U.S. patent application number 10/667698 was filed with the patent office on 2005-05-12 for method and apparatus for using hydroxyl to reduce pollutants in the exhaust gases from the combustion of a fuel.
Invention is credited to Caren, Robert P., Ekchian, Jack A..
Application Number | 20050100488 10/667698 |
Document ID | / |
Family ID | 27100651 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050100488 |
Kind Code |
A1 |
Caren, Robert P. ; et
al. |
May 12, 2005 |
Method and apparatus for using hydroxyl to reduce pollutants in the
exhaust gases from the combustion of a fuel
Abstract
A method and apparatus are provided for reducing pollutants in
the exhaust gases produced from the combustion of a fuel by
introducing hydroxyl and associated radicals and oxidizers into at
least one of the precombustion and postcombustion gas stream of the
combustion engine upstream of the catalytic converter and treating
the exhaust gases with the catalytic converter.
Inventors: |
Caren, Robert P.; (Westlake
Village, CA) ; Ekchian, Jack A.; (Belmont,
MA) |
Correspondence
Address: |
Muserlian, Lucas and Mercanti, LLP
600 Third Avenue
New York
NY
10016
US
|
Family ID: |
27100651 |
Appl. No.: |
10/667698 |
Filed: |
September 22, 2003 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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10667698 |
Sep 22, 2003 |
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09862112 |
May 21, 2001 |
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6716398 |
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09862112 |
May 21, 2001 |
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09516098 |
Mar 1, 2000 |
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6264899 |
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09516098 |
Mar 1, 2000 |
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09036493 |
Mar 6, 1998 |
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6048500 |
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09036493 |
Mar 6, 1998 |
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08768833 |
Dec 18, 1996 |
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5863413 |
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08768833 |
Dec 18, 1996 |
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08671955 |
Jun 28, 1996 |
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5806305 |
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Current U.S.
Class: |
422/186.04 ;
422/186.3 |
Current CPC
Class: |
F02M 27/06 20130101;
C10L 10/02 20130101; B01D 53/9495 20130101; B01D 53/9454 20130101;
Y02T 10/12 20130101; F01N 3/2086 20130101; C10L 1/1233 20130101;
F01N 3/005 20130101; F02M 25/00 20130101; Y02A 50/2324 20180101;
F01N 2240/28 20130101; F01N 3/20 20130101; F01N 2240/38 20130101;
Y02T 10/26 20130101; Y02A 50/20 20180101; F02M 25/12 20130101; C10L
1/1208 20130101; Y02T 10/121 20130101; F01N 3/206 20130101; Y02T
10/22 20130101; B01D 53/90 20130101; F01N 2260/022 20130101; F01N
2610/06 20130101; B01D 53/9445 20130101 |
Class at
Publication: |
422/186.04 ;
422/186.3 |
International
Class: |
B01J 019/08; B01J
019/12 |
Claims
What is claimed:
1. An apparatus for improving the performance of a catalytic
converter to decrease from a first concentration to a second lower
concentration at least one exhaust gas pollutant selected from the
group consisting of products of incomplete combustion and oxides of
nitrogen produced by the combustion of a fuel in an internal
combustion engine, comprising: a combustion chamber; a
post-combustion gas stream; at least one hydroxyl radical generator
adapted and configured to introduce hydroxyl radicals into the
post-combustion gas stream; a power supply adapted and configured
to provide high frequency current to the at least one hydroxyl
radical generator; and at least one catalytic converter, which
contains catalytically active material, located in the
post-combustion gas stream, wherein at least a portion of the
catalytically active material is located downstream from the at
least one hydroxyl radical generator, wherein exhaust gases are
formed from the combustion of a fuel in the combustion chamber and
at least a portion of the exhaust gases is exposed to the at least
one hydroxyl radical generator before being exposed to at least a
portion of the catalytic material in the catalytic converter.
2. The apparatus according to claim 1, wherein the generator
contains at least one ultraviolet lamp having a wavelength between
about 100 nanometers and about 200 nanometers.
3. The apparatus according to claim 1, wherein the generator
contains at least one electric discharge device.
4. The apparatus according to claim 1, wherein the power supply
provides high frequency current having a frequency of at least
about 1,000 Hz.
5. The apparatus according to claim 1, wherein the generator is
adapted and configured to be powered substantially whenever exhaust
gases are produced.
6. The apparatus according to claim 1, wherein the internal
combustion engine is a diesel engine.
7. The apparatus according to claim 1, wherein the internal
combustion engine is a spark-ignition engine.
8. The apparatus according to claim 1, wherein the power supply
supplies low power.
9. The apparatus according to claim 1, operated in the absence of
any reducing agent added to the post-combustion gas stream.
10. The apparatus according to claim 3, wherein the at least one
electric discharge device, comprises: at least one first electrode;
at least one second electrode; and at least one dielectric barrier
positioned between the first electrode and the second
electrode.
11. The apparatus according to claim 1, wherein the generator is
separated from the catalytic converter by a pre-determined
distance.
12. The apparatus according to claim 1, wherein the power supply is
adapted and configured such that the voltage and current may be
varied by a controller that monitors engine operating
conditions.
13. A method for improving the performance of a catalytic converter
to decrease from a first concentration to a second lower
concentration at least one exhaust gas pollutant selected from the
group consisting of products of incomplete combustion and oxides of
nitrogen produced by the combustion of a fuel in an internal
combustion engine, comprising: combusting a fuel and forming
exhaust gases in a combustion chamber; channeling the exhaust gases
into a post-combustion gas stream; exposing at least a portion of
the exhaust gases to at least one hydroxyl radical generator
located in the post-combustion gas stream; providing high frequency
power to the at least one hydroxyl radical generator; and passing
at least a portion of the exhaust gases that were exposed to the at
least one hydroxyl radical generator through at least one catalytic
converter, which contains catalytically active material, located in
the post-combustion gas stream, wherein at least a portion of the
catalytically active material is located downstream from the at
least one hydroxyl radical generator.
14. The method according to claim 13, wherein the generator
contains at least one electric discharge device.
15. The method according to claim 13, wherein the power supply
provides high frequency current having a frequency of at least
about 1,000 Hz.
16. The method according to claim 13, wherein the generator is
adapted and configured to be powered substantially whenever exhaust
gases are produced.
17. The method according to claim 13, wherein the power supply
supplies low power.
18. The method according to claim 17, wherein the power supply is
adapted and configured such that the voltage and current may be
varied by a controller that monitors engine operating
conditions.
19. The method according to claim 13, performed in the absence of
any reducing agent added to the post-combustion gas stream.
20. The method according to claim 14, wherein the at least one
electric discharge device, comprises: at least one first electrode;
at least one second electrode; and at least one dielectric barrier
positioned between the first electrode and the second
electrode.
21. An apparatus for decreasing from a first concentration to a
second lower concentration at least one exhaust gas pollutant
selected from the group consisting of products of incomplete
combustion and oxides of nitrogen produced by the combustion of a
fuel in a diesel engine, comprising: a post-combustion gas stream;
a passageway for channeling at least a portion of the
post-combustion gas stream from the engine; at least one hydroxyl
radical generator adapted and configured to introduce hydroxyl
radicals into the post-combustion gas stream in the passageway; a
power supply adapted and configured to provide current having a
frequency of at least about 1,000 Hz to the at least one hydroxyl
radical generator; and at least one catalytic converter, which
contains catalytically active material, located in the passageway,
wherein at least a portion of the catalytically active material is
located downstream from the at least one hydroxyl radical
generator, wherein at least a portion of the exhaust gases formed
from the combustion of fuel in the internal combustion engine is
exposed to at least a portion of the at least one hydroxyl radical
generator before being exposed to at least a portion of the
catalytic converter, wherein the apparatus is adapted and
configured to produce hydroxyl radicals substantially whenever the
internal combustion engine is producing exhaust gases and the
apparatus is adapted and configured such that no additional
reducing agent is added to the exhaust gases produced from the
combustion of the fuel.
22. The apparatus according to claim 21, wherein the at least one
hydroxyl radical generator is an electric discharge device,
comprising: at least one first electrode; at least one second
electrode; and at least one dielectric barrier positioned between
the at least one first electrode and the at least one second
electrode.
23. The apparatus according to claim 21, wherein the generator is
separated from the catalytic converter by a pre-determined
distance.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of co-pending U.S.
application Ser. No. 09/516,098, filed Mar. 1, 2000, which is a
continuation of U.S. application Ser. No. 09/036,493, filed Mar. 6,
1998, now U.S. Pat. No. 6,048,500, which is a division of U.S.
application Ser. No. 08/768,833, filed Dec. 18, 1996, now U.S. Pat.
No. 5,863,413, which is a continuation-in-part of U.S. application
Ser. No. 08/671,955, filed Jun. 28, 1996, now U.S. Pat. No.
5,806,305.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to a method and
apparatus for reducing pollutants in the exhaust gases produced by
the combustion of fuels. More particularly, the invention relates
to such a method and apparatus wherein the reduction in pollutants
is achieved by introducing hydroxyl radicals "OH" and other free
radical intermediaries and oxidizers such as O, H, HO.sub.2 and
H.sub.2O.sub.2 into the precombustion or postcombustion gas stream
of a combustion engine.
[0004] 2. Background
[0005] As is well-known in the art, an internal combustion engine
draws in ambient air which is mixed with fuel for combustion in a
combustion chamber or cylinder and the resulting exhaust gases are
expelled. Ignition of the air/fuel mixture in the cylinder is
typically achieved by an ignition device, such as, for example, a
spark plug or the like, or adiabatic compression to a temperature
above the fuel's ignition point.
[0006] In certain internal combustion engines, such as for example,
gasoline engines commonly in use today, air is inducted via an air
intake duct or port which conveys the ambient air to a carburetor
or a fuel injection arrangement where the air is mixed with fuel to
create an air/fuel mixture. The air/fuel mixture is then conveyed
via an intake manifold to the combustion chamber or cylinder of the
engine. In diesel-type engines and engines using fuel-injection
arrangements, the air and fuel are conveyed separately to the
combustion chamber or cylinder of the engine where they are
mixed.
[0007] After the air/fuel mixture has been burnt, the resulting
exhaust gases are expelled from the combustion chamber to an
exhaust manifold. The exhaust gases then may be conveyed by an
exhaust pipe to the catalytic converter where pollutants are
removed.
[0008] The flow of air to the combustion chamber, including the
flow of the air/fuel mixture if applicable, as used herein is
referred to as the precombustion gas stream, and the resulting flow
of exhaust therefrom is hereinafter referred to as the
postcombustion or exhaust gas stream. As used herein, the
precombustion and postcombustion gas streams are collectively
referred to as the combustion gas stream.
[0009] Internal combustion engines which operate by the controlled
combustion of fuels produce exhaust gases containing complete
combustion products of carbon dioxide (CO.sub.2) and water
(H.sub.2O) and also pollutants from incomplete combustion such as
carbon monoxide (CO), which is a direct poison to human life, as
well as unburnt hydrocarbons (HC). Further, due to the very high
temperatures produced by the burning of the hydrocarbon fuels
followed by rapid cooling, thermal fixation of nitrogen in the air
results in the detrimental formation of Nitrogen Oxides (NO.sub.x),
an additional pollutant.
[0010] The quantity of pollutants varies with many operating
conditions of the engine but is influenced predominantly by the
air-to-fuel ratio in the combustion cylinder such that conditions
conducive to reducing carbon monoxide and unburnt hydrocarbons (a
fuel mixture just lean of stoichiometric and high combustion
temperatures) cause an increased formation of NO.sub.x, and
conditions conducive to reducing the formation of NO.sub.x (fuel
rich or fuel lean mixtures and low combustion temperatures) cause
an increase in carbon monoxide and unburnt hydrocarbons in the
exhaust gases of the engine. Because in modern day catalytic
converters NO.sub.x reduction is most effective in the absence of
oxygen, while the abatement of CO and HC requires oxygen,
preventing the production of these emissions requires that the
engine be operated close to the stoichiometric air-to-fuel ratio
because under these conditions the use of three-way catalysts (TWC)
are possible, i.e., all three pollutants can be reduced
simultaneously. Nevertheless, during operation of the internal
combustion engine, an environmentally significant amount of CO, HC
and NOX is emitted into the atmosphere.
[0011] Although the presence of pollutants in the exhaust gases of
internal combustion engines has been recognized since 1901, the
need to control internal combustion engine emissions in the United
States came with the passage of the Clean Air Act in 1970. Engine
manufacturers have explored a wide variety of technologies to meet
the requirements of this Act. Catalysis has proven to be the most
effective passive system.
[0012] Automotive manufacturers have generally employed catalytic
converters to perform catalysis. The purpose is to oxidize CO and
HC to CO.sub.2 and H.sub.2O and reduce NO/NO.sub.2 to N.sub.2. Auto
emission catalytic converters are typically located at the
underbody of the automobile and are situated in the exhaust gas
stream of the engine, just before the muffler, which is an
extremely hostile environment due to the extremes of temperature as
well as the structural and vibrational loads encountered under
driving conditions.
[0013] Nearly all auto emission catalytic converters are housed in
honeycomb monolithic structures with excellent strength and
crack-resistance under thermal shock. The honeycomb construction
and the geometries chosen provide a relatively low pressure drop
and a high geometric surface area which enhances the mass transfer
controlled reactions. The honeycomb is set in a steel container and
protected from vibration by a resilient matting.
[0014] An adherent washcoat, generally made of stabilized gamma
alumina into which the catalytic components are incorporated, is
deposited on the walls of the honeycomb. TWC technology for
simultaneously converting all three pollutants comprises the use of
precious or noble metals Pt and Rh, with Rh being most responsible
for the reduction of NO.sub.x, although it also contributes to CO
oxidation along with Pt. Recently less expensive Pd has been
substituted for or used in combination with Pt and Rh. The active
catalyst is generally about 0.1 to 0.15% precious or noble metals,
primarily platinum (Pt), palladium (Pd) or rhodium (Rh).
[0015] Because the exhaust gases of the combustion engine oscillate
from slightly rich to slightly lean, an oxygen storage medium is
added to the washcoat which adsorbs (stores) oxygen during any lean
portion of the cycle and releases it to react with excess CO and HC
during any rich portion. Cerium Oxide (CeO.sub.2) is most
frequently used for this purpose due to its desirable
reduction-oxidation response.
[0016] The recent passage of the 1990 amendment to the Clean Air
Act requires further significant reductions in the amount of
pollutants being released into the atmosphere by internal
combustion engines. In order to comply with these requirements,
restrictions on the use of automobiles and trucks have been
proposed, such as, employer-compelled car pooling, HOV lanes,
increased use of mass transit as well as rail lines and similar
actions limiting automobile and truck usage at considerable cost
and inconvenience.
[0017] An alternative to diminished automobile and truck usage is
decreasing emissions by increasing the efficiency of the internal
combustion engine. This approach will have limited impact since
studies show that most of automobile-originated pollution is
contributed by only a small fraction of the vehicles on the road,
these vehicles typically being older models having relatively
inefficient engines and aging catalytic converters which inherently
produce a lot of pollution. Any technological improvements to the
total combustion process will not be implemented on these older
vehicles if they require extensive or expensive modification to the
engine or vehicle.
[0018] In addition, while considerable gains have been made in
recent years to reduce the amount of pollutants in the exhaust
gases of the internal combustion engine of vehicles such as
automobiles and trucks, it is a considerable technological
challenge and expensive to further reduce the amount of pollutants
in the exhaust gases of the internal combustion, even though
exhaust emissions of automobiles and trucks currently being
manufactured do not meet proposed Environmental Protection Agency
standards.
[0019] In lieu of decreasing exhaust emissions by increasing the
efficiency of the internal combustion engine or decreasing the use
of automobiles, a further alternative would be to increase the
efficiency of the catalytic converter or catalysis. The conversion
efficiency of a catalytic converter is measured by the ratio of the
rate of mass removal of the particular constituent of interest to
the mass flow rate of that constituent into the catalytic
converter. The conversion efficiency of a catalytic converter is a
function of many parameters including aging, temperature,
stoichiometry, the presence of any catalyst poisons (such as lead,
sulfur, carbon and phosphorous), the type of catalyst and the
amount of time the exhaust gases reside in the catalytic
converter.
[0020] Attempts to increase the efficiency of catalytic converters
has not been sufficiently successful. Modern TWC catalytic
converters help, but they are expensive, may have difficulty in
meeting the future emission requirements, and have limitations in
their performance lifetime. Catalytic converters also suffer from
the disadvantage that their conversion efficiency is low until the
system reaches operating temperature.
SUMMARY OF THE INVENTION
[0021] One object of the present invention is to provide a method
and apparatus for reducing pollutants in the exhaust gases of an
internal combustion engine without the need for major modifications
to the internal combustion engine or the catalytic converter.
[0022] Another object of the invention is to provide a method and
apparatus, which are inexpensive to employ and manufacture, and
simple in structure and operation, for reducing pollutants of
incomplete combustion in the exhaust gases of a combustion
engine.
[0023] In accordance with the invention, it is believed that
hydroxyl ion "OH" and other free radicals and oxidizers such as O,
H, HO and H.sub.2O.sub.2 can be introduced into the combustion gas
stream of a combustion engine to reduce pollutants and contaminants
such as CO and HC. It has been observed that OH in the presence of
oxygen can react rapidly with CO to produce CO.sub.2. It has also
been observed that OH in the presence of oxygen can react rapidly
with hydrocarbons (HC) to produce formaldehyde or other similar
intermediary products which then further react with OH to form
H.sub.2O, CO.sub.2, and OH. Moreover, there is evidence that the
series of reactions does not consume, but rather regenerates
OH.
[0024] In the case of CO, the following reaction steps convert CO
to CO.sub.2 and regenerate OH:
[0025] CO+OH.fwdarw.CO.sub.2+H
[0026] H+O.sub.2.fwdarw.HO.sub.2
[0027] HO.sub.2+h.nu..fwdarw.OH+O
[0028] The latter process of dissociation of hydroperoxyl to
hydroxyl can take place either via the absorption of ultraviolet
("UV") photon or by thermal decomposition.
[0029] In the case of HC, a typical reaction set may involve the
following steps:
[0030] HC+OH.fwdarw.HCHO
[0031] HCHO+OH.fwdarw.H.sub.2O+HCO
[0032] HCO+O.sub.2.fwdarw.CO.sub.2+HO
[0033] Depending upon the HC species, there may be branching
reactions and other free radical intermediaries and oxidizers such
as O, H, HO.sub.2 and H.sub.2O.sub.2 may be produced and either
enter into the reactions directly or through the products of other
reactions such as:
[0034] O+O.sub.2.fwdarw.O.sub.3, or
[0035] H.sub.2O.sub.2+h.nu..fwdarw.2OH
[0036] Particularly important in the present invention is that OH
is believed to be regenerated in the course of the reactions, i.e.,
it acts as a catalyst, and that the reaction sequence proceeds
rapidly due to the strong nature of the free radical reactions.
[0037] It is believed that the presence of OH, and other free
radical intermediates and oxidizers such as O, H, H.sub.2O.sub.2
and HO.sub.2, in the exhaust gases of a combustion engine leads, in
the presence of requisite oxygen, to a very effective catalytic
destruction of CO and hydrocarbons to non-polluting gas species
CO.sub.2 and water vapor. The OH and other related free radicals
and oxidizers created in the reactions can act as a catalyst
independent of or in conjunction with the normal catalytic function
of the precious metal particles (Pt, Pd, Rh and combinations
thereof) in the catalytic converter.
[0038] It is believed that the injection of OH into the combustion
gas stream results in rapid catalyzing of CO and HC reactions in
the exhaust gas stream. The reactivity of OH is believed to cause
much of the catalytic activity associated with the conversion of CO
to CO.sub.2 and hydrocarbon to CO.sub.2 and H.sub.2O to take place
in the gas phase and on the large surface area of the washcoat
surface of the catalytic converter. Thus, within a small region
near the entrance of the catalytic converter, the bulk of the
reactions converting CO and HC to CO.sub.2 and H.sub.2O occurs.
Because CO and the HC are oxidized in the gas phase and in the
washcoat of the catalytic converter, with resulting substantial
completion of the oxidation of CO and HC near the entrance to the
catalytic converter, the bulk of the precious metal catalytic
surface is freed from participating in these competing reactions.
For example, the converter's precious metal sites no longer need to
catalyze the less reactive hydrocarbon species such as methane,
ethane, ethene, benzene and formaldehyde. As a result, more
effective catalytic activity at the precious metal sites can be
directed toward reduction of nitrogen oxides to nitrogen and other
non-polluting gas species.
[0039] It is believed that the action of the hydroxyl can take
place over the volume of the exhaust gas and the entire surface
area of the catalytic converter, i.e., over the entire, large area
of the washcoat. This makes for a much larger, effective pollutant
reduction action over the catalytic converter operating in the
conventional manner. Under this new mode of catalytic conversion
operation, nitrogen oxide reduction can diminish below conventional
baselines. Alternatively, less precious metal content, or the use
of less costly metals or their oxides can be used to reduce the
nitrogen oxide compounds below allowable emission limits.
[0040] Several different modes of operation and devices may be
utilized to carry out the invention. In one embodiment, OH is
produced in a generator using mercury (Hg) vapor lamp radiation and
atmospheric air intake which is conditioned to be of sufficiently
high water vapor content, and preferably to about 100% saturation.
It is believed that in air of high water vapor content there are
two alternative competing reaction branches for creating OH. In the
first case, there is direct photodissociation of the water into OH
and H by the absorption of 185 nanometer ("nm") photons. To achieve
such high humidity, the water vapor can come from a heated water
source or it can be supplied from the exhaust gas stream of the
engine. The other reaction, which is favored at a lower, but still
sufficiently high, water vapor content, is that the 185 nm
ultraviolet ("UV") radiation from the lamp acts on the air to
produce atomic oxygen (O) and ozone (O.sub.3). The ozone is created
by a three-body reaction involving atomic oxygen, molecular oxygen
and any other molecular constituent of air, such as, for example,
Nitrogen (N.sub.2), Oxygen (O.sub.2), Water (H.sub.2O) or Argon.
The 253.7 nm UV radiation breaks down the ozone by
photodissociation into molecular oxygen O.sub.2 and a metastable
oxygen atom (O). If the air stream entering the generator has
sufficient water vapor content, then it is believed the metastable
atomic oxygen (O) combines with water molecules to form hydrogen
peroxide:
[0041] O+H.sub.2O.fwdarw.H.sub.2O.sub.2
[0042] Further, the 253.7 nm UV radiation photodissociates the
hydrogen peroxide into two hydroxyl molecules.
[0043] The generator thus injects ozone, atomic oxygen, hydrogen
peroxide, and hydroxyl into the engine via for example, the intake
manifold. It is believed that any hydrogen peroxide so injected
will dissociate into hydroxyl under the high engine temperature.
The hydroxyl which resides in the crevice regions of the combustion
chamber should survive the combustion process in the engine and act
upon the CO and HC remaining in the exhaust stream to produce
CO.sub.2 and H.sub.2O according to the reactions described
above.
[0044] A further embodiment of hydroxyl generation is to feed a
water vapor-rich input air stream into a glow discharge generator
(a generator in which a glow discharge occurs in water vapor
primarily or only). Another approach is an overvoltage electrolysis
cell to generate ozone in addition to oxygen and water vapor,
followed by 200-300 nm UV exposure to create atomic oxygen by
photodecomposition which in the presence of a water vapor-rich
input air stream initiates hydrogen peroxide creation, followed by
hydroxyl generation via UV dissociation of the hydrogen peroxide.
This latter device can be very compact using a mercury vapor lamp
as the UV source due to the high efficiency of the output at 253.7
nm and the high absorbability of ozone and hydrogen peroxide for UV
light of this wavelength.
[0045] The foregoing embodiments principally involve generators
injecting their streams of output gases into the intake manifold
region of the engines. A natural advantage of such methods is that
the low pressure condition in regions of the intake manifold
provides a natural pumping mechanism. However, a drawback of these
methods is that most of the highly chemically active species,
including the free radicals such as hydroxyl, are destroyed in the
combustion process and only those active species in the crevice
regions and at the walls of the combustion chamber can effectively
survive and enter into the exhaust gas stream where they are useful
in oxidizing CO and HC. In contrast, generators which inject
hydroxyl ion directly into or which create hydroxyl in the exhaust
(postcombustion) gas stream can more effectively deliver the active
species into the exhaust stream where CO and HC need to be
oxidized. Thus, less chemically active species source strength
would be required for equivalent emission reduction. This should
translate directly into proportionally lower electrical input
demands for the hydroxyl generator.
[0046] However, because of the higher pressures in the exhaust
system, pumping is required to accomplish direct injection of the
generator output into the exhaust gas stream. The use of a venturi
will assist this process. Alternatively, because of the high vapor
pressure of water at temperatures above approximately 120.degree.
C., using a water vapor discharge source in the hydroxyl generator
can also provide effective injection. Such water vapor can be
collected by condensation or equivalent means from the exhaust
system.
[0047] An embodiment creating hydroxyl in the exhaust gas stream is
the irradiation of the exhaust gas stream with UV radiation in the
120 to 185 nm wavelength range which in the presence of sufficient
water vapor produces catalytically active OH by direct
photodissociation. A still further embodiment is the use of UV
radiation in the 120 to 185 nm wavelength in an external generator
using atmospheric air intake and water vapor collected from the
exhaust gas stream and injecting water vapor, OH and H into the
exhaust gas stream prior to or in the catalytic converter.
[0048] The means described above for creation of these free radical
species and oxidizers include ultraviolet light-based generators,
glow discharge generators, and overvoltage electrolytic cells plus
UV radiation. Generator inputs can include electricity, water, air,
oxygen, water vapor, water vapor plus air and water vapor plus
oxygen.
[0049] Modes of possible introduction of the above species into the
engine system include into the precombustion gas stream, such as
the intake manifold, into the exhaust gas stream such as the
exhaust manifold, and into the catalytic converter. The generators
can be external or internal to these areas. A particularly
advantageous feature of the external generator is that it provides
the flexibility of installing the generator at a convenient
location in the engine compartment or elsewhere on the vehicle.
Another advantageous feature of the external generator embodiment
is that the hydroxyl could be introduced at almost any desirable
point in the intake or exhaust gas streams of the engine. A further
advantageous feature of this embodiment is that the flow rate of
hydroxyl from the hydroxyl generator is independent of engine
speed, i.e., flow of air to the combustion chamber or flow of
exhaust gases from the combustion chamber. Thus, at low engine
speeds, the mass flow rate of hydroxyl will not be affected by low
air mass flow through the combustion chamber. For external sources,
means of pumping of the generator gas products can include natural
low pressure areas in the engine, introduction of ventri regions,
external pumps, or natural generator pressurization as with higher
temperatures and water vapor sources.
[0050] Thus, the invention employs hydroxyl and its associated
reaction species, O, H, H.sub.2O.sub.2 and HO.sub.2 to provide a
catalytic cycle with OH playing the central role in reducing the CO
and HC outputs of engines to meet present and future Ultra Low
Emissions Vehicle "ULEV" and Low Emissions Vehicle "LEV" standards.
Because the OH acts as a catalyst, relatively small amounts of OH
need to be injected for orders of magnitude more CO and
hydrocarbons to be reduced to CO.sub.2 and H.sub.2O in the presence
of oxygen in the exhaust gas stream.
[0051] An advantageous feature of the invention is that reduced
emissions are achieved by adding hydroxyl radicals and other free
radical intermediaries and oxidizers such as O, H, HO.sub.2 and
H.sub.2O.sub.2 to modify the composition of the exhaust gases
without the need to store special chemical additives onboard.
[0052] Yet another advantageous feature of the invention is that it
can be applied to a variety of different types of engines including
gas turbine and internal combustion engines, including, but not
limited to, automobiles, trucks, stationary power generators,
motorboats, motorcycles, motorbikes, lawn mowers, chain saws or
leaf blowers which may use a variety of different fuels such as
gasoline, gasoline-based formulations, diesel fuel, alcohol,
natural gas and any other fuel where it is desired to reduce CO or
HC.
[0053] It is believed that a further advantageous feature of the
present invention is that due to the introduction of gas-phase
catalyst species, whose activities occur over the whole catalytic
converter surface, and the inherent reactivity of these species,
much earlier catalytic conversion of CO and unburned HC will occur
after engine start. In other words, the effective light-off delay
time after engine start will be reduced as compared to the use of a
typical catalytic converter.
[0054] In the case of combustion and other residential, commercial
and industrial systems which have exhaust gas streams which contain
volatile organic compounds (VOCs), but contain minimal or no
nitrogen oxides such as from some industrial processes, there would
be no need for the typical catalytic converter and certainly no
need for a precious metal catalytic converter. This invention would
provide for very low cost catalytic converter systems. In those
situations where only CO or HC and other VOC's are required to be
oxidized, it is contemplated that a typical catalytic converter
would not be required. However, it is contemplated that adequate
time and/or a large surface area similar to that provided by the
honeycomb structure of the typical catalytic converter would be
necessary to allow the CO, HC and VOC oxidation reactions to take
place.
[0055] These and other objects, advantages and features of the
invention are achieved, according to one embodiment, by an
apparatus comprising: 1) a combustion gas stream of an engine, 2) a
catalytic converter for treating the exhaust gases in the
combustion gas stream to reduce further the amount of at least one
pollutant from incomplete combustion of fuel and/or oxides of
nitrogen, and 3) a device for adding OH and associated free
radicals and oxidizers to the combustion gas stream upstream from
or at the catalytic converter to reduce further the amount of at
least one pollutant in exhaust gases treated by the catalytic
converter.
[0056] In accordance with the invention, a method is provided for
treating exhaust gases to reduce at least one pollutant from
incomplete combustion of a fuel having a precombustion gas stream
of at least ambient air to the combustion chamber and a
postcombustion gas stream of exhaust gases from the combustion
chamber, the method comprising the steps of: adding hydroxyl and
associated free radicals and oxidizers to at least one of the
precombustion and the postcombustion gas streams and providing
sufficient surface area in the postcombustion gas stream to allow
the hydroxyl to treat the exhaust gases produced from the
combustion of the fuel to at least reduce one pollutant from
combustion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0057] FIG. 1 is a side perspective view of an internal combustion
engine having a catalytic converter:
[0058] FIG. 2 is a side view, partially-in-section, illustrating
one embodiment of the apparatus of the invention wherein a hydroxyl
generating device is inserted into the precombustion gas
streams;
[0059] FIG. 3 is a front view, partially-in-section, illustrating
further arrangements of the apparatus of FIG. 2;
[0060] FIG. 4 is a block diagram illustrating another embodiment of
the apparatus of the invention wherein the device for adding
hydroxyl is positioned remotely of the precombustion and
postcombustion gas streams and hydroxyl enriched air is piped into
the combustion gas stream;
[0061] FIG. 5 is a schematic diagram showing a hydroxyl-generating
system according to one embodiment of the invention;
[0062] FIG. 6 is schematic diagram showing an alternative
hydroxyl-generating system according to a different embodiment of
the invention;
[0063] FIG. 7 is a schematic diagram of a hydroxyl generator
according to a further embodiment of the invention;
[0064] FIG. 8 is a block diagram illustrating a control arrangement
for the apparatus of the present invention.
[0065] FIG. 9 is a block diagram illustrating the method of the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
[0066] Referring to FIG. 1, a known configuration of an automobile
engine 11 having a catalytic converter 13 is illustrated. The
catalytic converter 13 is positioned at the underbody of the
automobile (not shown) and is situated in the exhaust gas stream A
from the engine, downstream from the exhaust manifold 15 and just
before the muffler 17.
[0067] The catalytic converter 13, as contemplated for use in the
present invention, includes any device which is provided for
treating exhaust gases from the combustion of a fuel, such as, for
example, gasoline, gasoline-based formulations, diesel fuel,
alcohol, natural gas and any other fuel where a catalytic converter
can be used to reduce at least one pollutant from combustion, such
as, for example, CO, and unburnt HC, and/or NO.sub.x, including,
but not limited to, a three way catalyst typically used in today's
modern automobile engines.
[0068] The catalytic converter 13 therefore comprises any device
that catalytically removes or participants in the removal of at
least one pollutant from an exhaust stream generated by burning a
fuel, including, but not limited to, those with monolithic or
granular ceramic substrates, metallic substrates, or substrates of
any kind, and devices with noble metals or any other type of
catalytic material. It would also include, without limitation,
devices having semiconductor catalysts such as oxides or sulphides
of transition elements, and devices having ceramic-type catalysts,
such as alumina, silica-alumina, and zeolites individually, in
combination with each other and oxygen storage media such as cerium
oxide or in combination with metal catalysts.
[0069] Referring to FIG. 2, one embodiment of an apparatus of the
invention is illustrated generally at 19. The apparatus 19
comprises a generator 20 for generating hydroxyl. In one
embodiment, generator 20 has an UV light-emitting lamp 21, for
example, a mercury vapor arc lamp emitting at about 185 and about
254 nanometers. The lamp has a light-transmitting envelope for
transmitting UV light having wavelengths of about 100-300 nm,
because this emission, in the presence of sufficient water vapor
content, is capable of producing hydroxyl from air. The light
transmitting envelope may be fused silica, or its equivalent
synthetic quartz, supersil, sapphire or any other material capable
of transmitting ultraviolet light having a wavelength down to about
100 nanometers, and preferably to at least 185 nanometers. Other UV
generating lamps such as those containing Neon, Argon and
combinations of these and other gases may be used.
[0070] The lamp 21 is excited by a power supply 23 capable of
providing an initial electric break down of the gas within the lamp
and further providing a sustaining voltage for the lamp radiant
output. The lamp radiant output can be further controlled as needed
by varying the lamp current. The power supply 23 is directly
connected to the electrical system 25 of the automobile by splicing
into the hot wire (not shown) of the system, for example, as
original equipment on a new vehicle. Alternatively, the power
supply 23 is connected to the electrical system 25 by using a plug
adapted to be .degree. inserted into a cigarette lighter receptacle
in the passenger compartment of the vehicle.
[0071] It is important in this embodiment for effective generation
of hydroxyl that sufficient water vapor, and preferably about 100%
saturated air, be present in the hydroxyl generator 20 utilizing
the UV lamp 21 as the means to generate the hydroxyl. This water
vapor may be delivered to the generator 20 via water vapor inlet
passage 65. Water vapor may be supplied to inlet passage 65 by any
number of alternative or combination of methods including heating
water supplied from a stored bottle of water as described and
illustrated with reference to FIG. 5. Alternatively, water vapor
may be separated from the exhaust gas stream A as illustrated in
FIG. 4 at an exhaust gas separator 43 and either directly supplied
to inlet passage 65 without being collected in a water storage
container, or alternatively through a storage container.
Alternatively, water vapor from the exhaust gas stream can be
condensed and stored in a container, and thereafter heated to form
water vapor. In yet an additional alternative embodiment the
exhaust gases may be supplied directly to the hydroxyl generator.
As an additional alternative embodiment, the air introduced into
the hydroxyl generator can be bubbled through water as described
and illustrated with reference to FIG. 5. This water can be
supplied from an external source or may be condensed from the water
vapor present in the exhaust gas stream.
[0072] It is contemplated that air of sufficiently high water vapor
content, and preferable about 100% saturated, passing through the
generator 20 as provided by the embodiment of FIG. 2 will result in
direct photodisassociation of the water into OH and H by the
adsorption of approximately 100-185 nm photons. Alternatively, the
100-185 nm UV radiation from lamp 21 acts on the air to produce
ozone and atomic oxygen. The 253.7 nm UV radiation breaks down the
ozone by photodissociation into molecular oxygen and a metastable
oxygen atom. The metastable oxygen combines with the water
molecules present to form hydrogen peroxide which photodissociates
in the presence of the 253.7 nm UV radiation into two hydroxyl
molecules.
[0073] In the apparatus 19 as illustrated by FIG. 2, the lamp 21 is
positioned upstream from the engine's carburetor or fuel injection
system, generally indicated at 31 in FIG. 1, for example, between
an air filter 27 and air intake duct 29. However, the present
invention additionally contemplates positioning the generator 20
anywhere along the precombustion gas stream.
[0074] In order to increase the effective absorption coefficient of
the oxygen in the air being inducted into the engine 11, the walls
adjacent to the lamp 21 are provided with a surface highly
reflective to ultraviolet light in the required wavelength range,
for example, made of aluminum, in order to increase the mean free
path of the ultraviolet light, since aluminum maintains its
reflectance to ultraviolet light down to at least 185 nm.
[0075] According to the teaching of the present invention, it is
possible to also place the hydroxyl generator 20 downstream from
the engine's carburetor or fuel injection system 31 and prior to
the combustion chamber, for example, in the intake manifold 35 as
best seen in FIG. 3.
[0076] Referring to FIG. 4, a further embodiment of the invention
is illustrated wherein the generator 20 is positioned remotely from
the precombustion and postcombustion gas streams, and
hydroxyl-enriched air, with other free radical intermediaries and
oxidizers, is piped into the combustion gas stream. In this
embodiment, hydroxyl generator 20 for generating hydroxyl from air,
draws in ambient air independently of the operation of the engine,
for example, using a pumping mechanism 39. The ambient air is mixed
with water vapor in the generator 20 or water vapor is added to the
ambient air before entering the generator and the high water vapor
content air, preferably 100% saturated, is converted to
hydroxyl-enriched air by exposure, for example, to UV light or by
means of a corona or glow discharge device, and added to at least
one of the precombustion or postcombustion gas streams in
accordance with the teachings of the invention.
[0077] Water vapor container 50 delivers water vapor to generator
20 to insure that the ambient air has sufficient water vapor
content, and preferably 100% saturated. The water vapor container
50 may be a storage bottle which contains water in any physical
form, i.e., as a solid, liquid, gas or as water vapor. The water
can be collected from the exhaust gases of the engine which
produces water vapor as a result of combustion or it can be stored
from an external source. If water vapor container 50 is liquid
water, it can be converted to water vapor using any of the
well-known methods such as heating in the presence of a gas such as
air, or air can be bubbled through the water to achieve the water
vapor input. The water vapor and air supplied to the generator 20
can be a single input into the generator wherein water or water
vapor is added to the air input supplied to the generator, this
embodiment being illustrated by dashed line 51 in FIG. 4. It should
be noted that water container 50 is not necessary and that water
vapor can be separated from the exhaust gas stream in a water vapor
separator 43 and added directly to the generator or the air inlet.
Alternatively, exhaust gas can be added directly to either the
generator or the air and/or gas supplied to the generator.
[0078] A mixing device 41 can be used to enhance mixing of the
hydroxyl-enriched air with the combustion gas stream. It should be
noted that in lieu of pumping mechanism 39, ambient air can be
drawn in using the vacuum generated by the engine 11. Where the
hydroxyl enriched air is introduced into the exhaust gas stream, a
venturi 55 may be necessary.
[0079] FIG. 5 illustrates a hydroxyl generator 20 which may be
utilized in the system shown in FIG. 4. Hydroxyl generator 20' has
a mercury vapor lamp 21 which is connected to a power supply 60.
The mercury vapor lamp 21 transmits ultraviolet light having a
wavelength of 100-300 nm because this emission in the presence of
sufficient water vapor content is capable of producing the needed
amount of hydroxyl from air.
[0080] Air inlet canister 62 has a screen and an air filter (not
shown) and supplies air to hydroxyl generator 20'. Air inlet
passageway or pipe 64 delivers the air from the inlet canister 62
to the generator 20'. Air inlet passageway 64 may contain a pump
(not shown) to facilitate the delivery of air to hydroxyl generator
20. It is important for effective generation of hydroxyl that
sufficient water vapor, and preferably 100% saturated air, be
present in the hydroxyl generator utilizing the UV lamp 21 as the
means to generate the hydroxyl. This water vapor may be delivered
to the generator 20' via water vapor inlet passage 65'. Water vapor
inlet passage 65' can collect the water vapor from the exhaust gas
stream A via passageway E utilizing water vapor separator 43 as
shown in FIG. 4, or any of the other alternative methods described
herein. In FIG. 5, the water vapor is supplied by heated water
source 68. Heated water source 68 is an external supply of water
which is circulated through the engine via circulation pipes 69 in
order to heat the water supply. The water is preferably heated to
or maintained at a temperature that is equal to or less than the
temperature within the hydroxyl generator. Water vapor is drawn
from heated water source 68 and delivered via water vapor inlet
passage 65' into the hydroxyl generator 20'.
[0081] Alternatively, water vapor inlet 65 can connect to air inlet
pipe 64 and both the air and water vapor can be mixed and then
delivered to the hydroxyl generator 20'. Water vapor can be
collected from the exhaust gas stream or the heated water source
system 68, 69 can be used to supply the water vapor to water vapor
inlet 65 or the alternative methods described herein can be
utilized.
[0082] A further alternative embodiment for delivering sufficient
water vapor to the hydroxyl generator 20' also is shown in FIG. 5.
In this embodiment, water is delivered to and collected in a
storage container 63 via water inlet 65. Air from air inlet
canister 62 is bubbled through the water to achieve sufficient
water content or humidity. The water collected in storage container
63 can be from an external source or water vapor or water from the
exhaust gas stream can be condensed.
[0083] The inside surface of the hydroxyl generator 20' is provided
with a surface highly reflective to ultraviolet light in the
required range such as aluminum which maintains its reflectance to
ultraviolet light down to at least 185 nm.
[0084] It is believed that air of sufficient water vapor content,
as supplied by the embodiment of FIG. 5, passing through the
generator 20 will result in direct photodisassociation of the water
into OH and H by the adsorption of 185 nm photons. Alternatively,
the 185 nm UV radiation from lamp 21 acts on the air to produce
ozone and atomic oxygen. The 253.7 nm UV radiation breaks down the
ozone by photodissociation into molecular oxygen and a metastable
oxygen atom. The metastable oxygen combines with the water
molecules present to form hydrogen peroxide which photodissociates
in the presence of the 253.7 nm UV radiation into two hydroxyl
molecules.
[0085] The hydroxyl, as well as any of the free radicals and
oxidizers H, O, HO.sub.2, H.sub.2O.sub.2, generated by the hydroxyl
generator 20' is delivered via the generator outlet 70 to the
combustion gas stream. The generator output may be added to the
precombustion or postcombustion gas streams. If the generator
output is delivered to the postcombustion gas stream, it is
anticipated that less hydroxyl output would be required for the
same level of performance than if it was added to the precombustion
gas stream because much of the hydroxyl, and the other free
radicals and oxidizers, added to the precombustion gas stream would
not survive the combustion process. The hydroxyl which survives
combustion or which is delivered to the postcombustion gas stream
acts upon the CO and HC in the exhaust stream to produce
non-polluting CO.sub.2 and H.sub.2O.
[0086] A further hydroxyl generator 20" is shown in FIG. 6. Air
having sufficient water vapor is delivered to corona or glow
discharge generator 20" and may be accomplished in the same manner
and according to the same alternative or combination of embodiments
described herein and especially when referring to FIGS. 2, 4 and 5.
Generator 20" has an outer electrode 81 with an inner electrode 83.
A dielectric coating or material 82 is inserted between outer
electrode 81 and inner electrode 83. One lead from a high voltage,
high frequency power supply is connected to the inner electrode 83
while the other lead is connected to the outer electrode 81. The
hydroxyl and other products of the glow discharge generator 20" are
delivered via outlet 70 to the combustion gas stream.
[0087] FIG. 7 illustrates a different embodiment of a hydroxyl
generator 20'". Hydroxyl generator 20'" contains an ozone generator
90 for ozone generation and an ultraviolet container 95 for ozone
dissociation and hydroxyl creation. The ozone generator 90 has an
electrolytic cell 91 which receives water via water inlet 92. Water
for the electrolytic cell 91 can be supplied from an external
source which is stored or it may be condensed and collected from
the water vapor in the exhaust gas stream and produced from
combustion. The electrolytic cell is connected to an overvoltage
power supply 93. An overvoltage electrolytic cell operates at a few
tenths of a volt above the voltage condition required for the
voltage threshold required for electrolysis. The electrolytic cell
91 generates ozone, oxygen and water vapor which is retained by
container 94. Container 94 has an ozone, oxygen and water vapor
outlet 96 which provides a passage to the ultraviolet container
95.
[0088] Ultraviolet container 95 has an ultraviolet lamp 21' which
produces 253.7 nm radiation in order to dissociate the ozone into
hydroxyl pursuant to the sequence of reactions described earlier in
connection with FIG. 5. The ultraviolet lamp 21' is connected to a
power supply 60. Unlike the ultraviolet lamp 21 in FIG. 5, lamp 21'
only needs to generate UV radiation having a wavelength of above
200 nm and preferably approximately 254 nm. The inside surface of
ultraviolet container 95 is provided with a surface which is highly
reflective of UV radiation having a wavelength above 200 nm and
preferably approximately 254 nm.
[0089] In a further alternative, lamp 21 can be mounted downstream
from the engine's combustion chamber, for example, in the exhaust
manifold 15 as best seen in FIG. 3. By irradiating the exhaust
stream with UV radiation in the 100 to 200 nm wavelength range, in
the presence of sufficient water vapor, hydroxyl will be produced
by direct photodissociation.
[0090] In addition, hydroxyl generators 20, 20', 20" and 20'" can
inject hydroxyl both upstream and downstream of the combustion
chamber.
[0091] It should be noted that the embodiments discussed above are
illustrative examples. In this regard, while the use of radiant
energy to produce hydroxyl is described above, the present
invention is not so limited and other devices well-known in the art
which produce hydroxyl are envisioned as sources for adding
hydroxyl to the combustion gas stream in accordance with the
teachings of the present invention.
[0092] In addition, it should be noted that the only requirement of
the present invention is that the hydroxyl is added to the
combustion gas stream at a point upstream of or at the catalytic
converter, for example, the air intake duct to the carburetor or
fuel-injection systems of the combustion chamber, the air/fuel
intake manifold to the combustion chamber, the combustion chamber
directly or the exhaust manifold of the combustion chamber, or the
exhaust pipe 12 as shown in FIG. 1.
[0093] Moreover, while the present invention has been described
with reference to a catalytic converter, it is contemplated that
only the high surface area provided by the converter in conjunction
with the introduction of hydroxyl would be required to reduce the
pollutants in the exhaust gases of a combustion engine.
[0094] A control arrangement can be employed according to a further
embodiment of the present invention as shown in FIG. 8, wherein an
engine sensor 16 is installed in the system. The sensor 16 is
connected to a controller 18 which can be an electronic system
which is controlled by the output of engine sensor 16 or as complex
as an engine control computer which analyzes the output of the
sensor 16 in conjunction with other engine parameters such as load,
temperature, throttle position, rpm and the like, and which can
modulate the output of the hydroxyl generator 20. Alternatively,
the controller 18 can vary the amount of hydroxyl generated by the
hydroxyl generator 20 by varying either the voltage or current
applied to the hydroxyl generator 20 by the voltage converter 24
based on inputs received from the engine sensor 16.
[0095] In an alternative embodiment a single hydroxyl generator may
contain more than one ultraviolet lamp 21a, 21b, 21c which each
convert air to hydroxyl at a level that is less than required for
complete elimination of pollutants produced by combustion of a
fuel. One lamp 21a is operated when determined necessary, such as
when the engine is operating, and the other lamp 21b is modulated
depending upon operating parameters as measured by the engine
sensor 16.
[0096] In this embodiment, a controller 18 is connected to an
engine sensor 16 to receive an input indicative of the current
engine operating parameters or conditions. When the controller 18
senses an engine condition or parameter, such as engine speed or
engine load at or above a predetermined level, the controller 18
modulates lamp 21b and the output of the hydroxyl generator. In
addition to a two generator or two lamp configuration, a plurality
of generators or lamps can be used such that one generator or lamp
is continuously operated when the engine is operating and each
additional generator or lamp is turned on in succession as
different and increasing levels of engine operating conditions or
parameters, such as rotation of the engine or engine load, are
sensed by the controller 18 so that all the generators or lamps are
operating when the engine parameter or condition, such as speed or
engine load, is at the highest predetermined level and sufficient
hydroxyl is generated to assure no excess pollutants are
generated.
[0097] In a similar arrangement, instead of a plurality of lamps
21, a plurality of sets of inner electrodes 83 and outer electrodes
81, or a plurality of ozone generators 90 and ultraviolet light
containers 95, or a plurality of lamps 21' can be utilized.
[0098] Alternatively, a single lamp 21 can be employed and the
controller 18 can vary the amount of hydroxyl generated by the lamp
21 by varying either the voltage or current applied to the lamp 21
by the voltage converter 24 based on inputs received from the
controller 18.
[0099] Referring to FIG. 9, the method of the present invention is
illustrated and comprises the steps of: 1) adding hydroxyl to the
combustion gas stream at a point upstream from a high surface area
receptacle, and 2) passing the exhaust gases through a high surface
area receptacle such as, for example, a typical automotive
catalytic converter.
[0100] Although the present invention has been described with
particular reference to its preferred embodiments, it should be
understood that many variations and modifications will now be
obvious to those skilled in that art and, therefore, the scope of
the invention should not be limited, by the specific disclosure
herein, but only by the appended claims.
* * * * *