U.S. patent application number 11/719578 was filed with the patent office on 2009-09-03 for burner for a heater with improved baffle plate.
This patent application is currently assigned to Webasto AG. Invention is credited to Michael Poehner, Jan Steffens, Steffen Weber, Friedrich Widemann.
Application Number | 20090220902 11/719578 |
Document ID | / |
Family ID | 35976457 |
Filed Date | 2009-09-03 |
United States Patent
Application |
20090220902 |
Kind Code |
A1 |
Poehner; Michael ; et
al. |
September 3, 2009 |
BURNER FOR A HEATER WITH IMPROVED BAFFLE PLATE
Abstract
A burner (10) for a heater, especially for use in motor
vehicles, with an essentially axially symmetrical combustion
chamber (22) and a baffle plate (36) which is located in the
combustion chamber. The baffle plate (36) has a defined curvature
in an axial direction and that there is a curvature in the
direction of the burnout zone (32). An outer periphery of the
baffle plate defines a plane and a maximum axial distance of the
baffle plate from this plane D.sub.m and the diameter of the baffle
plate B.sub.d have dimensions that have a ratio D.sub.m:B.sub.d
relative to each other that is between 0.07 and 0.21.
Inventors: |
Poehner; Michael; (Muenchen,
DE) ; Widemann; Friedrich; (Muenchen, DE) ;
Weber; Steffen; (Anklam, DE) ; Steffens; Jan;
(Mittelstetten, DE) |
Correspondence
Address: |
ROBERTS MLOTKOWSKI SAFRAN & COLE, P.C.;Intellectual Property Department
P.O. Box 10064
MCLEAN
VA
22102-8064
US
|
Assignee: |
Webasto AG
Stockdorf
DE
|
Family ID: |
35976457 |
Appl. No.: |
11/719578 |
Filed: |
November 16, 2005 |
PCT Filed: |
November 16, 2005 |
PCT NO: |
PCT/DE2005/002059 |
371 Date: |
May 6, 2009 |
Current U.S.
Class: |
431/171 ;
431/258 |
Current CPC
Class: |
F23D 9/00 20130101; F23D
11/24 20130101; F23D 2900/11401 20130101; F23D 11/408 20130101;
F23D 11/406 20130101 |
Class at
Publication: |
431/171 ;
431/258 |
International
Class: |
F23M 9/06 20060101
F23M009/06; F23Q 7/06 20060101 F23Q007/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2004 |
DE |
10 2004 055 487.0 |
Claims
1-13. (canceled)
14. Burner for a heater for use in motor vehicles, comprising: an
essentially axially symmetrical combustion chamber, and a baffle
plate which is located in the combustion chamber, wherein: the
baffle plate has a defined curvature in an axial direction toward a
burnout zone of the combustion chamber.
15. Burner as claimed in claim 14, wherein an outer periphery of
the baffle plate defines a plane and a maximum axial distance of
the baffle plate from said plane D.sub.m and the diameter of the
baffle plate B.sub.d have dimensions that have a ratio
D.sub.m:B.sub.d relative to each other that is between 0.07 and
0.21.
16. Burner as claimed in claim 15, wherein the ratio
D.sub.m:B.sub.d is about 0.14.
17. Burner as claimed in claim 15, further comprising a burner
nozzle for supplying fuel and primary air, a heat shield between
the burner nozzle and the combustion chamber, the heat shield
having openings with air guide elements for supplying secondary air
to the combustion chamber.
18. Burner as claimed in claim 17, wherein the air guide elements
are tabs which are integral parts of the heat shield and which
project toward the combustion chamber.
19. Burner as claimed in claim 18, wherein the tabs comprises
groups of tabs, the tabs of one of the groups having a different
angle relative to the surface of the heat shield than the tabs of
another group
20. Burner as claimed in claim 19, wherein the tabs comprises
groups of tabs, the tabs of one of the groups being located on the
heat shield at a different radial distance than the tabs of another
groups.
21. Burner as claimed in claim 18, wherein the tabs comprises
groups of tabs, the tabs of one of the groups being located on the
heat shield at a different radial distance than the tabs of another
groups.
22. Burner as claimed in claims 17, wherein the tabs are located on
the heat shield at the same radial distance.
23. Burner as claimed in claim 17, wherein the burner has a
starting zone and a burnout zone and wherein air guide elements are
adapted to cause secondary air supplied to the burnout zone to have
a higher angular momentum than secondary air which is supplied to
the starting zone.
24. Burner as claimed in claim 17, wherein the heat shield has an
opening for through which an ignition element is inserted.
25. Burner as claimed in claim 17, wherein the burner nozzle has a
fuel needle for supplying fuel to the burner and a primary
combustion air supply to the burner and wherein the fuel needle has
an inside diameter for producing an exit speed of the fuel during
the starting phase of the burner by which fuel in essentially
unatomized form reaches the starting zone.
26. Burner as claimed in claim 25, wherein the inside diameter of
the fuel needle is between 0.5 mm and 0.7 mm.
27. Burner as claimed in claim 25, wherein the inside diameter of
the fuel needle is about 0.6 mm.
28. Burner as claimed in claim 25, wherein the starting zone is a
starting chamber into which an ignition element projects.
29. Burner as claimed in claim 14, further comprising a burner
nozzle for supplying fuel and primary air, a heat shield between
the burner nozzle and the combustion chamber, the heat shield
having openings with air guide elements for supplying secondary air
to the combustion chamber.
30. Burner as claimed in claim 29, wherein the air guide elements
are tabs which are integral parts of the heat shield and which
project toward the combustion chamber.
31. Burner as claimed in claim 30, wherein the tabs comprises
groups of tabs, the tabs of one of the groups having a different
angle relative to the surface of the heat shield than the tabs of
another group
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] The invention relates to a burner for a heater, especially
for use in motor vehicles, with an essentially axially symmetrical
combustion chamber, and a baffle plate which is located in the
combustion chamber.
[0003] 2. Description of Related Art
[0004] Burners of the initially mentioned type, which are also
called atomization burners or spray burners, are used especially in
auxiliary heaters and engine independent heaters for motor
vehicles.
[0005] There are numerous requirements for these burners,
especially with respect to reliable and largely emission-free
starting behavior and stable combustion operation. Furthermore, an
effort is made to build heaters which can be used in different
installation positions.
[0006] With respect to starting behavior, various operating
parameters must be matched to one another. On the one hand, it is
necessary during burner starting to make available a relatively
rich fuel-air mixture in the starting zone, on the other hand,
however, making available a sufficient amount of primary combustion
air is necessary to ensure transport of fuel from the fuel needle
to the starting zone.
[0007] The requirement of allowing different installation positions
of the heater is associated with problems relating to starting
behavior. In order to be specifically able to transport fuel into
the starting zone with little primary air supply, in the past,
orienting the fuel needle with the outlet opening pointed down had
to be tolerated; this resulted in the entire burner having to be
mounted in a vertical installation position.
[0008] To ensure stable combustion operation of the burner,
likewise, mutually contradictory requirements must be satisfied. On
the one hand, good intermixing of the fuel and air is always
required, but, on the other hand, in the core region of the flame,
especially during the starting phase, it is undesirable to cause
overly high air proportions and overly high swirling.
SUMMARY OF THE INVENTION
[0009] The object of the invention is to overcome the described
problems of the prior art at least in part and especially to enable
reliable and low-emission starting behavior with little dense smoke
in different installation positions.
[0010] This object is achieved with a burner for a heater for use
in motor vehicles, that has an essentially axially symmetrical
combustion chamber, and a baffle plate which is located in the
combustion chamber, by the baffle plate having a defined curvature
in an axial direction toward a burnout zone of the burner.
[0011] The invention is based on a generic burner in that the
baffle plate has a defined curvature into the axial direction and
that there is a curvature in the direction of the burnout zone.
Based on the curvature of the baffle plate there is defined shaping
of the baffle plate which is independent of temperature. For the
baffle plates of the prior art, which are made flat, this is among
others not the case since depending on the temperature spontaneous
changes of shape can occur which can adversely affect the
combustion behavior of the burner. By arching the baffle plate in
the direction of the burnout zone, sufficient space is provided in
the region of the starting chamber. Furthermore, it has been found
that the curvature in the direction of the burnout zone does not
have an adverse effect on the flow behavior in this zone. In
particular, the pronounced swirled backflow region is maintained in
the radially inside region of the burnout zone.
[0012] According to one preferred embodiment of the invention, it
is provided that the outer periphery of the baffle plate defines a
plane and that the ratio between the maximum axial distance of the
baffle plate from this plane and the diameter of the baffle plate
is between 0.07 and 0.21. The most heavily arched point of the
baffle plate is preferably essentially in the center of the
arrangement with respect to the radial coordinate. From the plane
which is defined by the outer periphery of the baffle plate, this
point has an axial distance which is defined by the indicated ratio
to the diameter.
[0013] In this connection, it is especially preferred that the
ratio between the maximum axial distance of the baffle plate from
the plane and the diameter of the baffle plate is roughly 0.14. For
example the round diameter of baffle plate is roughly 40 mm, while
the curvature has a value of roughly 5.7 mm.
[0014] According to one especially preferred embodiment of the
invention, it is provided that there is a burner nozzle for
supplying fuel and primary air, that there is a heat shield between
the burner nozzle and the combustion chamber, the heat shield
having openings for supplying secondary air to the combustion
chamber and that the openings are provided with air guide elements.
A heat shield is fundamentally useful to shield the nozzle and the
fuel supply against the heat energy present in the combustion
chamber. Furthermore, secondary air is supplied to the combustion
space via the heat shield. By the openings for secondary air supply
being provided with air guide elements, this secondary air can be
supplied in a controlled manner so that combustion operation, both
with respect to starting operation and also for continuous
operation, can be influenced in a specific manner.
[0015] It is useful for the air guide elements to be formed by tabs
which are made integrally with the heat shield and which project in
the direction of the combustion chamber. This heat shield can be
easily produced, for example, by the tabs being formed with a
v-shaped punching tool and being bent out of the plane of the heat
shield after or with the punching process.
[0016] The invention is also usefully developed in that the tabs
are made at different angles to the surface of the heat shield
and/or to the radius of the heat shield. If the tabs extend almost
perpendicularly to the radius of the heat shield, they deliver
strong angular momentum, while tabs with a smaller angle relative
to the radius deliver smaller angular momentum. Tabs which assume a
small angle relative to the surface of the heat shield produce air
flows which have a large radial component and a small axial
component, while for tabs with large angles relative to the surface
of the heat shield, the axial component dominates. In this way, it
is possible to route secondary air with low angular momentum into
the core region of flame formation. Thus, on the one hand, the air
required for combustion is supplied; but there is no excess angular
momentum which would adversely affect stabilization of the flame.
In particular, the secondary air can be divided depending on the
alignment of the individual air guide elements.
[0017] According to another embodiment it is provided that the tabs
are grouped at essentially identical angles to the surface of the
heat shield and/or to the radius of the heat shield. Defined flow
states in the combustion chamber are formed by the collective
alignment of the tabs.
[0018] The invention is also usefully executed such that the burner
has a burnout zone and that the secondary air which is supplied to
the burnout zone has higher angular momentum than the secondary air
which is supplied to the starting zone. High angular momentum is
desired in the burnout zone. In particular, a radially inner
swirled backflow region improves burnout and effectively uses the
combustion chamber volume.
[0019] Furthermore, the heat shield has an opening for routing an
ignition element through.
[0020] According to an especially preferred embodiment of the
invention, it is provided that the burner nozzle has a fuel needle
for supplying fuel to the burner and a primary air supply for
supplying combustion air to the burner and that by choosing the
inside diameter of the fuel needle, the exit speed of the fuel is
predetermined such that, during the starting phase of the burner,
fuel in essentially unatomized form reaches the starting zone. By
reducing the inside diameter of the fuel needle compared to fuel
needles in the heaters of the prior art, at the same fuel delivery
volume, the exit speed of the fuel is increased. In this way, for
any installation position, it is possible for the fuel jet to reach
the starting zone from the exit opening of the fuel needle. In
particular, for a small primary air amount, for which the supplied
primary air should have only low angular momentum, an essentially
unatomized fuel jet can reach the starting zone. Consequently, the
burner starts reliably and formation of dense smoke during starting
is distinctly reduced.
[0021] It is preferred that the inside diameter of the fuel needle
is between 0.5 mm and 0.7 mm. Compared to exit speeds for fuel
needles of the prior art in which the inside diameter is in the
region of 0.8 mm, the exit speed for inside diameters between 0.5
mm and 0.7 mm can be almost doubled or even more than doubled.
[0022] It is especially preferred that the inside diameter of the
fuel needle is roughly 0.6 mm. At this inside diameter, in full
load operation, i.e., at a fuel mass flow of 0.5 kg/h exit speeds
of more than 0.6 m/s are possible, while for an inside diameter of
0.8 mm, the exit speed is in the region of 0.35 m/s. The exit speed
in partial load operation rises accordingly, i.e., for a fuel mass
flow of 0.2 kg/h, from roughly 0.14 m/s to roughly 0.25 m/s. For a
corresponding choice of construction properties or of operating
parameters, the goal of an essentially unatomized jet which reaches
the starting zone when the heater is being started can be achieved
even with a conventional fuel needle with an inside diameter of
roughly 0.8 mm.
[0023] It is useful for the starting zone to be made as a starting
chamber into which an ignition element projects. The wall of the
combustion chamber can surround the ignition element in this way.
During starting operation, the "ballistic" fuel jet can then wet
the ignition element and the combustion chamber wall with fuel so
that the combustion chamber wall and adjacent components after
their heating are used as wall vaporizers.
[0024] The invention is based on the finding that the novel curved
baffle plate, especially in combination with the novel fuel supply
and the novel heat shield, can greatly improve the operating
behavior of a burner. This relates especially to the starting
behavior, the stability of burner operation and possibilities with
respect to the installation position of the burner in the motor
vehicle.
[0025] The invention is explained by way of example with reference
to the accompanying drawings using preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a sectional view of the burner in accordance with
the invention;
[0027] FIG. 2 is a perspective of a burner flange with the heat
shield inserted into it; and
[0028] FIG. 3 is a perspective of the heat shield.
DETAILED DESCRIPTION OF THE INVENTION
[0029] In the following description of preferred embodiments of the
invention, the same reference numbers label the same or comparable
components.
[0030] FIG. 1 shows a sectional view of the burner in accordance
with the invention. The burner 10 in accordance with the invention
has a nozzle 12 which is securely joined to the heat shield 24. The
heat shield 24 together with a burner tube 40 which is connected to
the heat shield 24 defines the combustion chamber 22. The burner
tube 40 is surrounded by an outer pipe 42 which forms the burner
flange. A flame tube 38 is attached to this outer pipe 42. The
connections between the heat shield 24 and the combustion chamber
pipe 40 or between the combustion chamber pipe 40, the outer pipe
42 and the flame tube 38 are generally welded connections. On the
fuel nozzle 12, there is the fuel supply 50 which has a metal pipe
52 for supply of fuel and a fuel needle 14 for injection of fuel
into the combustion chamber 22. Furthermore, in the region of the
fuel nozzle 16, there are channels for supplying primary combustion
air into the fuel nozzle 20 which flows past the fuel needle 14 in
order to then flow along the radial widening air guide of the fuel
nozzle 12 in the direction of the combustion chamber, and finally,
into the combustion chamber 22. The radial widening of the air
guide achieves improves atomization due to the Venturi effect.
Within the combustion chamber 22, there is also a baffle plate 36
which has an advantageous curvature. This curvature in the
direction of the burnout zone 32 is advantageous since, in this
way, heat-induced spontaneous changes in the shape of the baffle
plate 36 are prevented. By curving the baffle plate 36 in the
direction of the burnout zone 32, moreover, a sufficient space is
available for accommodating the starting chamber 18. The wall which
defines the starting chamber 18 is welded to the baffle plate
36.
[0031] FIG. 2 shows a perspective of a burner flange with the heat
shield inserted into it, and FIG. 3 shows a perspective of the heat
shield. Furthermore, reference is likewise made below to burner
components as shown in FIG. 1. The heat shield 24 has a central
opening 48 through which the fuel-air mixture is delivered from the
nozzle 12 and enters the combustion chamber. Also, there is a
laterally arranged opening 34 through which the ignition element 20
is inserted. On the heat shield 24, there are attachment pins 44,
46 to which the nozzle 12 is attached. The heat shield 24 also has
a host of openings 26 through which secondary air can enter the
combustion chamber 22. On the side of the heat shield 24 facing the
combustion chamber 22, there are triangular air guide elements 28,
30. They cause division of the secondary air based on the different
angles to the radius of the heat shield 24. A first group of air
guide elements with members 28 are aligned at a large angle
relative to the radius of heat shield 24, i.e., their alignment is
essentially or almost tangential. Based on this alignment, the
secondary air passing through the corresponding openings 26 with an
exit flow direction indicated by the arrow, and will overflow past
the baffle plate 36 into the burnout zone 32 with a high angular
momentum. This air which is provided with a high angular momentum
flows in the radially outlying region of the burnout zone 32 into
the posterior region of the combustion chamber 22, i.e., into the
region of the combustion chamber 22 which faces away from the heat
shield 24, and then, with high swirling in the central region, back
in the direction of the baffle plate 36. Consequently, advantageous
mixing of the gaseous components in the burnout zone 32 occurs.
[0032] Another group of air guide elements 30, in their alignment,
has a smaller angle relative to the radius of the heat shield 24.
These air guide elements 30 also have a smaller angle relative to
the surface of the heat shield 24 than the air guide elements 28.
Consequently, these air guide elements 30 route the secondary air
with a low angular momentum, in an exit flow direction indicated by
another arrow, into the core region of the flame; this especially
benefits stable combustion chamber behavior.
[0033] Thus, a novel spray burner results which is improved with
respect to the possible installation positions, the starting
behavior and behavior in continuous operation. Furthermore,
problems with respect to the temperature-induced changes of the
shape of the baffle plate are avoided.
[0034] The features of the invention disclosed in the above
specification and accompanying drawings are important to the
implementation of the invention, both individually and also in any
combination.
* * * * *