Laminar Non-Premixed Counterflow Flames Manipulation through the Application of External Direct Current Fields

Electrostatically manipulated, laminar, non-premixed, counterflow methane flames were studied experimentally and computationally. It was established experimentally that the flame position could be controlled solely through control of the applied electric field, without any variation of the strain imposed on the flame. The computations were conducted using a commercially available finite-element software implementing a widely accepted detailed kinetic mechanism that was supplemented with a set of three reactions generating three chemi-ions: ${\mathrm{H}}_3{\mathrm{O}}^{+}$, ${\mathrm{HCO}}^{+}$, and ${\mathrm{e}}^{-}$. The electrostatic effect was 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 (i.e., ambipolar diffusion). The corresponding terms were introduced appropriately into the reactive Navier-Stokes equations. The contribution of the ambipolar diffusion is observed to be relatively small by comparing results with and without the ambipolar diffusion term, 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 shifts the flame to a different location without drastically affecting its structure.