No. 128 (2023)

The current issue of the Scientific Journal of Gdynia Maritime University contains publications on various topics, covering issues related to the field of engineering and technical sciences and the scientific discipline of mechanical engineering.

The article entitled “The impact of the addition of effective microorganisms on selected parameters of engine oil” suggested increasing the application time forlubricants used in piston combustion engines by adding dedicated microorganisms. This could potentially help reduce the amount of biocides added to engine oils and potentially extend the period between oil changes.

The author assessed the impact of intentionally introduced microbiological additives on the following properties of lubricating oil: kinematic viscosity, dynamic viscosity and density.

The aim of the article entitled “The influence of the burnishing process on the hardness and surface roughness of aluminum welded joints” was to assess the impact of the burnishing treatment on the quality of the surface layer of butt weld faces used to connect individual segments of pipelines. The pipes were made of the EN AW-6060 aluminum alloy. Method 141 (TIG) was chosen to join the segments. Parameters of the surface layer, such as roughness and hardness, were analysed.

The article entitled “Kinematic and dynamic modelling of nonholonomic mobile robots” presents the important and current problem of modelling the kinematics and dynamics of mobile robots. The usefulness of the mathematical model applied, Jacobian and Lagrange equations of the second kind, for designing the drive and actuator systems of a wheeled mobile robot was assessed. Computer simulations were performed using the Matlab/Simulink computer program.

The authors of the study entitled “Influence of added water mass on ship structure vibration parameters in virtual and real conditions” presented a method for assessing the impact of water attenuation on the natural frequency values of structural elements of the hull and superstructure of marine floating objects.

Both model tests using the finite element method and empirical experiments were performed. By comparing the results of both research methods, the error value of the mathematical analysis was assessed.

Based on their research, the authors concluded that the selected method of the numerical model – the finite element method on the Patran-Nastran software platform – provided relatively accurate calculation results with acceptable errors. The proposed calculation method may be applied in practice during the initial design of marine structures.

The issue discussed in the publication entitled “Evaluation of the process of condensation of water vapour in the presence of deposits using a single pipe in the heat exchanger of a condensing power plant as an example” is, according to the reviewers, important in the context of the use of power units and also for the design of micro- and low-power steam power plants offered for the distributed energy sector. The material material is based on the results of experimental research. It has been shown that the relative loss of the mass flow of water vapour condensing on a pipe covered with deposits with a determined value of thermal resistance of 1.9*10^-5 m²K/W ranges from 5% to 11%.

The last paper examines the dynamic characteristics of energy flows in electricity, heat, and gas sectors, focusing on the H2 microgrid's role in supplying heat and gas alongside electricity. The paper also analyzes the behavior and impact on grid stability of batteries, power electronics, and electrical loads in the microgrid, and compares overall efficiencies in coupling electric power and gas sectors through electrolysis and fuel cells.

Robert Starosta