Knowing the process of generating exhaust emissions and the determination of influential parameters are important factors in improving two-stroke slow-speed marine engines, particularly for further reductions in fuel consumption and stringent regulations on the limitation of nitrogen oxide emissions. In this article, a model of a marine low-speed two-stroke diesel engine has been developed. Experimental and numerical analyses of the nitrogen monoxide formations were carried out. When measuring the concentration of nitrogen oxides in the exhaust emissions, the amount of nitrogen dioxide (NO₂) is usually measured, because nitrogen monoxide is very unstable, and due to the large amount of oxygen in the exhaust gases, it is rapidly converted into nitrogen dioxide and its amount is included in the total emission of nitrogen oxides. In this paper, the most significant parameters for the formation of nitrogen monoxide have been determined. Model validation was performed based on measured combustion pressures, engine power, and concentrations of nitrogen oxides at 50% and 75% of maximum continuous engine load. The possibilities of fuel consumption optimization and reduction in nitrogen monoxide emissions by correcting the injection timing and changing the compression ratio were examined. An engine model was developed, based on measured combustion pressures and scavenging air flow, to be used on board by marine engineers for rapid analyses and determining changes in the concentration of nitrogen oxides in exhaust emissions. The amount of nitrogen oxide in exhaust emissions is influenced by the relevant features described in this paper: fuel injection timing and engine compression ratio. The presented methodology provides a basis for further research about the simultaneous impact of changing the injection timing and compression ratio, exhaust valve opening and closing times, as well as the impact of multiple fuel injection to reduce consumption and maintain exhaust emissions within the permissible limits.

Antonija Mišura; David Sopta; Ana Perić Hadžić; Review, pp. 69-77 Download

The maritime domain is the common domain of special interest, so it has special protection of the state and certain rules of use. One of the models of the maritime domains management in the territory of the Republic of Croatia is the concessioning system, and it is based on various legislation and by-laws that determine the type of concessions, the method of determining the concession fee and the methods and criteria for awarding the concession. The concessions’ management is primarily related to the economic use of maritime domains. The aim of this article is to carry out a comparative analysis of the concessioning model of maritime domains in the territory of the Republic of Croatia and the European Union with a focus on the seaports. For the purpose of economic use, today’s models of the maritime domains’ concessioning in the territory of the European Union are not unambiguous, as they depend on the tradition and historical development of the system even though they are subject to constant changes. The carried out research points to the need of developing the system in the Republic of Croatia with the obligation to harmonising legislation, strengthening criteria within the system and increasing the degree of openness of the market in accordance with the European acquis.

This paper presents research in the field of optimization in maritime passenger traffic that can ensure the long-term sustainability of coastal maritime passenger lines system. For the purpose of the research contained in this paper, it has been hypothesized that the optimal arrangement of boats within a coastal maritime passenger lines system will reduce the consumption of propulsion energy, the emission of harmful gasses and operating costs. The aim of this paper is to present an efficient algorithm for a reduction in propulsion energy consumption in coastal maritime passenger lines systems by reassigning boats to lines that they service. The problem is modeled using a bipartite graph and the solution is obtained by searching for optimal matching using Edmonds’ algorithm. The authors apply, for the first time, Edmonds’ algorithm to the problems of the optimization of assignments of boats to lines. The research results were confirmed by tests on a representative example. The optimization results on only 10 ships in the given example show yearly savings of 91,097.30 L of fuel (lowering costs by EUR 69,233.95) and reducing CO₂ by 243.59 tons, which proves that this algorithm found a much more efficient arrangement that could result in a significant reduction in propulsion energy consumption, thus providing economic and ecological benefits.

Every day we witness the introduction of technological innovations into our daily lives, which are changing significantly under their influence. In the past, roots were drawn by hand with paper and pencil, then calculators appeared. Today, nobody tries to draw the root by hand anymore. People used to look for important information in encyclopedias and various archives and libraries, but today they turn to Google for every little thing… Using an example from the field of applied mathematics, we want to show how technology is changing the approach to solving relatively complex technical problems. The example presented in this paper is solving complex mathematical problems such as optimization using a method that has only recently become available through the development of technology. Advanced methods for solving optimization problems such as the Brents method or the Limited memory Broyden–Fletcher–Goldfarb–Shanno method with boundaries are now partially replaced by the Brute Force method, which is much easier to handle. This example shows that we are constantly adapting to new circumstances and that each generation uses the latest knowledge available, changing the approach to daily practice. Adapting to new circumstances and technologies and abandoning and neglecting old methods (i.e. optimizing the necessary acquired knowledge) leads to the false claim that the new generation does not know and does not want to learn the basic methods.

One of the preconditions for good quality management of seaports is forecasting the traffic according to the number of passengers and the number of vehicles; in this way it is possible to plan and prepare activities for the smooth operation of the ports. This paper researches the port system as part of the coastal liner maritime transport. The set hypothesis is that the model of forecasting the traffic could be presented as a function of two variables. The Principal Component Analysis (PCA) method is used to select the forecasting parameters. Based on the choice of parameters, using the Least Squares Method (LSM), the trend analysis is performed to choose the forecasting functions for maritime liner transport on the example of the Split City port. The statistical analysis on the choosed forecasting model using the coefficient of determination r2 and adjusted r2 model is performed to confirm the choice.