U.S. patent application number 10/532592 was filed with the patent office on 2006-07-06 for combustion method and burner head, burner comprising one such burner head, and boiler comprising one such burner head.
This patent application is currently assigned to SWISS E-TECHNIC AG. Invention is credited to Jorg Fullemann.
Application Number | 20060147854 10/532592 |
Document ID | / |
Family ID | 32111462 |
Filed Date | 2006-07-06 |
United States Patent
Application |
20060147854 |
Kind Code |
A1 |
Fullemann; Jorg |
July 6, 2006 |
Combustion method and burner head, burner comprising one such
burner head, and boiler comprising one such burner head
Abstract
A burner head has at least two and preferably four openings (45)
in an aperture plate (37), with uniformly inclined guide blades
(23) for the delivery of incoming air in the direction of an axis
(31) to a combustion chamber (15) in the form of incoming air jets
(53) intersecting one another in the chamber. Between the openings
(45), blocking blades (27) are embodied, for forming peripheral
underpressure zones (55) between the incoming air jets (53). The
incoming air jets (53) are deflected by the guide blades (23) into
a position that is inclined relative to the axis (31). The incoming
air jets (53) therefore diverge and as a result create a central
underpressure zone (57) about the axis (31) between the incoming
air jets (53). By means of the central underpressure zone and the
inclination of the incoming air jets, a rotation of the incoming
air is achieved. In operation of the burner, hot gases from outside
are aspirated into the peripheral underpressure zones (55) and,
counter to the flow direction of the incoming air, into the central
underpressure zone (57) between the incoming air jets (53). These
flow conditions create ideal conditions for the combustion of
gaseous, liquid and/or particulate fuel in a calm, cool,
low-polluting flame. This combustion is practically independent of
the size and shape of the combustion chamber and of the pressure
conditions in the combustion chamber, for combustion installations
of 16 kW to 1000 kW, or more.
Inventors: |
Fullemann; Jorg; (Mastrils,
CH) |
Correspondence
Address: |
BUCHANAN INGERSOLL PC;(INCLUDING BURNS, DOANE, SWECKER & MATHIS)
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
SWISS E-TECHNIC AG
MASTRILS
CH
|
Family ID: |
32111462 |
Appl. No.: |
10/532592 |
Filed: |
October 23, 2003 |
PCT Filed: |
October 23, 2003 |
PCT NO: |
PCT/CH03/00691 |
371 Date: |
January 13, 2006 |
Current U.S.
Class: |
431/9 ;
431/185 |
Current CPC
Class: |
F23C 2202/50 20130101;
F23C 7/004 20130101; F23D 14/02 20130101; F23D 14/34 20130101; Y02E
20/34 20130101; F23C 2900/09002 20130101; F23C 9/006 20130101; F23C
2900/06041 20130101; F23D 11/404 20130101; Y02E 20/342 20130101;
F23D 17/002 20130101; F23C 6/045 20130101 |
Class at
Publication: |
431/009 ;
431/185 |
International
Class: |
F23M 3/00 20060101
F23M003/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2002 |
CH |
1777/02 |
Claims
1. A method for combusting a liquid, gaseous, and/or particulate
fuel at a low flame temperature and low pollutant emissions values,
in which method fuel and incoming air are delivered to a combustion
chamber and are ignited in the combustion chamber, wherein the
incoming air is blown into the combustion chamber in two or more
divergent incoming air jets spaced apart from one another; by
blowing in of incoming air, peripheral underpressure zones are
created in the combustion chamber between each two incoming air
jets, and oxygen-poor exhaust gases present in the combustion
chamber are aspirated from outside, as a consequence of an
underpressure in the peripheral underpressure zones, into the
peripheral underpressure zones between each two incoming air jets;
and in which method, by the divergent blowing in of the incoming
air jets centrally between the two or more incoming air jets, a
central underpressure zone is created, and oxygen-poor exhaust
gases present in the combustion chamber are aspirated axially and
counter to a flow direction of the incoming air into the central
underpressure zone.
2. The method according to claim 1, wherein a flow axis of each
incoming air jet is inclined relative to a center axis common to
the incoming air jets and has a minimal spacing from the center
axis that is greater than zero, and the flow axes of the incoming
air jets intersect one another in the chamber.
3. The method according to claim 1 wherein liquid fuel is injected
axially with a nozzle having a full-conical characteristic, mixed
characteristic, or conical-jacket characteristic.
4. The method according to claim 3, wherein the conical apex angle
of the nozzle is at least 45.degree., advantageously over
60.degree., and at most 90.degree., and preferably is
80.degree..
5. The method according to claim 1 wherein gaseous fuel is admixed
with the incoming air upstream of the blocking disk, advantageously
upstream of a fan for the incoming air.
6. The method according to claim 1 wherein the incoming air is
blown out at a dynamic overpressure of 4 to 50 millibars,
advantageously between 7 and 28 mbar.
7. A burner head for disposition on the end of an incoming air
conduit of a low-NOx burner, having a blocking disk closing off the
incoming air conduit on the downstream end, comprising: a plurality
of spaced-apart openings in the blocking disk, for splitting up a
majority of the incoming air into incoming air jets, which openings
are disposed in a ring; guide blades at the openings for guiding
each incoming air jet, flowing out of the incoming air conduit
through an opening, in a divergent direction relative to the other
incoming air jets; and blocking blades, which are disposed between
the openings, so as to reach peripheral underpressure zones between
the incoming air jets.
8. The burner head according to claim 7, wherein the guide blades
at the openings are uniformly inclined and guide the outflowing
incoming air jets in such a way that the flow axes of the incoming
air jets intersect both one another and the center axis, common to
the incoming air jets, in the chamber.
9. The burner head according to claim 7, wherein the blocking
blades and the guide blades are embodied integrally with the
blocking disk.
10. The burner head according to claim 9, wherein the blocking
blades and the guide blades are shaped from a flat piece of sheet
metal.
11. The burner head according to claim 7 wherein the blocking
blades are embodied trapezoidally, and the guide blades are
embodied adjoining one side of the trapezoid.
12. The burner head according to claim 11, wherein the guide
blades, along one edge, in particular a bending edge, adjoin the
blocking blades, and at this edge the guide blades and blocking
blades form an angle of between 95.degree. and 160.degree.,
preferably between 110.degree. and 140.degree..
13. The burner head according to claim 7 wherein the openings are
embodied around a central body.
14. The burner head according to claim 13, wherein the central body
is a fuel nozzle for liquid fuel, and this fuel nozzle has a
full-conical characteristic, mixed characteristic, or
conical-jacket characteristic.
15. The burner head according to claim 13 wherein the guide blades
accompany the central body in the flow direction of the incoming
air.
16. The burner head according to claim 14, wherein there is a fine
annular gap around the fuel nozzle, so as to deliver only a small
quantity of the incoming air to the fuel stream through the annular
gap.
17. The burner head according to claim 7 wherein around the ring of
openings, there are secondary air openings in the blocking disk,
spaced apart from the openings.
18. A blue-flame burner having an incoming air fan, an adjoining
incoming air conduit, a fuel delivery means, an electric ignition,
and a burner head as defined by claim 7.
19. The blue-flame burner according to claim 18, comprising a gas
delivery means and an oil nozzle.
20. A boiler having a boiler chamber, a heat exchanger, and a
burner as defined by claim 18.
21. The boiler according to claim 20, wherein the boiler chamber is
subdivided by a heat exchanger into a central combustion chamber
and an exhaust gas chamber encasing the combustion chamber parallel
to the inflow direction of the incoming air.
22. The boiler according to claim 21, wherein the heat exchanger is
a gap coil heat exchanger.
23. An aperture plate for a burner head of a low-NOx burner and for
use at the end of a burner pipe, comprising: a plurality of
spaced-apart openings for splitting up a majority of the incoming
air into incoming air jets, which openings are disposed in a ring;
guide blades at the openings for guiding each incoming air jet,
flowing out of the incoming air conduit through an opening, in a
divergent direction relative to the other incoming air jets; and
blocking blades, which are disposed between the openings, so as to
reach peripheral underpressure zones between the incoming air jets.
Description
[0001] In the conventional oil burner, the heating oil is injected
at high pressure into the incoming air flowing into the combustion
chamber. The difference in speed between the air and the oil
droplets favors evaporation of the oil and thus leads to a
reduction in the size of the oil droplet, until finally the
difference in speed between the air and the oil droplets has
vanished. As the speed decreases, the evaporated liquid around the
droplet forms a mixture of fuel vapor and air with an increasing
proportion of fuel vapor. The flammability of the mixture increases
during the combustion process. Because of the heat in the flame
that already exists in the burner, this increasingly more readily
flammable mixture ignites.
[0002] In yellow-flame burners, to prevent the flame from
separating from the burner head, an underpressure one is created,
centrally or annularly around a central region, with a blocking
disk. A lesser quantity of incoming air, set into rotation, is
delivered to this underpressure zone. The fuel is also injected
into this underpressure zone. In this flame core, it burns under
conditions of oxygen deficiency. Secondary air is delivered in
relatively large quantity centrally and/or through an annular slot
around this underpressure zone and allows the combustion of all the
delivered fuel in an elongated flame. Thanks to the central
underpressure zone and the supply of fresh air enveloping it, the
flame core and hence the entire flame is aspirated against the
blocking disk. The flame therefore persists downstream of the
blocking disk and does not separate from it.
[0003] In this combustion, however, a high flame temperature is
reached. This high temperature on the one hand leads to
carbonization of the fuel nozzle, which impairs the safety and
reliability of operation, and on the other hand leads to favorable
conditions for the combining of nitrogen from the air with oxygen
from the air. In this kind of combustion, the result is an
excessive concentration of nitrogen oxides (NOx). In this
combustion, the flame is yellow. The yellow light is given off by
glowing carbon, which is created by the decomposition of the
fuel.
[0004] It has been discovered that the concentration of the
resultant nitrogen oxides is very strongly dependent on the
combustion temperature. Each reduction of the temperature by
100.degree. C. reduces the NOx concentration to half the previous
value. If it is possible to lower the combustion temperature by
300.degree. C., the NOx concentration is accordingly then only
about 1/8 that of combustion with a yellow flame.
[0005] Cooling the flame is attained by means of an excess of
incoming air, a purposeful recirculation of exhaust gases, and/or a
spatial separation of the evaporation zone and the mixing zone.
[0006] To reduce NOx values in the flue gas in the combustion of
heating oil, so-called blue-flame burners have been developed. With
the blue-flame burners, the combustion zone is separated from the
evaporation and mixing zone as much as possible. In the process,
the fuel in the incoming air or in a mixture of incoming air and
combustion gas is evaporated and thereafter combusted. In burners
that make a virtually stoichiometric combustion possible,
recirculation of the exhaust gases must be provided for.
[0007] From European Patent Disclosure EP-A 0 321 809 (Brown Boveri
AG), a method and a burner are known for the premix kind of
combustion of liquid fuel in a burner. The burner has two
complementary that put together make a hollow cone, and between
which there are tangential air inlet slits. The hollow partial
conical bodies have a conical inclination that increases in the
flow direction. The cone axes of the partial conical bodies are
spaced apart from one another, and between these cone axes there is
a fuel nozzle, which injects a liquid fuel into the hollow cone at
an angle that assures that the fuel does not wet the wall of the
hollow cone. Through the tangential air inlet slits, air is
delivery, which forms a jacket around the fuel fog and rotates
around the fuel cone. In the region where the turbulence breaks up,
that is, in the region of a central return-flow zone in the orifice
region of the hollow cone, the fuel-air mixture reaches its
optimal, homogeneous fuel concentration via the cross section of
the turbulence. The ignition takes place at the tip of the
return-flow zone.
[0008] With this burner, the least pollutant emissions values are
achieved when the evaporation is concluded before the entry into
the combustion zone. This is equally true for combustion with an
air excess of 60%, and if this air excess is replaced with
recirculated exhaust gas. How the exhaust gases are recirculated
cannot be learned from this reference. In designing the partial
cone bodies in terms of their conical inclination and the width of
the tangential air inlet slits, narrow limits must be adhered to,
so that the desired flow pattern of the air with its return-flow
zone in the region of the burner orifice for flame stabilization
will be established.
[0009] According to European Patent Disclosure EP-A 0 491 079 (Asea
Brown Boveri AG), one disadvantage of this burner is that in some
cases, it cannot be used by atmospheric combustion installations.
This reference therefore proposes a burner head that has minimal
pollutant emissions and in which, by the shaping of the burner head
and the guidance of the incoming air through the burner,
stabilization of the flame is established at the end of a premixing
zone in the center and/or on the outer periphery of the combustion
chamber. Evidently, the flame stability of the burner of EP-A 0 321
809 was inadequate.
[0010] The burner head of EP-A 0 491 079 has a fuel lance with a
fuel nozzle. An incoming air conduit is disposed around this fuel
nozzle. On the downstream side, the fuel nozzle is closed off with
an aperture plate. Disposed around this first incoming air conduit
is a further incoming air conduit. This second incoming air conduit
is provided, on the downstream side, with a number of guide
devices. On the downstream side of the fuel nozzle is a combustion
chamber, which in the downstream direction comprises a premixing
pipe and an adjoining burnoff pipe whose diameter is larger than
that of the premixing pipe. Flame stabilization can be achieved as
needed by introducing an interference body downstream of the
premixing zone.
[0011] In operation of this burner, some of the incoming air is
introduced via at least one aperture plate into a premixing zone
located downstream of a fuel nozzle. Another portion of the
incoming air, before flowing into the premixing zone, is imparted a
swirl by a number of guide devices and is thereafter mixed with a
recirculated exhaust gas. Downstream of the premixing zone, at the
transition from the premixing pipe to the burnoff pipe, a
turbulence ring forms, which surrounds a turbulence return-flow
zone that develops at the end of the premixing zone. The initial
ignition of the mixture of incoming air and fuel takes place in the
turbulence ring.
[0012] In a departure from the mixing of the fuel with a mixture of
incoming air and recirculated exhaust gas, European Patent
Disclosure EP-A 867 658 describes a method for combusting liquid
fuel in which the fuel is first evaporated in recirculated exhaust
gas, and only after that is the mixture of fuel and exhaust gas
made turbulent with supplied fresh air to which a swirl has been
imparted, and ignited. The swirl is attained by providing an
annular opening, disposed around the fuel nozzle, in the blocking
disk with guide faces that generate a swirl. With the guidance of
the air, an underpressure is attained, by which recirculated gases
are aspirated into the flame pipe. This combustion is distinguished
by previously unattained, extremely low pollutant emissions values.
For forming a gasification zone with oxygen-poor hot gas and for
flame stabilization, a flame pipe is provided. Upstream, there are
recirculation openings on the flame pipe. On the downstream end of
the flame pipe, a constriction in the pipe diameter is embodied,
which lends stability to the flame.
[0013] A disadvantage of this and other burners is that for
stabilizing the flame, a flame pipe is required. Flame pipes are
very heavily stressed parts, which are worn down by use in the
combustion installation.
[0014] It is therefore an object of the invention to propose a
combustion method and a burner head for a low-NOx burner that
Allows virtually stoichiometric combustion, which assure that the
burner head makes do without a flame pipe yet good stability of the
flame is nevertheless achieved, and that the burner head can be
used practically regardless of the given conditions of a combustion
chamber or boiler chamber and can be adapted to any desired power
range.
[0015] This object is attained by the characteristics of
independent method claim 1 and by the characteristics of
independent apparatus claim 7, respectively.
[0016] In the method for combusting a fuel, fuel and incoming air
are delivered to a combustion chamber and ignited in the combustion
chamber. The combustion takes place inside a cool and therefore
blue flame and with low pollutant emissions values. The incoming
air is blown into the combustion chamber in a plurality of
divergent incoming air jets that are spaced apart from one another
and that intersect in the chamber. As a result, in the combustion
chamber, on the one hand underpressure zones are created between
each two incoming air jets, and on the other, a central
underpressure zone is also created centrally between the divergent
incoming air jets. Oxygen-poor exhaust gases present in the
combustion chamber are therefore aspirated from outside into the
underpressure zones between the incoming air jets and mix with the
incoming air. This delivery of recirculated gases to the flame from
outside will hereinafter be called external recirculation. In
addition to the external recirculation, oxygen-poor exhaust gases
are aspirated axially and counter to the flow direction of the
incoming air or of the mixture of incoming air and exhaust gas into
the central underpressure zone. This axial delivery will
hereinafter be called internal recirculation.
[0017] The incoming air jets intersecting one another in the
chamber also intersect a common center axis in the chamber. Because
of the inclination of the incoming air jets relative to a plane
that includes the common center axis and intersects the incoming
air jet, the incoming air jets cause a rotation of the incoming air
about the center axis.
[0018] The burner head has a blocking disk, with which an incoming
air conduit of a blue-flame burner can be closed off on the
downstream end. In the blocking disk, there are at least two
openings diametrically opposite one another, and preferably,
depending on the burner power, three, four, five, six, seven, or
eight openings arranged in a ring. For low power levels, optionally
up to 12 openings may be provided. These openings are equipped with
guide blades for guiding the air, flowing out of the incoming air
conduit through the openings, in the form of incoming air jets that
diverge from and intersect each other in the chamber. Between the
guide blades, blocking blades are embodied, so as to achieve
underpressure zones between the incoming air jets. Downstream of
the blocking disk, there is a chamber in which the incoming air
jets can spread apart from one another without hindrance. The guide
blades and blocking blades preferably form the final air-guiding
parts before the flame. As a consequence, a flame is entirely
surrounded by exhaust gases present in the combustion chamber.
Optionally, a short pip may be provided around the blocking disk,
for metering the recirculating exhaust gases along or near the
blocking disk.
[0019] With this method and this apparatus, the hydrodynamic and
physical-chemical preconditions have successfully been created for
stable, practically stoichiometric combustion of heating oil,
essentially regardless of the shape and size of the combustion
chamber. The combustion produces extremely little pollution, and
burners with power levels to suit heating requirements ranging from
those of a single-family house to those of entire housing
developments or industrial plants are feasible. Since the burner
has no flame pipe, it is practically maintenance-free. In a sense,
the flame floats at a distance from the blocking disk and the
nozzle in the combustion chamber. The flame is cup-shaped and has
very soft, frayed contours with innumerable tips that are oriented
outward and inward relative to the cuplike shape. The combustion is
very quiet and has almost no tendency to pulsation. The sound level
values measured in the combustion of heating oil are the quietest
of all, compared with those of the most commonly used yellow-flame
burners and blue-flame burners.
[0020] A flow axis of each incoming air jet preferably has a
minimum spacing from a center axis that is common to all the
incoming air jets. The spacing of the axes of the incoming air jets
from the center axis is everywhere greater than zero. Thus the flow
axes do not intersect the center axis. This creates a swirl effect
on the gas flow in the region of the flame. This swirl serves to
hold and stabilize the flame.
[0021] The angle between a center axis and the divergent incoming
air jets can be adjusted by the angular position of the guide
blades and the angular position of the blocking blades. As a
function of this angle of the incoming air jets, the cup shape of
the flame is more or less widely open. Preferred half-apex angles
of a cone, inscribed into the air jets and tangent to them at their
entry into the combustion chamber, are between 30.degree. and
45.degree.. However, the flame stability is not threatened even at
angles of 20.degree. or 60.degree.. The flow axes of the incoming
air jets assume an angle to a jacket line of a cone or cylinder
that touches the incoming air jet axis. Since the axes of the
incoming air jets do not intersect at a common point of the center
axis, the incoming air jets bring about a swirl about the center
axis. The incoming air jet axes are theoretically located in a
surface of rotation about the center axis that widens in the shape
of the bell of a trumpet. In actuality, however, because the cross
section of the cup shape of the flame increases with the distance
from the blocking disk, an underpressure zone develops in the
center of the flame. The effect of this is that the incoming air
jets and the recycled exhaust gases, fanned out between them, form
the shape not of the bell of a trumpet, but of a tulip. The
incoming air jets are therefore not rectilinear but instead rotated
about the center axis; depending on the angle of inclination of the
incoming air jet axis relative to the aforementioned conical jacket
line, they execute a rotation of from 20.degree. to 120.degree.,
and preferably of approximately 90.degree. about the center
axis.
[0022] The incoming air jets begin already spaced apart from one
another and then diverge. The minimum spacing of the axes of these
jets from the center axis may be located upstream of the blocking
disk, at the blocking disk, or downstream of the blocking disk. The
spacing between the centers of two adjacent incoming air jets in
the plane of the blocking disk is advantageously approximately
twice the mean diameter of the cross section of the incoming air
jets. These conditions can be adjusted by means of the size of the
openings in the blocking disk, the size of the blocking blades, or
the inclination of the guide blades.
[0023] A departure from the aforementioned ratio is possible to a
limited extend. The spacing of the centers may be six times the jet
diameter, or 1.5 times the jet diameter. The ratio of the
cross-sectional areas of the underpressure zone and air jets can be
varied between approximately 1:2 to 5:1. In no case does the ratio
of the cross-sectional areas of the underpressure zone and air jets
fall below a ratio of 1:3 or exceed a ratio of 8:1. From 70 to 95%,
and preferably 80 to 90%, of the incoming air forms the incoming
air jets. The rest of the incoming air flows into the combustion
chamber, optionally centrally around a central body, such as the
fuel nozzle. At high power levels, secondary air making whose
volume is 10 to 20% that of the incoming air may be brought to the
flame from the outside, through an annular gap in the blocking disk
or around the blocking disk. In no case, however, are the incoming
air jets disposed around a central incoming air jet.
[0024] If the desired external recirculation is to be achieved, the
dimensions of the underpressure zones appear to be significant. For
a smaller outermost width of the blocking blades, a greater
pressure gradient between the incoming air and the combustion
chamber pressure, or a larger cross section of the underpressure
zones, is necessary overall, in order to recirculate the same
quantity of combustion gas. A preferred outermost width at the
outermost base of trapezoidal blocking disks is at minimum 4 to 7
and at maximum 20 to 22 mm, and especially preferably 12 to 18 mm.
A preferred least spacing between round openings in a blocking disk
is likewise about 15 mm. A different spacing of openings and
blocking blades therefore results, depending on the diameter of a
blocking disk or the spacing of diametrically opposite incoming air
jets. For larger diameters and higher incoming air pressures,
lesser spacings between the incoming air jets are possible.
[0025] A dynamic overpressure of the incoming air, compared to the
combustion chamber pressure, of at least 4 to a maximum of 30 mbar,
depending on whether the burner has to produce 20 kW or 400 kW,
makes it possible to achieve the requisite air quantities and
feeding speeds that assure a formation of the underpressure zones
that stabilize the flame. At still higher power levels, even higher
overpressures must be employed.
[0026] The combustion method according to the invention is suitable
for both oil and gas and for dual-fuel burners. Gas is admixed with
the incoming air upstream of the blocking disk. Advantageously,
liquid fuel is injected axially with a nozzle of full-conical
characteristic or conical-jacket characteristic. A nozzle with a
mixture of full-conical characteristic and conical-jacket
characteristic, in which the fuel is not sprayed as densely in the
interior of the cone but is sprayed more densely on the periphery,
can also be used. This kind of characteristic is called a mixed
characteristic. The conical apex angle of the nozzle is at least
45.degree., advantageously 60.degree. or more, and at most
90.degree., and preferably approximately 80.degree..
[0027] It is even possible, alternatively or in addition to the
liquid and/or gaseous fuel, to admix solid fuel particles (such as
coal dust) to the incoming air. As a result, the power of the
burner can be increased. The key component of the combustion method
is the burner head with integrated incoming air guidance, where the
burner head is not adjoined downstream by any flame pipe that would
hinder the lateral propagation of the incoming air jets or the
external recirculation.
[0028] The mixing temperature of the incoming air, exhaust gas and
fuel vapor must, in a first phase until the complete evaporation of
the fuel, remain below the ignition temperature of this mixture;
that is, the recirculation quantity must not be too high. An overly
small recirculation quantity, conversely, would mean inadequate
evaporation and therefore suboptimal combustion and relatively high
pollutant values. Not until the three components have formed a
homogeneous gas mixture should the ignition be initiated, with a
second recirculation of gases that are as hot as possible.
[0029] With the aforementioned first recirculation of not
excessively hot exhaust gases, the thermal energy required for
evaporation is furnished. The admixing of this exhaust gas lowers
the oxygen content of the mixture and requires a flow distance that
creates a spacing between the root of the flame and the blocking
disk. The mixture ratio determines the gasification and combustion
temperature. The impetus generated by the air guidance and the
injected fuel generates suction and least to a first external
recirculation of hot combustion gases. This flow of hot gas is
aspirated inward between the incoming air jets. The first hot-gas
recirculation flow, together with the incoming air, consequently
forms an annular flow that propagates in cup-shaped fashion and
rotates about its center axis. The spreading apart of the laminar,
turbulent shear flow of the delivered incoming air into the
combustion chamber and the hot gases fanned out between the
incoming air jets creates a further underpressure zone in the
center axis, which causes the internal hot-gas recirculation.
Liquid fuel is injected into the hot gases of the internal
recirculation and into the cup-shaped flow. The hot gases of the
internal recirculation gradually mix with the cup-shaped flow. The
cup-shaped flow comprises an increasingly flammable mixture that
comes into contact on all sides with hot combustion gases and mixes
with them. Because of this mixing, the temperature of the mixture
rises to above the ignition temperature. The flame therefore burns,
with innumerable tongues of flame to all sides, inward and outward,
in countercurrent to a second hot-gas recirculation. The combustion
takes place with a blue, low-NOx hollow-conical flame and with NOx
values that are at the limit of what is theoretically feasible, and
moreover with a low level of sound.
[0030] A further advantage of the burner and the method is that the
burner and the method can be employed with natural gas as the fuel.
The gas may be admixed with the incoming air in the region of the
blocking disk, in the incoming air conduit between the fan and the
blocking disk, or on the intake side of the fan. With gas as the
fuel, the evaporation of the fuel is eliminated. Mixing in hot
recirculated gases raises the temperature of the mixture while
simultaneously reducing the oxygen concentration. A decisive aspect
here is the attainment of a completely homogeneous mixture in the
mixing zone, before the combustion is brought to ignition by the
second hot-gas recirculation at a distance from the blocking
disk.
[0031] The burners for oil and gas can be combined in a dual-fuel
burner. There is also the possibility of a further combination of a
fuel, such as coal dust, in high-power combustion
installations.
[0032] The stable internal flow conditions result in a very calm,
non-flickering flame, which decisively lessens both noise emissions
and the inducement of pressure pulsations in the chimney.
[0033] A burner head for disposition on the end of an incoming air
conduit of a blue-flame burner has a blocking disk that closes off
the incoming air conduit on the downstream end. In the blocking
disk, there are a plurality of spaced-apart openings arranged in a
ring. These openings serve to split up a majority of the incoming
air, advantageously over 70% of it, into incoming air jets. Guide
blades are provided at the openings. These blades serve to guide
each incoming air jet flowing out of the incoming air conduit
through an opening. They guide the incoming air jet in a direction
that diverges from the direction of the other incoming air jets.
Between the guide blades, blocking blades are embodied. With the
blocking blades, underpressure zone are achieved between the
incoming air jets. To enable the gas flow, in which the flame
develops, to develop unimpeded, the guide blades and the blocking
blades are advantageously the last flow-carrying parts, in terms of
the flow direction, before the flame.
[0034] The blocking blades and the guide blades are advantageously
embodied integrally with the blocking disk. The blocking blades are
advantageously embodied as trapezoidal. As a result, the blocking
blades, the guide blades, and the entire blocking disk can be cut
and shaped from a single piece of sheet metal. This makes the
production of the blocking disk very simple. Advantageously, the
guide blades adjoin the blocking blades along one edge, in
particular a bending edge, and at this edge the guide blades (23)
and blocking blades (27) form an angle of between 100.degree. and
160.degree., preferably between 110.degree. and 140.degree..
[0035] The openings are advantageously embodied around a central
body. In the case of an oil burner or a dual-fuel burner, the
central body is the oil nozzle. In a gas burner, the central body
has no further function. The central body helps to create a central
underpressure zone and already guides the air even in the incoming
air conduit. The guide blades accompany the sip in the flow
direction of the incoming air. The edge of a given guide blade
accompanying the central body forms an angle with a jacket line of
the central body.
[0036] Advantageously, however, the guide blade does not rest
completely on the central body, so that a fine annular gap exists
around the fuel nozzle. This gap allows a light quantity of
incoming air to be delivered to the fuel stream through the annular
gap, which is advantageous in terms of the performance of the
burner during starting.
[0037] A blue-flame burner having an incoming air fan, an adjoining
incoming air conduit, a fuel delivery means, and an electric
ignition is equipped with a burner head. Such a burner has the
advantages that are specific to this burner head. The incoming air
fan is dimensioned to suit the burner power. The fuel delivery may
be assured by a gas delivery means upstream of the blocking disk,
and/or by an oil nozzle in the center of the blocking disk.
[0038] Such a burner is expediently built into a boiler. The boiler
has a boiler chamber which is advantageously subdivided by a heat
exchanger into a central combustion chamber and an exhaust gas
chamber encasing the combustion chamber parallel to the inflow
direction of the incoming air. Advantageously, the heat exchanger
is a gap coil heat exchanger. With gap coil heat exchangers, a high
yield of convection heat is attained. Such a gap coil heat
exchanger is therefore especially well suited to blue-burning
flames, which radiate little heat.
[0039] The advantages of the method and the burner head are
especially these: [0040] their low production costs, [0041] since a
flame cup or flame pipe and in general wearing parts of any kind
toward the combustion chamber, such as built-in interference-body
fixtures, etc., are eliminated, and [0042] thanks to very simple
construction for the air guide; [0043] their great ease of serving,
[0044] thanks to the preclusion of soiling of the burner head,
[0045] thanks to which there are no wearing parts in the combustion
chamber; and [0046] their extremely low pollution values: [0047]
NOx with oil, ca. 40 mg/kWh [0048] NOx with gas, ca. 20 mg/kWh.
[0049] The invention is described in further detail below in terms
of exemplary embodiments, in conjunction with the drawings. Shown
are:
[0050] FIG. 1, a longitudinal section through a yellow-flame burner
of the prior art;
[0051] FIG. 2, a view of the air pattern in such a yellow-flame
burner;
[0052] FIG. 3, a longitudinal section through a burner head
according to the invention in a burner pipe, without a flame cup
that meters the first recirculation;
[0053] FIG. 4, a longitudinal section through a burner head
according to the invention in a burner pipe, with a flame cup that
meters the first recirculation;
[0054] FIG. 5, a perspective view of an aperture plate with four
openings and with a fuel nozzle placed between them;
[0055] FIG. 6, a perspective view of an aperture plate with four
openings and with a fuel nozzle placed between them, and with
schematically shown incoming air jets;
[0056] FIG. 7, a longitudinal section through a burner head in a
burner pipe, with an aperture plate with five circular
openings;
[0057] FIG. 8, a front view of the burner head of FIG. 7;
[0058] FIG. 9, and aperture plate with six trapezoidal openings and
six trapezoidal blocking blades between them;
[0059] FIG. 10, a cross section through the aperture plate of FIG.
9, in which the blocking blades are located in a single plane;
[0060] FIG. 11, a cross section through the aperture plate of FIG.
9, in which the blocking blades are bent upward in the shape of
pyramid;
[0061] FIG. 12, a longitudinal section through a burner head of a
gas burner, schematically showing the flows of fresh air and hot
exhaust gases;
[0062] FIG. 13, a longitudinal section through a burner head of an
oil burner, schematically showing the flows of fresh air and hot
exhaust gases;
[0063] FIG. 14, a longitudinal section through a boiler and a
burner with a burner head of FIG. 13;
[0064] FIG. 15, a longitudinal section through a short boiler with
a coiled gap heat exchanger and a burner with a burner head adapted
to the given spatial conditions.
[0065] Elements that are approximately equivalent to one another in
function are identified in the drawings by the same reference
numerals, even if they differ in shape.
[0066] In FIGS. 1 and 2, a longitudinal section through a
yellow-flame burner 10 and a view of the flows in the region of the
flame of such a yellow-flame burner 10 are shown. The blocking disk
17 of the yellow-flame burner 10 of FIG. 1 differs in shape from
the blocking disk 17 shown in FIG. 2. Nevertheless, the flow
pattern for a burner 10 as shown in FIG. 1 is very similar to the
flow pattern shown in FIG. 2.
[0067] In the yellow-flame burner 10 of FIG. 1, a burner pipe 13
and a blocking disk 18 that closes off the burner pipe 13 on the
downstream end, upstream of combustion chamber 15, are shown in
section. An oil nozzle 19 and two ignition electrodes 21 (only one
of them is shown) are disposed in the burner pipe 13. The blocking
disk 17 has a central opening 20, and around this opening is a
blocking ring 22 with eight guide blades 23, and around this
blocking ring 22 is an annular opening 26. Large blocking blades 27
are disposed between the guide blades 23 and together with an outer
region of the blocking ring 22 they create an annular underpressure
zone 28 (FIG. 2). In the center of the annular underpressure zone
28, the primary proportion of the incoming air flows in the form of
a sharply pointed incoming air jet 30 into the combustion chamber
15. An incoming air jacket flows around the underpressure zone 28
into the combustion chamber 14. Because of the pressure differences
and the differences in the flow speed of the incoming air, there
are resultant recirculation flows 34 at the inner edge of the
underpressure zone 28. A slight quantity of incoming air flows into
the underpressure zone through the small slit openings 36 between
the guide blades and the blocking blades and causes a rotation of
the gases in the underpressure zone 28 around the central incoming
air jet 30. The fuel is injected into the incoming air jet 30 and
partly made turbulent by the recirculation flows 34 in the
underpressure zone. In the underpressure zone, the fuel burns under
conditions of oxygen deficiency. These flow and pressure conditions
keep the flame at the blocking disk. No further provisions are
therefore necessary to obtain a stable flame. However, such a
burner burns with a yellow flame, and at high combustion
temperatures and with high pollutant emissions values.
[0068] With the invention, success has now been achieved in
creating pressure and flow conditions in a blue-flame burner 11
that keep a stable, quiet, blue-burning flame floating in the
combustion chamber 15.
[0069] In the longitudinal sections through two burner pipes in
FIGS. 3 and 4, no oil nozzles 19 are shown. However, the location
of the oil nozzle 19 can be seen in later figures. The burner pipe
13 of FIGS. 3 and 4 forms an incoming air conduit for fresh air and
if need be natural gas. On the axis 31, which can be called the
axis of symmetry or the flame axis, the oil nozzle is located with
its nozzle opening approximately in the plane of the blocking disk
17.
[0070] The burner pipe 13 is closed off on the downstream end by a
blocking disk 17. The blocking disk 17 is composed of a retaining
ring 35 with a central opening and an aperture plate 37 that covers
the central opening of the retaining ring 35. The retaining ring is
hammered onto a sealing ring 39 on the downstream end of the burner
pipe 13, in terms of the flow direction of the incoming air. On the
retaining ring 35, there are two ignition electrodes 21 (in FIGS. 3
and 4, only one is shown) and a mount 41 for the fuel nozzle 19
(not shown). The mount 41 is not shown in section. A pipe 43 for
flame monitoring is also mounted on the retaining ring 35.
[0071] The aperture plate 37 is hammered onto the retaining ring in
the flow direction and firmly screwed to it. The aperture plate 37
is an approximately circular disk with a central opening for the
tip of the fuel nozzle 19 (see FIG. 5). In a ring around the
central opening, the sheet metal from which the aperture plate 37
is made is cut to size and shape with a laser. In the process,
twelve laminations are cut out, which can be bent over to form
guide blades 23. Half of the guide blades 23 are visible in each of
FIGS. 3 and 4. These guide blades 23 are each located at the edge
of an opening 45. The openings 45, alternating with blocking blades
27 disposed between the openings 45, form a ring around the fuel
nozzle. The guide blades 23 are joined to the blocking blades 27
via approximately radially extending bending edges 47. The guide
blades 27 are cut to size and shape such that in the bent-over
state of the guide blades, an inner edge of the blade extends
approximately parallel to an outer shape of the fuel nozzle 19. The
inclination of the guide blades to the blocking blades is
approximately 45.degree., in the examples shown in FIGS. 3-6. The
blocking blades 27 are located in a common plane.
[0072] In FIG. 4, the same arrangement as in FIG. 3 is shown, but
with one difference: In FIG. 4, there is additionally a short flame
pipe, for metering the quantity of recirculated hot gas. This flame
pipe 49 has the same diameter as the burner pipe 13. It is
manufactured in one piece with the burner pipe 13. Between the
flame pipe 49 and the burner pipe 13, an annular gap 41 is
embodied. This annular gap meters the recirculation of the exhaust
gases. A flame pipe of this kind may be provided in the burner
according to the invention. However, it is not necessary. In
practically any combustion chamber 15 and at any power level,
stabilization of the blue flame can be achieved even without a
flame pipe 49, by means of the choice of aperture plate and its
adjustment.
[0073] The aperture plate 37 in FIG. 5 has four openings 45 around
the central opening. Four blocking blades 27 are disposed between
these openings 45. The blocking blades 27 are trapezoidal. The base
of the trapezoid is located on an outer arc. The two converging
sides of the trapezoid extend approximately radially. The openings
have practically the same cross section as the blocking blades 27.
The guide blades 23 do have a larger surface area than the blocking
blades 27, but the opening 45 is smaller than the area of the guide
blades 23, since the guide blades 23 are not perpendicular to the
plane of the aperture plate. The bending edge 47 between the
blocking blades 27 and guide blades 23 forms one of the converging
sides of the trapezoid. The other side of the trapezoid of the
blocking blades 27 is formed by a cutting edge. This cutting edge
and the bending edge 47 are more convergent relative to the
blocking blades 27 than relative to the opening 45 between two
blocking blades 27.
[0074] In FIG. 6, the aperture plate shown in FIG. 5 is shown at a
shallower angle of view and is provided with schematically shown
incoming air jets. The aperture plate 37 has four openings 45, from
which incoming air flow out during operation of the burner. The
incoming air is split up by the blocking blades 27 and the guide
blades 23, as well as the fuel nozzle 19 (or some other central
body), into four incoming air jets 53. These incoming air jets 53
are shown here as transparent bodies. The enter through the
openings 45 in the aperture plate 37 at an angle of other than
90.degree. to the plane of the aperture plate 37 and of the
blocking disk 17. In the process, the incoming air jets 53 force
gases located downstream of the blocking blades 27 to be entrained
with them. The resultant underpressure aspirates gases from the
surroundings, so that a slower gas flow develops between each two
incoming air jets 53. These gas flows are essentially formed by hot
gases, which are exhaust gases from combustion and therefore poor
in oxygen. Between the laminar flows of incoming air and hot gases,
mixed zones occur. In these mixed zones, incoming air and exhaust
gases are mixed with one another. The incoming air flowing into the
underpressure zones from the incoming air jets 53 become turbulent
from the hot gases. As a result, the incoming air jets 53 are
consumed. They are therefore shown in the form of arms, each ending
in a tip. Since the incoming air jets 53 diverge, not only a
peripheral underpressure zone 55 between each two incoming air
jets, but also a central underpressure zone 57 between the incoming
air jets 53 on the axis 31 are created. These underpressure zones
55, 57 prevent the incoming air jets 53 from propagating in a
straight line. The underpressure zones keep these incoming air jets
53 together and therefore cause the flame to burn in a tuliplike
shape.
[0075] The liquid fuel is injected into the turbulent gas flows. It
does not matter that the oil droplets get into not only the hot
gases but also the incoming air flows. In both cases, the
gasification and evaporation (depending on the temperature of the
ambient gases) occur before the ignition of the fuel. The flame
therefore burns blue. It is suspected that the gas temperature
within the incoming air jets, and the oxygen and fuel
concentrations in the hot gases, are not high enough until the fuel
is already in the gaseous state. The temperature of the gases
increases with the distance from the blocking disk 17, because of
the inflow of hot gases in a secondary recirculation. The secondary
recirculation takes place both from the inside and from the outside
toward the cup shape of the flame.
[0076] Because of the pressure conditions that arise with the
peripheral underpressure zones on the one hand, which are built up
by the expelled incoming air and shrink toward the blocking disk
17, and the central underpressure zone on the other, which is
generated by the flowing apart of the incoming air jets and the hot
gases entrained with them, an equilibrium of the underpressure
zones develops. In this state of equilibrium, turbulence is brought
about, which predominates over the dynamics of the highly
thermodynamic process and lends stability to the flame. The
thermodynamic process proceeds primarily not from back to front in
the outflow direction, but from the flame interior in the direction
of the tip of the flame. The top of the flame, however, is long
located on a flame axis. Instead, there are innumerable tips of
flame on the inside and the outside of the cup-shaped flame.
Because of this, it must be suspected, the influence of the
thermodynamic process on the stability of the flame is partly
canceled out, so that the dynamics of the flows suffices to hold
the flame securely.
[0077] It must therefore be assumed that the shape of the openings
plays a subordinate role. Thus in FIGS. 7 and 8, a burner head is
shown in which five openings, each of them circular, are stamped
out of the aperture plate 37. The stamping encompasses an arc of
approximately 300.degree.. Over an angle of 60.degree. there is a
bending edge 47, along which the guide blade 23 is joined to the
aperture plate 37. The direction of the incoming air jets entering
through these openings 45 must, because of the guide blades 23, be
at an angle to the axes (not shown) of the openings in the aperture
plate 37. The incoming air jets are furthermore oriented at a
tangent to a circular cylinder containing the axes of the openings,
and the place where the incoming air jets have the least spacing
from the axis 31 is therefore located in the plane of the aperture
plate 37.
[0078] In FIGS. 9-12, two aperture plates 37 are shown, which have
six openings 45. The aperture plates are formed from one piece of
sheet metal, on the order of the aperture plates shown in FIGS.
3-6. The guide blades 23 are joined to the blocking blades 27 via a
bending edge 47. In FIGS. 9 and 10, the six blocking blades 27 are
shown flat and disposed in the same plane. In FIG. 11, however, the
blocking blades 27 are bend upward in the flow direction of the
incoming air. As a result, the resultant incoming air jets are
inclined outward. Because of the angling of the blocking blades 27,
the primary recirculation of the hot gases along the blocking disk
17 is effected with less turbulence to a greater depth between the
incoming air jets.
[0079] The guide blades 23 are bent counter to the flow direction
of the incoming air. The result is tearing edges, at which the
incoming air flow detaches and an underpressure develops. A nozzle
opening is provided centrally in the aperture plate 37. It is
advantageously made so large that there is a fine air gap all the
way around the nozzle.
[0080] In FIGS. 12 and 13, the flow pattern and the flame pattern
of the gas flame and the oil flame are shown. The two flow patterns
are identical. Only the fuel delivery is different. In FIG. 12, the
fuel delivery means is formed by a gas nozzle 18 in the plane of
the blocking disk 17. The gas outlet openings are oriented at an
angle of 45.degree. to the axis 31. The gas therefore enters into
the incoming air flowing past the gas nozzle 18 and enters the
flame along with the incoming air jets 53. However, gas may also be
delivered to the incoming air upstream of the blocking disk.
[0081] In contrast to this, oil is injected directly into the
combustion chamber 15. The oil first reaches the region of the
central underpressure zone 57. In the hot gases in the central
underpressure zone 57, a large proportion of the fuel evaporates in
an oxygen-poor environment. A subordinate proportion of the fuel,
in droplet form, penetrates the hot gases in the peripheral
underpressure zones 55 and is suspected also to penetrate the
incoming air in the incoming air jets 53. Despite the fact that it
must be suspected that oil droplets get into the incoming air jets
53, no yellow flame is produced. The flame burns extremely calmly
and stably and with an extremely blue color. It must be assumed
that the oil droplets entering the incoming air jets have already
been heated and therefore evaporate very quickly in the incoming
air jets, that the temperature of the incoming air in this region
is below the ignition temperature, and that the proportion of fuel
entering the incoming air jets that has not yet been gasified is
only slight.
[0082] As can be seen from FIGS. 12 and 13, the incoming air 61
from the incoming air conduit or burner pipe 13 arrives through the
openings 45 in the aperture plate 37 in the form of incoming air
jets 53 that enter the combustion chamber 15. The incoming air jets
53 are oriented, thanks to the guide blades 23. Between the
incoming air jets 53, the blocking blades 27 between the openings
45 create peripheral underpressure zones 55 in which it is
primarily hot gases from outside that are recirculating. The
incoming air jets 53 and these primarily recirculating hot gases 63
in the peripheral underpressure zones 55 form a laminar, turbulent
shear flow and mix with one another and form a cup-shaped, rotating
jacket flow 65 with a central contrary flow 67 of oxygen-poor hot
gases. Because the cup-shaped jacket flow 67 is made turbulent by
the secondarily recirculating hot gases 67, 69 from the central
underpressure zone 57 and the periphery, a homogeneous mixing of
hot gases, incoming air and fuel gases occurs, making very
harmonious combustion possible.
[0083] The expansion of the gases that occurs in the flame can
expand toward the axis 31 and outward. The dynamics resulting from
the thermal development therefore lose tension predominantly
annularly and radially toward the inside and outside. The incident
forces are thus to a great extent oriented counter to one another.
As a result, in terms of stabilizing the flame, the dynamics that
are axially losing tension between the incoming air jets 53 and the
underpressure zones 44, 47 remain dominant over the thermodynamic
processes that are developing radially.
[0084] In FIG. 14, the burner head of FIG. 13 is used in a
conventional boiler. The burner is equipped with a fan, an oil
pump, and an electronic ignition. The dynamics of the flows that is
attained by means of the blown-in incoming air in the combustion
chamber 15 of the boiler are not addressed in this description.
This is because the shape and side of the combustion chamber 15 has
to meet only a single condition: The combustion chamber must offer
room for the flame to develop. Certainly pressure conditions and
other parameters of the combustion chamber and boiler do influence
the behavior of the flame and the combustion. However, so far no
boiler has been found in which stable, low-polluting combustion of
oil or gas with the burner head described would not be successful.
The flame even burns in the open and under spatially very tight
conditions.
[0085] The boiler of FIG. 14 is designed for a lance-shaped flame
and therefor offers too much room in the direction of the axis 31.
Nevertheless, the combustion proceeds very cleanly, calmly and
stably. The exhaust gases are turned around and delivered to the
chimney through a heat exchanger.
[0086] In FIG. 15, a very short boiler is shown. A flame deflector
71 is located diametrically opposite the burner head. Until now,
the short dimensions of the combustion chamber 15 were achieved by
deflecting the flame back to its root with the flame deflector 71.
However, with the composition of the boiler shown, this flame
deflector 71 is no longer required. It merely has to divide the
combustion chamber 15 from a flue-gas chamber 73 downstream of the
flame deflector 71. The flame formed by the method of the invention
burns radially in a cuplike shape and has a very short lengthwise
development. It is therefore suitable even for very short
combustion chambers 15.
[0087] In the boiler shown in FIG. 15, which is a wall-mounted
unit, a gap coil heat exchanger 75 is provided, which cylindrically
encases the combustion chamber 15. Between the gap coil heat
exchanger 75 and the wall of the boiler, a
cylindrical-jacket-shaped exhaust gas chamber 77 is formed. This
exhaust gas chamber is separated from the flue-gas chamber 73 by
the first several windings of the gap coil heat exchanger. The
flue-gas chamber 73 has an opening in a flue 79. The flue 79 has a
plastic pipe with an integrated fresh-air conduit 81.
[0088] The fresh air is aspirated through the fresh-air conduit 81
in countercurrent to the flue gas in the flue 79. With the fan 83,
the incoming air is guided through a very short burner pipe 13 to
against the blocking disk 17. With the aperture plate 37 in the
blocking disk, incoming air jets 53 are formed, which flow into the
combustion chamber 15. In the lee of the blocking blades 27 of the
aperture plate 37, peripheral underpressure zones form between the
incoming air jets 53 and a central underpressure zone 57 forms in
the center. The injected heating oil vaporizes/evaporates in
secondarily recirculated hot gases in the central underpressure
zone 57 and together with these hot gases is mixed into the
tulip-shaped jacket flow 65 made up of incoming air and primarily
recirculated hot gases and is burned in a blue flame. The resultant
hot gases are partly recirculated and escape from the combustion
chamber 15 into the exhaust gas chamber 77 between the gap coils of
the heat exchanger 75. In the process, they give up a majority of
their thermal energy to the heat exchanger by convection. These
already cooled exhaust gases pass through the gap coil heat
exchanger 75 a second time and enter the flue-gas chamber 73. Since
the supply line for the medium flowing in the heat exchanger is
provided in the region of the flue-gas chamber 73 and the diversion
of the medium is provided in the region of the burner head, the
exhaust gases flow first through a hotter region of the heat
exchanger and in the second pass through it flow through a cooler
region. After that, the cooled flue gases enter the flue and cool
down the aspirated fresh air before they escape into the
atmosphere.
[0089] In the following table, parameters for seven examples of
aperture plates of burner heads of the invention are listed. The
aperture plates are embodied on the order of the aperture plate of
FIG. 5. The burner heads are designed for power levels of 16 to 700
kW. The rings of openings in the aperture plates have an outer
diameter of 27 to 80 mm and therefore a circumference of 84.8 to
251.2 mm.
[0090] In experiments burners for high power levels, it has been
demonstrated that a smaller number of openings and blocking blades
is preferable to a larger number. The number of four openings and
for blocking blades has proved suitable for all power levels. A
division by four has therefore been used for all the examples. The
dimensions of the blocking blades and of the openings between the
blocking blades are arrived at as follows. The terms are given in
FIG. 5. The length of the shorter side of the trapezoid of the
blocking blades, which adjoins the fuel nozzle, is marked A. C is
the width of the base of the trapezoid of the blocking blades. H is
the greatest width between two adjacent blocking blades 27. This is
the spacing of the bending edge and the cutting edge, diametrically
opposite it relative to the opening, at their points of
intersection with the circumferential circle of the ring of
openings. H/C represents the ratio of the dimensions H and C on the
circumferential circle. This ratio is approximately equivalent to
the ratio of the cross-sectional areas of incoming air jets and
underpressure zones. This ratio varies approximately inversely
proportionately to the dynamic pressure P of the incoming air. The
rated values for the fans are indicated in millibars in column P.
Despite major differences in terms of power (1:45), the ratio of C
to H (1:5), and the dynamic pressure of the incoming air (1:4), the
product of P(mbar) and C/H for the burners is within relatively
narrow limits between 7.3 and 11.7 (1:1.6). TABLE-US-00001 POWER O
P*C (kW) DIAMETER PITCH A C H CURCUMFERENCE H/C P(mbar) H 16 27 4 2
12 9 84.8 1:1.3 9 11.7 22 30 4 2 13 10.5 94.2 1:1.24 7.5 9.3 28 35
4 2 14 13.5 109.9 1:1.04 7.5 7.8 45 40 4 2 16 15.4 125.6 1:1.04 9
9.4 70 45 4 2 18 17.3 141.3 1:1.04 10.5 10.9 250 60 4 2 15 32.1
188.4 1:0.47 17 8 700 80 4 2 13 49.5 251.2 1:0.26 18 7.3
[0091] In summary, a burner head in an aperture plate 37 has at
least two and preferably four openings 45 in an aperture plate 37,
with uniformly inclined guide blades 23 for the delivery of
incoming air to a combustion chamber 15 in the form of incoming air
jets 53. Between the openings 45, blocking blades 27 are embodied,
for forming peripheral underpressure zones 55 between the incoming
air jets 53. The incoming air jets 53 are deflected by the guide
blades 23 into a position that is inclined relative to a common
center axis 31. The incoming air jets 53 therefore diverge and as a
result create a central underpressure zone 57 about the axis 31
between the incoming air jets 53. By means of the central
underpressure zone and the inclination of the incoming air jets
relative to the center axis, a rotation of the incoming air about
the center axis 31 is achieved. In operation of the burner, hot
gases from outside are aspirated into the peripheral underpressure
zones 55 and, counter to the flow direction of the incoming air,
into the central underpressure zone 57 between the incoming air
jets 53. These flow conditions create ideal conditions for the
combustion of gaseous, liquid and/or particulate fuel in a calm,
cool, low-polluting flame. This combustion is practically
independent of the size and shape of the combustion chamber and of
the pressure conditions in the combustion chamber. This combustion
method and such apparatuses are suitable for combustion
installations of 16 kW to 1000 kW, or more.
* * * * *