U.S. patent application number 11/218792 was filed with the patent office on 2009-12-24 for fuel injector utilizing non-thermal plasma activation.
This patent application is currently assigned to The Regents of the University of California. Invention is credited to Don M. Coates, Louis A. Rosocha.
Application Number | 20090317310 11/218792 |
Document ID | / |
Family ID | 41350859 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090317310 |
Kind Code |
A1 |
Coates; Don M. ; et
al. |
December 24, 2009 |
FUEL INJECTOR UTILIZING NON-THERMAL PLASMA ACTIVATION
Abstract
A non-thermal plasma assisted combustion fuel injector that uses
an inner and outer electrode to create an electric field from a
high voltage power supply. A dielectric material is operatively
disposed between the two electrodes to prevent arcing and to
promote the formation of a non-thermal plasma. A fuel injector,
which converts a liquid fuel into a dispersed mist, vapor, or
aerosolized fuel, injects into the non-thermal plasma generating
energetic electrons and other highly reactive chemical species.
Inventors: |
Coates; Don M.; (Santa Fe,
NM) ; Rosocha; Louis A.; (Los Alamos, NM) |
Correspondence
Address: |
LOS ALAMOS NATIONAL SECURITY, LLC
LOS ALAMOS NATIONAL LABORATORY, PPO. BOX 1663, LC/IP, MS A187
LOS ALAMOS
NM
87545
US
|
Assignee: |
The Regents of the University of
California
|
Family ID: |
41350859 |
Appl. No.: |
11/218792 |
Filed: |
September 1, 2005 |
Current U.S.
Class: |
422/186.04 ;
204/172 |
Current CPC
Class: |
Y02T 10/126 20130101;
F23C 2900/99005 20130101; F02M 31/18 20130101; F02M 27/042
20130101; Y02T 10/12 20130101; F23D 11/32 20130101; F23D 11/24
20130101 |
Class at
Publication: |
422/186.04 ;
204/172 |
International
Class: |
B01J 19/08 20060101
B01J019/08; H05H 1/24 20060101 H05H001/24 |
Goverment Interests
STATEMENT REGARDING FEDERAL RIGHTS
[0001] This invention was made with government support under
Contract No. W-7405-ENG-36 awarded by the U.S. Department of
Energy. The government has certain rights in the invention.
Claims
1. A non-thermal plasma assisted combustion fuel injector,
comprising: a. an outer electrode and an inner electrode that
provide surfaces to create an electric field therebetween; b. a
high voltage power supply to induce said electric field; c. a
dielectric material, operatively disposed between said outer
electrode and said inner electrode to prevent arcing and promote
said non-thermal plasma formation; and, d. a fuel injector
configured to convert a liquid fuel into a dispersed mist, vapor,
or aerosolized fuel; wherein a non-thermal plasma is created with
the electric field between the outer electrode and the inner
electrode.
2. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a basket.
3. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a needle.
4. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a brush.
5. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a spiral
wire.
6. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a cone with
electric field-enhancing perforations throughout.
7. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a cylinder
with electric field-enhancing perforations throughout.
8. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode is configured as a series of
pointed washers.
9. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner and said outer electrodes are made from
material selected from the group consisting of stainless steel
alloys, tungsten, tungsten alloys, refractory metals, carbon-based
composites, carbon nanotubes, and graphitic surfaces.
10. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said dielectric material is selected from the group
consisting of alumina, porcelain, machinable glass ceramic,
glasses, high temperature plastics, polimides and polyamides, and
rubber compounds.
11. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said power supply operates in a range of about 1 to
50 kV and of about 10 Hz to 20 kHz.
12. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said inner electrode and said outer electrode are
spaced apart in a range of about 0.5 mm to 20 mm.
13. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said outer electrode is configured in a conical
shape.
14. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said outer electrode resides within said dielectric
material.
15. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said non-thermal plasma assisted combustion fuel
injector is mounted in a port fuel injection configuration.
16. The non-thermal plasma assisted combustion fuel injector of
claim 1, where said non-thermal plasma assisted combustion fuel
injector is mounted in a cylinder head configuration.
17. (canceled)
18. (canceled)
Description
FIELD OF THE INVENTION
[0002] The present invention relates generally to non-thermal
plasmas, and, more particularly, to the use of non-thermal plasmas
in the design of a fuel injector that feeds internal combustion
engines or other combustion devices employing fuel injectors.
BACKGROUND OF THE INVENTION
[0003] The present invention is a device that employs electrical
discharges/non-thermal plasmas in a gaseous medium to activate a
fuel derived from a fuel injector to promote more effective and
efficient combustion. In non-thermal plasmas, the electrons are
`hot`, while the ions and neutral species are `cold`--which results
in little waste enthalpy being deposited in a process gas stream.
This is in contrast to thermal plasmas, where the electron, ion,
and neutral-species energies are in thermal equilibrium (or `hot`)
and considerable waste heat is deposited in the process gas.
[0004] The present invention utilizes a type of electrical
discharge called a dielectric barrier discharge (DBD) or silent
discharge plasma (SDP) to: 1) break up large organic fuel molecules
into smaller ones that are more easily and completely combusted;
and 2) create highly reactive free-radical chemical species that
can promote more efficient combustion by their strong "redox" power
(fuels become strong reducing agents, oxygen becomes more
oxidizing) or by their ability to promote combustion-sustaining
chain reactions or chain reactions that further generate active
species. This device is envisioned for application to a variety of
internal combustion engines, such as automobile engines and all
turbine engines that normally employ fuel injectors.
[0005] U.S. Pat. No. 6,606,855, Plasma Reforming and Partial
Oxidation of Hydrocarbon Fuel Vapor to Produce Synthesis Gas And/Or
Hydrogen Gas, by Kong et al., teaches methods and systems for
treating vapors from fuels with thermal or non-thermal plasmas to
promote reforming reactions between the fuel vapor and re-directed
exhaust gases to produce carbon monoxide and hydrogen gas, 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. However, a problem with
the reactions taught in Kong et al. includes the fact that
hydrocarbon gases, when formed, are accompanied with carbon
particles (ie. Soot). Introduction of carbon particles into a
working engine is considered undesirable due to the engine damage
that can be caused and, in particular, the difficulty in combusting
the carbon particles.
[0006] In contrast, the present invention is a specific non-thermal
plasma fuel injector, designed to make free radicals and more
easily-combusted cracked species of out of injected fuel to enhance
combustion with no formation of soot. There are no oxidative
reactions as in Kong et al. and only fuel is treated, not O2 or
exhaust gases as described in Kong et al.
[0007] U.S. Pat. No. 6,322,757, Low Power Compact Plasma Fuel
Converter, by Cohn et al., also teaches the conversion of fuel,
particularly into molecular hydrogen (H.sub.2) and carbon monoxide
(CO). The invention of Cohn et al, like Kong et al., suffers from
rampant soot production, as well as electrode erosion (because the
Plasmatron converter actually employs a hot-arc, thermal plasma,
rather than a low-temperature, non-thermal plasma). Further, it is
not clearly evident that molecular hydrogen is the key promoter of
more stable/complete combustion.
[0008] Various objects, advantages and novel features of the
invention will be set forth in part in the description which
follows, and in part will become apparent to those skilled in the
art upon examination of the following or may be learned by practice
of the invention. The objects and advantages of the invention may
be realized and attained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
[0009] In accordance with the purposes of the present invention, as
embodied and broadly described herein, the present invention
includes a non-thermal plasma assisted combustion fuel injector
that uses a first and second electrode to create an electric field
from a high voltage power supply. A dielectric material is
operatively disposed between the two electrodes to prevent arcing
and to promote the formation of a non-thermal plasma. A fuel
injector, which converts a liquid fuel into a dispersed mist,
vapor, or aerosolized fuel, injects into the non-thermal plasma
generating energetic electrons and other highly reactive chemical
species.
[0010] In another embodiment, the present invention includes a
method for cracking fuel using a fuel injector to create a fuel
mist and then subjecting the fuel mist to a non-thermal plasma
created between an outer electrode and an inner electrode, thereby
cracking the fuel mist and creating fuel fragments
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate the embodiments of the
present invention and, together with the description, serve to
explain the principles of the invention. In the drawings:
[0012] FIG. 1 pictorially shows one embodiment of the plasma
assisted combustion fuel injector device.
[0013] FIG. 2 pictorially shows a cross section of one embodiment
of the plasma assisted combustion fuel injector device.
[0014] FIG. 3 pictorially shows a basket electrode embodiment.
[0015] FIG. 4a pictorially shows a tapered "brush" inner electrode
embodiment.
[0016] FIG. 4b pictorially shows a spiral wire inner electrode
embodiment.
[0017] FIG. 4c pictorially shows a perforated cone inner electrode
embodiment.
[0018] FIG. 4d pictorially shows a perforated cylinder inner
electrode embodiment.
[0019] FIG. 4e pictorially shows a series of pointed washers used
as an inner electrode embodiment.
[0020] FIG. 5 graphically shows the test results using a tapered
"brush" electrode embodiment.
[0021] FIG. 6 pictorially shows a cross section of an internal IC
engine port fuel injection configuration for mounting the
PACFI.
[0022] FIG. 7 pictorially shows a direct injection configuration
for mounting the PACFI.
DETAILED DESCRIPTION
[0023] The present invention uses a
silent-discharge/dielectric-barrier non-thermal plasma (NTP)
reactor to generate energetic electrons and other highly reactive
chemical species (such as free radicals) in a fuel that feeds
internal combustion engines, or other combustion devices employing
fuel injectors. The highly reactive chemical species: 1) break up
large organic fuel molecules into smaller ones that are more easily
and completely combusted; and 2) create highly reactive
free-radical chemical species that can promote more efficient
combustion through enhanced reactive power, ability to promote
combustion-sustaining chain reactions, and follow on chain
reactions that generate more active species.
[0024] Referring now to FIG. 1, NTPs can be created by several
types of electric discharge configurations known to those skilled
in the art. In the present invention, the reactor makes use of a
dielectric-barrier discharge arrangement. Here, two conducting
electrodes, outer electrode 10 and inner electrode 20, one or both
of which are covered by a dielectric material, are separated by
gas-containing gap 30. Gap 30 may range from about 0.5 mm to 20
mm.
[0025] Dielectric materials that may be used include, but are not
limited to: dielectric ceramics such as alumina, porcelain,
Macor.RTM. machinable glass ceramic, glasses of various types, high
temperature plastics such as Teflon.RTM., polimides and polyamides,
dielectrics such as those used in capacitors (e.g. Mylar.RTM. and
Kapton.RTM.--DuPont Company), and rubber compounds.
[0026] Materials used for the electrodes may include, but are not
limited to: conductive, corrosion-resistant metals, such as
stainless steel alloys, tungsten and tungsten alloys, and any other
refractory metals and alloys that are resistant to erosion in the
plasma environment; and, carbon-based composites, carbon nanotubes,
and graphitic surfaces, which are particularly resistant to etching
in plasma environments (such as those used in plasma television
electrodes or other related applications).
[0027] One or both electrodes must be shielded from the other
electrode by a dielectric material so that arcing is avoided and
streamer formation (a streamer is a fast-time microdischarge
characteristic of DBDs) is induced, i.e. a dielectric plasma is
made. Electrodes can be made with sharp points, roughness or edges
to enhance high field concentrations so as to aid breakdown and
thus plasma initiation
[0028] A high-voltage source sufficient to electrically break down
(i.e, make conductive, make a plasma) the fuel (typical range of 1
kV to 50 kV, depending on the fuel and the gap spacing)
(alternating current, frequency in a typical range of 10 Hz-20 kHz;
or voltage pulse) is applied to electrodes 10 and 20 creating
electrical-discharge streamers in the gas passing between. An
inverter and step-up transformer produces the high voltage that
boots the 12 V DC battery supply in a typical automotive electrical
system, to the required voltage. Such circuits can be made very
small and lightweight, using today's advanced semiconductor
switching inverter/converter circuits.
[0029] The discharges are the source of the active non-thermal
plasma. The embodiment presented here is a cylindrical, coaxial
dielectric barrier discharge/silent discharge plasma (DBD/SDP)
reactor, however, other arrangements (e.g., planar, rectangular)
may also be employed by one skilled in the art. Additionally, other
embodiments utilizing clusters of reactors can also be employed by
on skilled in the art. The wave form of the alternating current can
be sine, square, or complex, so as to aid plasma initiation by the
applied voltage rise time, and to promote electrode self-cleaning
that is aided by the breakdown follow-on wave shape.
[0030] Referring now to FIG. 2, a cross section of one embodiment
of the plasma assisted combustion fuel injector device (PACFI),
pintle needle valve 40 is opened and closed by activation of
solenoid 41 through input wires 42. Spring 43 returns valve 40 to
the closed position when solenoid 41 is not energized. When valve
40 is open, fuel from hose connection 44 sprays out as an atomized
mist 45 into conical chamber 46. A nonthermal plasma is created
within conical chamber 46 by the input of a high voltage
alternating current through power wires 39 that are connected to
the external "basket" electrode 47 and outer electrode 48 that
resides within insulator block 49. Insulator block 49 is made from
a dielectric material.
[0031] Referring also now to FIG. 3, where the inner electrode
configuration is basket electrode 47 that is composed of wire hoop
50 connected with vertical wires 51 to larger diameter wire hoop 52
(additional wire hoops may also be employed between 50 and 51).
Basket electrode 47 is suspended from insulator block 53 by
horizontal support wires 54. The open structure of basket electrode
47 allows atomized mist 45 essentially unrestricted passage and yet
provides the electrode surface required to generate the nonthermal
plasma.
[0032] Other inner electrode configurations provide electric field
enhancement within gap 30 so as to reduce the power required to
generate the required strength of non-thermal plasma. FIG. 4a is an
embodiment where inner electrode 100 is configured in an array of
wires in a tapered "brush" configuration. FIG. 4b is an embodiment
where inner electrode 110 is a spiral wire. FIG. 4c is an
embodiment where inner electrode 120 is a cone with electric
field-enhancing perforations throughout. FIG. 4d is an embodiment
where inner electrode 130 is a cylinder with electric
field-enhancing perforations throughout. FIG. 4e is an embodiment
where inner electrode 140 is a series of pointed washers. All of
the aforementioned inner electrode embodiments may be made from
stainless steel, copper, tungsten, tungsten alloys, refractory
metals, and carbon-based composite.
[0033] A dielectric barrier electrode configuration creates
high-energy streamers that produce both intense ultra violet light
and strong electric/magnetic fields that are more effective in
generating cracked (i.e. lower molecular weight), chemically
different fuels, compared to a corona discharge processes. Thus,
for example, a residual gas analyzer looking at the effect of
plasma cracking of propane shows that methane sized free-radical
fragments is created by the present invention. Methane, being of
lower molecular weight, burns at a higher rate than does propane,
and, thus, more efficiently. Thus, lower quality fuels may be used
to replace previously necessary high-grade fuels, e.g. use diesel
fuel in a jet engine in lieu of Jet A.
[0034] By improving the burning propensity of fuels by converting
them to smaller compounds, it is now possible to dilute the
combustion mixture with more air than was possible with prior art
inventions. Increasing dilution with air improves reduction in the
amount of nitrogen oxides (NOx) that is created by dropping the
overall combustion temperature. Thus, there are at least three
important results provided by the present invention: first, less
fuel is consumed due to the enhanced combustion efficiency; second,
there is a reduction in the number of unburned hydrocarbons; and
third, lower amounts of oxides of nitrogen produced.
Testing
[0035] Referring now to FIG. 5, graphically showing the results of
testing the center electrode 100 embodiment shown in FIG. 4a.
Non-thermal plasma created in the gap between the brush center
electrode and the dielectric cone decomposes ("cracks") the
atomized liquid fuel into simpler hydrocarbons. For this test, the
PACFI unit was mounted inside a clear plastic (polycarbonate)
enclosure that allowed: isolation of the high-voltage unit,
observation of the injector spray pattern, and collection of
residual fuel. Iso-octane (a common surrogate for gasoline) was
used as the input fuel.
[0036] The test was conducted in two stages: first, fuel was
injected without a nonthermal plasma present and analyzed with a
residual gas analyzer; second, fuel was injected with a nonthermal
plasma present and analyzed with a residual gas analyzer. The
results were then compared to determine the distribution of
products with and without the influence of the plasma.
[0037] An electric fuel pump was used to, delivered liquid
iso-octane to the fuel injector at a pressure of about 80 psig.
While injecting the iso-octane (8 pulse shots), the resulting
iso-octane spray mass spectrum coming out of the PACFI unit was
measured using a residual gas analyzer. The mass peaks that were
obtained were then compared with reference mass-spectral data to
confirm the signature peaks for iso-octane. Common signature mass
peaks, such as M29, M41, M43, and M57, were observed, appearing in
the measuring range from 1 to 65 amu of the instrument.
[0038] In the second stage, the plasma reactor was activated using
a power supply with an AC frequency of 566 Hz and voltage of
10.+-.0.5 kV. The delivered nonthermal plasma power was about
2.+-.0.5 W. Pressurized iso-octane was again sprayed from the
injector and analyzed with the residual gas analyzer, providing the
mass spectrum of a sample collected from the chamber. The test was
repeated twice more, providing a total of three datasets for fuel
only runs and three datasets for fuel with nonthermal plasma runs.
These six datasets are normalized to the signal of mass 28
(nitrogen) in order to provide a simple means of comparing the
strengths of the peaks on a common scale.
[0039] FIG. 5 shows two averaged datasets, one for a fuel only run
(shaded) and one for a fuel with plasma run (closed circles). With
just 2 W of plasma power, increased iso-octane fragment peaks are
observed especially for the lower mass peaks M15, M27, M29, M39,
M41, M43, M56, and M57. For example, the molecular formula of M29
is CH.sub.2-CH.sub.3. The increased M29 implies that the plasma
cracked the iso-octane and produced more CH.sub.2-CH.sub.3, which
is an easily burnable species. The fact that significant increases
in these lower-mass peak signals were observed in the presence of
the plasma confirms that the PACFI unit cracks the more-complicated
hydrocarbon gasoline-surrogate (iso-octane) into smaller fragments.
Furthermore, because there is very little change in the M2 peak
(hydrogen) with the plasma, our invention is distinguished from
those prior art inventions taught in Cohn et al., and Kong et al.,
which are fuel converters (mainly to hydrogen), rather than fuel
"crackers" and active-species producers.
Internal Combustion Configurations
[0040] The following are illustrations of possible internal
combustion (IC) engine configurations for using the present
invention PACFI device, but are not limited to these examples.
Engine types can include, conventional fuel injected gasoline
engines, diesel IC engines, turbine engines and in fact any engine
that utilizes fuels in liquid or low melting-point form (kerosene,
jet fuels, gasoline, diesel, heating oils etc.) or gaseous forms
(LP, propane, methane, marsh gases, LNG, natural gas etc.).
[0041] Referring now to FIG. 6 showing is a cross section of an
internal IC engine port fuel injection configuration for mounting
the PACFI. Here, the PACFI is a direct replacement for a
conventional fuel injection device, but has additional wiring to
supply the high voltage AC to drive the plasma component. PACFI 60
is mounted in port 75 of intake manifold 70 and sprays the plasma
treated fuel mist in the direction of intake valve 65.
[0042] Referring now to FIG. 7, showing a direct injection
configuration that is quite similar to a diesel engine's
configuration. PACFI 80 is mounted in cylinder head 85 of the
engine and is centrally located so that the plasma treated fuel is
directed down into engine cylinder 88. Note that use in a diesel
engine would require a higher-pressure PACFI device as the fuel is
continuously injected during combustion.
[0043] The foregoing description of the invention has been
presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the precise
form disclosed, and obviously many modifications and variations are
possible in light of the above teaching.
[0044] The embodiments were chosen and described in order to best
explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated. It
is intended that the scope of the invention be defined by the
claims appended hereto.
* * * * *