Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED PIJLSATING COMBUSTION DEVICE:
This invention relates to the principle of
pulsating combustion and is specifically related to the
use of high frequencies and a split exhaust system,
whereby the exhaust system i~3 spread over a wider area
than in the conventional single tube linear pulse
combustor. When used as a burner thesP tubes have a
large surface area and,due to the sweeping action o~ the
shock waves, a better heat transfer can be obtained than
is possible in a standard fire tube boiler system. When
used as a generator of vibratory shock waves this device
is of use to match these shock waves into a large
exhaust duct through which the du~t i5 ~lowing, thereby
coagulating the dust to enhance its removal.
BAC~GROUND OF THIS INVENTION
Linear pulsating combustion devices have been known
for many years. These units have been tubular in shape
and have been used for propulsion, the V-l roaket of
Norld War II being an infamous example. They have been
used also for heating purposes. The LENNOXTM domestic
burner using natural gas is a typically North ~merican
example. All these units have, in common, a single
exhaust tube, the length of which determines the
frequency of operation. The LENNOX~M burner ~or
instance has a long exhaust pipe bent like a trombone
which has a frequency of about 50Hz. This frequency has
a long wavelength and therefore khe noise is dif~icult
to suppress in a dome~tic environment. If that unit
were scaled down in length so that the frequency of
operation became higher, then the entire unit would be
too small to operate ef~ectively as a domestic burner.
G~RAL DESCRIPTION OF T~E INVENTION
The unit that is the subject o~ this invention is
comparatively short in length but has an elongated
combustion chamber and multiple exhaust tubes. This
2 ~:0~97~38
configuration enables the frequency to be kept hiyh
while maintaining the fuel input at an acceptable level.
More particularly, this invention provides the
combination of means defining a container for fluid with
at least one pulsating combustion unit, said at least
one unit comprising:
a) a plurality of exhaust tubes o~ uniform cross-
section, the tubes being of a material and wall
thickness which allows heat energy within said tube~ to
be rapidly transferred to a fluid outside of the tubes,
the tubes being situated such that substantially all o~
the outer surface of each tube is in conta t with fluid
in said container;
b) an elongate combustion chamber communicating with
said exhaust tubes, the chamber being situated such that
substantially all of its outer surface is in contact
with fluid in said container;
c) inlet means for admitting a combustible fuel
mixture to the combustion chamber;
d) ignition means for igniting the fuel mixture to
initiate pulsating combustion; and
e) collection means for removing exhaust gases from
said exhaust tubes.
Further, this invention provides a method of
heating a fluid in a container, comprising the steps:
a) providing at least one pulsating combustion unit,
said at least one unit including a plurality of exhaust
tubes of uniform cross-section, the tubes being o~ a
material and wall thickness which allow heat energy
within said tubes to be rapidly transferred to a fluid
outside of the tubes; an elongate combustion chamber
communicating with said exhaust tubes; inlet means for
admitting a combustible fuel mixture to the combustion
chamber; and ignition means for igniting the fuel
mixture;
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b) placing the unit within the container such that
substantially the entirety of the external surfaces of
the tubes and of the combustion chamber are in contact
with the fluid; and
c) admitting a combustible fuel mixture to the
combustion chamber and ignit:ing the mixture to initiate
pulsating combustion and eje!ct hot gases through the
exhaust tubes, whereby agitation of the hot gases in the
exhaust tubes due to the pul.sating shocX waves produced
by the pulsating combustion enhances heat trans~er to
and through the exhaust tube walls and into the fluid.
Finally, this invention provides a method v~
enhancing the collection of dust or aerosol ~rom gas
flowing through an exhaust duct, comprising the steps:
a) providing at least one pulsating combustion unit,
said at least one unit including a plurality o~ exhaust
tubes of uniform cross-section; an elongate comhustion
chamber communicating with said exhaust tubes; inlet
means for admitting a combustible ~uel mixture to the
combustisn chamber; and ignition means for igniting the
fuel mixture;
b) placing the unit within the exhaust duct; and
c) admitting a combustible ~uel mixture to the
combustion chamber and igniting the mixture to initiate
pulsating combustion and eject hot gases through the
exhaust tubes, whereby agitation of the hot gases in the
exhaust tubes due to the pulsating shock waves produced
by the pulsating combustion is transferred to the gas in
the exhaust duct, thereby coagulating the dust or
aerosol to improve collection.
GENERAL DESCRIPTION OF TEIE DRAWINGS
Two embodiments o~ this invention are illustrated
in the accompanying drawings, in which like numerals
denote like parts throughout the several views, and in
which:
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Figure 1 is a vertical sectional view of a
pulsating combustion unit constructed in accordance with
this invention, taken along khe line 1-1 in Figure 2,
Figure 2 is a vertical sectional view of the unit
shown in Figure I, taken along the line 2-2 in Figure 1;
Figures 3, ~, 5, 6, 7, 3 and 9 are horizontal
sectional views taken at the lines 3-3, 4-4, 5-5, 6-6,
7-7, 8-8, and 9-9 in Figures 1 and 2;
Figure 10 is a schematic plan view of a dusk
conditioning system utilizing the unit of thi~
invention;
Figure 11 is a schematic vertical sectional view o~
one embodiment of this invention showing the use o~ a
plurality of units with separate containers; and
Figure 12 is a schematic vertical sectional view
similar to Figure 11, but showing the use of a plurality
of units within a common container.
DETAILED DESCRIPTION OF THE DRAWINGS
Attention is now directed to Figures 1 and 2, which
show respectively the side and front elevations of a
pulsating combustion unit 10 constructed in accordance
with this invention. The combustion unit 10 includes a
plurality of exhaust tubes 16 with substantially uniform
cross-section throughout their length. The tubes may
typically be circular, square or elliptical in cross-
section. The tubes 16 are preferably made ~rom a
material and have a thickness such as to allow rapid
transfer of heat energy from the interior of each tube
16 to a fluid surrounding the tube. Suitable materials
for the tubes 16 would be aluminum, copper and stainless
steel.
The fluid in which the tubes 16 are immersed may be
either a liquid or a gas. In Figures 1 and 2 there is
schematically drawn a container 16a having a fluid
outlet 16b and a fluid inlet 16c. A common combustion
chamber 11 receives a combustible mixture through
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suitable transfer ports in a mixing chamber 13, which in
turn receives a combustible mixture from a chamber 17
through mechanical valves 17a (see Figure 4). The
valves 17a allow the combustible mixture to enter the
S combustion chamber 11 (after traversing chambers 13),
but substantially prevent the products of combustion
from leaving the combustion chamber 11 other than
through the exhaust tubes 16 and subsequently into
exhaust outlet 12.
It will be noted that the outlet 12 is coaxial with
and communicates with a conical chamber 50 defined by a
frusto-conical wall 52 having an annular, outwardly
projecting flange 54. The Elange 54 lies against and is
secured to an inwardly directed ~lanqe 56 at the bottom
of the substantially cylindrical container 16a. These
two flanges 54 and 56 may be secured together by any
suitable means, for example bolts or other fasteners. A
gasket may be provided between the flanges.
The tubes 16 extend downwardly in a parallel
manner, and the bottom ends thereof are welded to an
oval flange 58 which rests against the inner upper
corner of the flange 56 of the container 16a. Pressure
between the plate 58 and the flange 56 prevents
communication between the conical chamber 50 and the
space within the container 16a, thus keeping the water
separated from the combustion gases.
At the top of Figures 1 and 2, the numeral 40
designates a ~uel plenum which receives ~uel through two
inlet pipes 42, and which distributes the fuel to a
plurality of fuel needles 44 that are spaced above
corresponding, over-sized openings at the top of the
chamber 17, shown in broken lines at 45 in Figure 3.
The needles 44 produce jets of gaseous fuel which
entrain air as they enter the chamber 17.
Although Figure 4 shows mechanical valves 17a, it
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will be understood that aerodynamic val~es could be
used in place of the mechanical valves.
Also included is a means for igniting the fuel
mixture initially in the combustion chamber 11, this
means being schematically illustrated as a spark plug
46.
The embodiment illustrated in Figures 1 and 2
includes sixty-four exhaust tubes 16, however it will be
understood that the actual number of tubes could vary
in accordance with various design constraints.
Figures 3 through 9 ar~e cross-sectional drawings
taken through the section lines 3-3 through 9-9,
respectively, in Figures 1 and 2.
In Figure 3 there is shown the plenum 40, along
with the needles 44.
Figure 4 shows the mechanical valves 17a and is
taken through the location where the ~uel and the
entrained air are initially mixed.
Figure 5 shows the mixing chamber transfer ports
49.
Figure 6 is taken through the combustion chamber
11 .
Figure 7 is taken at the location of transition
from the combustion chamber 11 to the tubes 16.
Figure 8 shows the exhaust tubes 16.
Figure 9 is taken through the plate stabilizing the
lower ends of the exhaust tubes 16.
Figure 10 is a schematic drawing showning a dust
conditioning duct 21 through which dust-laden air or gas
30 flows. At a bend in the duct 21, one or a plurality
of pulsating combus ion units 24 are placed. Fuel is
fed at 32 to the unit or units. The shockwaves produced
by the pulsating combustion units condition the dust by
substantially agglomerating the fine dust particles so
that they can be dealt with more efficiently in a
collector 28, which may be a venturi scrubber, an
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electrostatic collector, or a similar device. Energy i8
saved in view of the fact that larger dust particles
take substantially less energy to collect than do small
particles.
Figures 11 and 12 indicate the use of the pulsating
com~ustion unit as a boiler or heater of a fluid in two
different configurations. Figure 11 shows a plurality
of containers 34 each containing a pulsating combustion
unit, and each unit containing a means for supplying
fuel 32, whether by mechanic:al or aerodynamic valving.
Further, each separate container has a separate fluid
inlet 38 and a separate fluid outlet 40. Figure 12 is
substantially the same as Figure 11, except for the
single container 36 which has a single inlet 38a, a
sing}e outlet 40a, and a plurality of pulsating
combustion units incorporated into it.
Test Results from a Device Using Natural Gas
and Water Coolinq
A test unit designed substantially as seen in
Figures 1 and 2 was assembled for test purpose~. This
unit was an effective hot water heater and used natural
gas as fuel and water as the coolant. The overall size
of the burner was 16.5 inches long, 7.5 inches broad and
2.5 inches wide not including the water jacket. This
25 size was nominally rated at 50,000 B.T.U/Hr. with 7
inches water column gas pressure.
Preliminary tests with gas pressure at 6 psig. and
a gas flow at a nominal 80 Cfh. using a teflon laminated
mesh flap valve, 0.008 inches thickness, gave the
following results:
Over a typical 100 seconds of operation the
temperature of the cooling water, both incoming and
outgoing, was taken every five seconds by means of
temperature sensors, and was ~ed into a computer. The
average energy in the water, flowing at 2.0 U.S. gpm.,
was calculated to be 76,896 B.T.u./~r. representing an
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approximate efficiency of 96%. The burner was run for
about one hour and the results were substantially the
same throughout that time. The exhaust gas temperature
at the point of exit ~rom the exhaust tubes 12 varied
between 170 and 180F.
While several embodiments of this invention have
been illustrated in the accompanying drawings and
described hereinabove, it w.ill be evident to thoæe
skilled in the art that changes and modifications may
be made therein without departing from the essence of
this invention, as set forth in the appended claims.
