Note: Descriptions are shown in the official language in which they were submitted.
B~JRNER FOR DIESE:L }~GI~3 EX}IAIJST GAS
PARTICI.}3 FILTE~
The invention relates to a burner for producing the
heat required for thermal regeneration of particle
filters for diesel engine exhaust gas.
As generally known, the exhaust gas of diesel engines
contains particles consisting mainly of soot. Endea-
vors are being made for finding practicable ways of
retaining these particles before the diesel engine
exhaus~ gas is blown into the environment, and the
most promising approach in this respect are particle
filters in the exhaust gas line of the particular
diesel engine. However, it has turned out that the
particle filters become increasingly clogged already
after relatively short times of operation of the
diesel engine, so that the particle filters must be
freed from the particles retained therein in rela-
tively short time intervals. To this end, the thermal
regeneration of particle filters is known in which,
for one regeneration phase each, the temperature at
the particle filter is increased, i.e. usually brought
to at least 650 to 700 C, by supply of heat from a
burner, such that the particles retained in the par-
ticle filter burn off.
The technically as ad~antageous as possible design of
burners for thermal regeneration of particle filters
~ b ~3
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is problematic. A particular difficulty re~ides in
that the burners during the regeneration phase as a
rule must produce a greatly differring amount of heat
per unit of time, which in essence depends on the
exhaust gas quan~ity produced at the particular moment
per unit of time and the temperature of the exhaust
gas in the region of the particle filter, with the
exhaust gas quantity per unit of time in turn being
dependent on the instantaneous speed of the diesel
engine. Another difficulty resides in that a~ least at
certain times during the regeneration phase, the pro-
duction of very high amounts of heat by the burner is
necessary. The difficulties mentioned make themselves
particularly felt in diesel engines of large volume,
as used e.g. in trucks or busses, especially since the
burner should also be as compact and space-saving as
possible.
It is the object of the invention to provide a burner
~or producing the heat required for thenmal re~enera-
tiOIl of particle filters for diesel engine exhaust
gas, the calorific output of which can be regulated in
a very wide range and which provides a maximum calori-
fic output while being of compact construction.
To meet this object, the burner according to the
invention is characterized in
(a) that it has a main combustion chamber in the
peripheral wall of which are provided a fuel
upply opening for a fuel main quantity and a
combustion air supply opening for a combustion
air main quantity;
(b) that a precombustion chamber is at~ached to the
combustion chamber floor of the main combustion
chamber;
(c) that a projecting hollow connecting piece is
provided on said peripheral wall of the precom-
- 3 ~
bustion chamber, in which an electrical ignition
means is disposed and which has a fuel supply
opening for a fuel basic quantity; and
(d) that a combustion air supply opening for a com-
bustion air basic quantity is provided in said
peripheral wall of the precombustion chamber.
A basic calorific output - which preferably can be
regulated - is produced in the precombustion chamber,
and the combustion chamber floor and the peripheral
wall of the main combustion chamber are brought to or
held at high temperatures by said basic calorific
output. The main combustion chamber does not have an
electrical ignition means of its own. Rather the fuel-
air mixture of the main combustion chamber ignites by
the hot combustion chamber floor thereof. Conse-
quently, the fuel supply and the combustion air supply
to the main combustion chamber can be varied within
wide ranges so that an in total extremely large calo-
rific output control or regulating range of the burner
results.
The burner according to the invention is intended
primarily for the so-called full-flow regeneration of
particle filters. Full-flow regeneration takes place
during operation of the diesel engine, with the burner
producing so much heat in controlled manner that the
exhaust gas entering the particle filter has such a
high temperature that the particle filter is thermally
regenerated.
Preferably the combustion air supply opening of the
main combustion chamber and/or the combustion air
~upply opening of the precombustion chamber i~ con-
nected to one combustion air blower each or to a
common combustion air blower. In addition thereto, it
is preferred that these combustion air blowers or this
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common combustion air blower, respectively, be de-
signed such that the amount of delivered air per unit
of time is a function of the speed of the diesel
engine having associated therewith the particle filter
to be regnerated, so that at higher speeds of the
diesel engine the amount of air delivered is higher,
and vice versa, with substantial proportionality
between the speed of the diesel engine and the (parti-
cular) air delivery quantity being preferred. This
dependency of the air delivery quantity on the diesel
engine speed may be realized e.g. by a blower of
variable speed, which in particular may be driven
mechanically by the diesel engine. Another possibility
consists in providing electric blowers whose speed can
be regulated. Still a further possibility consists in
providing a location with controllably variable flow
cross-section somewhere in the flow path of the com-
bustion air from the (respective) combustion air
blower to the respective combustion air supply
opening.
The fuel supply opening of the main combustion chamber
and/or the fuel supply opening of the precombustion
chamber preferably is connected to a means of its own
or to a common means for supplyiny fuel under
pressure or also in nearly unpressurized manner. This
means is preferably constituted by a fuel pump that is
driven mechanically by the diesel engine or is driven
elec~ricall~. It is preferred furthermore that this
means be designed such that the amount of fuel de-
livered per unit of time is a function of the speed of
the diesel engine having associated therewith the
particle filter to be regenerated. Preferred possi-
~ilities are in this respect again a means of con-
trolled variable speed and a location with controlled
variable cross-section of flow; in this respect, re-
ference is made in addition to the statements made
~r~
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hereinbefore in conjunction with the combustion air
supply.
Finally, it is preferred to design the means for
supplying the fuel main quantity such that its fuel
delivery quantity - preferably in addition to the
dependency on the diesel engine speed - is a function
of the exhaust gas temperature in the region of the
particle filter. In this manner, the exhaus~ gas
temperature can be regulated excactly to the required
regeneration temperature.
It is pointed out that the term ~'periphexal wall" used
in claim 1 is not to be understood as a restriction to
a substantially cylindrical configuration of the main
combustion chamber and the precombustion chamber,
although such a configura~ion is preferred.
The in~ention and developments of the invention will
now be elucidated in more detail by way of an embodi-
ment shown in the drawings in which
ig. 1 shows a burner for a particle filter as seen
in a longitudinal sectional view along the
axis thereof;
ig. 2 shows a schematic view of the arrangement of
the burner of Fig. 1 on the particle filter.
The burner 2 shown in Fig. 1 comprises a substantially
cylindrical main combustion chamber 4 and a substan-
tially cylindrical precombustion chamber 6 which is,
but not necessarily has to be, of smaller diameter
than the main combu~tion chamber 4. The precombustion
chamber 6 has its downstream open end portion a in-
serted in the combu~tion chamber floor 10 of the main
-- 6
combustion chamber 4, which has a corresponding
opening there, the end portion 8 of the precombustion
chamber 4 projecting a distance into the main com-
bustion chamber 4. The main combustion chamber 4 and
the precombustion chamber 6 are provided with a common
aligned axis 12. On the right side in Fig. 1, the main
combustion chamber 4 has its downstream open end
portion 14 that is connected to the particle filter
proper (cp. Fig. 2).
On the outside of the main combu tion chamber 4 there
is provided an annular flange 16 by means of which the
burner 2 can be secured for instance to the associated
particle filter.
Mounted radially in the peripheral wall of the main
combustion chamber 4 is a ~uel supply connecting piece
18 having a nozzle-like opening 20 near its end on the
side of the combustion chamber. Near said nozzle 20, a
combustion air line opens into the peripheral wall of
the main combustion chamber 4, having its combustion
air supply opening 22 directed substantially in
tangential direction. The combustion air supply
opening 22 and the fuel nozzle 20 are located a short
distance downstream in axial direction from the down-
stream end o~ the precombustion chamber.
A further combustion air line opens into the peri-
pheral wall of the precombustion chamber 6, having a
combustion air supply opening 24 directed substan-
tially in tangential direction. The combustion air
supply opening 24 has a smaller cross-section of flow
than combustion air supply opening 22. Upstream of the
combustion air supply opening 24, i.e. further to the
left in Fig. 1, ~he precombustion chamber has a
radially attached hollow connecting piece 26 into
which a glow plug 28 as electrical ignition means i9
r
threadedly engaged from the outside. A fuel line 32
having a fuel supply opening 34 opens into an annular
space 30 between the helically wound filament of the
glow plug 28 and the inner circumference of the con-
necting piece ~6. The fuel supply opening 34 in the
connecting piece 26 or to the precombustion chamber 6
is of smaller cross-section of flow than the fuel
supply opening 20 or nozzle to the main combustion
chamber 4.
~iquid fuel, eOg. diesel fuel, entering through the
fuel ~upply line 34 is ignited in the region of the
glow plug 28 and burns together with combustion air
entering through supply opening 24. In doing so, the
combustion flame may be restricted to the interior of
the precombustion chamber 6 or may extend a distance
into the main combustion chamber 4. The end portion of
the precombustion chamber 6 projecting into the main
combustion chamber 4, as well as the radially adjacent
remainder of the combustion chamber floor 10 of the
main combustion chamber 4 are at a high temperature
due to the combustion described. The amount of fuel
supplied to precombustion chamber 6 is referred to as
fuel basic quantity, and the amount of combustion air
supplied to the precombustion chamber 6 is referred to
as combustion air basic quantity.
Fuel fed through said nozzle 20 to the main combustion
chamber 4 evaporates in the hot upstream end portion
of the main combustion chamber 4 and is mixed with the
combustion air supplied through supply opening 22 and
is ignited by the combustion gases from precombustion
chamber 6 or by the hot end portion 8 of the precom-
bustion chamber. The amount of fuel supplie~ through
said nozzle 20 i~ referred to as fuel main quantitiy,
and the amount of combu~tion air supplied through
.~ .. . . ... . . . ... ..
mouth opening 22 is referred to as combustion air main
quantity.
Fig. 2 displays the manner in which the afore-de-
scribed burner 2 is attached to a substantially cylin-
drical particle filter 40 on the face ~ide thereof, 30
as to be aligned with the longitudinal axls of the
particle filter 40. The particle filter housing has a
particle filter body 42 disposed therein, which is
provided for in~tance in the foxm of a ceramic filter
body. The exhaust gas of a diesel engine flows through
an exhaust gas line 46 into a space 44 upstream of
filter body 42. The exhaust gas is discharged from the
particle filter 40 through an exhaust gas line 4a
leading away from the face side thereof. The main
combustion chamber 4 of the burner 2 opens into the
space 44, and the burner 2 i9 attached on the face
side of the particle filter 40 located opposite the
discharging exhaust gas line 4a.
Fig. 2 depicts furthermore a blower 50 connected, via
lines 52 and 54, to the afore-described combustion air
supply openings 22 and 24. Furthermore, a fuel pump 56
can be seen connected, via fuel lines 58 and 60, to
the afore-described fuel supply openings 20 and 34. In
fuel line 58 leadi~g to the fuel supply opening 20 of
the main combustion chamber 4, there is disposed a
regulating or control valve 62. Finally an electric
control device 64 can be seen, having connected
thereto a temperature sensor 66 in space 44 of the
particular filter 44, the blower 50, the fuel pump 56,
and the control valve 62.
The blower 50 and the fuel pump 56 are designed such
that they deliver a combu3tion air quantity and fuel
quantity, respecti~ely, that increa es with increasing
speed of the die~el engine having the paxticle filter
~:s ' J~
g
40 associated therewith. The amount of fuel 3upplied
per unit of time through the fuel 9upply opening 20 of
the main combustion chamber 4 can be regulated
furthermore by means of the control valve 62.
It i8 pointed out that a separate blower each may be
provided for each combustion air line 52 and 54 and
that a separate fuel pump each may be provided for
each fuel line 58 and 60. Furthermore, it i~ pointed
out that it i9 indeed possible to operate the precom
bustion chamber 6 with an uncontrolled, i.e. constant,
combuskion air quantity and fuel quantity in term~ of
time.
