Large eddy simulation of combustion using linear-eddy subgrid modeling
Doktorsavhandling, 2019

As emissions regulations are getting stricter and efficiency requirements of internal combustion engines (ICE) are increasing, different concepts to improve combustion are being investigated. For example lean stratified premixed combustion, homogeneous charge compression ignition (HCCI), use of more exhaust gas recirculation (EGR) to reduce NOx etc. In all these concepts, combustion happens at lower temperatures, higher pressures, and higher level of air dilution than today's typical spark ignition or diesel engines.
Many combustion models in computational fluid dynamics (CFD) today describe either premixed or non-premixed mode of combustion, assuming fast chemistry regimes only. There is a great need for new combustion models that are mode (premixed/non-premixed) and regime (fast/non fast chemistry) independent. The linear-eddy model (LEM) of Kerstein used as a subgrid combustion model for large eddy simulation (LES) called LES-LEM is regarded as a truly mode and regime independent combustion model as it models all the physical processes, i.e. large and small scale turbulent advection, molecular diffusion and chemical reactions at their respective length and time scales.
In this dissertation, a new LEM closure for LES-LEM using the reaction-rate approach is proposed in which the LEM provides closure for the chemical source terms in the conservation equations of the sensible enthalpy and species mass. The new LEM closure is tested on a bluff-body premixed flame problem and simulation results are compared with experiments.
Furthermore, a new splicing approach for modeling large-scale advection in LES-LEM is presented. The approach links the subgrid LEM implementation
to a concept of control-volume crossing rate. A dedicated investigation of splicing is done by simulating passive scalar mixing without the complexity of
chemically reacting flow physics.
Lastly, an improved modeling technique called super-grid LES-LEM is proposed to computationally speed-up LES-LEM.

LES-LEM

splicing

turbulent combustion

super-grid LES-LEM

CFD

linear eddy model

reaction-rate closure

large eddy simulation

KB-salen, Kemigården 4, Göteborg
Opponent: Associate Professor Kendal Bushe, Department of Mechanical Engineering, The University of British Columbia, Vancouver, Canada

Författare

Salman Arshad

Chalmers, Mekanik och maritima vetenskaper, Förbränning

A strategy for large-scale scalar advection in large eddy simulations that use the linear eddy sub-grid mixing model

International Journal of Numerical Methods for Heat and Fluid Flow,; Vol. 28(2018)p. 2463-2479

Artikel i vetenskaplig tidskrift

Turbulent-combustion closure for the chemical source terms and molecular mixing using the linear-eddy model

53rd AIAA/SAE/ASEE Joint Propulsion Conference, 2017,; (2017)

Paper i proceeding

Effect of the turbulence modeling in large-eddy simulations of nonpremixed flames undergoing extinction and reignition

AIAA SciTech Forum - 55th AIAA Aerospace Sciences Meeting,; (2017)

Konferensbidrag (offentliggjort, men ej förlagsutgivet)

Subgrid reaction-diffusion closure for large eddy simulations using the linear-eddy model

Environment and society are affected by emissions from combustion engines. New concepts of combustion reduce engine emissions and increase efficiency. There is a great need for new computational tools which can predict combustion happening in these new concepts. A model which is able to predict combustion under these non-standard combustion conditions is employed and developed further in this thesis. New and improved concepts are implemented in the model. The thesis contributes to development of cleaner and higher efficiency engines.

LES-LEM modellering av förbränning under olika förbränningsmetoder

Vetenskapsrådet (VR), 2018-01-01 -- 2021-12-31.

Ämneskategorier

Annan maskinteknik

Teknisk mekanik

Strömningsmekanik och akustik

Styrkeområden

Transport

Infrastruktur

C3SE (Chalmers Centre for Computational Science and Engineering)

ISBN

978-91-7597-882-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4563

Utgivare

Chalmers tekniska högskola

KB-salen, Kemigården 4, Göteborg

Opponent: Associate Professor Kendal Bushe, Department of Mechanical Engineering, The University of British Columbia, Vancouver, Canada

Mer information

Senast uppdaterat

2019-02-28