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Prilog modeliranju prostorne distribucije zračenja u ložištu kotla za sagorevanje ugljenog praha

Contribution to the modeling of the spatial distribution of radiation inside the furnace of the pulverized coal fired boiler.

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2012
Disertacija.pdf (2.388Mb)
Author
Crnomarković, Nenad Đ.
Mentor
Tucaković, Dragan
Committee members
Živanović, Titoslav
Belošević, Srđan
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Abstract
zračenjem za ložište za sagorevanje ugljenog praha. Primena modela prikazana je na primeru ložišta energetskog bloka snage 210 MW. Zapremina ložišta je podeljena na 7956 zapreminskih zona, a zidovi ložišta na 2712 površinskih zona. Za svaki par zona izračunate su direktne i totalne površine razmene, za medijum koji apsorbuje, emituje i izotropno rasipa zračenje. Razmena energije zračenjem određena je na gruboj numeričkoj mreži koju su sačinjavale zapreminske zone. Ostale fizičke veličine određene su na finoj numeričkoj mreži, koja je dobijena podelom svake zapreminske zone na određeni broj kontrolnih zapremina. Formirane su tri fine numeričke mreže da bi se pokazalo da su rezultati nezavisni od numeričke mreže. Usvojena fina numerička mreža sastojala se od 573 440 kontrolnih zapremina. Matematički model je verifikovan kroz poređenje rezultata sa rezultatima merenja temperatura i upadnih flukseva zračenja na levom zidu ložišta. Matematičkim modelom je pokazano da gasna faza plamena u lo...žištu formira centralni vrtlog, kojim su zahvaćene i čestice ugljenog praha. Visokotemperatursko jezgro plamena se formira u središtu ložišta. Maksimalna vrednost apsorbovanih flukseva zračenja po zidovima ložišta dobijena je u neposrednoj blizini gorionika, što je u skladu sa poznatom raspodelom flukseva zračenja za ložišta sa tangencijalnim rasporedom gorionika. Matematički model je primenjen za određivanje razmene energije zračenjem u uslovima smanjenog opterećenja kotla. Pokazano je da sa smanjenjem produkcije pare kotla opadaju temperatura na kraju ložišta i vrednosti apsorbovanih flukseva zračenja na zidovima ložišta. Formiran je i istovetan matematički model koji sadrži model zračenja šest flukseva. Poređenjem rezultata numeričkih simulacija, dobijeno je zadovoljavajuće slaganje dva matematička modela ložišta. Formirani matematički model može se koristiti za analizu procesa u ložištu, kao i za ispitivanje procesa razmene energije zračenjem u ložištu.

A mathematical model that contained Hottel’s zonal model of radiative heat exchange was formed for the pulverized coal fired furnace. Application of the mathematical model was shown on the example of a furnace that was a part of 210 MW thermal unit. The furnace volume was divided into 7956 volume zones, whereas furnace walls were divided into 2712 surface zones. For each pair of zones, direct exchange areas and total exchange areas were calculated. Radiative heat exchange was determined using the coarse numerical grid that was composed of volume zones. All other physical variables were determined using the fine numerical grid that was formed by division of each volume zone to a certain number of control volumes. Three fine numerical grids were formed to show that results were grid independent. Adopted fine numerical grid comprised 573 440 control volumes. Mathematical model was verified through the comparison with results of the temperature and incident wall radiative fluxes measuremen...ts. It was shown by mathematical modeling that gas phase formed central vortex, which influenced the motion of the pulverized coal particles. The hightemperature core of the flame was formed in the center of the furnace. Maximal values of the absorbed wall radiative heat fluxes were obtained in the vicinity of the burners, in accordance with the known distribution of the wall radiative fluxes for the tangentially fired furnace. Mathematical model was applied for the calculation of the radiative heat exchange in the conditions of reduced boiler loads. It was shown that temperature at the furnace outlet and the absorbed wall radiative fluxes decreased with the decreased boiler load. Mathematical model that contained six-flux model of radiation was also formed. Comparison of the results of numerical simulations showed acceptable level of agreement between mathematical models. Investigation showed that mathematical model, which contained Hottel’s zonal model of radiative heat exchange, could be used for the analysis of the process inside the furnace and for investigation of the radiative heat exchange, as well.

Faculty:
Универзитет у Београду, Машински факултет
Date:
21-09-2012
Keywords:
Hottel-ov zonalni model / Hottel’s zonal model / toplotno zračenje / razmena energije zračenjem / ložište / ugljeni prah / matematički model / temperatursko polje / radijaciono polje / fluksevi zračenja na zidu / opterećenje kotla / thermal radiation / radiative heat exchange / furnace / pulverized coal / mathematical model / temperature field / radiative field / wall radiative heat fluxes / boiler load

DOI: 10.2298/bg20120921crnomarkovic

[ Google Scholar ]
Handle
https://hdl.handle.net/21.15107/rcub_nardus_2283
URI
http://eteze.bg.ac.rs/application/showtheses?thesesId=376
https://nardus.mpn.gov.rs/handle/123456789/2283
https://fedorabg.bg.ac.rs/fedora/get/o:6035/bdef:Content/download
http://vbs.rs/scripts/cobiss?command=DISPLAY&base=70036&RID=513958307

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