Eulerian-Lagrangian Approach for Modeling and Simulations of Turbulent Reactive Multi-Phase Flows under Gas Turbine Combustor Conditions

The work presented in this thesis resulted in the development and application of different mathematical sub-models to describe the physics of turbulent reacting spray typical for gas turbine combustors. The resulting complete models were formulated in the Eulerian-Lagrangian context. Emphases were primarily put on the interaction between solid particles and turbulence seeking a correct prediction of turbulent quantities in turbulent two phase flows. The investigation of the feedback mechanism of particles on the continuous phase within the turbulent two-phase flow which is known as turbulence modulation was carried out with three different modulation models. Computations reveal that the obtained results of the turbulent kinetic energy using the thermodynamically consistent model, reproduce well both the turbulence attenuation and production. Indeed, the standard model underestimates the turbulence. This model is dissipative for small and big particles, whereas the model by Crowe is overall productive. Two evaporation models have been developed, integrated in FASTEST/LAG3D code and subsequently applied. The computations were achieved using a fully two-way coupling process. A systematical study of the interaction processes including turbulence, turbulence modulation, mass and heat transfer has been satisfactory carried out. Simulations showed that non equilibrium model agree most favorably with experimental measurements of the droplet mass flux. In order to characterize the turbulence-droplet vaporization interaction regimes, a vaporization Damkoehler number (Dav) has been introduced. Numerical results have demonstrated that in case of Dav>1 turbulence augmentation enhances the evaporation rate, whereas for DaviU1 the opposite phenomenon takes place, namely the rate of evaporation is reduced. The spray combustion was studied in a complex industrial configuration, which consists of a single annular combustor that was experimentally measured by Rolls-Royce Deutschland. Simulations were performed using k-eps as well as Reynolds Stress model (Jones Musonge) for turbulence, an assumed shape of probability density function to prescribe turbulence combustion interaction and different models describing the turbulence modulation. Equilibrium and a flamelet chemistry approaches were used. Results showed that predicted RTDF distributions are satisfactory and provide plausible results compared with measurements. The use of the thermodynamically consistent modulation model allows an acceptable behavior of the temperature distribution compared to the standard modulation model. On the other hand, both evaporation models (equilibrium and non-equilibrium) provided similar results for the temperature distribution. Numerical computations including the flamelet turbulent combustion model predicted a lower peak reaction temperature and a more gradual temperature decrease than predictions using equilibrium chemistry. As final conclusion one can reiterate that the combination of the following sub-models: thermodynamically consistent model for the turbulence modulation, Langmuir-Knudsen non-equilibrium model for the evaporation, Reynolds Stress Model for the turbulence and flamelet model for the chemistry establish a reliable complete model that seems to allows a better description of reactive multi-phase flow studied in the frame of this work.