Electrohydrodynamic Gas Pump in a Vertical Tube

Abstract

The characteristics of an electrohydrodynamic (EHD) gas pump were experimentally evaluated in this study. Experiments were conducted using positive DC voltage (13.0 kV – 30.0 kV), applied to a thin corona wire of diameter 0.51 mm. The ground plate used in the study was mounted on the inner surface of a cylinder and had a width of 12.7 mm and a total exposed surface area of 1.52 × 10−3 m2. The pumps tested were identical except for their spacing between the emitting electrode and the ground plate, which varied from 0.66D to 1.33D. The results show that the current on the ground plate increases as the applied voltage increases. It is also observed that the applied voltage at which flow was first detected in the cylinder correlates well with the electrode spacing. It appears that the four electrodes placed along the surface of the pipe were able to disturb the boundary layer enough to create a uniform flow profile within the pipe. As a result, flow as high as 2.5 m/s was observed in the cylinder with an electrode spacing of L/D = 1.33. The results also show that the ionic wind velocity increases with an increasing EHD Reynolds number for L/D = 0.66 and 1.0, but decreases with the EHD Reynolds number for L/D > 1.

Flow characteristics of a single stage EHD gas pump in circular tube

“…8 shows the variation of axial flow velocity along and between the emitting electrodes (i.e., YY and XX axis) in the smalldiameter tube. Since the emitting electrodes are flush mounted on the tube wall, one observes that the velocity near the wall (P6) is considerably higher than that away from the wall (P5) for both cases, which is again consistent with the previous reports [24,25]. Also observed, the velocity along the direction of emitting electrode (YY-axis) is higher than that between the electrodes (XX-axis) for all applied voltages.…”

“…With an increase in the applied voltage, the strength of corona jets increases and their effect can be felt deeper into the core region as well as further downstream of the tube. When comparing with the data reported by Brown and Lai [25] for the same geometry and applied voltage but with only four emitting electrodes employed, the velocities attained in the present study (along both XX-and YY-axis) are considerably higher. This clearly indicates that an increase in the electrode number is necessary for an increase in the induced flow velocity as well as its volume flow rate for a large-diameter tube.…”

“…This trend of limiting volume flow rate has been first reported by Brown and Lai [25]. It suggests that there is a maximum flow rate (which depends on the size of the tube) that an EHD gas pump can deliver.…”

“…Flow characteristics of an EHD gas pump with four emitting pins flush mounted on a circular pipe wall have been studied by Brown and Lai [25]. Their results show that ionic wind velocity approaches an asymptotic value as the applied voltage increases.…”

“…The tube diameters are roughly twice of those tested by Brown and Lai [25]. The number of emitting electrodes is also intentionally doubled to check if the previous results can be proportionally scaled up.…”