Professor Fokion N. Egolfopoulos
OVERVIEW AND APPROACH
Overview:
The research performed in the Combustion and Fuels Research Laboratory, focuses primarily on the fundamental physical and chemical processes that control the conversion of chemical to thermal energy in high-temperature, high-activation reacting flows. The approach taken is interdisciplinary, as it addresses the interplay of chemical thermodynamics, chemical kinetics, molecular transport, and fluid dynamics, and involves in addition, the use of advanced laser diagnostics and multi-scale computing. The results of this research are of immediate interest to ground, sea, and air transportation, defense, space propulsion, power generation, air pollution, energy efficiency, sustainability, and chemical warfare agent reduction. The experience obtained in the Combustion and Fuels Research Laboratory prepares students and researchers to advance their careers in combustion, as well as in other fields including materials, nanotechnology, and bioengineering in which there is also interplay of similar and/or analogous processes.
Approach:
The conversion of the chemical to thermal energy in any practical combustion device takes place in the presence of intense turbulence and it involves hundreds of chemical species and frequently thousands of elementary reactions. Thus, the various processes that occur simultaneously are rather complex and coupled, and data obtained in practical devices cannot be used to gain insight into the fundamental processes that control the combustion efficiency and pollutant emissions. In order to produce concrete scientific evidence into the various processes, they have to be isolated and controlled. This is possible by reducing the dimensionality of the reacting configuration by eliminating as many temporal and spatial dependencies as possible. Eliminating all spatial dependencies results in homogeneous reactors that can be modeled using time-dependent models in which effects of molecular transport are absent. While results obtained in homogeneous reactors are of particular importance in providing insight into the underlying chemical kinetics, such data are obtained typically for a narrow temperature window, and the effects of fluid mechanics and molecular transport cannot be assessed. One-dimensional flames constitute the simplest reacting configuration in which the evolution of chemical kinetics can be characterized in the presence of molecular transport and well-controlled flow fields. The presence of steep species concentration and temperature gradients as well as non-uniform flow fields can result in rather complex but clearly identifiable modifications of the rates of chemical reactions as well as the structure of the flame at its most elementary level.
Regarding laminar flames, the activities of the Combustion and Fuels Research Laboratory involve experimental, computational, and theoretical studies of one-dimensional flames obtained largely in two distinctly different configurations, namely opposed-jet and spherically expanding flames. The measurements include temperatures, flow velocities, NOx concentrations, soot volume fractions, flame front tracking, and transient plasma characteristics. The experiments are designed so that they produce flames that conform as close as possible to the assumptions of hydrodynamic models that can be used thus with detailed description of molecular transport and chemical kinetics to simulate directly a variety of flame phenomena that are studied in the experiments. The experimental data are of fundamental value for any reacting system, and they can be used for the validation of chemical kinetics and molecular transport models.
Regarding turbulent flames, an atmospheric pressure piloted premixed flame facility. This facility is unique in that it is capable of handling simple gaseous as well as complex liquid fuels (as heavy as Diesel) in order to provide insight into fuel effects on turbulent combustion, a topic that has not attracted proper attention in the long history of turbulent combustion research. The facility is integrated to an array of diagnostics for velocity and scalar quantity measurements. The facility is about to be installed in a pressure vessel that will allow also for assessing both fuel and pressure effects on turbulent combustion.
