PhD Defense : Varun SHASTRY ” Simulation of multicomponent spray combustion in gas turbine engines “
Liquid fuels are the dominant source of energy from combustion and will continue to be so until the maturity of emerging technologies. During this transition phase the use of Sustainable Aviation Fuels (SAF) as blends or in totality inside existing infrastructure is an attractive option. The operational aspects of these new fuels inside the combustion chambers are not known in detail. Further, gas turbine engines operate under high pressure ratios and lean conditions to achieve emission targets making them susceptible to thermo-acoustic oscillations. Large Eddy Simulations (LES) have proven to be a successful tool in understanding fuel combustion processes. The focus of this thesis is on the modelling and simulation of complex multicomponent spray flame combustion in realistic systems.
First step deals with the multi-component evaporation of the liquid fuel. Realistic fuels have hundreds of components each with their vapourisation characteristics. The Abramzon-Siringnano evaporation in the AVBP solver is extended to handle this complex compositional aspect of realistic fuels. Comparison of the implemented model with experimental and numerical studies show a good agreement and ability to capture the preferential evaporation characteristics of multicomponent fuels.
Second, this multicomponent evaporation model is used in a canonical 1D laminar spray flame setup. A three-component jet fuel surrogate is coupled with Analytically Reduced Chemistry (ARC) to study the effects of droplet sizes, equivalence ratios and relative velocities on the spray flame structures. Correlations developed to estimate the spray flame speed agree with the numerical experiments indicating the correct physical parameters have been chosen to describe multicomponent spray flame propagation.
Third part of the thesis deals with the simulations of swirled multicomponent spray flames in a large-scale LOTAR configuration. A three component description of conventional jet fuel and sustainable aviation fuel spray is coupled with turbulent combustion models and complex chemistry description to perform 3D-LES. The fuels composition effects on the overall vapour distribution and its effects on the spray flame structure indicate the role of preferential evaporation on flame stabilisation and combustion regimes.
Finally, the forced response of the spray flame in the configuration is studied. The flame transfer function extracted using global chemistry agrees well with the experimental trends. Varying injection patterns to account for the effects of forcing on the droplet distribution shows a change in the flame response. The multicomponent spray flame response shows a strong role of composition and volatility of the fuel components.
|Benoît Fiorina||EM2C, CentralSupelec||Reviewer|
|J.B.W. Kok||University of Twente||Reviewer|
|Laurent Gicquel||CERFACS||Invited Member|