Metoda harmoničke ravnoteže za kontrarotirajuće propelere

master's thesis

• Title (english): Harmonic balance method for contra-rotating propellers
• Author: Franko Ćurčin
• Mentor: Hrvoje Jasak (mentor)
• Committee member: Vladimir Soldo (predsjednik povjerenstva)
• Committee member: Hrvoje Kozmar (član povjerenstva)
• Committee member: Zvonimir Guzović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2022-04-01, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

Računalna dinamika fluida (RDF) postala je gotovo konvencionalnim alatom u inženjerskoj praksi. Numeričkim rješavanjem setova jednadžbi dobiva se uvid u strujanje fluida u prostoru, a dobivena rješenja inženjerima i znanstvenicima daju mogućnost kvantifikacije strujanja u smislu sila, momenata i iskoristivosti na promatranom problemu. Visoki zahtjevi za računalnim resursima te vrijeme trajanja proračuna jedni su od glavnih izazova. Kako bi se smanjilo vrijeme potrebno za simulaciju uz očuvanje vremenske rezolucije rješenja, zbog periodičnosti strujanja u turbostrojevima moguće je koristiti tzv. spektralne metode. Spektralne metode zasnivaju se na pretvorbi veličina iz vremenske domene u frekvencijsku i obrnuto. Harmonička ravnoteža jedna je od spektralnih metoda, a često je primjenjiva u turbostrojevima. Harmonička ravnoteža svodi se na rješavanje određenog broja stacionarnih jednadžbi čiji se rezultati dobivaju za cijeli period T. Veća točnost rješenja ili smanjenje trajanja simulacije postiže se ovisno o odabranom broju harmonika. U sklopu ovog rada, izložena je teorijska pozadina matematičkog modela harmoničke ravnoteže te njegova implementacija u metodi kontrolnih volumena. Simulacije su provedene u svrhu validacije korištenja metode harmoničke ravnoteže u turbostrojevima. Proučavana su dva slučaja interakcije rotirajućih lopatičnih rešetki. U prvom slučaju razmatrana je rotirajuća rešetka rotora s mirujućom rešetkom statora, a u drugom slučaju razmatrane su rotirajuće rešetke oba rotora. Provedene su iduće simulacije: simulacija harmoničke ravnoteže na primjeru hidromlaznice uz primjenu različitog broja harmonika te simulacija harmoničke ravnoteže na primjeru kontrarotirajućih propelera. Provedena je analiza rezultata navedenih simulacija na temelju dostupnih rezultata stacionarnih i tranzijentnih simulacija. Pokazano je da harmonička ravnoteža, uz korištenje niskog broja harmonika, daje detaljniji prikaz rezultata uspoređujući sa stacionarnom MRF simulacijom, dok je za dobivanje rezultata približnima rezultatima tranzijentne simulacije broj harmonika potrebno povećati.

Abstract (english)

Computational Fluid Dynamics (CFD) has become almost conventional tool in engineering practice. Solving sets of equations numerically can provide insight into fluid flow, thus giving engineers and scientists opportunity to quantify flow in terms of forces, torques and the efficiency of given problem. High demands for computer resources and simulation time are one of main drawbacks. In order to reduce simulation time while preserving the time resolution of the solution, due to periodicity of the flow in turbomachines it is possible to use the so-called spectral methods. Spectral methods are based on conversion of quantities from time domain to frequency domain and vice versa. Harmonic balance is one of spectral methods and it is often used in turbomachines. Harmonic balance is based on solving a number of stationary equations whose results are obtained for the entire period $ T $. Higher accuracy of the solution or reduction of the simulation time is achieved depending on the selected number of harmonics. As a part of this thesis, the theoretical background of the mathematical model of harmonic balance and its implementation in the finite volume method are presented. The simulations were performed for the purpose of validating the use of harmonic balance method in turbomachines. Two types of rotating grids interaction were studied. In the first case, the rotating grid of the rotor and the stationary grid of the stator was considered. In the second case, the rotating grid of both rotors was considered. The following simulations were performed: simulation of harmonic balance method on the water jet with different number of harmonics and simulation of harmonic balance method on the contra-rotating propellers. The analysis of the results was based on the available results of steady-state and transient simulations. It has been shown that with the use of lower number of harmonics given results are of high accuracy and more detailed compared to steady-state simulation, while compared to transient simulation results, the number of harmonic has to be increased.

• Keywords: računalna dinamika fluida; spektralne metode; harmonička ravnoteža; hidromlaznica; kontrarotirajući propeleri; OpenFOAM
• Keywords (english): computational fluid dynamics; spectral methods; harmonic balance; water jet; contra-rotating propellers; OpenFOAM
• Language: croatian
• URN:NBN: urn:nbn:hr:235:706026
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-03-31 09:26:36