Paraelectric gas flow accelerator

Details Paraelectric gas flow accelerator Paraelectric gas flow accelerator

1999-07-20

2001-03-13

Mayekar, Kishor (Department: 1741)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

With means applying electromagnetic wave energy or...

C204S164000, C422S022000, C588S253000

Reexamination Certificate

active

06200539

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma generators, and, in particular, to electrohydrodynamic (EHD) flow control of a discharge plasma, such as a one-atmosphere, uniform glow discharge (OAUGD) plasma.
2. Description of the Related Art
The use of magnetohydrodynamics (MHD) to control the turbulent viscous drag due to aerodynamic boundary layer flow has received considerable attention over the years. Most concepts have been based on ionized flow around a magnetized hypersonic vehicle, or on achieving such a plasma with ion seeding techniques. Emphasis has been placed on the magnetohydrodynamic approach in hydrodynamics due to the electrically conducting nature of seawater and perceived high economic or performance payoffs. However, in terms of a net energy balance, performance enhancement has proven elusive.
An alternative to MHD flow control which has received far less attention in the field of boundary layer research is based on the electric field alone, or electrohydrodynamic (EHD) control. In partially ionized gases, the electric field itself, or the paraelectric effects associated with an electric field gradient, can be used to accelerate ions and, via particle collisions (mobility drift), the neutral gas. In the past, a difficulty with the EHD approach, especially in non-hypersonic flight applications, is generating an energy-efficient ionized flow near the surface at one atmosphere.
SUMMARY OF THE INVENTION
Aerodynamic data have been acquired from planar panels with a uniform glow discharge surface plasma at atmospheric pressure. Flat plate panels with either stream-wise or span-wise arrays of flush, closely spaced symmetric or asymmetric plasma-generating surface electrodes were studied with laminar, transitional, and fully turbulent boundary layer flow in a low-speed wind tunnel. The term “stream-wise” refers to orientations in which the flow is parallel to the array of parallel electrodes, while the term “span-wise” refers to orientations in which the flow is perpendicular to the electrodes.
It was observed that EHD forces can produce dramatic effects, which arise from paraelectric, RF forcing of the flow. Notable effects include large increases in measured drag due to either vortex formation (symmetric electrode case) or directed thrust (asymmetric electrode case). In the more dramatic cases, the entire thickness of the boundary layer was affected by either flow acceleration or retardation. The effects of heating are discounted and the primary cause of the observed flow phenomena attributed to electrohydrodynamic (EHD) forcing of the flow by a paraelectric RF body force.
The present invention is directed to a paraelectric gas flow generator that applies a novel approach to electrohydrodynamic flow control of a discharge plasma, such as a one-atmosphere, uniform glow discharge (OAUGD) plasma. An OAUGD plasma is a surface-generated, atmospheric, RF (radio frequency) plasma. One significant feature that distinguishes an OAUGD plasma from other RF plasmas is its efficient ability to create a uniform glow discharge at atmospheric pressure on an extended flat surface. The present invention can be implemented using electrodes having characteristics, such as simplicity, robustness, low cost, and reliability, that lend themselves to practical engineering applications. In order to employ an OAUGD plasma for laminar or turbulent boundary layer control, the present invention generates EHD forces with magnitudes sufficient to alter boundary layer flow dynamics, where such forces constitute a useful flow control mechanism.
In one embodiment, the present invention is directed to an apparatus for generating a flow in gas, comprising (a) a substrate; (a) a first plurality of electrodes configured on the substrate; (b) a second plurality of electrodes configured on the substrate, wherein each electrode in the second plurality is positioned along a first direction between a pair of adjacent electrodes in the first plurality such that said each electrode is closer to one of the pair of the adjacent electrodes that to another of the pair of adjacent electrodes; and (c) a voltage generator configured to the first and second pluralities of electrodes and adapted to apply a voltage to the first and second pluralities of electrodes to generate a discharge plasma in the gas located on at least one side of the substrate adjacent to one of the pluralities of electrodes, whereby the relative positioning of the first and second pluralities of electrodes along the first direction results in a force being imparted onto the gas parallel to the first direction.
In another embodiment, the present invention is a method for generating a flow in gas, comprising the steps of (a) providing a substrate configured with first and second pluralities electrodes, wherein each electrode in the second plurality is positioned along a first direction between a pair of adjacent electrodes in the first plurality such that said each electrode is closer to one of the pair of the adjacent electrodes that to another of the pair of adjacent electrodes; and (b) applying a voltage to the first and second pluralities of electrodes to generate a discharge plasma in the gas located on at least one side of the substrate adjacent to one of the pluralities of electrodes, whereby the relative positioning of the first and second pluralities of electrodes along the first direction results in a force being imparted onto the gas parallel to the first direction.


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“Multiple Electrode Plasma Accelerate Incorporate Odd Number Extra Gas Permeable Electrode Main Electrode Alternate Connect Power Source Earth”, by Kolchenko A I, Derwent Publications Ltd., Jan. 1987, 87-275756.

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