Competitive pressure and stringent emissions legislation have placed an urgent
demand on research to improve our understanding of the gas turbine combustor flow
field. Flow through the air admission ports of a combustor plays an essential role in
determining the internal flow patterns on which many features of combustor
performance depend. This thesis explains how a combination of experimental and
computational research has helped improve our understanding, and ability to predict,
the flow characteristics of jets entering a combustor.
The experiments focused on a simplified generic geometry of a combustor port system.
Two concentric tubes, with ports introduced into the inner tube's wall, allowed a set of
radially impinging jets to be formed within the inner tube. By investigating the flow
with LDA instrumentation and flow visualisation methods a quantitative and
qualitative picture of the mean and turbulent flow fields has been constructed. Data
were collected from the annulus, port and core regions. These data provide suitable
validation information for computational models, allow improved understanding of the
detailed flow physics and provide the global performance parameters used traditionally
by combustor designers.
Computational work focused on improving the port representation within CFD
models. This work looked at the effect of increasing the grid refinement, and
improving the geometrical representation of the port. The desire to model realistic port
features led to the development of a stand-alone port modelling module. Comparing
calculations of plain-circular ports to those for more realistic chuted port geometry, for
example, showed that isothermal modelling methods were able to predict the expected
changes to the global parameters measured. Moreover, these effects are seen to have
significant consequences on the predicted combustor core flow field.
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.