm water, with a constant speed for the ship, propeller and engine under steady conditions. The ship then encounters regular head waves with a known time series of the total resistance of the ship in waves. Large motions of the ship create propeller emergence, which in turn reduces the propeller thrust and torque. This study shows that for a specific ship, the mean ship speed, shaft angular velocity, and engine power were slightly reduced in submerged conditions with respect to calm water. We compared the mean values of the variables to those in the emerged condition, and found that the shaft angular velocity was almost the same, the ship speed was considerably reduced, and the engine power significantly dropped with respect to calm water. The ratios of the amplitude of fluctuation to the mean (Amp/Mean) for the ship speed and angular velocity of the shaft under both conditions were considerable, while the Amp/Mean for the power delivered by the engine was extremely high. The outcomes of the study show the degree of influence of propeller emergence on these variables. We identify the extent of each change and categorise the variables into three main groups based on the results.

ENERGY AND EMISSION QUALITY RANKING OF NEWLY PRODUCED LOW-SULPHUR MARINE FUELS

2023-01-19T11:58:42+01:00

The article describes the methodology of engine tests on new types of low-sulphur marine fuels in laboratory conditions in order to conduct a comprehensive assessment of their suitability for powering full-size marine engines. The innovativeness of the proposed solution consists of adapting the laboratory Diesel Engine Test Bed to carry out experimental tests using residual and alternative fuels so that it is possible to imitate the real operating conditions of the ship engine. The main aim of the research program was to assess the energy efficiency of six different low-sulphur marine fuels and their impact on the chemical emissivity of engine exhaust gases and air pollution with toxic and harmful chemical compounds. In order to achieve the research purpose formulated in this way, it was necessary to: (1) equip the constructed laboratory stand with highly specialised measuring equipment and (2) develop a technology for determining diagnostic parameters representing the basis for developing a ranking of the energy and emission quality of the tested marine fuels according to the proposed physical model. The model distinguishes 10 diagnostic parameters that, after normalisation, form two subsets of evaluation parameters - stimulant and destimulant. Determining their values made it possible to estimate a synthetic variable, according to which all the tested fuels were adjusted in the order from the “ best” to the “worst”, in accordance with the adopted qualitative criteria of such an assessment. The results of the laboratory tests show that among the considered fuels, i.e., MDO, MGO, RMD 80/L, RMD 80/S, RME 180, and RMG 380 type, the best solution is to use MDO distillate fuel to power full-size marine engines. However, taking into account its high purchase price, a rational alternative decision is to choose RMG 380 type residual fuel, which ranks second in the ranking of the functional quality of the tested marine fuels.

CONCEPT OF VIBROACOUSTIC DIAGNOSTICS OF THE FUEL INJECTION AND ELECTRONIC CYLINDER LUBRICATION SYSTEMS OF MARINE DIESEL ENGINES

2023-01-19T12:09:39+01:00

Although direct measurements of the fuel injection pressure and the travel of the injector needle in conjunction with measurements of the valve train mechanism timing can provide complete diagnostic information about the technical conditions of the fuel injection and valve train systems, this requires the installation of sensors and other equipment directly into the systems, which is possible within research laboratories but is generally forbidden during operation of the ship. Malfunctions in the fuel injection and valve train systems can also be identified from the indicator diagrams of an engine operating cycle, expressed as P(V) and P(deg) diagrams. The basic parameters of the engine operating cycle, such as the maximum combustion pressure Pmax, compression pressure Pcompr, and indicated mean effective pressure IMEP, can also be used to indicate deviations from proper engine operation. Using a combination of a vibration sensor with an in-cylinder gas pressure sensor widens the capabilities of diagnostics for marine diesel engines under operational conditions. A vibration sensor with a magnetic base can help in determining the timings of the lifting and landing of the injector needle, fuel delivery by the fuel injection pump, opening and closing of the circulation of heated heavy fuel oil, and opening and closing of the gas distribution valves. This also offers a promising solution for diagnostics of the cylinder lubrication oil injectors. The proposed approach allows valuable information to be received during engine operation in accordance with the principle of non-destructive control, and can help in early detection of possible engine malfunctions.

OPTIMISATION OF RELIABILITY AND MAINTENANCE PLAN OF THE HIGH-PRESSURE FUEL PUMP SYSTEM ON MARINE ENGINE

2023-01-19T12:33:32+01:00

This paper presents a method of adjusting and designing the maintenance scheme for the high-pressure fuel pumps of a slow-speed two-stroke marine engine, MAN 6S70MC-C. The maintenance database for the marine fuel system was obtained from the planned maintenance software, and covered a period of 11 years. During this period, 29 failures occurred that required corrective actions. Our methodology includes failure mode analysis, risk analysis, reliability calculation and maintenance interval adjustment. Each failure is described using a failure mode analysis, based on a combination of the mode and cause of failure. The objective of this study is to recommend a new preventive maintenance interval based on the exponential reliability results and the analysed maintenance data. The initial maintenance plan for each fuel pump was set to 8,000 running hours, whereas in the modified plan, it is recommended to set this to 4,000 hours. Our results show an increase in the system reliability from 60% to 95% when the new modified maintenance plan is applied. In addition, the results and the recommended initial maintenance schedule are validated based on three similar types of engine with the same fuel pump system. The new maintenance approach can reduce the risk of component failure, which will lead to increased reliability of the fuel pump system and the optimisation of maintenance costs.

A Convolutional Neural Network-Based Method of Inverter Fault Diagnosis in a Ship’s DC Electrical System

2023-01-19T12:48:29+01:00

Multi-energy hybrid ships are compatible with multiple forms of new energy, and have become one of the most important directions for future developments in this field. A propulsion inverter is an important component of a hybrid DC electrical system, and its reliability has great significance in terms of safe navigation of the ship. A fault diagnosis method based on one-dimensional convolutional neural network (CNN) is proposed that considers the mutual influence between an inverter fault and a limited ship power grid. A tiled voltage reduction method is used for one-to-one correspondence between the inverter output voltage and switching combinations, followed by a combination of a global average pooling layer and a fully connected layer to reduce the model overfitting problem. Finally, fault diagnosis is verified by a Softmax layer with good anti-interference performance and accuracy.

DESIGN AND OPERATIONAL DIAGNOSTICS OF MARINE PROPELLERS MADE OF POLYMER MATERIALS

2023-01-19T12:54:12+01:00

There has been a rapidly growing interest in the use of composite and polymer materials for the construction of marine propellers for over 20 years. The main advantages of these materials are a reduction in the weight of the propeller, increased efficiency due to the hydroelasticity effect, a reduction of the hydroacoustic signature, and a cost reduction for serial production. This paper presents an overview of diagnostic methods that can be applied at the design level and during the operation of marine propellers made of polymeric materials. Non-invasive contact and non-contact-based diagnostic techniques for evaluating the technical state of the propeller are reviewed, and the advantages and disadvantages of qualitative and quantitative methods are identified. Operational diagnostic procedures for propellers are areessential for the safety of vessels at sea. Finally, the structure of a diagnostic system is proposed. It combined diagnosis process with the genesis of damage and the prognosis of the technical condition, i.e. production and in-service diagnostics.

Monitoring the Gas Turbine Start-Up Phase on a Platform Using a Hierarchical Model Based on Multi-Layer Perceptron Networks

2023-01-19T12:58:50+01:00

Very often, the operation of diagnostic systems is related to the evaluation of process functionality, where the diagnostics is carried out using reference models prepared on the basis of the process description in the nominal state. The main goal of the work is to develop a hierarchical gas turbine reference model for the estimation of start-up parameters based on multi-layer perceptron neural networks. A functional decomposition of the gas turbine start-up process was proposed, enabling a modular analysis of selected parameters of the process. Real data sets obtained from observations of the turbo-generator set located on a North Sea platform were used.

EXPERIMENTAL RESEARCH OF THE IMPACT OF SHIP’S ROLLING ON THE PERFORMANCE OF PV PANELS

2023-01-19T13:02:05+01:00

The aim of the International Maritime Organization (IMO) to reduce by half the amount of greenhouse gases emitted by marine ships by 2050, and its vision of the fastest total decarbonisation in the maritime shipping industry within the present century, calls for implementation with various means of decarbonisation. The IMO approaches the process of decarbonisation in two phases. Firstly, short-term, compact projects are to be considered, next, more complex, medium- and long-term solutions should be aimed at. The preferred arrangements to be applied are photovoltaic systems. Their performance depends to a high degree on the solar incidence angle. In the case of a ship swinging as a result of its course in relation to the wave and incidence direction, the incidence angle undergoes significant periodic changes with a significant effect on the power generated by the PV panels. As a result, the total amount of energy produced by the PV panels diminishes. The paper presents experimental research results obtained on the stand that allowed the investigation of PV panels in simulated marine conditions. Two characteristic positions of a PV panel’s rotation axis in relation to the solar rays’ incidence direction were investigated. It was proved for both variants that the rolling period and solar incidence angle affected the power generated by the PV panel.

Dynamic analysis and experiment of underactuated double-pendulum anti-swing device for ship-mounted jib cranes

2023-01-19T13:09:10+01:00

This paper proposes a three degrees of freedom parallel anti-swing method by the main and auxiliary cables to address the problems related to underactuated double-pendulum anti-swing for a ship-mounted jib crane. By analysing the dynamic coupling relationship between the swing of the hook and the payload, it seeks to establish an accurate dynamic model of the anti-swing device under the ship’s rolling and pitching conditions, and discusses the influence of ship excitation, the crane state, load posture and anti-swing parameters on the in-plane and out-of-plane swing angles. The analysis shows that the primary pendulum reduces the in-plane angle by 90% and the out-of-plane angle by 80%, the in-plane angle of the secondary pendulum is reduced by 90%, and the out-of-plane angle is reduced by 80%. The reliability of the simulation data is verified through experiments.

A TRIBOELECTRIC NANOGENERATOR BASED ON A PENDULUM-PLATE WAVE ENERGY CONVERTER

2023-01-19T14:12:37+01:00

Ocean waves are a promising source of renewable energy, but harvesting this irregular low-frequency energy is challenging due to technological limitations. In this paper, a pendulum plate-based triboelectric nanogenerator (PP-TENG) is proposed. The PP-TENG absorbs wave energy through the pendulum plate installed at the bottom of the device, which generates a swing effect. This drives the motion of the upper TENG power generation unit and generates a charge transfer on the surface of a film of polymer PTFE and nylon, materials which are very sensitive to the low-frequency wave environment. The PP-TENG was tested after building a semi-physical simulation test platform. When the polymer materials were PTFE with a thickness of 0.01 mm and nylon with a thickness of 0.02 mm, 33 commercial LED lamps could be lit simultaneously. Moreover, under short-circuit conditions, the current reached 2.45 μA, and under open-circuit conditions, the voltage reached 212 V. When the PP-TENG was connected in series with a resistor with a resistance of 3 x 105 Ω, its maximum peak power density reached 6.74 mW/m2. It can be concluded that the PP-TENG is characterised by low fabrication costs and excellent energy conversion efficiency. The combination of a pendulum wave energy converter with a TENG shows great output performance. This research lays a solid foundation for practical applications of the proposed structure in the future.