Fluid sprinkling – spraying – and diffusing – Electrostatic type – Pressurized spray material
Reexamination Certificate
2000-10-31
2001-11-20
Shaver, Kevin (Department: 3752)
Fluid sprinkling, spraying, and diffusing
Electrostatic type
Pressurized spray material
C239S107000, C239S455000, C126S00900B
Reexamination Certificate
active
06318648
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrostatic atomizers and, in particular, electrostatic atomizers for fuel and combustion devices for burning atomized fuel.
BACKGROUND OF THE INVENTION
Electrostatic atomizers for producing atomized liquids are known. Electrostatic atomizing devices for atomizing a liquid having low conductivity are disclosed in U.S. Pat. Nos. 4,255,777, 4,380,786, 4,581,675, 4,991,774, and 5,093,601 to Kelly, the disclosures of which are hereby incorporated by reference herein. The electrostatic atomizer of U.S. Pat. No. 4,255,777 is capable of forming droplets having an average diameter of less than about 1 millimeter for a liquid having a low conductivity. Using an electrostatic atomizer like that of U.S. Pat. No. 4,255,777, hydrocarbon fuels can be efficiently burned in a combustion device because the atomizer can produce droplets of fuel of such a small size. Fuels which are challenging to burn can be atomized with a sufficient flow rate for a compact combustion device utilizing such an atomizer.
A combustion device using an electrostatic atomizer is disclosed by U.S. Pat. No. 5,695,328 to DeFreitas et al., the disclosure of which is hereby incorporated by reference herein. This patent discloses an ignition device useful for engine combustors in which the electrostatic atomizer of U.S. Pat. No. 4,255,777 may be used. In this device, the voltage is varied to vary the fuel droplet size produced by the atomizer and to thereby vary the thermal output for the device.
In electrostatic atomization according to the aforementioned patents and patent applications, electrical charges from an electrode are injected into the fluid to be atomized, so that the fluid has a net charge, typically a negative charge. Fuel droplets are formed in the above-discussed electrostatic atomizers under the influence of electrostatic forces within the fluid. The size of the fuel droplets produced is independent of the flow rate. Droplet sizes which are a fraction of the orifice diameter can be produced. Thus, details of the orifice cross-section, such as the geometry of the orifice and its alignment with the emitter, do not affect the atomizer's ability to produce a regularly shaped plume of self-dispersed fuel. In certain atomizers according to U.S. Pat. Nos. 5,093,602, 5,378,957, 5,391,958, and 5,478,266 of Kelly, the disclosures of which are also hereby incorporated by reference herein, a charge is injected onto the fluid using an electron beam. These designs provide similar atomization.
It would be desirable to provide an electrostatic atomizer and a combustion device incorporating an electrostatic atomizer having an orifice design which exploits the fact that the orifice design and flow rate are independent of the atomization of the liquid.
SUMMARY OF THE INVENTION
The present invention addresses these needs.
An electrostatic atomizer in accordance with one aspect of the present invention comprises a body having a downstream end and including a plurality of orifice elements defining a variable orifice at the downstream end, charge-providing means disposed in the body, and means for passing a stream of liquid past the charge-providing means to the downstream end so that a net charge is applied to the liquid and a stream of atomized liquid is discharged from the variable orifice, the liquid being atomized at least partially under the influence of the net charge, and the variable orifice being openable and closeable to control the flow of the stream of atomized liquid.
This aspect of the invention exploits the fact that atomization under the influence of a net charge injected into the fluid is independent of the shape and size of the orifice. within extremely broad limits. Thus, varying the orifice geometry opening to control the flow rate does not impair the atomization. The preferred atomizers according to this aspect of the invention can provide reliable atomization over a broad range of flow rates. Moreover, because the same elements which define the atomizing nozzle also provide variable control of the flow rate, there is no need for separate flow-control devices, making the entire structure simple and economical.
Because the droplet size is independent of the orifice geometry, a number of orifice designs can be used. In theory, any shape for a three-dimensional orifice may be used. For instance, the orifice may be a triangular orifice, conically-shaped orifice, a slit orifice, a circular or a scalloped circular orifice. This is particularly useful in small scale combustion devices, in which extremely small orifices must be provided. For small scale combustion systems, the ability to use small components affects the portability and feasibility of the combustion device. The plurality of orifice elements may include a first orifice element and at least one other orifice element slidable across the first orifice element to define the variable orifice. The plurality of orifice elements may include an element having a V-shaped edge.
The first orifice element may comprise a surface defining a hole having a first width and the at least one other orifice element may comprise a narrow element disposed across the hole and having a second width less than the first width to define at least one aperture comprising the orifice of the atomizer.
At least one aperture may also be defined by at least one wire disposed across the hole of the aforementioned first orifice element, which may also include at least one groove having a width for receiving the at least one wire. At least one wire may be movable away from the hole in response to the flow of liquid through the orifice so that the variable orifice is flushable with a flow of liquid sufficient to flush the orifice. Thus, clogging of the orifice may be corrected. The plurality of orifice elements may define a variable orifice in the shape of a triangle including a 90° angle, which is preferable because the 90° angle is more easily flushed to remove debris.
The charge-providing means may include a conically-shaped element having a pointed forward end and being disposed in the body so that the forward end points towards the downstream direction, a surface spaced from the conically-shaped element, and a power source. The power source provides a potential difference between the conically-shaped element and the surface so that a net charge may be applied to the liquid. Other charge injection devices may be used to effect the atomization of the fluid. For example, an electron gun may be used to inject the fluid with a net charge, thereby atomizing the fluid.
The plurality of orifice elements may be moveable relative to one another between a minimum flow position in which the orifice elements define a relatively small orifice and a maximum flow position in which the orifice elements define a relatively large orifice. Where the charge-providing means includes the conically-shaped electrode, the orifice elements may be moveable relative to one another so that the orifice of the atomizer is aligned with the conically-shaped electrode. The at least one other orifice element may be slidable across the hole in the first surface of the first orifice element to define the orifice. At least one other orifice element may have a second surface defining a second hole to define the orifice.
The plurality of orifice elements may also include a tubular case so that the other of the plurality of orifice elements are disposed in the tubular case. Thus, the orifice elements including the tubular case may be rotatable relative to one another between the minimum flow position and the maximum flow positions. The plurality of positions of the plurality of orifice elements may include a fully off position in which no orifice is defined and the flow of atomized fuel is prevented.
The electrostatic atomizer may include anti-clogging means so that the orifice may be flushed with a liquid to prevent clogging. The anti-clogging means may include the plurality of orifice elements, where the orifice elements include a flush position in which the o
Charged Injection Corporation
Hwu Davis
Lerner David Littenberg Krumholz & Mentlik LLP
Shaver Kevin
LandOfFree
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