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You are invited to a PhD proposal
Advisor: Prof. Tim Lieuwen
Food Processing Technology Building, Auditorium (Room 103)
(Opposite to Ben T. Zinn Combustion Lab, NARA)
ABSTRACT
Turbulent combustion, particularly premixed combustion has great practical importance due to their extensive industrial usage in gas turbines, internal combustion engines etc. However, the physics governing the inherent multi- scale interactions of turbulence, flow-field and chemistry is not yet well established. A complete understanding of each of these interactions and their coupling is essential for the development of models that can aid simulations of realistic engines (using Large Eddy Simulations (LES) or Reynolds averaged Navier-Stokes equations (RANS).
Particularly, understanding the flame structure and its stabilization requires an understanding of the turbulence-chemistry interactions. This can manifest itself in many different forms. For example, flame wrinkling gives rise to flame stretch that can modify the local temperature and species concentrations in turn altering the local chemistry. Also, the smaller eddies in a turbulent flow can penetrate into the preheat and reaction zones changing the species’ gradients within the flame.
In this work, the effect of increasing turbulence on chemical pathways for fuel oxidation is investigated using Direct Numerical Simulations (DNS). Important metrics are identified to effectively quantify these changes using multiple data conditioners such as fuel consumption, curvature etc. To explore fuel effects, this analysis is performed for characteristically different fuels such as H2, CH4 and heavier fuels such as n-C12H26 (a good surrogate for kerosene based fuels). The results are also compared and contrasted with simple 0D/1D laminar flame models. A simple analytical model using thermodynamics and reaction kinetics is developed to emphasize the universality of the results obtained. Finally, reaction pathways (and their sensitivity to increasing turbulence) for different combustion modes (such as auto-ignition, extinction, assisted ignition) are also explored.
Committee:
