Thermodynamic Analysis and Comparison of Two Marine Steam Propulsion Turbines

This paper presents thermodynamic (energy and exergy) analysis and comparison of two different marine propulsion steam turbines based on their operating parameters from exploitation. The first turbine did not possess steam reheating and had only two cylinders (high-pressure and low-pressure cylinders), while the second turbine possesses steam reheating and has one additional cylinder (intermediate-pressure cylinder). In the literature at the moment, there cannot be found a direct and exact comparison of these two marine steam turbines and their cylinders based on real exploitation conditions. Along with energy and exergy analyses, the research it is investigated the sensitivity of exergy parameters to the ambient temperature change for both turbines and each cylinder. It is also presented the influence of the steam reheating process on the energy and exergy efficiency of the entire power plant. For both observed turbines and their cylinders it is valid that relative losses and efficiencies (both energy and exergy) are reverse proportional. The operation of an intermediate pressure cylinder from a steam turbine with reheating is the closest to optimal. Due to the different origins of losses considered in energy and exergy analyses, each analysis detects different turbine cylinders as the most problematic ones. The steam reheating process decreases losses and increases efficiencies (both energy of each turbine cylinder and the whole turbine. The whole turbine with reheating has an energy efficiency equal to 81.46% and an exergy efficiency equal to 86.48%, while the whole turbine without reheating has energy and exergy efficiencies equal to 76.47% and 80.94%, respectively. Exergy parameters of a steam turbine without reheating as well as its cylinders are much more influenced by the ambient temperature change in comparison to the steam turbine with reheating and its cylinders. The steam reheating process will increase the efficiency of the whole power plant in real exploitation conditions between 10% and 12%

Revitalisation of the Lisičine Arboretum

Arboretum Lisičine nalazi se na Papuku. Njime upravljaju Hrvatske šume d.o.o. Zagreb, Uprava šuma podružnica Našice, Šumarija Voćin. Os no van je 1979. godine, na površini od oko 45 ha. U sjevernom dijelu Ar boretuma nalazi se prirodna bukova šuma. Južni dio, koji je arboretum u užem smislu, podijeljen je na tri dijela: 1. hortikulturni dio na kojem je posađeno ukras no drveće i grmlje, 2. dio zasađen biljkama s područja Europe i Azije i 3. dio zasađen biljkama s područja Amerike. Tijekom Domovinskog rata Arboretum je bio okupiran i devastiran. Dio biljaka se osušio, zasađene biljke nisu primjereno održavane, dosta ih je posađeno preblizu jedna drugoj, a neke su se pokazale invazivne te su se nekontrolirano proširile po ostalim dijelovima Arboretuma. Također je došlo i do zarastanja bagremom, kupinom i drugim samoniklim vrstama. U okviru projekta “Revitalizacija Arboretuma Lisičine”, od 2006. godine radi se na uređenju Arboretuma. Za svaki pojedini slučaj bilo je potrebno odlučiti što treba učiniti kako bi se što više biljaka očuvalo. Dokumentacija o biljkama ne postoji, te se sukcesivno, po poljima, radi na determinaciji i označavanju biljaka. U hortikulturnom dijelu, na dvanaest polja, determinirano je 416 različitih svojti, iz 113 rodova. Od toga su 202 listopadne, a ostale vazdazelene ili zimzelene. Najzastupljeniji rodovi su: Picea (32 različite svojte), Juniperus (23 svojte), Chamaecyparis (23 svojte), Prunus (20 svoj ti), Pinus (15 svoj ti), Thuja (14 svojti), Berberis (13 svojti), Viburnum (13 svojti), Taxus (12 svoj ti), Spiraea (12 svojti), Acer (11 svojti), Cotoneaster (11 svojti), Abies (9 svojti), Cornus (9 svojti), Ilex (9 svojti) i Sorbus (9 svojti). Hortikulturni dio može poslužiti kao ogledni dio za uređenje cijelog Arboretuma te ima prioritet tijekom revitalizacije. Posebnu vrijednost imaju brojni kultivari četinjača, pa se može reći da je Arboretum Lisičine među najbogatijim živim zbirkama različitih svojti četinjača u Hrvatskoj. Zbog vrijednosti i jedinstvenosti Arboretuma Lisičine potrebno je uložiti što je moguće više truda i sredstava kako bi se primjereno uredio, a zatim održavao i služio za edukaciju i znanstvena istraživanja, kao i za odmor i šetnju svih dobronamjernih posjetitelja.The Arboretum Lisičine is located on the Papuk mountain. It is managed by Hrvatske šume d.o.o., Zagreb (Croatian Forests Ltd., Zagreb), Forest Administration Našice, Forest Office Voćin. It was founded in 1979 on an area of about 45 ha. In the northern part of the Arboretum there is a natural beech forest. The southern part, which is the arboretum in the true sense of the word, is divided in 3 parts: 1. horticultural part, on which ornamental trees and shrubs are planted, 2. part planted with European and Asian plants, 3. part planted with American plants. During the Homeland War the Arboretum was occupied and devastated. A part of the plants dried out, some plants were not properly cultivated, many of them were placed too close to each other, and some turned out to be invasive and spread without control over other parts of the Arboretum. In addition, black locust, blackberry bushes and other species started overgrowing the cultivated plants. Since 2006, within the project “Revitalisation of the Lisičine Arboretum”, the arrangement of the Arboretum has been on-going. In each individual case decisions have to be made about what needs to be done to preserve as many plants as possible. There is no documentation about the plants, and the determination and marking of the plants has to be done successively field by field. In the horticultural part, on 12 fields, 416 different taxa of 113 genera have been determined. Of these 202 are deciduous, whereas the others are evergreen or leaf-exchanging. The most represented genera are: Picea (32 taxa), Juniperus (23 taxa), Chamaecyparis (23 taxa), Prunus (20 taxa), Pinus (15 taxa), Thuja (14 taxa), Berberis (13 taxa), Viburnum (13 taxa), Taxus (12 taxa), Spiraea (12 taxa), Acer (11 taxa), Cotoneaster (11 taxa), Abies (9 taxa), Cornus (9 taxa), Ilex (9 taxa) and Sorbus (9 taxa). The horticultural part can serve as the model part for arranging the whole Arboretum, having priority during revitalisation. Numerous conifer cultivars are specially valuable, so that we can say that the Lisičine Arboretum is one of the richest living collections of different conifer species in Croatia. Due to the value and uniqueness of the Lisičine Arboretum, as much effort as possible has to be made for its arrangement and later maintenance, so it can serve for education and scientific research, as well as relaxation and strolls of visitors

Fuel mass flow variation in direct injection diesel engine – influence on the change of the main engine operating parameters

A change in the main operating parameters of a high speed turbocharged direct injection diesel engine MAN D0826 LOH15 during the fuel mass flow variation has been analyzed. On the basis of two measurement sets, on two different engine rotational speeds, performed with standard diesel fuel, several operating parameters have been calculated: engine torque, effective power, excess air ratio, specific effective fuel consumption and heat released per engine process. The calculated parameters are presented for a wide engine operating range. In addition to measurement sets, several important parameters have been measured. Additional measured parameters have been lubrication oil temperature and exhaust gas temperature before and after the turbocharger turbine. The presented engine operating parameters allow deep insight into the analyzed diesel engine process

Computerized Planned Maintenance System Software Models

Classification societies certify computerized planned maintenance systems, which have to comply with ISM, IMO and IASC standards. This paper aims at presenting standard requirements and a short history outlook for three planned maintenance software solutions: Amos, Bassnet and Titan. Software packages are scanned through their modules and features. The maintenance module overview, with all related features, is selected for three software solutions where the maintenance module is the only module which is related to the Class requirements. The aim of this paper is to discuss the advantage and disadvantage of each software separately and their application in the shipping industry

Exergy Analysis of Steam Pressure Reduction Valve in Marine Propulsion Plant on Conventional LNG Carrier

Paper has presented an exergy analysis of steam pressure reduction valve, unavoidable element in the steam propulsion plant on LNG carrier. The steam pressure reduction valve was analyzed in a wide range of steam system loads. Along with pressure decrease, through the valve also occur decrease in steam temperature and increase in steam specific entropy. The pressure decrease of the analyzed valve ranges from 4.846 MPa up to 5.027 MPa while the average steam temperature decrease for the whole observed operating range amounts 74.8 °C. At the ambient temperature of 25 °C, valve exergy destruction ranges from 121.72 kW up to 180.64 kW, while exergy efficiency amounts from 80.28 % up to 80.54 %. Variation in the ambient temperature, for the expected engine room temperature range, showed that the exergy destruction of pressure reduction valve increases and exergy efficiency decreases during the increase in the ambient temperature. The lowest average value of pressure reduction valve exergy destruction was obtained at the ambient temperature of 10 °C and amounts 152.03 kW, while at the same ambient temperature was obtained the highest average exergy efficiency of 82.77 %. The highest valve exergy destruction and the lowest exergy efficiency were obtained at the highest observed ambient temperature of 40 °C

A gas turbine combustion chamber modeling by physical model

The validity of the gas turbine unit model largely depends on the accuracy of the flue gas temperature value calculation at the gas turbine inlet (TIT). This temperature is determined by the maximum combustion temperature. In variable running mode, the temperature value is regulated by changing the ratio of air and fuel at the inlet to the combustion chamber. The paper presents a model of a gas turbine combustion chamber using Modelica, an object-oriented language for modeling complex physical systems with the aim of determining the temperature of combustion flue gases, specific heat capacity, enthalpy, and flue gas composition at different gas turbine loads

Analysis and Comparison of Ship Propulsion Systems

One of the highest cost of building the ship refers to the ship’s propulsion system. It is therefore very important to know all the types and specificities of propulsion systems for the optimal selection. This paper presents the conventional and the combined propulsion systems, where are briefly given their characteristics and specificities. Special attention is given to the combined propulsion systems, whose extensive use is still under expectation. At the end, the paper discusses the cost calculation of a marine propulsion system of selected passenger cruiser and comparison to the possible alternative system

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

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