Experimental and numerical investigation of electrohydrodynamic flow in a point-to-ring corona discharge

An electrohydrodynamic (EHD) flow in a point-to-ring corona configuration is investigated experimentally and via a multiphysics computational model. The model couples the ion transport equation and the Navier-Stokes equations (NSE) to solve for the spatiotemporal distribution of electric field, flow field, and charge density. The numerical simulation results are validated against experimental measurements of the cathode voltage, ion concentration, and velocity profiles. The maximum flow velocity is at the centerline, and it decays rapidly with radial distance due to the viscous and electric forces acting on the partially ionized gas. To understand this coupling, a nondimensional parameter, $X$, is formulated as the ratio of the local electric force to the inertial term in the NSE. In the region of $X\ge 1$, the electric force dominates the flow dynamics, while in the $X\ll 1$ region, the balance of viscous and inertial terms yields traditional pipe flow characteristics. This approach expands on the analytical model of Guan et al. by adding a description of the developing flow region. The approach allows the model to be used for the entire EHD domain, providing insights into the near-field flow in the corona region.

Figure 1

Schematic of the experimental setup. A high voltage is applied between the corona anode needle and the ion-collecting cathode ring. The distance and voltage are varied.

Figure 2

The computational domain used for the numerical simulation; the model includes the ion generation region $\mathrm{\Psi }$, defined by the thresholds of electric field values: $E_0$ and $E_1$.

Figure 3

Plots of the electric field, ion concentration, and velocity for different conditions in the point-to-ring corona generator $(I=6.15\mu \mathrm{A},16.04\mu \mathrm{A},4.28\mu \mathrm{A}$, respectively). The dash lines on the velocity contours indicate the location at which the velocity of the EHD flow is compared with the experiments.

Figure 4

Maximum velocity as a function of corona voltage and electrode geometry for the experimental data, analytical [32], and CFD results.

Figure 5

Comparison between simulations and experiments for the velocity profiles at the outlet of the EHD generator: (a) varying corona voltages at a fixed distance and (b) varying anode-cathode distance $\left(L\right)$ at a fixed corona voltage.

Figure 6

Electric field lines colored by the nondimensional parameter $X$. The red zone, $X\ge 1$, indicates the regions of EHD-dominated flow. The color map is limited to $X=1$; the value $X$ can be as high as 400 in the regions near the ionization zone and the low-velocity region near the wall.

Figure 7

Energy transfer efficiency from the experiments (symbols) and simulations (dashed and dash-dotted lines).