Thesis-2007-Almutlaq.pdf (29.4 MB)
Density-based unstructured simulations of gas-turbine combustor flows
thesis
posted on 2013-12-23, 14:22 authored by Ahmed N. AlmutlaqThe goal of the present work was to identify and implement modifications to a
density-based unstructured RANS CFD algorithm, as typically used in
turbomachinery flows (represented here via the RoIIs-Royce 'Hydra' code), for
application to Iow Mach number gas-turbine combustor flows. The basic algorithm
was modified to make it suitable for combustor relevant problems. Fixed velocity
and centreline boundary conditions were added using a characteristic based
method. Conserved scalar mean and variance transport equations were introduced
to predict scalar mixing in reacting flows. Finally, a flarnelet thermochemistry
model for turbulent non-premixed combustion with an assumed shape pdf for
turbulence-chemistry interaction was incorporated. A method was identified
whereby the temperature/ density provided by the combustion model was coupled
directly back into the momentum equations rather than from the energy equation.
Three different test cases were used to validate the numerical capabilities of the
modified code, for isothermal and reacting flows on different grid types. The first
case was the jet in confined cross flow associated with combustor liner-dilution jetcore
flow interaction. The second was the swirling flow through a multi-stream
swirler. These cases represent the main aerodynamic features of combustor
primary zones. The third case was a methane-fueled coaxial jet combustor to assess
the combustion model implementation. This study revealed that, via appropriate
modifications, an unstructured density-based approach can be utilised to simulate
combustor flows. It also demonstrated that unstructured meshes employing nonhexahedral
elements were inefficient at accurate capture of flow processes in
regions combining rapid mixing and strong convection at angles to cell edges. The
final version of the algorithm demonstrated that low Mach RANS reacting flow
simulations, commonly performed using a pressure-based approach, can
successfully be reproduced using a density-based approach.
History
School
- Aeronautical, Automotive, Chemical and Materials Engineering
Department
- Aeronautical and Automotive Engineering
Publisher
© A. N. AlmutlaqPublication date
2007Notes
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.EThOS Persistent ID
uk.bl.ethos.445369Language
- en