Regimes of plasma-assisted ignition of turbulent hydrocarbon mixtures

University Of Texas At Austin, Austin TX

Investigators

Abstract

Experiments indicate that a special class of plasmas known as non-thermal plasmas can ignite hydrocarbon/air mixtures under extremely fuel-lean condition where conventional ignition approaches have failed. These non-thermal plasmas act through highly reactive molecules that stimulate the combustion process with low energy input. In this project, we will develop and implement a robust and accurate predictive model that can be used to optimize the plasma- assisted ignition of turbulent flows in combustion devices. If successful, the model developed holds enormous potential to reduce combustion-generated emissions and improve thermal cycle efficiency with positive outcomes for energy security and the environment. The project features activities that seek to enhance undergraduate STEM education at UT Austin and are likely to be adopted in high schools (G9-12) throughout the United States upon completion of the project. Despite the technological promise with regard to improving energy conversion processes, a systematic understanding of the interaction of plasma discharges, coupled plasma and combustion chemical kinetics, and turbulent transport is lacking. Such understanding is required in order to implement plasma-assisted ignition (PAI) in practical devices towards low-emission and high-efficiency energy-conversion technology. The outcome of a PAI event depends on the competition between transport of energy and plasma-generated radicals out of the igniting kernel and accelerating chemical kinetics and heat release. In this project, we will identify the non-dimensional parameters that govern PAI of turbulent reactive mixtures and define regime diagrams by leveraging massively parallel and large-scale simulations. The high-fidelity physical models employed ensure that no closures are invoked. The flow configuration considered in our approach is a canonical homogeneous isotropic turbulent flow whereby the rates of turbulent transport and all other relevant scales may be carefully controlled. Consideration will be given to temporal and spatial scales of plasma discharges, turbulent flow, chemical kinetics, and rates of molecular diffusion of heat and mass. Data from simulations will be analyzed using powerful new mathematical techniques that quantify the competition of chemical reactions and transport locally and instantaneously during transient ignition events. An important aspect of our approach is that simulations will closely mirror PAI experiments in a turbulent combustion vessel conducted in parallel by our collaborators, providing the unique opportunity for direct comparisons. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.