The Application of Electric Control of Combustion to Counterflow Non- Premixed Flames

Abstract

The effect of electrostatic fields on the dilute plasma of chemi-ions generated by a nonpremixed, N2-diluted, methane-oxygen flame was studied experimentally and computationally. Flames were established in an experimental burner whereby a counterflow-flame was positioned between the parallel plates of a large-scale capacitor through the control of the applied electric field, and without any variation of the strain imposed on the flame. The location of the flame was controlled through an applied voltage, virtually independent of the overall mixture composition and strain rate applied on the flame. The computations were conducted using an ANSYS-Fluent platform implementing the GRI-Mech 3.0 kinetic mechanism that was supplemented with a set of three reactions generating three chemi-ions: H3O+, HCO+, and e-. Electrostatic effects were coupled with the reactive flow equations through two distinct mechanisms. First, the electric field introduced a body force that affected the momentum balance. Second, for the charged species, a diffusion mechanism developed in addition to the Fickian diffusion, which involved the generation of a diffusion velocity that was determined by the charged species mobility (ambipolar diffusion). The corresponding terms were introduced through appropriate codes in the momentum, species evolution, and energy equations of the ANSYS-Fluent solver. By switching on and off the ambipolar diffusion terms, we were able to show that their contribution was relatively small, which made the application of the body force the main means through which electrostatics affected the flame. Computations and experiments support the notion that the application of the electric force can shift the flame to a different location without drastically affecting its structure.

Date of Award	Dec 2016
Original language	American English
Supervisor	Dimitrios Kyritsis (Supervisor)