CFD simulacija nenominalnih radnih točaka centrifugalnog kompresora

master's thesis

• Title (english): CFD simulation of off-design operating points of a centrifugal compressor
• Author: Matej Čorak
• Mentor: Hrvoje Jasak (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2021-03-24, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

Korištenje CFD simulacija ustaljena je praksa u procesu konstruiranja turbostrojeva. Međutim, korištenje CFD-a u kasnijim fazama konstruiranja s ciljem istraživanja nenominalnih radnih točaka i nestabilnosti strujanja je vrlo rijetko i ima jedino akademski značaj. Cilj rada je istražiti mogućnosti CFD softwarea foam-extend za izračunavanje polja strujanja u nenominalnim radnim točkama. Kako bi se skratilo vrijeme trajanja simulacija, odabrano je modelirati samo jedan kanal koji se nalazi između dvije rotorske lopatice. Kako bi se reprezentativno modelirao samo jedan prolaz potrebno je pripremiti mrežu sa specifičnim alatima koji se često koriste kod CFD simulacija turbostrojeva. U radu je opisana procedura pokretanja simulacije jer je početne uvjete trebalo mijenjati, kako bi se ostvarila konvergencija nelinearnog sustava jednadžbi turbulentnog strujanja s izmjenom topline. Postepeno je mijenjana razlika tlaka između ulaza i izlaza na kompresoru, sve do postizanja ciljanog masenog protoka. Rezultati su dopuna rezultata iz literature, a cilj rada je prikazati mapu rada kompresora, uključujući i stanje zagušenja toka.

Abstract (english)

CFD simulations of turbomachinery are now a part of the standard approach in the design process. However, CFD as an investigation tool in the later stages of the design process, namely to investigate off–design operating points and fluid flow instabilities are rarely used in practice. The main objective of this work is to investigate the applicability of CFD software, eg. open–source library foam-extend to predict the flow field corresponding to off-design operating conditions of a centrifugal compressor. Since a full rotor geometry is challenging to model due to the size of the computational mesh, we decided to investigate performing the simulations on a single blade passage using cyclic boundary conditions for non–conforming meshes (Generalised Grid Interface – GGI). The mesh is block–structured, created in Pointwise with 7.2 million cells. A Multiple Reference Frame approach is used to model the rotation, which means that the obtained flow field corresponds to a single rotor position. Start–up of the simulation if very sensitive due to the extreme operating conditions of the nominal operating–point, and it is necessary to introduce the boundary conditions gradually. Thus, the total pressure ratios and MRF angular velocity are increased progressively to prevent the simulation from crashing due to local extreme velocities and pressure values. To validate the simulation approach, a comparison is made to experimental and numerical data provided by Dewar and Tiainen [8]. The final objective is to create a compressor map with the established flow field features corresponding to different operating points, and some close surge and choke conditions.

• Keywords: CFD; OpenFOAM; foam-extend; turbostrojevi; centrifugalni kompresor
• Keywords (english): CFD; OpenFOAM; foam-extend; turbomachinery; centrifugal compressor
• Language: english
• URN:NBN: urn:nbn:hr:235:516890
• 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: 2021-03-24 10:30:20