As a part of ongoing research into the use of fuel cells to power underwater platforms, studies have been conducted to investigate the effect of change in oxygen flow through the proton exchange membrane fuel cell (PEM-FC) cathode channel, to develop a method for controlling this flow. Due to the lack of specific information or studies on the effect of pure oxygen flow through the PEM-FCs cathode channel on the correctness of its work, a series of experiments have been carried out within the framework of in-house research to determine this dependence. The experiment was conducted in series, during which the only change in the operating parameter of the PEM-FC stack was the stoichiometric flow rate of oxygen supplied to the cathode channel of the fuel cells’ stack. The research shows that for the PEM-FCs stack fed with pure oxygen, the cathode stoichiometry can be kept at a much lower level comparing to the systems supplied with air. It has been found that the fuel cells’ stack fed with pure oxygen will perform well in steady state while reducing the cathode stoichiometry by as much as 40% compared to systems utilising oxidant from atmospheric air.

This paper presents an alternative approach to the flow control of an oxidizer in a proton exchange membrane (PEM) fuel cell system in which pure oxygen is the gas supplied to the cathode channel of the stack. The proposed oxygen flow control is implemented based on information about the current drawn from the fuel cell stack and the voltage variation in the stack. This information and a fuzzy-logic-based control algorithm are used to increase oxygen utilization in a PEM fuel cell system without a recirculation system in relation to the control, in which the oxygen flow rate is determined only in proportion to the current drawn from the stack. To verify the validity of the adopted assumptions, simulation tests of the proposed fuzzy control algorithm were conducted, for which parameters were adopted arbitrarily and determined with help of genetic algorithms. For simulation research, the proposed empirical mathematical model was used, which describes the mathematical relationship between voltage variation in the stack and the stoichiometry of oxygen flow through the cathode of a fuel cell stack. The simulation results confirm that the proposed control method leads to an increase in the oxygen utilization in the system without oxygen recirculation compared to an open system with cathode stoichiometry set to a constant level.

For ships, the total loss of electrical power, ‘blackout’, is a critical failure. The failure of the marine power supply system not only results in loss of ability to perform tasks, but also poses a threat to human life and often to the environment. No less serious emergency is ‘partial blackout’, i.e. the loss of electricity in parts of the electrical system. Designers are introducing technical and system solutions to minimise the likelihood of power failure and to support its recovery in a timely manner. One of the methods to minimise the likelihood of power failure is to identify and then monitor diagnostic symptoms that are susceptible to approaching the failure of key components of the power system. This article discusses the use of recording and analysis of changes in voltages and excitation currents in parallel synchronous generators to determine the threshold above which their parallel operation can lead to an emergency power failure.

This paper investigates the detection of broken rotor bar in squirrel cage induction motors using a novel approach of randomly positioning a triaxial sensor over the motor surface. This study is conducted on two motors under laboratory conditions, where one motor is kept in a healthy state, and the other is subjected to a broken rotor bar (BRB) fault. The induced electromotive force of the triaxial coils, recorded over ten days with 100 measurements per day, is statistically analyzed. Normality tests and graphical interpretation methods are used to evaluate the data distribution. Parametric and non-parametric approaches are used to analyze the data. Both approaches show that the measurement method is valid and consistent over time and statistically distinguishes healthy motors from those with BRB defects when a reference or threshold value is specified. While the comparison between healthy motors shows a discrepancy, the quantitative analysis shows a smaller estimated difference in mean values between healthy motors than comparing healthy and BRB motors.

This article deals with the problems related to the difficulties in the vibration diagnostics of modern marine engines. The focus was on the injection system, with a particular emphasis on injectors. An unusual approach to the implementation of research enabling the smooth regulation of the opening pressure of the mechanical injector during engine operation at a constant load was presented. This approach obtained repeatability of conditions for subsequent measurements, which is very difficult to achieve when using the classic approach that forces the injector to be disassembled after each test.

The paper presents issues related to the operational safety of lithium-based batteries on vessels. In the first part of the paper the regulations of the Polish Register of Shipping (PRS), regarding the requirements for the batteries on a vessel are analysed. The next section presents the risks related to the use of lithium-based electric energy storage technology. The last part discusses the principles to be adopted during operation of lithium batteries to minimize the risk of threats.