US20090151322A1

US20090151322A1 - Plasma Assisted Combustion Device

Info

Publication number: US20090151322A1
Application number: US11/959,451
Authority: US
Inventors: Don M. Coates
Original assignee: Perriquest Defense Research Enterprises LLC
Current assignee: Perriquest Defense Research Enterprises LLC
Priority date: 2007-12-18
Filing date: 2007-12-18
Publication date: 2009-06-18
Also published as: WO2009079420A3; WO2009079420A2

Abstract

A plasma assisted combustion device includes a dielectric housing that defines a plasma chamber having an input that receives media for processing and an output that passes processed media. A ground electrode plate is positioned proximate to a first surface of the dielectric housing forming a first dielectric barrier. A hot electrode plate is positioned proximate to a second surface of the dielectric housing forming a second dielectric barrier. A power supply generates a waveform that energizes the hot electrode plate with a voltage that strikes a double dielectric barrier plasma discharge in the plasma chamber. A media injector is positioned at an input of the plasma chamber. The media injector includes a nozzle that converts a liquid media into an aerosolized media and then sprays the aerosolized media into the plasma chamber. The plasma in the plasma chamber processes the aerosolized media into at least some lower molecular weight media and activating at least some free radicals.

Description

The section headings used herein are for organizational purposes only and should not be construed as limiting the subject matter described in the present application.

BACKGROUND OF THE INVENTION

The methods and apparatus of the present invention relate to Plasma Assisted Combustion (PAC) devices that use non-equilibrium dielectric barrier discharges for fuel activation. Plasma assisted combustion devices create electrical discharges or non-thermal plasmas in a gaseous medium. Such plasma assisted combustion devices can be used to activate fuel in an internal combustion engine to reduce hazardous emissions and to increase the efficiency of the engines.
Non-thermal plasmas generate electrons that are “hot,” while the ions and neutral species are “cold,” which results in minimal waste enthalpy being deposited in media, which can be a gas, aerosol, or vapor stream. Other plasmas are known as thermal plasma. In thermal plasmas, the energies of the electron, ion, and neutral-species are all in thermal equilibrium. Electrons, ions, and neutral-species in thermal plasmas are all referred to as being “hot.” Thermal plasmas are undesirable for many applications because they generate considerable waste heat and this waste heat is typically absorbed in the media. In addition, thermal plasmas are undesirable for many applications because they do not allow selective chemical processes to be performed in the plasma.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects of this invention may be better understood by referring to the following description in conjunction with the accompanying drawings. Identical or similar elements in these figures may be designated by the same reference numerals. Detailed description about these similar elements may not be repeated. The drawings are not necessarily to scale. The skilled artisan will understand that the drawings, described below, are for illustration purposes only. The drawings are not intended to limit the scope of the present teachings in any way.

FIG. 1A illustrates a three-dimensional perspective view of a plasma assisted combustion device according to the present invention.

FIG. 1B illustrates a side cross-sectional view of the plasma assisted combustion device according to the present invention that is shown in FIG. 1A.

FIG. 2 illustrates a cross-sectional view of a portion of an intake manifold for an internal combustion engine including the plasma assisted combustion device described in connection with FIGS. 1A and 1B.

FIG. 3 illustrates a cross-sectional view of a portion of a turbine engine including the plasma assisted combustion device described in connection with FIGS. 1A and 1B.

DETAILED DESCRIPTION

Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
It should be understood that the individual steps of the methods of the present invention may be performed in any order and/or simultaneously as long as the invention remains operable. Furthermore, it should be understood that the apparatus and methods of the present invention can include any number or all of the described embodiments as long as the invention remains operable.
The present teachings will now be described in more detail with reference to exemplary embodiments thereof as shown in the accompanying drawings. While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications and equivalents, as will be appreciated by those of skill in the art. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present disclosure as described herein.
Combustion-based engines, such as aircraft jet turbines, ground based turbines, such as turbines used to generate electric power, internal combustion engines, such as engines used in trucks and automobiles, and other engines produce emissions that are considered harmful to the atmosphere. One type of emission that is considered to be particularly harmful is nitrogen oxide (NOX). It is highly desirable to reduce NOX emissions in combustion-based engines.
U.S. Pat. No. 6,606,855 to Kong et al., entitled “Plasma Reforming and Partial Oxidation of Hydrocarbon Fuel Vapor to Produce Synthesis Gas And/Or Hydrogen Gas,” describes methods and apparatus for treating fuel vapors with thermal or non-thermal plasmas to promote reforming reactions between the fuel vapor and re-directed exhaust gases. These reactions include partial oxidation reactions between the fuel vapor and air to produce carbon monoxide and hydrogen gas, or direct hydrogen and carbon particle production from the fuel vapor. One disadvantage of the methods and apparatus described in Kong et al. is that the hydrocarbon gases are formed with carbon particles (i.e. soot). Introduction of carbon particles into a working engine is highly undesirable because carbon particles are difficult to combust, can cause pre-ignition, and can cause engine damage.
U.S. Pat. No. 6,322,757 to Cohn et al., entitled “Low Power Compact Plasma Fuel Converter,” also teaches the conversion of fuel, particularly into molecular hydrogen (H2) and carbon monoxide (CO). The apparatus described in Cohn et al. also generates high levels of soot. In addition, the apparatus described in Cohn experiences electrode erosion because the apparatus employs a hot-arc thermal plasma, rather than a low-temperature, non-thermal plasma.
Various plasma assisted combustion devices for internal combustion engines which do not generate high levels of soot are described in U.S. patent application Ser. No. 11/543,400, filed Oct. 5, 2006, and entitled “Fuel Injection Device Including Plasma-Inducing Electrode Arrays” and U.S. patent application Ser. No. 11/218,792, filed Sep. 1, 2005, and entitled “Fuel Injector Utilizing Non-Thermal Plasma Activation.” U.S. patent application Ser. Nos. 11/543,400 and 11/218,792 are assigned to the present assignee.
The plasma assisted combustion devices described in U.S. patent application Ser. Nos. 11/543,400 and 11/218,792 use a silent-discharge, dielectric-barrier non-thermal plasma (NTP) reactor. A silent-discharge or dielectric barrier discharge is a high pressure non-equilibrium discharge which occurs when alternating voltages are applied between two electrodes separated by a non-conducting media. Silent-discharge, dielectric-barrier non-thermal plasmas are not in thermodynamic equilibrium. This type of discharge is similar to glow discharges and radio-frequency and microwave discharges at pressures below 10 kPa.
Non-thermal plasmas have relatively low gas temperature and energy-conversion rates. Thus, the electrons in these plasmas typically have a much higher temperature than the heavy ions and neutral particles. One important feature of non-equilibrium dielectric barrier discharges is that they can be sustained at elevated pressures. Therefore, dielectric barrier discharges are particularly useful for applications where a high mass flow and/or a high operating pressure, such as atmospheric pressure, are required. Another important feature of non-equilibrium dielectric barrier discharges is that they can operate over wide temperature ranges. Another important feature of non-equilibrium dielectric barrier discharges is that they can operate over wide power ranges.
Non-equilibrium dielectric barrier discharges are commonly used for large scale industrial ozone generation. Non-equilibrium dielectric barrier discharges are also commonly used to form excimers for generating ultraviolet radiation in excimer lasers. The features of non-equilibrium dielectric barrier discharges also make them suitable for plasma assisted combustion.
A plasma assisted combustion device according to the present invention forms a dielectric-barrier non-thermal plasma comprising energetic electrons and other highly reactive chemical species, such as free radicals, in a process media, such as a fuel. The plasma assisted combustion caused by the dielectric-barrier non-thermal plasma “cracks” long, complex-chain hydrocarbon fuels into lower molecular weight fuels. The plasma assisted combustion caused by the dielectric-barrier non-thermal plasma also creates short-lived “free radical” species.
It has been shown that lower molecular weight fuels and free radicals promote better overall combustion. In addition, it has been shown that lower molecular weight fuels and free radicals significantly enhance “lean-burn” mode combustion, which is a fuel lean, air rich mode of combustion. Operating in the “lean burn” mode reduces the production of NOX pollutants by reducing the temperature of the combustion process and thus reducing the oxidation of nitrogen in the combustion mixture.
In addition, plasma assisted combustion improves the efficiency of combustion in these engines by achieving a more complete combustion. It has been demonstrated that more complete combustion results from combusting relatively low molecular weight fuels. Also, cracking fuels into lower molecular weight fuels allows engines to burn “lower grade” fuels, which are generally less expensive and more abundant. Thus, plasma assisted combustion provides for greater flexibility in the type of fuel used in these engines.
More specifically, a plasma assisted combustion device according to the present invention includes a dielectric housing that forms a plasma chamber. In some embodiments, the dielectric housing is wedge shaped. In other embodiments, the dielectric housing is rectangular in shape. Flat plate electrodes are positioned on top of or recessed into the dielectric housing. The liquid fuel is converted into a dispersed mist, vapor, or aerosolized fuel by a fuel injector and the mist, vapor, or aerosolized fuel is then sprayed into the plasma chamber formed by the dielectric housing. In some embodiments, the angle of the dielectric housing is chosen so as to approximately match the angle of the process media sprayed into the plasma chamber by a process media injector. An electric field is applied to the flat plate electrodes to form a non-thermal plasma. The plasma assisted combustion device feeds an internal combustion engine, or other combustion device employing process media injectors.
FIG. 1A illustrates a three-dimensional perspective view of a plasma assisted combustion device 100 according to the present invention. The plasma assisted combustion device 100 includes a dielectric housing 102 that defines a plasma chamber 104, which contains the plasma. The dielectric housing 102 includes an input 106 that receives a process media, such a fuel or a chemical to be processed. The dielectric housing 102 also includes an output 108 that transports the processed media, such as a processed fuel or other chemical, to a downstream device. For example, in some embodiments, the downstream device is an intake manifold of an internal combustion engine. In other embodiments, the downstream device is an instrument, such as a spectrometer, which analyzes processed media. In yet other embodiments, the output 108 of the dielectric housing 102 is vented into the atmosphere for abatement and other applications.
The dielectric housing 102 must be dimensioned to provide both a sufficient high voltage breakdown resistance necessary to prevent undesirable arcing and a physical size and physical volume which interfaces with practical down stream devices. For example, in some embodiments of the present invention, the dielectric housing 102 is dimensioned to interface with an intake manifold of an internal combustion engines as shown in FIG. 2. One feature of the plasma assisted combustion device of the present invention is that the plasma chamber 104 can have significantly less volume compared with other known plasma assisted combustion devices.
In some embodiments, a relatively small shape and volume is achieved by constructing the plasma assisted combustion device of the present invention with a dielectric housing 102 that is formed of a high-dielectric ceramic material. The dielectric housing 102 can be formed of any one of numerous types of dielectric materials. In some embodiments, the dielectric housing 102 of the present invention is formed of a high dielectric material which reduces the probability of forming an undesirable discharge. Also, in some embodiments, the dielectric housing 102 of the present invention has a shape that is chosen to reduce the probability of forming an undesirable discharge.
For example, in one embodiment, the dielectric housing 102 is formed of Macor® which is a glass ceramic made by Corning Incorporated. For example, the dielectric housing 102 can be carved out of a Macor® block or other similar material. Macor® is well suited for the dielectric housing 102 of plasma assisted combustion devices according to the present invention. Macor® is available in many different forms and can also be machined with ordinary machine tools. Macor® is well suited for containing a plasma in the plasma assisted combustion device of the present invention because it has good chemical resistance, is physically strong, and is dimensionally stable at high temperatures up to 1000° C. Macor® also has thermal expansion characteristics which are similar to metals. In addition, Macor® has a high dielectric strength which makes it is an excellent insulator with a high breakdown voltage.
In another embodiment, the dielectric housing 102 is a formed fired ceramic material, similar to the material used to form the insulator in commercial spark plugs for internal combustion engines. A fired ceramic material can be molded like clay into the desired shape and is then heated to a high temperature in a furnace. Such fired ceramics have a high dielectric strength which makes them an excellent insulator with a high breakdown voltage, which are desirable characteristics for the plasma assisted combustion device of the present invention.
In other embodiments, numerous types of dielectric materials are used for the dielectric housing 102 of the present invention. For example, the dielectric housing 102 can be formed of alumina, porcelain, glass, a high-temperature plastic, such as Teflon®, a polyimide, or a polyamide. Numerous other types of high-dielectric strength materials, such as some dielectrics commonly used in electronic capacitors, are suitable. For example, the dielectric housing 102 can be formed of Mylar® and Kapton®, which are both manufactured by DuPont Company. In addition, the dielectric housing 102 can be formed of high temperature rubber compounds.
A hot electrode plate 110 is positioned on one surface of the dielectric housing 102. The hot electrode plate 110 is formed of a conductive material. A potting material can be used to insulate the hot electrode plate 110 from any possible electrical paths to ground. For example, the potting material can be a high temperature ceramic casting compound. A suitable high temperature ceramic casting compound is available from Morgan Technical Ceramics (McDaniel Advanced Ceramics).
The hot electrode plate 110 is electrically connected to a high voltage power supply 114 with an electrical transmission line 116. The power supply 114 generates a high voltage that is sufficient to break down the process media and cause a plasma discharge. In one embodiment, the power supply 114 generates a high voltage waveform having an amplitude that is in the range of about 1 kV to 50 kV and a frequency that is in the range of about 10 Hz-20 kHz. The high voltage waveform can be a sine wave, a square wave, or some complex waveform.
A ground electrode plate 112 is positioned on another surface of the dielectric housing 102. For example, the ground electrode plate 112 can be positioned on a surface that is opposite to the hot electrode plate 110. The ground electrode plate 112 is electrically connected to ground potential with an electrical connection 117. The ground electrode plate 112 is formed of a conductive material.
One advantage of the plasma assisted combustion device of the present invention is that the hot electrode plate 110 and the ground electrode plate 112 do not have to be constructive of a material that is resistant to plasma because the hot electrode plate 110 and the ground electrode plate 112 are not directly exposed to the plasma. In addition, the hot electrode plate 110 and the ground electrode plate 112 do not have to be formed of a high conductivity material because it is driven by an AC waveform. Therefore, the hot electrode plate 110 and ground electrode plate 112 can be formed of a relatively inexpensive conductor for some applications.
In one embodiment, the plasma assisted combustion device of the present invention is used to crack fuel in the intake manifold of an internal combustion engine. In this embodiment, a relatively low temperature material can be used to form the hot electrode plate 110 and the ground electrode plate 112 because the plasma assisted combustion device will be relatively far away from the combustion chamber.
In another embodiment, the plasma assisted combustion device of the present invention is used to crack fuel in the fuel system of a turbine engine. In this embodiment, a higher temperature material is used to form the hot electrode plate 110 and the ground electrode plate 112 because the plasma assisted combustion device is typically closer to the combustion chamber and, therefore, will experience relatively high temperatures.
In various other embodiments, the hot electrode plate 110 and the ground electrode plate 112 can be formed of various materials depending upon the operating temperature and the environmental conditions. For example, the hot electrode plate 110 and the ground electrode plate 112 can be formed of relatively inexpensive and commonly available conductive materials that are easy to use, such as silver loaded epoxy. Also, the hot electrode plate 110 and the ground electrode plate 112 can be formed of high melting temperature materials, such as stainless steel alloys, tungsten, tungsten alloys, or one of a number of other refractory metals and refractory metal alloys. In addition, the hot electrode plate 110 and the ground electrode plate 112 can be formed of a carbon-based composite material, such as a carbon nanotube material, or a graphitic surface material.
The geometry of the dielectric housing 102, hot electrode plate 110, and the ground electrode plate 112 can be chosen to minimize the probability of creating an undesirable electrical discharge to ground. In one embodiment, the hot electrode plate 110 and the ground electrode plate 112 are recessed into the dielectric housing 102 as shown in FIG. 1B. This geometry forms a double dielectric barrier. That is, there are separate dielectric barriers between the hot electrode plate 110 and the ground electrode plate 112. It has been discovered that a double dielectric barrier configuration provides a more uniform plasma and improved filling of the plasma chamber 104 compared with a single dielectric barrier configuration that is used in known devices. In particular, single dielectric barrier configurations do not result in uniform plasmas.
In one embodiment, the hot electrode plate 110 and the ground electrode plate 112 are positioned at a relative angle that is chosen to closely match the angle of injection of the process media. For example, the hot electrode plate 110 and the ground electrode plate 112 can be positioned at a relative angle that is chosen to closely match the angle of an envelope or spray pattern of a process media being injected into the plasma chamber 104.
In many embodiments, the plasma assisted combustion device 100 includes a process media injection device 118, such as a fuel injector for injecting fuel into the plasma chamber 104. The process media injection device 118 provides a spray of process media into the plasma chamber 104 when activated. The output of the process media injection device 118 is positioned proximate to the input of the plasma chamber 104. In some embodiments, the angle of the plasma chamber 104 is chosen to closely match the angle of the spray pattern produced by the process media injection device 118.
FIG. 1B illustrates a side cross-sectional view of the plasma assisted combustion device 100 according to the present invention that is shown in FIG. 1A. A side cross-sectional view of the dielectric housing 102, the hot electrode plate 110, and the ground electrode plate 112 are shown. The side cross-sectional view of the plasma assisted combustion device 100 shows that the hot electrode plate 110 and the ground electrode plate 112 are flat plates that are recessed entirely into the dielectric housing 102. In other embodiments the hot electrode plate 110 and the ground electrode plate 112 are only partially recessed into the dielectric housing 102. In yet other embodiments, the hot electrode plate 110 and the ground electrode plate 112 are positioned on top of the dielectric housing 102 and are not recessed into the dielectric housing material.
The geometry of the dielectric housing 102, hot electrode plate 110, and the ground electrode plate 112 form a double dielectric barrier. This geometry is used to form a double dielectric barrier discharge in the plasma chamber 104. One feature of a double dielectric barrier discharge is that such discharges are considerably more uniform than a single dielectric barrier discharge.
Recessing the hot electrode plate 110 and the ground electrode plate 112 into the dielectric housing 102 decreases the probability of establishing an undesirable electrical discharge between the hot electrode plate 110 and grounded surfaces including the ground electrode plate 112 because possible arcing surfaces are then positioned behind high dielectric strength materials. In addition, using a flat geometry hot electrode plate 110 and a flat geometry ground electrode plate 112 also decreases the probability of establishing an undesirable electrical discharge.
Furthermore, the plasma assisted combustion device geometry shown in FIGS. 1A and 1B physically separates possible arcing surfaces far enough to further reduce the probability of establishing an undesirable electrical breakdown condition. That is, the plasma assisted combustion device geometry shown in FIGS. 1A and 1B is designed to provide relatively long pathway for arcing from excited plasma gases to ground surfaces.
The side cross-sectional view of the plasma assisted combustion device 100 also shows the plasma process media envelope 120 that is sprayed out of the process media injector 118 and into the plasma chamber 104. The side cross-sectional view indicates that the plasma chamber 104 does not obstruct the flow of process media through the plasma chamber. In contrast, many known plasma assisted combustion devices have geometries that obstruct the flow of process media through the plasma chamber 104 to the down stream system.
One feature of the plasma assisted combustion device 100 is that it has a simpler design with fewer parts and, therefore, can be easier and less expensive to manufacture compared with known plasma assisted combustion devices. Another feature of the plasma assisted combustion device 100 is that all of the process media in the plasma chamber 104 is directly exposed to the plasma which enhances the probability of cracking the fuel. In contrast, devices that include conical-shaped electrodes may not expose all or even a high fraction of the fuel to the plasma, which can lower the efficiency of the combustion. These features make the plasma assisted combustion device 100 particularly well suited for use in internal combustion engines. Also, the plasma assisted combustion device 100 is well suited for turbine engines which combust kerosene based fuels. Kerosene based fuels condense more readily than many other fuels, so it is important to expose as much of the fuel to the plasma as possible to increase the probability of cracking the fuel and thus, the efficiency of the combustion.
Referring to FIGS. 1A and 1B, in operation, an aerosolized process media is injected by the process media injector 118. In various embodiments, the aerosolized process media can be a high molecular weight fuel or numerous types of fuels and chemicals. The hot electrode plate 110 is then energized with a relatively high voltage waveform. For example, the hot electrode plate 110 can be energized with a 10 kV waveform. Many different types of waveforms can be used to form a plasma according to the present invention. The high voltage waveform strikes a non-thermal plasma in the plasma chamber 104 between the hot electrode plate 110 and the ground electrode plate 112. In some embodiments, a relatively high frequency waveform is used to reduce the probability of generating an electrical discharge. In some embodiments, the waveform includes one or more high voltage spikes that assists in striking the plasma.
The non-thermal plasma cracks the aerosolized process media into lower molecular weight chemicals and creates free radicals. Parameters of the plasma can be chosen for a particular application. For example, the parameters of the plasma can be chosen to crack fuel in the plasma chamber before the fuel is injected into the intake manifold of an engine. In this application, the non-thermal plasma cracks the fuel and generates energetic electrons, which aid in the formation of “free radical” species in the fuel. The resulting free radicals are highly reactive chemical species that promote combustion reactions. The enhanced combustion greatly reduces soot production and production of undesirable oxidative reactions. The enhanced combustion also has relatively high fuel efficiency.
Similarly, the parameters of the plasma can be chosen so that toxic chemicals are abated when they react with the plasma. In this application, the non-thermal plasma cracks the toxic chemicals and generates energetic electrons, which aid in the formation of “free radical” species in the fuel. The resulting free radicals are highly reactive chemical species which promote combustion reactions that break apart the toxic chemical molecules. The enhanced combustion greatly reduces soot production and production of undesirable oxidative reactions.
Experiments with the plasma assisted combustion device 100 indicate that the plasma uniformity is relatively high compared with known plasma assisted combustion devices. The plasma uniformity is relatively high because electrons alternate streaming from the ground electrode plate to the hot electrode plate and from the hot electrode plate to the ground electrode plate during AC cycles while building up on both dielectric barriers. The concentration of electrons reaches a point where the electrical driving force is negated by the reverse field at a single spot on the dielectric barriers. The spot moves back and forth as a function of time on both dielectric surfaces so as to greatly improve uniformity of the resulting plasma.
Experiments with the plasma assisted combustion device 100 also indicate that the plasma density in this device is relatively high compared with known plasma assisted combustion devices. The relatively high plasma density results, at least in part, from the geometry of the plasma chamber 104 and the double dielectric barrier discharge generated in the plasma chamber 104. In addition, the plasma utilization was relatively high. The term “plasma utilization” is defined herein as the ratio of the plasma volume to the volume of the plasma chamber 104. Also, the cracking efficiency achieved with the plasma assisted combustion device 100 was measured to be about five times greater than the cracking efficiency of known plasma assisted combustion devices. Furthermore, experiments have shown that the power consumption is relatively low compared with known plasma assisted combustion devices.
FIG. 2 illustrates a cross-sectional view of a portion of an intake manifold 200 for an internal combustion engine including the plasma assisted combustion device 100 described in connection with FIGS. 1A and 1B. One skilled in the art will appreciate that the portion of the intake manifold 200 shown in FIG. 2 represents one intake port of a multi-port intake manifold in most engine designs. The dielectric housing 102 of the plasma assisted combustion device 100 is positioned in the intake manifold 200 so that the output of the plasma chamber 104 formed by the dielectric housing 102 has an unobstructed path to the downstream portion of the intake manifold 200. The dielectric housing 102 can be attached to the intake manifold in numerous ways. In some embodiments, a high temperature epoxy or other high temperature adhesive can be used to attach the plasma assisted combustion device to the intake manifold. In other embodiments, the dielectric housing 102 is attached to the intake manifold 200 with one of numerous types of fasteners, such as bolts and screws. A gasket can be used between the dielectric housing 102 and the intake manifold 200 to prevent gases from escaping.
In some embodiments, the shape of dielectric housing 102 including the angle from the input 106 to the output 108 of the plasma chamber 104 defined by the dielectric housing 102 is chosen to maximize the space that the intake manifold 200 can utilize to provide fuel. Also, in some embodiments, the shape of dielectric housing 102 including the angle from the input 106 to the output 108 of the plasma chamber 104 defined by the dielectric housing 102 is chosen to improve the performance of a particular engine design. In one embodiment, the dielectric housing 102 described in connection with FIGS. 1A and 1B is used. However, one skilled in the art will appreciate that various geometries of dielectric housings can be used to interface with particular intake manifold designs.
The hot electrode plate 110 and the ground electrode plate 112 are recessed into the dielectric housing 102 as described in connection with the plasma assisted combustion device shown in FIGS. 1A and 1B. The electrical transmission line 116 coupled from the high voltage power supply 114 to the hot electrode plate 110 and the electrical connection 117 coupled from the ground electrode plate 112 to ground are not shown to simplify the drawing. In some embodiments, the electrical transmission line 116 and the electrical connection 117 are electrically coupled using a silver loaded epoxy. The hot electrode plate 110, the ground electrode plate 112, and the fuel injector 118 are positioned so that there is a seam-free barrier to “line-of-sight” electrical discharges from the hot electrode plate 110 to grounded surfaces, such as the ground electrode plate 112.
An electronic process media injector or fuel injector 118 interfaces with the dielectric housing 102 and intake manifold 200. A first 202 and second O-ring 204 are positioned in grooves in the fuel injector 118 and are used to seat the output tip of the fuel injector 118 into the input of the plasma chamber 104. The first and second O- rings 202, 204 prevent unwanted air from entering into the plasma chamber 104 and into the intake manifold 200. In many embodiments, the angle of the plasma chamber 104 that is defined by the dielectric housing 102 is chosen to closely match the angle of the spray pattern of the fuel injector 118. Also, in many embodiments, the angle of the spray pattern of the fuel injector 118 is chosen to avoid condensation of fuel on the intake manifold 200. In various embodiments, the fuel injector 118 can spray many different spray patterns, such as an elliptical, single cone, or dual cone spray pattern.
Suitable electronic fuel injectors are commercially available from manufacturers, such as Delphi and Bosch. Other manufactures sell suitable fuel injectors for aircraft and watercraft that can also be used with the plasma assisted combustion device of the present invention. The fuel injector 118 includes an electrical connector 206 that provides an interface for control wires.
A method of operating a plasma assisted combustion device according to the present invention to crack fuel in the intake manifold of an internal combustion engine includes providing a spray of fuel from a fuel injector 118 into the plasma chamber 104 when activated. The fuel injector 118 converts a liquid fuel into a dispersed mist, vapor, or aerosolized fuel. The ground electrode plate 112 is coupled to ground potential. The hot electrode plate 110 is then energized with a relatively high voltage waveform, such as a 10 kV waveform. Many different types of waveforms can be used to form a plasma according to the present invention. The high voltage waveform strikes a non-thermal plasma in the plasma chamber 104 between the hot electrode plate 110 and the ground electrode plate 112. In some embodiments, a relatively high frequency waveform is used to reduce the probability of generating an undesirable arc or electrical discharge.
The non-thermal plasma cracks the dispersed mist, vapor, or aerosolized fuel and generates lower molecular weight fuel and energetic electrons, which aid in the formation of “free radical” species in the fuel. The resulting free radicals are highly reactive species that promote combustion reactions. The intake manifold mixes air with the resulting lower molecular weight fuel and “free radical” species. The resulting mixture is injected into a cylinder or other ignition chamber within the engine (not shown) where it is ignited to power the engine.
Some methods according to the present invention include increasing or maximizing the fuel efficiency of the engine by properly selecting at least one of the high voltage waveform applied to the hot electrode plate 110, the dimensions of the plasma chamber 104, the dimensions of the intake manifold 200, and the amount of air mixed with the lower molecular weight fuel and the free radicals.
Also, some methods according to the present invention include decreasing or minimizing undesirable emissions by properly selecting at least one of the high voltage waveform applied to the hot electrode plate 110, the dimensions of the plasma chamber 104, the dimensions of the intake manifold 200, and the amount of air mixed with the lower molecular weight fuel and the free radicals.
Using the methods of the present invention will result in a higher flame propagation rate. The term “flame propagation rate” is defined herein to mean the speed of travel of ignition through a combustible mixture. A higher flame propagation rate results from the fact that the fuel is cracked. Cracking fuel into small molecules will improve combustion and result in more complete combustion because the fuel is cracked into smaller compounds and because free radicals are present. Achieving more complete combustion allows the use of a more diluted combustion mixture having a relatively high fraction of air, which increases the overall fuel efficiency of the engine. In addition, the more complete combustion reduces undesirable emissions.
FIG. 3 illustrates a cross-sectional view of a portion of a turbine engine 300 including the plasma assisted combustion device described in connection with FIGS. 1A and 1B. One skilled in the art will appreciate that the portion of the turbine engine 300 shown in FIG. 3 represents a portion of a fuel injection system for a commonly used turbine engine. Referring to FIGS. 1A, 1B and 3, the dielectric housing 102 of the plasma assisted combustion device 100 is positioned proximate to a compressed air diffusion chamber 302 in the turbine engine 300 so that the output of the plasma chamber 104 formed by the dielectric housing 102 has an unobstructed path into the combustion chamber 304.
The dielectric housing 102 can be attached to the compressed air diffusion chamber 302 in numerous ways. In some embodiments, a high temperature ceramic adhesive can be used to attach the plasma assisted combustion device to the compressed air diffusion chamber 302. In other embodiments, the dielectric housing 102 is attached to the compressed air diffusion chamber 302 with one of numerous types of fasteners, such as bolts and screws. A gasket can be used between the dielectric housing 102 and the compressed air diffusion chamber 302 to prevent gases from escaping.
In some embodiments, the shape of the dielectric housing 102 including the angle from the input 106 to the output 108 of the plasma chamber 104 defined by the dielectric housing 102 is chosen to maximize the volume of fuel injected into the combustion chamber 304 for a particular fuel injection system. Also, in some embodiments, the shape of dielectric housing 102 including the angle from the input 106 to the output 108 of the plasma chamber 104 defined by the dielectric housing 102 is chosen to improve the performance or to reduce emission of a particular turbine engine design. In one embodiment, the dielectric housing 102 described in connection with FIGS. 1A and 1B is used. However, one skilled in the art will appreciate that various geometries of dielectric housings can be used to interface with particular turbine engine fuel intake designs.
The hot electrode plate 110 and the ground electrode plate 112 are recessed into the dielectric housing 102 as described in connection with the plasma assisted combustion device shown in FIGS. 1A and 1B. The hot electrode plate 110, the ground electrode plate 112, and the fuel injector 118 are positioned so that there is a seam-free barrier to “line-of-sight” electrical discharges from the hot electrode plate 110 to grounded surfaces, such as the ground electrode plate 112.
The fuel injector 118 includes an electrical connector 206 that provides an interface for control wires as described herein. The electrical transmission line 116 coupled from the high voltage power supply 114 to the hot electrode plate 110 and the electrical connection 117 coupled from the ground electrode plate 112 to ground are not shown to simplify the drawing.
The fuel injector 118 can include O-rings, such as the O- rings 202, 204 described in connection with FIG. 2. The O-rings can be used to seat the output tip of the fuel injector 118 into the input of the plasma chamber 104 and to prevent unwanted air from entering into the plasma chamber 104 and into the combustion chamber 304. In many embodiments, the angle of the plasma chamber 104 that is defined by the dielectric housing 102 is chosen to closely match the angle of the spray pattern of the fuel injector 118. In various embodiments, the fuel injector 118 can spray many different spray patterns, such as an elliptical, single cone, or dual cone spray pattern.
A method of operating a plasma assisted combustion device according to the present invention to crack fuel in the fuel injection system of a turbine engine is similar to the method of cracking fuel in the intake manifold of an internal combustion engine that was described in connection with FIG. 2. The method includes providing a spray of fuel from a fuel injector 118 into the plasma chamber 104 when activated. The fuel injector 118 converts a liquid fuel into a dispersed mist, vapor, or aerosolized fuel. The ground electrode plate 112 is coupled to ground potential. The hot electrode plate 110 is then energized with a relatively high voltage waveform, such as a 10 kV waveform. Many different types of waveforms can be used to form a plasma according to the present invention. The high voltage waveform strikes a non-thermal plasma in the plasma chamber 104 between the hot electrode plate 110 and the ground electrode plate 112. In some embodiments, a relatively high frequency waveform is used to reduce the probability of generating an undesirable arc or electrical discharge.
The non-thermal plasma cracks the dispersed mist, vapor, or aerosolized fuel and generates lower molecular weight fuel and energetic electrons, which aid in the formation of “free radical” species in the fuel. The resulting free radicals are highly reactive species that promote combustion reactions. The combustion chamber 304 mixes compressed air from the compressed air diffusion chamber 302 with the resulting lower molecular weight fuel and “free radical” species. The resulting mixture is ignited in the combustion chamber 304 to power the turbine engine 300.
Some methods according to the present invention include increasing or maximizing the fuel efficiency of the engine by properly selecting at least one of the high voltage waveform applied to the hot electrode plate 110, the dimensions of the plasma chamber 104, the dimensions of the compressed air diffusion chamber 302, the dimensions of the combustion chamber 304, and the amount of air mixed with the lower molecular weight fuel and the free radicals.
Also, some methods according to the present invention include decreasing or minimizing undesirable emissions by properly selecting at least one of the high voltage waveform applied to the hot electrode plate 110, the dimensions of the plasma chamber 104, the dimensions of the compressed air diffusion chamber 302, the dimensions of the combustion chamber 304, and the amount of air mixed with the lower molecular weight fuel and the free radicals. Using the methods of the present invention will result in a higher flame propagation rate for turbine engines.

EQUIVALENTS

While the present teachings are described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments. On the contrary, the present teachings encompass various alternatives, modifications and equivalents, as will be appreciated by those of skill in the art, may be made therein without departing from the spirit and scope of the invention.

Claims

1. A plasma assisted combustion device comprising:

a) a dielectric housing that defines a plasma chamber having an input that receives media for processing and an output that passes processed media;

b) a ground electrode plate positioned proximate to a first surface of the dielectric housing forming a first dielectric barrier;

c) a hot electrode plate positioned proximate to a second surface of the dielectric housing forming a second dielectric barrier;

d) a power supply having an output that is electrically connected to the hot electrode plate, the power supply generating a waveform that energizes the hot electrode plate with a voltage that strikes a double dielectric barrier plasma discharge in the plasma chamber; and

e) a media injector that is positioned at an input of the plasma chamber, the media injector having a nozzle that converts a liquid media into an aerosolized media and then sprays the aerosolized media into the plasma chamber, the plasma in the plasma chamber processing the aerosolized media into at least some lower molecular weight media and activating at least some free radicals.

2. The plasma assisted combustion device of claim 1 wherein the dielectric housing is wedge shape.

3. The plasma assisted combustion device of claim 1 wherein the dielectric housing is rectangular shape.

4. The plasma assisted combustion device of claim 1 wherein the dielectric housing is shaped to prevent fuel from condensing.

5. The plasma assisted combustion device of claim 1 wherein the dielectric housing is shaped to approximately match an angle of the media sprayed into the plasma chamber by the media injector.

6. The plasma assisted combustion device of claim 1 wherein the dielectric housing is shaped to prevent obstructions to the media so that substantially all of the media is directly exposed to the plasma

7. The plasma assisted combustion device of claim 1 wherein the dielectric housing is shaped to reduce condensation of the media on surfaces of the plasma assisted combustion device.

8. The plasma assisted combustion device of claim 1 wherein the media comprises fuel.

9. The plasma assisted combustion device of claim 8 wherein the dielectric housing is shaped to improve cracking efficiency of the fuel in the plasma chamber.

10. The plasma assisted combustion device of claim 1 wherein the first surface of the dielectric housing is positioned opposite to the second surface of the dielectric housing.

11. The plasma assisted combustion device of claim 1 wherein at least one of the ground electrode plate and the hot electrode plate is at least partially recessed into the dielectric housing.

12. The plasma assisted combustion device of claim 1 wherein at least one of the ground electrode plate and the hot electrode plate is substantially flat in shape.

13. The plasma assisted combustion device of claim 1 wherein dimensions of the dielectric housing are chosen to reduce a probability of generating an undesirable electrical discharge in the plasma chamber.

14. The plasma assisted combustion device of claim 1 wherein the dielectric housing is formed of a ceramic material.

15. A method of plasma assisted combustion, the method comprising:

a) forming a plasma chamber with a dielectric housing;

b) injecting an aerosolized media into the plasma chamber;

c) electrically connecting a ground electrode plate positioned proximate to a first surface of the dielectric housing, which forms a first dielectric barrier, to ground potential; and

d) energizing a hot electrode plate positioned proximate to a second surface of the dielectric housing, which forms a second dielectric barrier, with a high voltage waveform that strikes a double dielectric barrier plasma discharge in the plasma chamber, the plasma in the plasma chamber cracking the aerosolized media into lower molecular weight media and activating free radicals.

16. The method of claim 15 further comprising selecting a frequency of the high voltage waveform that reduces a probability of generating an undesirable electrical discharge.

17. The method of claim 15 further comprising shielding at least one of the hot electrode plate and the ground electrode plate with a high dielectric material that reduces a probability of generating an undesirable electric discharge.

18. The method of claim 15 further comprising positioning at least one of the hot electrode plate and the ground electrode plate to reduce a probability of generating an undesirable electric discharge.

19. The method of claim 15 further comprising positioning at least one of the hot electrode plate and the ground electrode plate to increase a probability of striking the plasma discharge.

20. The method of claim 15 wherein at least one of the high voltage waveform and the dimensions of the plasma chamber is chosen to improve cracking efficiency of media in the plasma chamber.

21. The method of claim 15 further comprising mixing the lower molecular weight processed media and free radicals with air and igniting the mixture outside of the plasma chamber.

22. The method of claim 21 further comprising compressing the air that is mixed with the lower molecular weight combustion products and free radicals before igniting the mixture.

23. The method of claim 21 wherein at least one of the voltages applied to the hot electrode plate, the dimensions of the plasma chamber, and the amount of air mixed with the lower molecular weight fuel and the free radicals are chosen to improve ignition efficiency.

24. The method of claim 21 wherein at least one of the voltages applied to the hot electrode plate, the dimensions of the plasma chamber, and the amount of air mixed with the lower molecular weight fuel and the free radicals is chosen to reduce undesirable emissions in the ignition products.

25. A plasma assisted combustion device comprising:

b) a means for injecting an aerosolized media into the plasma chamber; and

c) a means for striking a double dielectric barrier plasma discharge in the plasma chamber, the plasma in the plasma chamber processing the aerosolized media into lower molecular weight processed media and activating free radicals.