Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lQS~Z54
The present invention relates to industrial gas burners and more
particularly to silencers to be used with inspirating gas burners.
Inspirator type burners employ a gas orifice inserted close to the
throat of a venturi. Gas is discharged at pressures as high as 30 p.s.i.
through the orifice to create a low pressure area in the throat of the
venturi for entraining the combustion air. Actual burner pressures produced
by this type of mixing are quite low which means that large open areas are
required for the combustion air in order to avoid excessive pressure drop.
With such large areas, the noise generated by the high pressure, high
velocity gas can readily escape from the furnace. It is not unusual for the
high pressure jet to produce noise levels above 100 decibels.
This type of noise can be quite objectionable and is believed,
after prolonged exposure to levels above 90 decibels, to result in some loss
of hearing. Consequently, many furnace users are now specifying equipment
with low noise levels. ~ -
The present invention provides, for use with a burner having a
portion adapted to be inserted in a furnace wall and provided with a venturi
having an open bell spaced from said wall and means to discharge gas under -~
pressure into said bell thereby to aspirate air through said annular passage,
a sound absorbing device comprising a cylindrical casing having one end
closed, means to mount said casing surrounding and spaced from a said bell
with the closed end thereof facing the op~n end of the bell, a layer of sound
absorbing material lining the interior of said casing, a sleeve of sound
absorbing material adapted to be mounted on and to surround said bell, the
exterior of the sleeve and the interior of the casing lining forming an -
annular passage for primary air to the burner.
According to another aspect of the invention, there is provided,
for use with a burner having a venturi with a bell and means to discharge
gas under pressure into said bell thereby aspirating air through said annular
passage, the end of the bell being open, a sound absorbing device comprising
a cylindrical casing having one end closed, means to mount said casing in
a position surrounding a said bell with the closed end of the casing facing
~: -
lO5,~Z5~
the open end of the venturi bell, a layer of sound insulating material on
the interior surface of said casing, and a sleeve of sound insulating mater-
ial adapted to surround said bell to provide an annular air passage between
the interior of said casing and the exterior of said sleeve.
The construction of this invention substantially encloses the noise
producing gas flows in a sound absorbing chamber thereby trapping the noise
by repeated exposure to sound absorbing surfaces. The result is that burner
noise is reduced to such an extent that it is well below objectionable levels.
Fig. 1 is a sectional view of the silencer showing it mounted on
a burner, and
-la-
~OS~Z5~
Fig. 2 is a view taken on line 2-2 of Fig. 1
Referring to the drawing, there is shown a portion of
a furnace wall 1 having a metal backing plate 2. Both the wall
and the plate are provided with an opening through which a burner
is inserted for heating the furnace. As shown, the burner com-
prises a venturi 3 having its discharge end extending through the
wall opening into the furnace interior. The venturi is provided
with a radially and axially extending flange 4 by means of which
it is fastened in position on the furnace wall. A secondary air
shutter 5 is slideable on the venturi and is held in adjusted
position by a thumb screw 6. This shutter is of a size to close
the opening in the furnace wall as shown. Axial adjustment of ~-
this shutter along the venturi regulates the amount of secondary -
air that can flow through the wall opening and around the burner ~ -
into the furnace. ;
The left or inlet end of venturi 3 is provided with the
usual bell 7 that has a spider 8 supporting concentrically a
sleeve 9. An orifice, or spud as it is usually called, 11, is
threaded into sleeve 9. Fuel gas under pressure is supplied to
the burner by a pipe 12 to be discharged through the spud. As
the fuel gas is discharged through orifice 11 it will aspirate ~
primary air in the bell 7 and supply a fuel air mixture to the -
furnace. The amount of primary air aspirated is controlled by a
shutter 13 attached to a sleeve 14 that is slideably received on
pipe 12. The shutter is held in its adjusted position by a
thumb screw 15. The escaping fuel gas produced a noise, varying
with the pressure and the gas composition, that can be quite loud
and objectionable.
A silencer to be used with the burner is mounted on
the furnace wall by a pair of studs 16. The silencer includes a
first part 17 that is attached to studs 16 by bolts 1~. Part 17 ~-
is provided with a radial flange 19 to which is attached by a
54
similar flange, a cup-shaped part 21 which, along with part 17
forms a silencer casing. As best shown in Fig. 2, the end face
of part 17 is provided with a central opening 22 that is moved
over bell 7 when this part is being mounted on studs 16. The
face is also provided with a plurality of arcuate openings 23
through which primary air flows to the burner.
The interior surface of the cylindrical portion of
parts 17 and 21 are lined with a thick layer 24 of sound absorb-
ing material such as fiberglas. A similar layer 25 of fiberglas
or the like is placed against the radially extending wall of
part 21. The diameter of the casing will depend upon the size of
the burner with which it is used. As an example, a burner in
which bell 7 is five inches in diameter would have a casing
approximately fourteen inches in diameter and the sound absorbing
material will be about two inches thick.
Additional sound absorbing material in the form of a
sleeve 26 is held in place by a strap 27 with the ends of the
sleeve abutting against a flange on bell 7 and the end face of
part 17. Thus, an annular passage for air is formed between two
bodies of sound absorbing material. In addition, shutter 13 is
shown as being dish-shaped and provided with a disc 28 of sound
absorbing material immediately back of the primary air opening
in bell 7.
It will be seen that the construction requires sound
waves produced by the jet of fuel gas exiting from spud 11 must
move in a tortuous or labyrinth path and against the flow of
primary air before they are dissipated to the surroundings. The
entire path of travel of the sound waves is lined on both sides
by heavy layers of sound absorbing material. Thus, the sound
waves are substantially reduced as they travel outwardly from the
burner. Any noise that might be produced by the inflowing prim-
ary air is also dampened as it moves toward bell 7. It is noted
lO5;~ZS~
.' that the passages provided for the air are large enough so that
there is no real reduction of its pressure or velocity as it
flows into the burner.
' ~ ~
'
~ ' '
`' .:
~ ~ .
i :
.'. :' .
; ., :
~ ' '
."
Y ' -
.,
:,:
, ' "
.' ;,,
4 ;`~
~.
,: . .. .. ~ , - . . .
