Abstract:
The main objective of this work is to create a robust model for two-phase liquid spray
combustion flow using vegetable oils, to investigate the flow structure generated by a
swirler array with different fuels, and secondly to assess and optimise the capability of
the CFD to predict accurately the results obtained experimentally and eventually
enhance CFD model development and simulation. Validation is achieved by
comparing the numerical results obtained with CFD with the experimental
measurements.
The purpose of this research is to increase the scientific understanding of the
fundamental mechanisms of the spray combustion process using a carbon neutral fuel
such as ethanol and biodiesel. In fact, very few numerical simulations of liquid
biomass fuels in gas turbine systems are available in the literature.
The flames are simulated using the commercial code FLUENT. The
combustion/turbulence interaction is modelled using the laminar flamelet approach
with detailed chemistry modelled using the OPPDIFF model from CHEMKIN.
While the experiments could be carried out only up to 3 atm, the simulations were
further extended to a maximum pressure of 10 atm. The FLUENT results were
assessed qualitatively and quantitatively between the experimental measurements and
the simulation. The cold flow features have been captured by the present simulations
with a good degree of accuracy. Effect of air preheating was investigated for the
biodiesel, and sensitivity to droplet size and spray angles variation were analysed.
Good agreement was obtained for ethanol except in the fuel lean region due to failure
of the FLUENT laminar flamelet model to capture local flame extinction while
biodiesel simulation resulted in a significant overprediction of the flame temperature
especially in the downstream region and satisfactory results further upstream. The
results show the importance of setting proper droplet initial conditions, since it will
significantly affect the structure of the flame.
