U.S. patent application number 11/516528 was filed with the patent office on 2007-02-01 for method and device for influencing combustion processes involving combustibles.
Invention is credited to David Walter Branston, Gunter Lins, Jobst Verleger.
Application Number | 20070026354 11/516528 |
Document ID | / |
Family ID | 7693988 |
Filed Date | 2007-02-01 |
United States Patent
Application |
20070026354 |
Kind Code |
A1 |
Branston; David Walter ; et
al. |
February 1, 2007 |
Method and device for influencing combustion processes involving
combustibles
Abstract
A method and device are for influencing combustion processes,
and include an electrical device. The electrical device engages
with the flame front so that the electrical field thus produced,
only penetrates areas of the flame front in which a stabilizing and
harmful-substance-reducing effect is produced. The electrodes of
the burner are arranged outside the region of the flame in the
associated device.
Inventors: |
Branston; David Walter;
(Effeltrich, DE) ; Lins; Gunter; (Erlangen,
DE) ; Verleger; Jobst; (Erlangen, DE) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 8910
RESTON
VA
20195
US
|
Family ID: |
7693988 |
Appl. No.: |
11/516528 |
Filed: |
September 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10485401 |
Jan 30, 2004 |
7137808 |
|
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PCT/DE02/02815 |
Jul 31, 2002 |
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11516528 |
Sep 7, 2006 |
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Current U.S.
Class: |
431/350 |
Current CPC
Class: |
F23C 99/001 20130101;
F23D 2210/00 20130101; F23D 14/74 20130101; F23N 5/16 20130101;
F23D 14/02 20130101 |
Class at
Publication: |
431/350 |
International
Class: |
F23D 14/46 20060101
F23D014/46 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2001 |
DE |
DE 101 37 683.9 |
Claims
1-23. (canceled)
24. A method for influencing a combustion operation, comprising:
exerting an electric force on charge carriers produced by a flame
in the combustion operation; arranging field-generating electrodes
for generating an electric field on a side of a burner opening
which is opposite to the direction of the flame, such that there is
no straight connecting line can be drawn between electrodes of
opposite polarity which passes through the flame; and exposing the
electric field to the flame during a combustion operation by
passing the electric field through only those areas of the flame in
which the electric field has a stabilizing, pollutant-reducing
effect.
25. The method as claimed in claim 24, wherein premixed gases are
used.
26. The method as claimed in claim 24, wherein thermo-acoustic
emissions are reduced.
27. A device for carrying out the method as claimed in claim 24,
comprising field-generating electrodes for generating an electric
field which is adapted to influence a flame during a combustion
operation, the electrodes being arranged outside an area of the
flame by exerting an electric force on charge carriers produced by
the flame and being arranged on a side of a burner opening which is
remote from the flame, wherein there is no straight connecting line
between electrodes of opposite polarity which passes through the
flame.
28. The device as claimed in claim 27, further comprising at least
one annular electrode, surrounding the burner.
29. The device as claimed in claim 28, further comprising an
annular electrode directly on the burner, on the side of the burner
opening which is remote from the flame.
30. The device as claimed in claim 27, wherein a rod electrode is
arranged coaxially inside the burner.
31. The device as claimed in claim 27, wherein the burner is
surrounded by a plurality of electrodes arranged on the
circumference around the flame.
32. The device as claimed in claim 31, wherein the electrodes are
arranged symmetrically around the burner.
33. The device as claimed in claim 32, wherein the electrodes are
rod electrodes directed centrally at the burner.
34. The device as claimed in claim 27, further comprising: sensors
for recording the frequency and amplitude of at least one of
combustion oscillations and pollutant concentration in an
exhaust-gas stream, the sensors, via at least one control device,
being adapted to control frequency, amplitude and phase of an
applied voltage in such a way that at least one of the combustion
oscillations and pollutant concentration in the exhaust gas are
minimized.
35. The device as claimed in claim 29, wherein a rod electrode is
arranged coaxially inside the burner.
36. The device as claimed in claim 30, wherein the burner is
surrounded by a plurality of electrodes arranged on the
circumference around the flame.
37. The device as claimed in claim 36, wherein the electrodes are
arranged symmetrically around the burner.
38. The device as claimed in claim 37, wherein the electrodes are
rod electrodes directed centrally at the burner.
39. A device for influencing a combustion operation, comprising:
field-generating electrodes for generating an electric field which
is adapted to influence a flame by exerting an electric force on
charge carriers produced by the flame during a combustion
operation, the electrodes being arranged outside an area of the
flame and being arranged on a side of a burner opening which is
opposite to the direction of flame propagation, wherein there is no
straight connecting line between electrodes of opposite polarity
which passes through the flame.
40. The device as claimed in claim 39, further comprising at least
one annular electrode, surrounding the burner.
41. The device as claimed in claim 39, further comprising an
annular electrode directly on the burner, on the side of the burner
opening which is remote from the flame.
42. The device as claimed in claim 39, wherein a rod electrode is
arranged coaxially inside the burner.
43. The device as claimed in claim 42, wherein the burner is
surrounded by a plurality of electrodes arranged on the
circumference around the flame.
44. The device as claimed in claim 39, wherein the electrodes are
arranged symmetrically around the burner.
45. The device as claimed in claim 44, wherein the electrodes are
rod electrodes directed centrally at the burner.
46. The device as claimed in claim 39, further comprising: sensors
for recording the frequency and amplitude of at least one of
combustion oscillations and pollutant concentration in an
exhaust-gas stream, the sensors, via at least one control device,
being adapted to control frequency, amplitude and phase of an
applied voltage in such a way that at least one of the combustion
oscillations and pollutant concentration in the exhaust gas are
minimized.
Description
[0001] This application is a continuation of and claims the benefit
of priority under 35 U.S.C. .sctn.120 from U.S. application Ser.
No. 10/485,401 filed Jan. 30, 2004, which is the national phase
under 35 U.S.C. .sctn.371 of PCT International Application No.
PCT/DE02/02815 having an International filing date of Jul. 31,
2002. PCT International Application No. PCT/DE02/02815 designates
the United States of America and claims the benefit of priority
under 35 U.S.C. .sctn.119 from German Patent Application number DE
101 37 683.9 filed Aug. 1, 2001. The entire contents of U.S.
application Ser. No. 10/485,401, PCT International Application No.
PCT/DE02/02815 and German Patent Application number DE 101 37 683.9
are hereby incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The invention generally relates to a method for influencing
combustion operations or processes involving combustibles,
including fuels. Preferably, it relates to a method in which
electrical devices are used to guide and/or alter a flame at a
burner. In addition, the invention also generally relates to a
device for carrying out the method; preferably using stabilizing,
pollutant-reducing devices to influence the flame during the
combustion operation.
BACKGROUND OF THE INVENTION
[0003] The advantageous influences which electric fields can have
on combustion flames are known. According to the publications
[0004] Industrial and Engineering Chemistry 43 (1951), pages 2726
to 2731,
[0005] 12th Annual energy-sources technology conf. (1989), pages 25
to 31 and
[0006] AIAA Journal 23 (1985), pages 1452 to 1454
the effects of the electric field reside in an improvement to the
flame stability. According to
[0007] Combust. Flame 78 (1989), pages 357 to 364 and
[0008] Combust. Flame 119 (1999), pages 356 to 366
the carbon emissions are reduced. Further, according to
[0009] Fossil Fuel Combustion, ASME 1991, pages 71 to 75 and
[0010] Fluid Dynamics 30 (1995), pages 166 to 174 the emission of
gaseous pollutants is reduced.
[0011] It is also known from Combust. Flame 55 (1984), pages 53 to
58 to influence combustion operations by electric discharges, in
particular corona discharges. In this case too, the flame stability
can be improved and the pollutant emissions can be reduced.
Technical applications of the abovementioned effects are described
in WO 96/01394 A1, U.S. Pat. No. 3,416,870 A and U.S. Pat. No.
4,111,636 A.
[0012] A common feature of the known methods is that the electrodes
which are required in order to generate the electric field or a
discharge in the flame, are arranged in such a manner that the
flame is either located between the field-generating electrodes or
is surrounded by one electrode. This electrode can be identical to
the combustion chamber. An arrangement of this nature is
illustrated with reference to FIG. 1 of the description. In any
event, it is possible to draw a straight connecting line between
electrodes of opposite polarity in such a manner that the
connecting line passes through the flame which is to be
influenced.
[0013] In FIG. 1, the direction of propagation of a flame 2 or the
direction of flow of the exhaust gases is indicated as the z
direction. The location z=0 is determined by the position at which
the solid, liquid or gaseous fuel is transformed into the flame. No
significant ionization caused by the combustion process occurs at
locations z<0.
[0014] Arrangements which correspond to the known art include at
least one electrode or one or more parts of such an electrode
extending exclusively or predominantly over areas where z>0. In
this case, it is also possible for the combustion chamber which
surrounds the flame to be an electrode or part of an electrode. In
extreme cases, the arrangement is such that partial areas of the
flame may touch an electrode. In any event, it is possible to draw
a straight connecting line from one electrode to an electrode of
opposite polarity in such a way that the connecting line passes
through the flame.
[0015] One drawback of the known art described above is that the
electric field which is generated by way of the electrodes passes
through a large area of the flame, while the actual effect of the
electric field occurs in what is known as the flame front. The
flame front is a narrow area, compared to the dimensions of the
flame, between the cold fuel and the flame in which the chemical
reactions leading to the formation of the flame take place. Since
the flame has an electrical conductivity which is not negligible,
on account of the charge carriers contained therein, the fact that
the electric field passes through wide areas of the flame indicates
that an electric current flows throughout the flame area which is
enclosed by the electrodes. This causes an increased energy
consumption without contributing to the desired effect within the
flame front. This is the case in particular if electrically
conductive areas of the flame or its surroundings are in direct
contact with the electrodes.
SUMMARY OF THE INVENTION
[0016] Working on this basis, it is an object of an embodiment of
the invention to provide a method and to create the associated
device which improve the influencing of combustion operations with
fuels in a simple and economic way. The fuels to be used are in
particular, although not exclusively, gases, preferably in premixed
form.
[0017] According to an embodiment of the invention, an object may
be achieved by a method for influencing combustion operations with
fuels. An associated device forms the subject matter of another
embodiment. Refinements to the method and/or device are further
provided.
[0018] In one embodiment of the invention, the flame is exposed to
the action of an electric field. The field is configured in such a
way that it passes through only those areas of the flame in which
it has a stabilizing, pollutant-reducing effect. For this purpose,
in the associated device of another embodiment, electrodes are
arranged and acted on by a voltage in such a way that an electric
field preferably passes through those areas of the flame in which
it produces its stabilizing, pollutant-reducing effect. This may be
achieved by virtue of all the field-generating electrodes being
arranged in areas in which no ionization or no significant
ionization brought about by the combustion process occurs. This
condition may be satisfied if the electrodes are arranged on the
side of the burner not facing the burner mouth, such that no
straight line can be drawn between the electrodes, that passes
through the flame.
[0019] Particular advantages of an embodiment of the invention
result if the system is assigned sensors and control devices which
control the voltage applied to the electrodes in such a way that
the combustion process is influenced in the desired way. There are
advantageously sensors, one of which measures the frequency of any
combustion oscillation which may be present and another of which
measures the pollutant concentration in the exhaust gas. The
sensors supply the input signal to a control unit which controls
frequency, amplitude and phase of the voltage applied to the
electrodes in such a way that the combustion oscillations and/or
the pollutant concentration are minimized.
[0020] Further advantages, features and details of the invention
will become evident from the description of illustrated exemplary
embodiments given hereinbelow and the accompanying drawing, which
is given by way of illustration only and thus is not limitative of
the present invention, wherein:
[0021] FIG. 1 diagrammatically depicts an arrangement of the known
art,
[0022] FIGS. 2 and 3 diagrammatically depict two different
embodiments of the invention,
[0023] FIGS. 4 and 5 diagrammatically depict a plan view and
sectional illustration of a further embodiment, and
[0024] FIG. 6 diagrammatically depicts a use of an embodiment of
the invention for the combustion of solid materials.
[0025] In the individual exemplary embodiments, identical parts are
provided with identical reference symbols. The embodiments are
partially described jointly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] In all the examples, in each case the burner is denoted by 1
and the flame by 2. The burner I has a gas feed 3. Furthermore, the
arrangement includes at least one electrode 6, which can be used to
apply electric fields to the flame. The flame is scaled along the Z
coordinate.
[0027] FIG. 1 has already been dealt with in the introduction, with
corresponding statements relating to the known art, to which
reference is made in detail.
[0028] The first exemplary embodiment of the invention, shown in
FIG. 2, illustrates the flame 2 which is generated by the burner 1
for combustibles, including fuels which are in gas form, in liquid
form or in the form of a solid powder transported in gas or
liquids. The fuel is guided through the burner 1 into a combustion
space 4 through the fuel inlet 3. The burner 1 may include
electrically conductive or nonconductive material. In the former
case, the burner serves as electrode, while in the latter case an
electrode 5, which in this example is in the form of a ring and
closely surrounds the burner 1, is fitted. A further electrode 6 is
arranged in such a way as to lie completely in the area indicated
by z.ltoreq.0. The electrodes are electrically connected to the
main part 7.
[0029] In the exemplary embodiment shown in FIG. 3, a rod electrode
6a is arranged coaxially inside the burner, in such a manner that
it only projects into the area z>0 sufficiently far to satisfy
the condition that there should be no straight connecting line
between the electrodes that passes through the flame. An electric
field in the sense of an embodiment of the invention is formed
between the electrode 6a, on the one hand, and the burner 1, on the
other hand, if the latter includes electrically conductive
material, or a further electrode 5, which in this specific case
surrounds the burner, which is assumed to be nonconductive, in a
form-fitting manner.
[0030] In a modification of an embodiment of the invention, the rod
electrode 6a located inside the burner can be replaced by a tube or
nozzle or a plurality of tubes and nozzles through which
combustible or noncombustible gases or mixtures can flow. On
account of the short electrode-to-electrode distance compared to
the known art shown in FIG. 1, it is already possible to generate
an electric field with correspondingly lower voltages.
[0031] The use of embodiments of the invention is not restricted to
the combustion of liquid or gaseous fuels. FIG. 6 indicates a
combustion chamber 8 in which a pile 11 of solid fuel, for example
coal, is burning on a grate 10 which is electrically insulated from
the combustion chamber by nonconductive support elements 9. The
plane z=0 is defined by the top edge of the grate 10 or, if the
fuel is electrically conductive, by the upper limit of the pile 11.
An annular electrode 12 is arranged in such a way that it projects
into the area z>0 at most sufficiently far to satisfy the
condition that there must be no straight connecting line between
the electrodes which passes through the flame.
[0032] Embodiments of the invention are not restricted either to
systems which include just two electrodes, one of which may be the
burner; or to electrodes which are rotationally symmetrical with
respect to the burner axis, i.e. in particular annular, toroidal or
cylindrical. FIGS. 4 and 5 show an exemplary embodiment in which a
plurality of rod electrodes 13a, 13b, 13c, 13d are arranged
radially with respect to a burner 1.
[0033] In the arrangements described with reference to FIGS. 2 to
6, the desired influencing of the combustion process by electric
fields is achieved without the electric field passing through
extensive parts of the flame in which it does not have a
stabilizing or pollutant-reducing effect. Contact with the
electrodes by electrically conductive areas of the flame is as far
as possible avoided. As a result, the current induced by the
electric field is considerably reduced, and the demand for electric
power is reduced to the same degree. Furthermore, the likelihood of
disruptive electrical sparkovers greatly decreases. The relatively
short electrode-to-electrode distance leads to a reduced voltage
consumption compared to the known art for the same electric field
strength.
[0034] The arrangements according to an embodiment of the invention
for influencing flames with the aid of electrical devices are
equally suitable for operation with DC voltage, pulsed or clocked
DC voltage and AC voltage, as well as DC voltage with superimposed
AC voltage. If a DC voltage is used, the polarity of the burner is
preferably negative.
[0035] Furthermore, sensors can be assigned to the system: a first
sensor records the frequency of any combustion oscillations which
may be present. A second sensor measures the pollutant
concentration in the exhaust-gas stream from the flame. The sensors
supply input signals for a control unit (not shown in detail) which
controls the frequency, amplitude and phase of the voltage applied
to the electrodes in such a manner that the combustion oscillations
and the pollutant concentration are minimized.
[0036] Exemplary embodiments being thus described, it will be
obvious that the same may be varied in many ways. Such variations
are not to be regarded as a departure from the spirit and scope of
the present invention, and all such modifications as would be
obvious to one skilled in the art are intended to be included
within the scope of the following claims.
* * * * *