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|Title: ||Computational and experimental study of a multi-stream swirler.|
|Authors: ||Hughes, Nicola J.|
|Issue Date: ||2003|
|Publisher: ||© Nicola Jane Hughes|
|Abstract: ||The fuel injector in a modern gas turbine encompasses a multi-stream swirler, the shear layers
from which are used to atomise the liquid fuel. The aerodynamic characteristics of the swirler
are known to affect the placement of the fuel directly, and, ultimately, the emissions produced.
A full appreciation of the aerodynamics potentially enables improved injector design
and hence lower emissions. A rig was designed to study the flow resulting from three axial,
co-rotating swirler passages, separated by shrouds, with the downstream flow field being confined
in a duct. The swirler module was three times full size and has a 450 repeatable sector.
A detailed survey of the downstream flow field has been carried out using a five hole pressure
probe and a three component laser doppler anemometry (LDA) system. A gearing mechanism
was employed to rotate the swirler within the rig casing such that the extent of any three dimensionality
in the flow field could be assessed. The central recirculation caused by the highly
swirling flow was found to extend beyond the final measurement plane, prompting the
moderately loaded exhaust nozzle to be replaced by a cylinder positioned centrally within the
rig. LDA measurements were taken at thirty downstream planes, providing sufficient detail
for validation of a computational model. The three dimensionality of the flow field was found
to be minimal, which has direct implications for the requirements of computational modelling.
A three-dimensional computational fluid dynamics (CFD) code, encompassing both k - E
and Reynolds Stress Transport (RST) turbulence models was employed to model the flow.
Test cases from the open literature were utilised to validate the physical models within the
code on simple geometries, with the results comparing favourably to those previously published.
A solid model of the experimental geometry was created using a CAD package, which
was extracted and used as direct input to the grid generator. A structured grid was employed,
with the calculation including both flow through the swirler passages and in the downstream
mixing duct. The experimental results were used to validate the computational model. Calculations
starting downstream of the swirler exit plane, utilising experimental measurements as
inlet boundary conditions, indicated that the improved physical description of the RST model
provided enhanced results over the simpler k - E model. Calculations performed through the
swirler vane passages using the k - E model indicated that the results were improved significantly
by moving the inlet boundary condition to an upstream location, possibly due to the
estimation of the turbulence dissipation.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Aeronautical and Automotive Engineering) |
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