Numerical modelling of combustion process using flamelet generated manifold and coherent flame combustion models

master's thesis

• Title (croatian): Numeričko modeliranje procesa izgaranja pomoću tabeliranih podataka propagacije plamena i modela izgaranja koherentnih plamenova
• Author: Marija Stipić
• Mentor: Milan Vujanović (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2019-12-06, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; Process Energy Engineering

Abstract

In recent times, combustion modelling employing computational fluid dynamics (CFD) in combination with experiment has become an irreplaceable tool in the design process of the diesel engines. Combustion process as a phenomenon of exceptional complexity can be numerically solved with detailed chemical kinetics or with the utilisation of approximated combustion models. Detailed chemical kinetics provides a comprehensive insight into the chemical aspect of the combustion process, while combustion models are described with approximated chemical kinetics in order to reduce the computational demand. An appropriate modelling approach to overcome these challenges is the Flamelet generated manifold (FGM) combustion modelling approach, which computes the chemistry kinetics in preprocessing and stores the result data in a look-up table that is interpolated during the CFD simulations. One of the combustion models, which has proven an ability to simulate the combustion process in internal combustion engines is Three-zones extended coherent flame model (ECFM-3Z+). In this thesis, ECFM-3Z+ and FGM approaches were employed for the calculation of combustion process in a diesel engine. The primary aim of the thesis is to analyse and validate numerical results obtained with FGM and ECFM-3Z+ models against experimental data. Numerical simulations are performed using commercial CFD software AVL FIRE TM, where the calculated results such as mean in-cylinder pressure, mean temperature, rate of heat release and NO emissions are calculated for single and multi-injection strategies. The NO emission trend observed in the experiment is well reproduced with both combustion models, while the computational time for CFD simulations with FGM is reduced by half. The results obtained with both combustion modelling approaches are found to be in a good agreement with the experimental data. Thus it is conducted, that both ECFM-3Z+ and FGM combustion modelling approaches are capable of predicting the combustion process in the real industrial diesel engines.

Abstract (croatian)

Korištenje računalne dinamike fluida (RDF) u kombinaciji s eksperimentalnim istraživanjima je postao nezaobilazan pristup u razvoju dizel motora. Proces izgaranja je vrlo kompleksan fenomen, a numerički se može opisati pomoću dva pristupa: detaljne kemijske kinetike i modela izgaranja. Detaljna kemijska kinetika pruža opsežan uvid u kemijske aspekte procesa izgaranja, dok su modeli izgaranja opisani s aproksimiranom kemijskom kinetikom s ciljem smanjenja potrebe za računalnim resursima. Pristup u modeliranju izgaranja koji omogućava efikasno numeričko rješavanje procesa izgaranja bez ograničenja na složenost kemijske kinetike ili dostupnih računalnih resursa je metoda tabeliranja kemijskih vrsta u predprocesoru (engl. Flamelet generated manifold, FGM). Ovim pristupom detaljna kemijska kinetika se izračunava u predprocesoru, a rezultati se spremaju u tablicu koja se interpolira tijekom RDF procedura. Jedan od konvencionalnih modela izgaranja u motorima s unutarnjim izgaranjem je model koherentnih plamenova (engl. Three-zones extended coherent flame model, ECFM-3Z+). U ovom radu za modeliranje procesa izgaranja u dizel motoru korišten je FGM pristup i ECFM-3Z+ model. Cilj ovog rada je analizirati i validirati rezultate numeričkih simulacija s eksperimentalnim podacima. Numeričke simulacije izvršene su korištenjem komercijalnog programskog paketa AVL FIRE TM. Rezultati poput tlaka, temperature, brzine oslobađanja topline i NO emisija izračunati su za radne točke motora s jednim i s tri ubrizgavanja goriva u cilindar. Trend emisija NO-a izmjeren u eksperimentu dobro je reproduciran s oba modela. Budući da se rezultati oba korištena pristupa u modeliranju izgaranja dobro poklapaju s eksperimentalnim podacima, zaključeno je da su i ECFM-3Z+ model i FGM pristup valjani za opisivanje procesa izgaranja u industrijskim dizel motorima.

• Keywords: Combustion modelling; Tabulation; Diesel engine; NO Emissions
• Keywords (croatian): Modeliranje izgaranja; Tabelacija; Dizel motor; NO emisije
• Language: english
• URN:NBN: urn:nbn:hr:235:851716
• 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; Embargo expiration date: 2021-09-30
• Created on: 2019-11-27 16:11:42