Pomorstvo 

About: Pomorstvo is an academic journal. The journal publishes majorly in the area(s): Port (computer networking) & Tourism. Over the lifetime, 257 publications have been published receiving 965 citations.

Exergy analysis of marine steam turbine labyrinth (gland) seals

Abstract: The paper presents an exergy analysis of marine steam turbine labyrinth (gland) seals - an inevitable component of any marine steam turbine cylinder, in three different operating regimes. Throughout labyrinth seals, steam specific enthalpy can be considered as a constant because the results obtained by this assumption do not deviate significantly from the results of complex numerical models. Changes in labyrinth seals exergy efficiency and specific exergy destruction are reverse proportional. The analyzed labyrinth seals have high exergy efficiencies in each observed operating regime at the ambient temperature of 298 K (above 92%), what indicates seals proper operation. An increase in the ambient temperature resulted with a decrease in labyrinth seals exergy efficiency, but even at the highest observed ambient temperature of 318 K, seals exergy efficiency did not fall below 90.5% in each observed operating regime.

Change in Steam Generators Main and Auxiliary Energy Flow Streams During the Load Increase of LNG Carrier Steam Propulsion System

Abstract: In this paper is presented an analysis of main and auxiliary steam energy flow streams from steam generators during the increase in steam system load at conventional LNG carrier. During the steam system load increase was presented differences in steam pressure and temperature between main and auxiliary steam flow streams. Energy power of the auxiliary flow stream is higher than energy power of the main flow stream only at the lowest steam system loads after which main flow stream takes over primacy at middle and high steam system loads. Cumulative auxiliary energy flow stream was divided on energy flow streams to each auxiliary device and energy power consumption of each auxiliary device was also investigated throughout number steam system loads. Analysis of steam production from marine steam generators presented in this paper provides insight into the operation dynamics of the entire steam propulsion system.

Factors influencing the formation of freight rates on maritime shipping markets

Abstract: Maritime shipping has a significant role in maritime policies and overall economic development of every maritime country. The fact that 2/3 of the total world trade of goods are done by maritime routes and that the sea is the least expensive trade route is enough to see the importance of its existence for every maritime country. The whole world and overall world trade, in maritime and other sectors, are defined by the relationship between supply and demand and prices on the market. Precisely for this reason it is important to well understand these relations and their mutual impacts. Therefore, in order to present the changeable state of shipping markets, in this paper we will use the supply and demand model which is connected to the freight rate i.e. the price of maritime transport service, which through its influence on the shipper and the shipowner balances the supply and demand. The aim of this paper is to point out the factors which influence the maritime shipping markets. In the paper we indicated and analyzed ten main factors; five influencing the demand, and five influencing the supply on the maritime transport market. © Faculty of Maritime Studies Rijeka, 2015.

Multilayer Perceptron approach to Condition-Based Maintenance of Marine CODLAG Propulsion System Components

Abstract: In this paper multilayer perceptron (MLP) approach to condition-based maintenance of combined diesel-electric and gas (CODLAG) marine propulsion system is presented. By using data available in UCI, online machine learning repository, MLPs for prediction of gas turbine (GT) and GT compressor decay state coefficients are designed. Aforementioned MLPs are trained and tested by using 11 934 samples, of which 9 548 samples are used for training and 2 386 samples are used testing. In the case of GT decay state coefficient prediction, the lowest mean relative error of 0.622 % is achieved if MLP with one hidden layer of 50 artificial neurons (AN) designed with Tanh activation function is utilized. This configuration achieves the best results if it is trained by using L-BFGS solver. In the case of GT compressor decay state coefficient, the best results are achieved if MLP is designed with four hidden layers of 100, 50, 50 and 20 ANs, respectively. This configuration is designed by using Logistic sigmoid activation function. The lowest mean relative error of 1.094 % is achieved if MLP is trained by using L-BFGS solver.

Efficiency and losses analysis of low-pressure feed water heater in steam propulsion system during ship maneuvering period

Abstract: Dominant propulsion systems of today’s LNG carriers are steam propulsion systems. Although a number of alternatives are developed, only steam propulsion systems in LNG carriers can fulfill a double function: the function of propulsion and on the other side the combustion of large amounts of BOG (Boil Off Gas) in one or more steam generators. In this paper was provided an analysis of the low- pressure feed water heater, as one of the important components of LNG carrier steam propulsion system. Based on the measured data for all flowing substances throughout the low-pressure feed water heater, it was performed numerical analysis of his energy and exergy efficiency, as well as calculation of energetic and exergetic power losses. The measurements were performed during LNG carrier maneuvering period, what enables insight into the operating parameters of heat exchanger during partial loads of steam propulsion system. From the energetic point of view the low-pressure feed water heater is a nearly perfect balanced device. Analyzed heat exchanger noticeable problems can be seen in exergy efficiency and exergy losses. Exergy represent the maximum available energy potential of any observed component in relation to the environment state. Impact of ambient temperature on the size of the exergy losses has been investigated at the end of conducted analysis. The low-pressure feed water heater is an example of a device which is very well balanced on the one side, even in the conditions of the steam system partial loads, and on the other side his available exergy potential is very poorly exploited.