doktorska disertacija
David Greif (Author), Breda Kegl (Mentor), Leopold Škerget (Co-mentor)

Abstract

Predložena doktorska disertacija se ukvarja z numeričnim modeliranjem erozijskih efektov kot posledico kavitacijskega toka. Tovrstni tokovi se pojavljajo v različnih industrijskih procesih in so še posebej pomembni v industriji, ki proizvaja ali uporablja komponente za dovod in vbrizg goriva pod visokimi tlaki. Zmožnost numeričnih simulacij tovrstnih notranjih tokov s pomočjo računalniške dinamike tekočin (CFD) omogoča učinkovito oblikovanje vbrizgalnih šob in drugih komponent za dovod goriva, kot so tlačilke, skupni vodi, različni ventili. Ustrezno fizikalno modeliranje samega kavitacijskega toka je predpogoj za določitev agresivnosti obravnavanih pogojev in erozijskih posledic kavitacije. Gonilna sila za nastanek erozijske škode so implozije parnih mehurčkov v kavitacijskem toku. Ponavljajoče se implozije parne faze na površini izpostavljenega materiala sčasoma povzročijo površinske poškodbe. Pravilna ocena nastanka in transporta parne faze v obliki mehurčkov je ključnega pomena. Polidisperzni kavitacijski model v komercialnem CFD programu AVL FIRE je bil uporabljen kot osnova predstavljene disertacije. Materialni erozijski model je bil modificiran in prilagojen v okvirje dinamike tekočin ter implementiran v CFD program. Predvideva, da material ne prenese obremenitev nad mejo plastičnosti materiala in ocenjuje agresivnost kavitacijskega toka kot funkcijo števila implozij mehurčkov na enoto površine in velikosti le-teh ob imploziji na površini. Model omogoča numerične simulacije erozijskih efektov, kar ima izredno vrednost pri oblikovanju komponent za dovod in vbrizg goriva. Kombinacija materialnega erozijskega modela z večfaznim modelom za dinamiko tekočin je unikatna in predstavlja jedro disertacije. Prikazanih je več rezultatov, ki kažejo na zmožnost modela za kvantitativno in kvalitativno oceno verjetnosti nastanka erozijskih poškodb materiala. Prikazane so tudi posledice erodirane površine izvrtin vbrizgalne šobe na širjenje curka goriva. To nakazuje na vpliv erozije na pripravo mešanice goriva in samo zgorevanje.

Keywords

vbrizg goriva;računalniška dinamika tekočin;kavitacija;erozija;injektor;vbrizgalne šobe;vbrizgalne komponente;

Data

Language: Slovenian
Year of publishing:
Source: [Maribor
Typology: 2.08 - Doctoral Dissertation
Organization: UM FS - Faculty of Mechanical Engineering
Publisher: D. Greif]
UDC: 621.436:532.528(043.3)
COBISS: 16158230 Link will open in a new window
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Other data

Secondary language: English
Secondary title: Cavitation erosion in injection components with polidispersed cavitation model
Secondary abstract: This disertation deals with numerical prediction of erosive effects due to cavitation. Such flows appear in many industrial applications and are of special interest within industries producing and using fuel injection components. Ability to predict such internal flows by means of Computational Fluid Dynamics (CFD) allows for efficient design of injectors and other fuel delivery components, such as pumps, common rails, throttles. Accurate modelingof cavitating flows is a prerequisite for the prediction of flow aggressiveness and finally its erosive effects. Driving force for the onset oferosion damage are bubble collapses during vapor condensation. Repetitive implosions on the same surface of the exposed material will eventually result in material damage. Prediction of vapor generation and accurate transport of the bubbles is therefore crucial. Polidispersed cavitation model of AVL FIRE was taken as the basis of the disertation work. Material based erosion model was modified to fit into the fluid dynamics framework and implemented into theCFD code. The model assumes that the material cannot withstand hydrodynamicloads above the yield strength and estimates the aggressiveness ofthe cavitating flow as function of bubble collapses per unit area and the size of the collapses on the surface. It allows for prediction of erosion effects, which has extreme value in the design process of injection components. Combination of material based erosion model with the multiphase two fluid model is unique and it represents the core of the disertation. Several results are presented to demonstrate model's capability to quantitatively and qualitatively predict probability for erosion existence. Finally, the effects of eroded injector surface on spray propagation are outlined, hinting that erosion inside an injector will affect the combustion process.
Secondary keywords: cavitation;erosion;erosion damage;injectors;injector flow;injector equipment;Kavitacija;Disertacije;
URN: URN:SI:UM:
Type (COBISS): Dissertation
Thesis comment: Univ. Maribor, Fak. za strojništvo
Pages: XI, 101 f.
Keywords (UDC): applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;engineering;technology in general;inženirstvo;tehnologija na splošno;mechanical engineering in general;nuclear technology;electrical engineering;machinery;strojništvo;heat engines (except steam engines);toplotni pogonski stroji (razen parnih);mathematics;natural sciences;naravoslovne vede;matematika;physics;fizika;fluid mechanics in general;mechanics of liquids (hydromechanics);mehanika tekočin;mehanika kapljevin;liquid motion;hydrodynamics;
ID: 990124