Papers selected for Conference Session titled : Thermal, hydro, wind and other Power Plants | Eksploatacioni problemi termo, hidro, vetro i drugih elektrana
Nenad Miloradovic - JKP "Beogradske elektrane" , Olga S. Milosavljević - Istraživačko-razvojni institut „Kirilo Savić“ Vojvode Stepe 51, 11.000 Beograd, Srbija
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In the frame of cooperation of Electro-technical Faculty in Belgrade, Energy Administration of City Belgrade, Ministry of mining and energetic Republic of Serbia and Public Utility Company Beogradske elektrane, at location of Heating Plant “Cerak” was anticipated setting up of mobile windsolar
hybrid system, which will be settled at HP “Cerak” for one year. Components of mobile hybrid wind-solar system are windmill 8 meters tall, 2 m2 of solar photovoltaic panels, fuel battery, inverter and logger for measured data. Because of grass soil and rare ground, foundation was made of concrete, so the mobile system become are stabile stationary system. In the paper was presented details of setting up of the system with photos.
Postavljanje prenosivog vetar-solarnog hibridnog sistema na lokaciji TO “Cerak”
Na lokaciji toplane “Cerak” u Beogradu predviđeno je postavljanje hibridnog vetar-solarnog prenosivog sistema, koji bi bio smešten na pomenutoj lokaciji godinu dana. Hibridni vetar-solarni sistem se sastoji od vetrenjače sa stubom visine 8 metara, 2 m2 solarnih fotonaponskih panela na poklopcu prikolice i prikolice sa akumulatorskim baterijama, invertorom i logerom za očitavanje izmerenih podataka. Nasut teren lokacije “Cerak” uslovljava primenu betonskog temelja sa ankerima.
dr Dragan Tucaković - Mašinski fakultet, Kraljice Marije 16, 11120 Beograd 35, Srbija , dr Titoslav Živanović - Mašinski fakultet, Kraljice Marije 16, 11120 Beograd 35, Srbija , dr Vladan Ivanović - Mašinski fakultet, Džordža Vašingtona bb, 81000 Podgorica, Crna Gora , dipl. ing. Miloš Milić - PD TE Nikola Tesla, Bogoljuba Uroševića – Crnog 44, 11500 Obrenovac 25, Srbija , dipl.ing. Mile Jovanović - PD TE Nikola Tesla, Bogoljuba Uroševića – Crnog 44, 11500 Obrenovac 25, Srbija
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ANALYSIS OF THE RESULTS ACHIEVED BY INSTALLING THE LOUVERS INTO COAL DUST PREPARING FACILITIES FOR STEAM BOILERS IN TP NIKOLA TESLA B
ABSTRACT: During the operation of steam boilers in TP Nikola Tesla B, before installation of louvers in the air ducts, it was common for flame in furnace to rise. As a consequence there were: a rise in the temperature of flue gases on the furnace outlet, superheater overload, increased water injection for regulation of outlet temperatures for superheated and reheated steam and a loss due to incomplete mechanical combustion. With consideration to the conditions under which boiler operated, it was decided to place louvers in the air ducts on the beater wheel mill outlet, for the purpose of improving the regulation of coal dust in stage burners. Lower and middle stages get 45% of coal dust each, and the upper one gets 10%. In order to show what effect the installment of louvers would have, we made a series of thermal calculations before and after the actual installment. In this paper we have shown the analysis of individual measurements which made the greatest effect towards the improvement of steam boiler operation.
ANALIZE POSTIGNUTIH REZULTATA UGRADNJOM ŽALUZINA NA POSTROJENJIMA ZA PRIPREMU UGLJENOG PRAHA PARNIH KOTLOVA BLOKOVA 1 I 2 U TE NIKOLA TESLA B
ABSTRAKT: Pri radu parnih kotlova u TE Nikola Tesla B, pre ugradnje žaluzina u kanale aerosmeše, dolazilo je do pojave podizanja plamena u ložištu što je za posledicu imalo povišenje temperature dimnih gasova na izlazu iz ložišta, preopterećenje pregrejača sveže pare, povećano ubrizgavanje vode u cillju regulisanja izlaznih temperatura sveže i naknadno pregrejane pare, kao i povećan gubitak usled mahaničke nepotpunosti sagorevanja. S obzirom na uslove pod kojima je radio kotao, odlučeno je da se u kanale za aerosmešu na izlazu iz ventilatorskog mlina postave žaluzine u cilju poboljšanja raspodele ugljenog praha po etažama gorionika i to tako da u donje dve etaže dospeva po 45 % ugljenog praha, a u gornju 10 %. Da bi se prikazao efekat ugrađivanja žaluzina izvršen je niz termičkih proračuna parnog kotla sa današnjim kvalitetom goriva i parametrima rada kotla, kako pre, tako i nakon ugradnje žaluzina. U radu je prikazana analiza pojedinih veličina koje su najviše uticale na poboljšanje rada kotla.
Ključne reči: parni kotao, ventilatorski mlin, kanali aerosmeše, žaluzine.
N. Đ. Crnomarković*, M. A. Sijerčić*, S. V. Belošević*, B. D. Stanković*, D. R. Tucaković**, T. V. Živanović** - *Institut za nuklearne nauke Vinča, Univerzitet u Beogradu Laboratorija za termotehniku i energetiku P. Fah 522, 11001 Beograd, Srbija, **Mašinski Fakultet, Katedra za termotehniku, Kraljice Marije 16, 11120 Beograd, Srbija
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Radiation is dominant mode of heat exchange between hot combustion products and furnace walls in the processes of pulverized coal combustion. Up to 95% of the exchanged heat in furnace is due to radiation. That is why the accurate evaluation of radiant heat exchange is important for numerical simulations, by which the behavior of the steam boiler is predicted in various operating situations.
Radiation models, which are used in numerical simulations of pulverized coal furnaces, can be divided in two basic groups: flux models and zonal models. Determination of radiant heat exchange by flux models is based on evaluation of spatial and angular distribution of radiation intensity, or spatial distribution of radiant fluxes. Incident or absorbed fluxes at the furnace walls are determined on the base of known radiant intensities or fluxes inside the furnace. Zonal models are based on division of furnace volume and furnace walls to volume and surface zones. For each pair of zones, firstly direct exchange areas are determined, as auxiliary parameters by which total exchange areas are determined. Total exchange areas are used to find the radiative heat exchange, when multiple reflection on the furnace walls exists.
Influence of the radiation models on the results of numerical simulations of pulverized coal furnaces has been analyzed in the paper. Furnace of the 210 MWe steam boiler has been modelled. Results of numerical simulation which contains Hottel zonal model, which is typical of zonal models of radiation, are compared to results of numerical simulation which contains six flux model, which is typical of flux models of radiation.
Radiative source term of the gas phase enthalpy equation, which represents net radiative heat exchange of volume zones (control volumes), is determined by models of radiation. In both analyzed radiation models, net radiative heat exchange of the volume zones is determined as a difference between absorbed radiative energy and energy loss due to emission of energy. Models are distinguished by the method of absorbed energy determination. In the Hottel zonal model, absorbed energy of the volume zones is determined by means of total exchange areas and temperature of each zone. In the six flux model, absorbed energy of the volume zones are obtained on the base of the total radiation fluxes, which are calculated by solving the partial differential equations of the second order.
Optimization of the radiative heat exchange determination by the Hottel zonal model has been done in the paper. After evaluation of the direct exchange areas, total exchange areas are determined by the method of the original emitters of the radiation. Values of the total exchange areas are corrected by the method of gradual approach, so that they satisfy the conservation principle. Influence of the radiation models is investigated by comparison of the temperature fields and net radiative exchange fields. It is shown that six flux model produces greater values of net radiative heat exchange and greater values of temperature inside the furnace.
Saša Milić - Elektrotehnički institut Nikola Tesla, Beograd, Srbija , Milesa Srećković - Elektrotehnički fakultet, Beograd, Srbija , Nebojša Karanović - HE Đerdap, Srbija , Zoran Kršenković - HE Đerdap, Srbija , Jasna Marković Petrović - HE Đerdap, Srbija
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On-line remote monitoring of generators and transformers in this work is a necessity, both in terms of monitoring the production cycle and in terms of maintenance. The use of computer and communications equipment significantly improves the maintenance of uninterruptible power systems and controls the manufacturing process in order to increase the reliability of electric power generation. The paper presents two concepts of on-line remote monitoring measuring systems: a concept system for measuring the temperature of hydro rotor poles in the work and a concept system for complete remote monitoring of a multi-parameter power transformer. The focus of this paper is to show the practical implementation and development of measurement methodology using computer and communication systems and newly developed measurement algorithms. In addition to displaying the hardware concepts of two measuring systems, there is a software for the visualization of the measurement processes. The paper gives an overview of a complex integrated monitoring systems, which itself includes the following sub-systems for measuring: the temperature of hydro rotor poles, the temperature of hydro stationary sensors, analyzing the gas and the moisture of power transformer oils, partial discharge in generators, temperature monitoring of power transformers with an optional cooling function for managing groups. The above mentioned systems are interfaced witg SCADA systems in power plants. With each of these supervisory systems, results obtained through real exploitation will be presented.
Sadržaj – Daljinski nadzor generatora i transformatora u radu predstavlja neophodnost, kako u smislu praćenja proizvodnog ciklusa, tako i u smislu održavanja. Upotreba računarske i komunikacione opreme značajno unapređuje održavanje energetskih sistema i besprekidni nadzor proizvodnog procesa, a sve u cilju povećanja pouzdanosti proizvodnje električne energije. U radu su prikazane dve koncepcije daljinskih nadzornih mernih sistema: koncepcija sistema za merenje temperature polova rotora hidrogeneratora u radu i koncepcija sistema za kompletan daljinski višeparametarski nadzor energetskog transformatora. Težište rada je na prikazu praktične realizacije i razvijene merne metodologije upotrebom računarskih i komunikacionih sistema i novorazvijenih mernih algoritama. Pored prikaza hardverske koncepcije dva merna sistema, dat je i prikaz računarskih programa za vizualizaciju mernih procesa. Rad daje prikaz integrisanih složenih nadzornih sistema koji u sebi podrazumevaju sledeće merne podsisteme za: merenje temperature polova rotora, merenje temperature sa stacionarnih davača hidrogeneratora, analizu gasova i vlage u energetskim transformatorima, parcijalna pražnjenja na generatorima, termoslike energetskih transformatora sa dodatnom funkcijom za upravljanje rashladnim grupama. Pomenuti sistemi su povezani na SCADA sisteme u elektranama. Uz svaki, od pomenutih nadzornih sistema, će biti dati i rezultati dobijeni iz realne eksploatacije.
Ključne reči: Daljinski nadzor, temperatura, polovi rotora, gasna anliza, parcijalna pražnjenja, termoslika, SCADA, virtualni instrumenti.
Zdravko Ivancic - NUMIKON Ltd. , Misa Jocic - PIPETECH Jocic
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The paper will outline innovative piping design solution for distribution of steam from the exit of combined cycle power plants steam turbine to Air Cooled Condenser System – ACC. The distribution system can only conditionally be called piping system, because diameters range from 2.4 to 5.5 meters while wall thicknesses range from 10 to 20 mm. As a consequence common methods for piping flexibility and stress analysis cannot be applied (software applications based on beam elements) so all required calculations had to be carried out using finite elements analysis methods – FEM (shell/plate).
The innovativeness of the design solution is reflected in the design of supporting system. In defining solutions for supports, the main aim was to reduce the effects of friction as much as possible. Variant with completely eliminated friction proved to be costly, so finally a compromised solution was adopted.
The design solution also involved installing In-line Pressure Balanced Expansion Joint to absorb piping systems thermal dilatation. The installation of such device was essential in order to protect the turbine from forces created by piping thermal expansion, as well as from large unbalanced forces that are induced with the installation of expansion joint themself. Innovative design solution of the In-line Pressure Balanced Expansion Joint has been patented.
Zdravko Ivancic - NUMIKON Ltd , Darko Seremet - KONCAR - Institut za elektortehniku d.d.
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Optimization of the vital parts of hydrogenerator takes increasing importance nowadays. Among the other one of the most important is the pole of the rotor. Sizing of its fixation, whether is made in form of "dove-tail", "hammer", or their combination, significantly affects the producing costs, the material price and the overall price of the product.
The main goal of this work consists of presenting correct and quality modes dimensioning of the pole fixation and getting to know all involved with the same. Also to point out very important deficiencies that now exists in both design and tender/contractual documentation.
All deficiencies are derived from the results of classical methods of stress calculation which has the widest use, thereof in the work is shown comparative analysis of stresses and a way of getting more accurate results and modern methods of calculation (theory of elasticity, photoelasticiometry, the finite element method - FEM) in order to overcome these shortcomings.
Misa Jocic - PIPETECH Jocic
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Due to an incident at the Combined Cycle Power Plant where a weld seam at HP OTC (High Pressure Once Through Cooler) steam outlet failed producing considerable damage, an investigation into the incident was carried out. The aim was to find possible design reasons for failure and generate necessary corrective design actions, which shall rectify the situation and produce a new solution ensuring future integrity of this type of piping designs.
The development of a new design solution and the evaluation of pressure and thermal stresses in dissimilar (bi-metallic) welds (DMW) have been performed in accordance with generalized extension of the method recommended in API 579 for high temperature evaluations. The modified method follows PRG (Paulin Research Group) approach, which addresses a more general situation than that from API standard.
The method has been combined with stress results at dissimilar weld points from ASME B31.1 beam type CAESAR II analysis, as well as from shell type elements FEM / FEPipe analysis, of the models that contain complete OTC Steam piping system as well as OTC Air System. The Air System was included in the analysis to properly identify, evaluate and integrate its impact on OTC Steam System, thus bringing even more clarity to the investigation.
The new design solution for dissimilar welds, described with the selected Material Combination Option, fulfils the requirements of API 579 and ASME B31.1 as well as ASME Sec VIII Div 2 for both, Stress Fraction Approach and Strain approach for the required design life of 80000 to 100000 hrs, correlating well with plants C inspection intervals.
Vladimir Mijakovski - Faculty of Technical Sciences, Ivo Lola Ribar bb, 7000 Bitola, Macedonia , Kire Popovski - Faculty of Technical Sciences, Ivo Lola Ribar bb, 7000 Bitola, Macedonia
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Several parameters affect the performance of the cooling tower (part of the power plant's cold end): heat load Q, cooling range tw, approach to the wet-bulb temperature todd and wet-bulb temperature tvt (cooling tower's boundary temperature value). An analysis of the influence of climatic curve values (for the months of April, May, June, July, August and September) for a defined size of heat exchanger (cooling tower fill for designed operating regime) on the thermal performance of the cooling tower is presented in this article. This also allows following of the designed operating regimes of the turbine.
A. Stojanović, B. Repić, S. Nemoda, D. Dakić, A. Erić, D. Đurović - Institute of Nuclear Sciences Vinca, P. O. Box 522 11 001 Belgrade, Serbia
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The burn-out of char in power facilities is commercially important. Interest in the burn-out of biomass char is growing because biomass is increasingly being fired to reduce the carbon dioxide emissions. The Laboratory for Thermal Engineering and Energy of the Vinca Institute, has developed a technology for combustion of biomass bales of various sizes and shapes for energy production. Experimental facility of 1,5 MW has been built with cigarette type of combustion for the purposes of greenhouse and office heating in the PKB. In it’s lower part char is burning-out in fluidized bed. This paper attempts to estimate combustion efficiency and performance for this experimental facility calculating the unburnt char fraction in the zone of baled biomass combustion. The mass and heat balances have been written for part of the boiler where unburnt char is burning-out in fluidized bed. On the basis of known temperatures, air mass flows and char temperature, which has been accepted to be equal to the temperature of baled biomass combustion , mass flow of char, which is falling into the burning zone with fluidized bed, has been estimated. An approach for assessing biomass combustion performance is also discussed.
Milan B. Banjac, Miloš M. Despić, Milan V. Petrović - University of Belgrade – Faculty of Mechanical Engineering
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This paper describes the development of a new through flow method for the analysis of axial multistage compressors. The method is based on a stream function approach and a finite element solution procedure. It includes a high-fidelity loss and deviation model with improved correlations and endwall boundary layer calculation. A radial distribution model of losses and a new spanwise mixing model are applied to simulate 3D flow effects. The calibration of the models is made by calculation a number of test cases with different configurations with the aim of achieving high accuracy and optimum robustness for each of the test cases considered.