U.S. patent application number 12/801817 was filed with the patent office on 2010-12-30 for combustion apparatus.
This patent application is currently assigned to NORITZ CORPORATION. Invention is credited to Yoshinori Kanda.
Application Number | 20100330520 12/801817 |
Document ID | / |
Family ID | 43381131 |
Filed Date | 2010-12-30 |
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United States Patent
Application |
20100330520 |
Kind Code |
A1 |
Kanda; Yoshinori |
December 30, 2010 |
Combustion apparatus
Abstract
A combustion apparatus mainly consists of burners, a fuel supply
channel having branched channels, an air feeder for supplying air
to the burners, and a pressure regulator and has a combustion
space. The branched channels allow fuel gas supplied to the burners
to pass therethrough and are provided with shutoff valves. The
pressure regulator includes a signal-pressure inlet and a
secondary-pressure inlet. A signal pressure introduced through the
signal-pressure inlet is detected at a downstream of the air feeder
and a secondary pressure introduced through the secondary-pressure
inlet is detected at a vicinity of a boundary of the branched
channels in the fuel supply channel. Fuel gas discharged from the
pressure regulator is regulated so as to satisfy a predetermined
relationship between the signal pressure introduced through the
signal-pressure inlet and the secondary pressure introduced through
the secondary-pressure inlet.
Inventors: |
Kanda; Yoshinori; (Hyogo,
JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING, 1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
NORITZ CORPORATION
Hyogo
JP
|
Family ID: |
43381131 |
Appl. No.: |
12/801817 |
Filed: |
June 28, 2010 |
Current U.S.
Class: |
431/350 |
Current CPC
Class: |
F23D 14/60 20130101;
F23N 2005/185 20130101; F23N 2237/02 20200101; F23N 2241/04
20200101; F23N 2235/18 20200101; F23D 23/00 20130101; F23D
2900/14003 20130101; F23N 5/184 20130101; F23N 2005/181 20130101;
F23N 2233/08 20200101; F23N 1/022 20130101 |
Class at
Publication: |
431/350 |
International
Class: |
F23D 14/46 20060101
F23D014/46 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 29, 2009 |
JP |
2009-153593 |
Jun 29, 2009 |
JP |
2009-154223 |
Jul 2, 2009 |
JP |
2009-157664 |
Claims
1. A combustion apparatus, comprising: a plurality of burners; a
fuel supply channel having a plurality of branched channels at its
downstream; an air feeder for supplying air to the burners; and a
pressure regulator, and having a combustion space containing a
combusting area, the branched channels allowing supplied fuel to
the burners to pass therethrough, at least one of the branched
channels having a shutoff valve, which is either opened or closed
so as to either increase or decrease the combusting area in the
combustion space, and the pressure regulator having a
signal-pressure inlet through which a signal pressure to be based
on is introduced and a secondary-pressure inlet through which a
secondary pressure is introduced and being designed to regulate
fuel gas supplied at a primary pressure to gas having a discharge
pressure satisfying a predetermined relationship between the signal
pressure introduced through the signal-pressure inlet and the
secondary pressure introduced through the secondary-pressure inlet,
wherein the signal pressure introduced through the signal-pressure
inlet is detected at a position selected from the air feeder and a
downstream of the air feeder, and the secondary pressure introduced
through the secondary-pressure inlet is detected at a position
selected from the branched channels and a vicinity of a boundary of
the branched channels within the fuel supply channel.
2. The combustion apparatus as defined in claim 1, the fuel supply
channel having a secondary-pressure outlet through which the
secondary pressure to be introduced into the pressure regulator is
taken out, the secondary-pressure outlet being disposed at upstream
of the shutoff valves in the branched channels.
3. The combustion apparatus as defined in claim 2, the
secondary-pressure outlet being disposed at one of the branched
channels where a flow of fuel gas is protected from being blocked
even with either increase or decrease of the combusting area in the
combustion operation.
4. The combustion apparatus as defined in claim 1, having a
plurality of secondary-pressure outlets through which the secondary
pressure to be introduced into the pressure regulator is taken out
and being designed to change positions where the secondary pressure
is detected.
5. The combustion apparatus as defined in claim 1, having a
pressure modification means for modifying a pressure to be
detected, the pressure modification means being disposed adjacent
to the position where either the signal pressure or the secondary
pressure is detected and being controlled so as to modify the
detected pressure.
6. The combustion apparatus as defined in claim 5, the pressure
modification means being controlled so as to increase the detected
pressure in ignition in the combustion space.
7. The combustion apparatus as defined in claim 1, the pressure
regulator having inside a main valve and a main-valve drive
mechanism for driving the main valve, the main-valve drive
mechanism being designed to drive the main valve with a gas
composed of one selected from fuel gas and air from the air feeder,
and comprising a chamber into which the gas is introduced, a gas
supply part for supplying the gas to the chamber, and a leak
channel for leaking the gas within the chamber, wherein the gas
supply part is temporally closed in decreasing the combusting area
in the combustion space.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a combustion apparatus used
in a device such as a water heater.
[0003] 2. Description of the Related Art
[0004] Recently, water heaters are in widespread use at home. Water
heaters for household use must supply hot water to a number of
places solely by one heater. For example, each home has water taps
or showers in a kitchen, a bathroom, and a washbasin in its house.
One water heater supplies hot water to those. Further, a large
number of water heaters for household use have functions such as
filling a bathtub with hot water and heating a remaining bath water
again.
[0005] In this way, since hot water from a water heater for
household use is used at a plurality of places, the required amount
and temperature of hot water from the water heater change
frequently. Thus, a combustion apparatus incorporated in such a
water heater must change a combustion amount in response to a
change of the amount and temperature of hot water.
[0006] For that reason, a combustion apparatus incorporated in a
water heater for household use is provided with a gas proportional
valve so as to change the combustion amount. More specifically, the
combustion amount is changed by a control of the amount of fuel gas
by regulation of a valve opening degree of the proportional valve,
which is disposed at a fuel supply channel of the combustion
apparatus, in response to the required amount of heat
generation.
[0007] Further, a type of combustion apparatuses includes a
so-called total primary-air type combustion apparatus. This type of
apparatus is designed to mix most of air required for combustion in
advance in a burner, so as to discharge the resulting mixture gas
from burner ports for use in combustion.
[0008] The patent document 1 specified below discloses a total
primary-air type combustion apparatus provided with a proportional
valve at a fuel gas supply channel.
[0009] Patent Document 1: JP 2003-214622 A
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0010] A total primary-air type combustion apparatus, as described
above, is designed to mix most of air required for combustion in
advance in a burner. That gives narrow acceptable range of error in
an air-fuel ratio, which is a ratio of an amount of air to be
supplied to the burner to an amount of fuel gas to be supplied to
the burner.
[0011] Thus, the combustion apparatus in the conventional art is
designed to set a target value of an opening degree of a fuel-gas
proportional valve and a target value of the number of rotations of
an air feeder so as to keep the air-fuel ratio within the
acceptable range, and to electrically control the apparatus so as
to conform actual values of those described above to the target
values.
[0012] In other words, the combustion apparatus in the conventional
art controls the opening degree of the proportional valve to be
conformed to the target opening degree thereof, and simultaneously
controls the number of rotations of the air feeder to be conformed
to the target number thereof.
[0013] In a case where a required combustion amount has changed,
the apparatus recalculates the target values to get new target
values respectively and controls the opening degree of the
proportional valve to be conformed to the new target value thereof
and simultaneously controls the number of rotations of the air
feeder to be conformed to the new target value thereof.
[0014] However, according to a configuration of the conventional
art, in the above mentioned case, the air-fuel ratio might be out
of the acceptable range until the opening degree of the
proportional valve and the number of rotations of the air feeder
are conformed to the respective new target values, resulting in an
unstable combustion. Therefore, the combustion apparatus in the
conventional art has a technical problem to be solved such that
combustion becomes unstable in the transition in changing of the
combustion amount.
[0015] Further, though the fuel-gas proportional valve is essential
for the combustion apparatus of the conventional art, the
proportional valve is a precision instrument to be electrically
controlled, being generally expensive. Thus, there is a desire to
eliminate the proportional valve.
[0016] The present inventor experimentally produced a combustion
apparatus 101, as shown in FIG. 9, having a pressure equalizing
valve 106 disposed at a fuel gas supply channel so that a pressure
signal for the pressure equalizing valve 106 is taken out from an
air feeder 103.
[0017] Herein, the pressure equalizing valve 106 is a pressure
regulator for reducing a primary pressure of supplied gas to a
secondary pressure and for discharging the regulated gas, having a
signal pressure inlet 132 through which a pressure is introduced as
a signal, so as to discharge the gas with a pressure reduced to the
secondary pressure in accordance with a pressure introduced through
the signal pressure inlet 132.
[0018] In the combustion apparatus 101 experimentally produced by
the present inventor, because the pressure signal is taken out from
the air feeder 103, a supply pressure of fuel gas is changed in
accordance with either increase or decrease of the air feeding
amount by the air feeder 103. That solves the above-mentioned
technical problem such as an unstable combustion in the transition
in changing of the combustion amount. Further, the experimentally
produced combustion apparatus 101 changes the combustion amount by
changing of the air feeding amount by the air feeder 3, thereby
eliminating the fuel-gas proportional valve.
[0019] However, the combustion apparatus 101 includes a plurality
of branched channels 109a to 109g in a fuel supply channel 109 with
shutoff valves 121a to 121g, respectively. Changing of the fuel
amount by either opening or closing of the shutoff valves 121a to
121g may cause an unstable combustion.
[0020] The reason is as follows: The pressure equalizing valve or
the pressure regulator 106 employed in the combustion apparatus 101
is designed to regulate a secondary pressure of fuel gas so as to
substantially conform a pressure introduced through the signal
pressure inlet 132 to a discharge pressure of the fuel gas
discharged from the pressure regulator 106. When some of the
shutoff valves 121a to 121g are closed, for example, a flow amount
of fuel gas flowing in a common flow channel 109y of the fuel
supply channel 109 is reduced and a flow rate of the gas in the
fuel supply channel 109 is lowered, compared to those before
closing of the valves 121. Herein, in view that a pipe resistance
of fuel gas is proportional to the square of the flow rate of fuel
gas according to Bernoulli's principle, a flow resistance of the
common flow channel 109y is lowered. As a consequence, when some of
the shutoff valves 121a to 121g are closed, the secondary pressure
of the fuel gas flowing in the remaining branched channels 109a to
109g having the opened shutoff valves 121 is increased. That may
change the air-fuel ratio of the gas mixture, resulting in an
unstable combustion. Shortly, the fuel gas may become thick and
combustion may become unstable.
[0021] As described above, water heaters for household use each
require an amount and a temperature of hot water changing greatly.
Therefore, a combustion apparatus must change a combustion amount
depending on a condition such as the amount of hot water. However,
the experimentally produced combustion apparatus 101 may cause an
unstable combustion each time the combustion amount is changed by
using the shutoff valves 121a to 121g.
[0022] An object of the present invention made in view of the
problems and drawbacks in the conventional art described above is
therefore to further improve the experimentally produced combustion
apparatus and develop a combustion apparatus solving the technical
problem in which changing of the combustion amount by using the
shutoff valves 121 causes an unstable combustion.
Means to Solve the Problem
[0023] Generally, a pressure regulator is designed to regulate a
discharge pressure from the pressure regulator to be in conformity
with a signal pressure. The pressure regulator generally has a
portion where the discharge pressure is detected within the
regulator. In contrast, a pressure regulator employed in a
combustion apparatus in the present invention is designed to
introduce a signal for a secondary pressure (discharge-side) from
outside of the pressure regulator.
[0024] Specifically, in order to solve the problems and drawbacks
described above, an aspect of the present invention provided herein
is a combustion apparatus including a plurality of burners, a fuel
supply channel having a plurality of branched channels at its
downstream, an air feeder for supplying air to the burners, and a
pressure regulator, and having a combustion space containing a
combusting area, the branched channels allowing supplied fuel to
the burners to pass therethrough, at least one of the branched
channels having a shutoff valve, which is either opened or closed
so as to either increase or decrease the combusting area in the
combustion space, and the pressure regulator having a
signal-pressure inlet through which a signal pressure to be based
on is introduced and a secondary-pressure inlet through which a
secondary pressure is introduced and being designed to regulate
fuel gas supplied at a primary pressure to gas having a discharge
pressure satisfying a predetermined relationship between the signal
pressure introduced through the signal-pressure inlet and the
secondary pressure introduced through the secondary-pressure inlet,
wherein the signal pressure introduced through the signal-pressure
inlet is detected at a position selected from the air feeder and a
downstream of the air feeder, and the secondary pressure introduced
through the secondary-pressure inlet is detected at a position
selected from the branched channels and a vicinity of a boundary of
the branched channels within the fuel supply channel.
[0025] The combustion apparatus in this aspect employs the pressure
regulator including the signal-pressure inlet through which a
signal pressure detected at the air feeder or the downstream of the
air feeder is introduced and the secondary-pressure inlet through
which a secondary pressure detected at the fuel supply channel is
introduced.
[0026] As described above, the experimentally produced combustion
apparatus is designed to regulate a secondary pressure of fuel gas
so that a pressure introduced through the signal-pressure inlet
becomes substantially equal to a discharge pressure of the fuel gas
to be discharged from the pressure regulator. That
disadvantageously causes an unstable combustion resulting from a
change of the air-fuel ratio of the gas mixture of air and fuel gas
when, for example, some of the shutoff valves disposed at the
branched channels are closed.
[0027] Therefore, the combustion apparatus in this aspect is
provided with the secondary-pressure inlet, so as to regulate a
discharge pressure from the pressure regulator satisfying a
predetermined relationship between the signal pressure introduced
through the signal-pressure inlet and the secondary pressure in the
fuel supply channel, which is detected at the vicinity of the
boundary upstream of the branched channels in the fuel supply
channel. Thereby, the secondary pressure in the fuel supply channel
is maintained constantly because being regulated in accordance with
the basic signal pressure even when some of the shutoff valves
disposed at the branched channels are closed. Consequently, by the
combustion apparatus in this aspect, even when the combusting area
is either increased or decreased by a control of either opening or
closing of the shutoff valves, the air-fuel ratio of the gas
mixture of fuel gas and air undergoes very little change though the
amount of fuel gas undergoes a change by the control, thereby
preventing an unstable combustion, because of a direct control of
the secondary pressure in the vicinity of the boundary upstream of
the branched channels in the fuel supply channel adjacent to the
burners.
[0028] Preferably, the fuel supply channel has a secondary-pressure
outlet through which the secondary pressure to be introduced into
the pressure regulator is taken out, the secondary-pressure outlet
being disposed at upstream of the shutoff valves in the branched
channels.
[0029] By such the combustion apparatus, the secondary-pressure
outlet is disposed at the branched channels, so that the secondary
pressure at a position closer to the burners is regulated in
accordance with the basic signal pressure. That minimizes the
influence such as a pipe resistance onto the fuel gas supplied to
the burners, thereby ensuring a constant air-fuel ratio. Further,
even when the combusting area is decreased by closing of the
shutoff valves, the detected secondary pressure undergoes very
little change because the secondary-pressure outlet is disposed at
upstream of the shutoff valves in the branched channels. Therefore,
the air-fuel ratio is substantially accurately regulated.
[0030] The secondary-pressure outlet is preferably disposed at one
of the branched channels where a flow of fuel gas is protected from
being blocked even with either increase or decrease of the
combusting area in the combustion operation.
[0031] By such a configuration, the secondary pressure is detected
at one of the branched channels through which fuel gas usually
flows, and whereby the air-fuel ratio is more accurately regulated
even with closing of the shutoff valves.
[0032] Preferably, the combustion apparatus has a plurality of
secondary-pressure outlets through which the secondary pressure to
be introduced into the pressure regulator is taken out and is
designed to change positions where the secondary pressure is
detected.
[0033] It is also recommended that the combustion apparatus has a
pressure modification means for modifying a pressure to be
detected, the pressure modification means being disposed adjacent
to the position where either the signal pressure or the secondary
pressure in accordance with the signal pressure is detected and
being controlled so as to modify the detected pressure.
[0034] Such the combustion apparatus allows the ratio of fuel gas
to be modified compared to the air-fuel ratio in the normal
combustion, as needed.
[0035] By this combustion apparatus, for example, in a case where
the pressure modification means is disposed adjacent to the
position where the signal pressure is detected, the pressure
modification means is controlled to direct an air flow to the
detecting position, thereby making a dynamic pressure of the fed
air to act on the detecting position. That raises the signal
pressure without increasing the number of rotations of the air
feeder, enabling a control to increase the ratio of fuel gas than
the air-fuel ratio in the normal combustion. Alternatively, the
pressure modification means is controlled to block an air flow to
the detecting position, thereby blocking a dynamic pressure of the
fed air from acing on the detecting position. That allows the
signal pressure (static pressure) in accordance with the original
number of rotations of the air feeder to be introduced into the
pressure regulator, enabling combustion at the air-fuel ratio in
the normal combustion. Further, by application of the
characteristic features of the pressure modification means, only
with a control of the pressure modification means to slightly
direct an air flow to the detecting position (viz. control to make
a dynamic pressure to slightly act) in the normal combustion, more
dynamic pressure can act on the detecting position by the control
of the means to direct more air to the detecting position in order
to raise the signal pressure than that in the normal combustion,
whereas the dynamic pressure is blocked from acting on the
detecting position and the static pressure can act thereon by the
control of the means to block an air flow to the detecting position
in order to reduce the signal pressure than that in the normal
combustion. That enables the control to modify the air-fuel ratio
that is constantly regulated by the pressure regulator, as
needed.
[0036] On the other hand, in a case where the pressure modification
means is disposed adjacent to the position where the secondary
pressure is detected, the pressure modification means is controlled
to direct a flow of fuel gas to the detecting position, thereby
making a dynamic pressure to act on the detecting position. A
pressure larger than the original secondary pressure (static
pressure) of fuel gas actually flowing in the flow channel is
detected, so as to be regulated to become equal to the signal
pressure. That makes fuel gas supplied to the combustion space to
have a smaller ratio than the air-fuel ratio in the normal
combustion. Alternatively, the pressure modification means is
controlled to block a flow of fuel gas to the detecting position,
thereby blocking a dynamic pressure from acing on the detecting
position and making a static pressure to act thereon. That allows
fuel gas having the original secondary pressure in accordance with
the signal pressure to be introduced into the pressure regulator.
Thus, the fuel gas has a ratio equal to the air-fuel ratio in the
normal combustion. Consequently, as well as in the above-mentioned
description, by application of the characteristic features of the
pressure modification means, only with a control of the pressure
modification means to make a dynamic pressure to slightly act on a
flow of fuel gas in the normal combustion, the means can be
controlled to direct more fuel gas to the detecting position in
order to reduce the ratio of fuel gas than the air-fuel ratio in
the normal combustion, whereas the means can be controlled to block
a flow of fuel gas to the detecting position in order to increase
the ratio of fuel gas than the air-fuel ratio in the normal
combustion. That also enables the control to modify the air-fuel
ratio that is constantly regulated by the pressure regulator, as
needed.
[0037] Consequently, by this combustion apparatus, the control of
the pressure modification means arranged adjacent to the detecting
position of either of the pressures regulates fuel gas with a ratio
shifted from the air-fuel ratio in the normal combustion, as
needed. That improves ignition performance in ignition and reduces
an unstable combustion such as an oscillating combustion within a
certain period of time after ignition.
[0038] The pressure modification means is preferably controlled so
as to increase the detected pressure in ignition in the combustion
space.
[0039] Such a configuration increases a ratio of fuel gas in
ignition than the air-fuel ratio in the normal combustion, thereby
ensuring an improved ignition performance. Herein, the term "in
ignition" includes timing before and after generation of flames in
the combustion space.
[0040] Preferably, the pressure regulator has inside a main valve
and a main-valve drive mechanism for driving the main valve, the
main-valve drive mechanism being designed to drive the main valve
with a gas composed of one selected from fuel gas and air from the
air feeder, and including a chamber into which the gas is
introduced, a gas supply part for supplying the gas to the chamber,
and a leak channel for leaking the gas within the chamber, wherein
the gas supply part is temporally closed in decreasing the
combusting area in the combustion space.
[0041] The pressure regulator may be either a direct acting type or
a pilot type. The gas (working fluid) may be either air from the
air feeder or fuel gas.
[0042] This configuration solves the technical problem such as an
unstable combustion even when the combusting area is changed with
the shutoff valves and the like.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0043] The present invention can provide a combustion apparatus to
solve the technical problem such as an unstable combustion even
when the combustion amount is changed with the shutoff valves and
the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] FIG. 1 is a configuration diagram showing a combustion
apparatus relating to an embodiment of the present invention;
[0045] FIG. 2 is a configuration diagram showing a modified
embodiment of the combustion apparatus of the present
invention;
[0046] FIG. 3 is a configuration diagram showing another modified
embodiment of the combustion apparatus of the present
invention;
[0047] FIG. 4 is a configuration diagram showing still another
modified embodiment of the combustion apparatus of the present
invention;
[0048] FIG. 5 is a configuration diagram showing yet another
modified embodiment of the combustion apparatus of the present
invention;
[0049] FIGS. 6A to 6C are conceptual diagrams each showing a
control state of a pressure modification board. FIG. 6A shows a
state at a position in a stable combustion, FIG. 6B shows a state
at a position in an increased dynamic pressure, and FIG. 6C shows a
state at a position in a decreased dynamic pressure;
[0050] FIG. 7 is a configuration diagram showing a further modified
embodiment of the combustion apparatus of the present
invention;
[0051] FIG. 8 is a configuration diagram showing a further modified
embodiment of the combustion apparatus of the present invention;
and
[0052] FIG. 9 is a configuration diagram showing a combustion
apparatus experimentally produced by the present inventor.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0053] Now, an embodiment of the present invention will be
described below in detail, making reference to the accompanying
drawings. Hereafter, a positional relationship of the left, right,
top, and bottom is described on a basis of the drawings unless
otherwise noted.
[0054] A combustion apparatus 1 shown in FIG. 1 is housed in a
water heater not shown so as to heat a heat exchanger 4 and the
like and mainly consists of a main body 2, an air feeder 3, a
forming unit 5 for forming a fuel supply channel, and a pressure
regulator (hereinafter also referred to as a pressure equalizing
valve) 6.
[0055] The air feeder 3 employed in the present embodiment is
constituted by a moving vane housed rotatably in a casing, like a
sirocco fan and a turbo fan. A motor for driving the air feeder 3
is either a DC motor or an inverter-controlled AC motor, changing
an air feeding amount by either increase or decrease of the number
of rotations.
[0056] The main body 2 includes twenty (20) burners 8a to 8t housed
in a burner casing 7, in which the burners 8a to 8t consist of
seven burner groups 19a to 19g. More specifically, as shown in FIG.
1, a first group 19a consists of four burners 8a to 8d, a second
group 19b consists of four burners 8e to 8h, a third group 19c
consists of three burners 8i to 8k, a fourth group 19d consists of
two burners 8l to 8m, a fifth group 19e consists of two burners 8n
to 8o, a sixth group 19f consists of two burners 8p to 8q, and a
seventh group 19g consists of three burners 8r to 8t. Herein, all
the burners 8a to 8t employed in the present embodiment have the
same configuration and the same capacity.
[0057] The burner casing 7 is, as shown in FIG. 1, divided into two
tiers by a partition. A part downstream in an air flowing direction
functions as a burner mounting part 10, whereas another part
upstream in the air flowing direction functions as an air-passage
forming part 11. The air-passage forming part 11 functions as a
passage through which air is introduced into the burners 8a to 8t
and forms a portion of an air supply passage 37. Flames are to be
generated at an upper part of the burner mounting part 10, that is:
the upper part of the burner mounting part 10 functions as a
combustion space 14.
[0058] The burner mounting part 10 defines seven chambers. The
burners 8a to 8t are sorted into the numbers set with respect to
each chamber as described above and inserted into the respective
chambers.
[0059] Each of the burners 8a to 8t has an air-gas inlet 18 at its
end and burner ports not shown at its top face. The burner ports
are disposed at the most downstream in a gas-mixture flowing
direction in the burners 8a to 8t, so as to generate flames in the
combustion space 14.
[0060] In the present embodiment, there are respectively provided
nozzles 20a to 20t adjacent to the air-gas inlets 18 of the burners
8a to 8t, so that fuel gas is introduced into the burners 8a to 8t
through the respective nozzles 20a to 20t. Further, the air-passage
forming part 11 is communicated with ends of the burners 8a to 8t,
so that air is introduced into the burners 8a to 8b through the
air-gas inlets 18 from the air-passage forming part 11.
[0061] Air and fuel gas are introduced through the air-gas inlets
18 and mixed passing in the burners 8a to 8t and the resulting gas
mixture is discharged from the burner ports.
[0062] The fuel-supply-channel forming unit 5 includes a fuel
supply channel 9 for supplying fuel gas to the burners 8a to 8t
through the respective nozzles 20a to 20t.
[0063] The fuel supply channel 9 consists of seven branched
channels 9a to 9g at downstream in the fuel-gas flowing direction
and a common channel 9y through which fuel gas flows to all the
branched channels 9a to 9g at upstream in the fuel-gas flowing
direction.
[0064] The combustion space 14 has a plurality of combustion areas
defined by the groups 19a to 19g. Specifically, the combustion
areas are divided into the number of the groups 19a to 19g, and
more specifically into seven divided areas 15a to 15g.
[0065] Therefore, the combustion apparatus 1 in the present
embodiment generates uniform flames in the respective burners 8a to
8t and allows uniform combustion in the respective areas 15a to
15g.
[0066] The forming unit 5 is provided with conventional art shutoff
valves (electromagnetic valves) 21a to 21g in the branched channels
9a to 9g respectively.
[0067] Next, the pressure regulator 6 employed in this embodiment
will be described in detail below.
[0068] The pressure regulator 6 is specifically a pressure
equalizing valve, a kind of a pressure reducing valve, and is
designed to reduce a primary pressure of supplied fuel gas to a
secondary pressure, so as to discharge the resulting gas with a
reduced pressure. An ordinary pressure reducing valve is designed
to regulate a secondary pressure to a predetermined pressure,
whereas the pressure equalizing valve employed in this embodiment
is characteristically designed to change a discharge pressure in
accordance with a signal pressure.
[0069] Specifically, the pressure regulator 6 mainly consists of a
gas inlet 30, a gas outlet 31, a signal-pressure inlet 32 through
which a pressure is introduced as a signal, and a
secondary-pressure inlet 29 through which a secondary pressure in
the fuel supply channel 9 is introduced. The pressure regulator 6
is designed to reduce a primary pressure of fuel gas introduced
from the gas inlet 30 to a secondary pressure and discharge the
resulting gas from the gas outlet 31. The pressure regulator 6 is
designed to reduce the pressure of fuel gas so as to satisfy a
predetermined relationship between a signal pressure (also referred
to as a basic signal pressure) introduced through the
signal-pressure inlet 32 and a secondary pressure introduced
through the secondary-pressure inlet 29.
[0070] The pressure regulator 6 is defined by an outer frame 6h
forming a gas passage and incorporates a valve body 6a for
controlling an opening degree of the gas passage, a diaphragm 6b, a
spring 6c, and a controlling mechanism 6d.
[0071] Within the outer frame 6h, the diaphragm 6b defines a signal
pressure chamber 6i, in which the signal-pressure inlet 32 is
formed. The signal-pressure inlet 32 is connected to the air feeder
3 via a signal-pressure conducting pipe 35. Therefore, the signal
pressure chamber 6i is subjected to a signal pressure introduced
through the signal-pressure inlet 32. That applies the signal
pressure upon one side facing the signal pressure chamber 6i of the
diaphragm 6b.
[0072] Meanwhile, the diaphragm 6b also defines a secondary
pressure chamber 6j at a side opposed to the signal pressure
chamber 6i (the other side), in the chamber 6j the
secondary-pressure inlet 29 is formed. The secondary pressure
chamber 6j is communicated with the fuel supply channel 9 (a
secondary-pressure side) via a secondary-pressure conducting pipe
34. Thus, the diaphragm 6b is subjected to a pressure difference
between a signal pressure Pt and a secondary pressure P2 of the
fuel supply channel 9. In this embodiment, the diaphragm 6b is
subjected to a pressure difference between the signal pressure Pt
and the secondary pressure P2 of the branched channel 9g.
[0073] The spring 6c supports the diaphragm 6b and strength of the
spring 6c is controlled by the controlling mechanism 6d.
[0074] The valve body 6a is, as described above, designed to
control the opening degree of the gas passage and connected to the
diaphragm 6b via a stem 6m.
[0075] By the pressure regulator 6 employed in this embodiment,
when a primary pressure P1 of fuel gas introduced into the pressure
regulator 6 is increased, for example, the secondary pressure
(pressure in the branched channel 9g) P2 is increased in accordance
with the pressure change of the primary pressure P1. The pressure
change of the secondary pressure P2 makes the valve body 6a to move
downwardly. Specifically, a pressure balance between the secondary
pressure P2 introduced through the secondary-pressure inlet 29 and
the signal pressure Pt acting on the opposite side across the
diaphragm 6b is temporally lost. The secondary pressure P2 becomes
larger than the signal pressure Pt and the increased secondary
pressure P2 induces the diaphragm 6b to expand downwardly. That
moves the valve body 6a downwardly, whereby an area in which fuel
gas passes is narrowed. The secondary pressure P2 of the fuel gas
having passed in the narrowed area is reduced and thus regulated so
as to become substantially equal to the signal pressure Pt
again.
[0076] When the signal pressure Pt is increased, for example, the
valve body 6a moves upwardly in accordance with the pressure change
of the signal pressure Pt so as to increase the secondary pressure
P2, thereby regulating the secondary pressure P2 to become
substantially equal to the signal pressure Pt. Specifically, a
pressure balance between the secondary pressure P2 introduced
through the secondary-pressure inlet 29 and the signal pressure Pt
acting on the opposite side across the diaphragm 6b is temporally
lost. The signal pressure Pt becomes larger than the secondary
pressure P2 and the increased signal pressure Pt induces the
diaphragm 6b to expand upwardly. That moves the valve body 6a
upwardly, whereby the area in which fuel gas passes is widened. The
secondary pressure P2 of the fuel gas having passed in the widened
area is increased and thus regulated so as to become substantially
equal to the signal pressure Pt again. In this way, the secondary
pressure P2 in the branched channel 9g is regulated so as to be
substantially equal to the signal pressure Pt even when the primary
pressure P1 or the signal pressure Pt changes.
[0077] The pressure regulator 6 is connected to a fuel gas supply
source not shown via the gas inlet 30 and to one end (upstream end
in the fuel-gas flowing direction) of the forming unit 5 near the
common channel 9y via the gas outlet 31. The branched channels 9a
to 9g are connected to the other end (downstream end in the
fuel-gas flowing direction) of the common channel 9y.
[0078] The branched channel 9g is provided with a
secondary-pressure outlet 28 above the shutoff valve 21g in the
fuel-gas flowing direction. The secondary-pressure outlet 28 is
connected to the secondary-pressure inlet 29 of the pressure
regulator 6 via the secondary-pressure conducting pipe 34. This
embodiment has a configuration in which the secondary-pressure
inlet 29 and the secondary-pressure outlet 28 are integrated with
the secondary-pressure conducting pipe 34, but it is possible to
have a configuration in which the conducting pipe 34 is connected
to the inlet 29 and the outlet 28 by a fixing means such as a bolt
and a nut not shown. This configuration is attachable to an
existing combustion apparatus, thereby reducing a manufacturing
cost.
[0079] The signal pressure of the pressure regulator 6 is detected
at an outlet of the air feeder 3. Specifically, as shown in FIG. 1,
the signal pressure is detected at a middle portion between the air
feeder 3 and the burner casing 7. Therefore, there is provided a
signal-pressure outlet 33 in the middle portion (air supply passage
37) between the air feeder 3 and the burner casing 7. The
signal-pressure outlet 33 and the signal-pressure inlet 32 are
connected by the signal-pressure conducting pipe 35.
[0080] The above-mentioned embodiment illustrates the pressure
equalizing valve 6 of a direct acting type, but the present
invention may employ a pressure equalizing valve of a pilot type
not shown.
[0081] Next, a function of the combustion apparatus 1 will be
described in detail below.
[0082] In the combustion apparatus 1 in the present embodiment, the
air feeder 3 is driven and the shutoff valves 21a to 21g are
opened, so as to introduce fuel and air into the burners 8a to 8t,
in which the fuel and the air are mixed to produce a fuel-air gas
mixture. The resulting gas mixture is discharged from the burner
ports not shown of the burners 8a to 8t so as to generate flames
within the combustion space 14.
[0083] More specifically, the air feeder 3 is driven to feed air
into the burner casing 7. The air having been fed from the air
feeder 3 is once introduced into the air-passage forming part 11 in
the burner casing 7, then flowing through the part 11 to the ends
of the burners 8a to 8t, and finally being supplied to each of the
burners 8a to 8t through the air-gas inlets 18.
[0084] The amount of air to be introduced into each of the burners
8a to 8t varies as a function of an air pressure in the vicinity of
the respective air-gas inlet 18 of each of the burners 8a to 8t, an
opening area of the air-gas inlet 18, an internal resistance of
each of the burners 8a to 8t, a resistance (exhaust air resistance)
at downstream of each of the burners 8a to 8t in the air flowing
direction, and an atmospheric pressure.
[0085] The opening area of the air-gas inlet 18 remains unchanged
during combustion. The internal resistance in each of the burners
8a to 8t is also constant. Further, it is taken for granted that
the resistance at downstream of each of the burners 8a to 8t
(exhaust air resistances) and the atmospheric pressure are
substantially constant.
[0086] Thus, variations of the amount of air to be introduced into
each of the burners 8a to 8t correlates most strongly with changes
in air feeding pressure in the vicinity of the respective air-gas
inlet 18. That is, it is practically convenient to regard that the
amount of air to be introduced into each of the burners 8a to 8t is
varied only by changes in pressure in the vicinity of the air-gas
inlet 18.
[0087] Further, it may be said that the pressure in the vicinity of
the air-gas inlet 18 is determined by a discharge pressure of the
air feeder 3, ignoring a condition such as pressure loss in the
burners 8a to 8t.
[0088] On the other hand, the fuel gas is introduced from the fuel
gas supply source into the pressure regulator 6, which reduces the
pressure of the fuel gas. The regulated fuel gas having flowed out
of the pressure regulator 6 enters the fuel supply channel 9 of the
fuel-supply-channel forming unit 5, flows through the branched
channels 9a to 9g, and is discharged through the nozzles 20a to
20t. The nozzles 20a to 20t are disposed at positions opposite the
air-gas inlets 18 of the respective burners 8a to 8t. The fuel gas
having been discharged from each nozzle 20a to 20t enters each of
the burners 8a to 8b through the air-gas inlet 18, so as to be
mixed with air and to be discharged from the respective burner
ports not shown. Flames are generated in the combustion space
14.
[0089] The amount of fuel gas to be introduced into each of the
burners 8a to 8t is equal to the amount of fuel gas flowing through
each of the branched channels 9a to 9g.
[0090] The amount of fuel gas flowing through each of the branched
channels 9a to 9g varies as a function of a gas pressure at
upstream of each of the branched channels 9a to 9g in the fuel-gas
flowing direction, an opening area of each of the branched channels
9a to 9g, an internal resistance of each of the branched channels
9a to 9g, an opening diameter of each of the nozzles 20a to 20t,
and an atmospheric pressure at an outlet of each of the nozzles 20a
to 20t.
[0091] The opening area and the internal resistance of each of the
branched channels 9a to 9g and the opening diameter of each of the
nozzles 20a to 20t remain unchanged during combustion. Further, the
atmospheric pressure at the outlet of each of the nozzles 20a to
20t is substantially constant.
[0092] Thus, variations of the amount of fuel gas to be introduced
into each of the burners 8a to 8t correlates most strongly with
changes in pressure of fuel gas at upstream of each of the branched
channels 9a to 9g. That is, it is practically convenient to regard
that the amount of fuel gas to be introduced into each of the
burners 8a to 8t is determined only by changes in gas pressure at
upstream of each of the branched channels 9a to 9g.
[0093] The combustion apparatus 1 in this embodiment detects a
signal pressure of the pressure regulator 6 at the vicinity of the
outlet of the air feeder 3, so as to change a secondary pressure of
the branched channel 9g connected to the pressure regulator 6 in
accordance with the detected signal pressure.
[0094] Therefore, the amounts of air and fuel gas to be introduced
into the respective burners 8a to 8t are changed by the discharge
pressure of the air feeder 3, which is substantially equal to the
signal pressure of the signal-pressure outlet 33. Increasing of the
amount of air introduced into the burners 8a to 8t by raising of
the discharge pressure of the air feeder 3 raises the discharge
pressure of fuel gas from the pressure regulator 6 in accordance
with raising of the signal pressure of the pressure regulator 6,
thereby increasing the amount of the fuel gas flowing in the fuel
supply channel 9, so that the amount of the fuel gas introduced
into the burners 8a to 8t is increased. Consequently, in this
embodiment, a ratio between the amounts of air and fuel gas to be
introduced into each of the burners 8a to 8t is constant at all
times. Shortly, air and fuel gas are introduced into each of the
burners 8a to 8t at an appropriate ratio between those.
[0095] Further, in the combustion apparatus 1 in the present
invention, closing of some of the shutoff valves (electromagnetic
valves) 21a to 21g disposed in the respective branched channels 9a
to 9g can change the combustion amount. By the combustion apparatus
1 in this embodiment, such a case also achieves the similar effect
as described above.
[0096] Closing of the five shutoff valves 21a to 21e among the
seven valves 21a to 21g shown in FIG. 1, for example, stops supply
of fuel gas to the burners 8a to 8o in the groups 19a to 19e, so
that the burners 8p to 8t in the groups 19f and 19g generate
combustion in the combustion space 14. Even in the above-mentioned
case, the ratio between the amounts of air and fuel gas introduced
into the burners 8a to 8h remains unchanged due to the pressure
regulator 6.
[0097] That means, because air is continuously introduced into all
the burners 8a to 8t even when the shutoff valves 21a to 21e are
closed, a total amount of air discharged outside through the
burners 8a to 8t remains unchanged. That allows no change in the
discharge pressure of the air feeder 3. Consequently, the signal
pressure of the pressure regulator 6 remains unchanged.
[0098] Further, because the pressure regulator 6 has the
secondary-pressure inlet 29 and is communicated with the
secondary-pressure outlet 28 of the branched channel 9g via the
secondary-pressure conducting pipe 34 as described above, the
secondary pressure in the vicinity of the branched channel 9g is
regulated to be constant in accordance with the signal pressure. In
other words, even when some of the shutoff valves 21a to 21g are
closed, the pressure regulator 6 modifies the pressure of fuel gas
to be discharged so as to constantly maintain the secondary
pressure in the vicinity of the branched channel 9g. Further, the
secondary-pressure outlet 28 is near to the burners 8a to 8t
because being disposed in the branched channel 9g. That allows a
small influence by pressure loss, making the air-fuel ratio in the
burners 8a to 8t less likely to change.
[0099] Specifically, even when the shutoff valves 21a to 21e are
closed to stop fuel gas flowing to the closed branched channels 9a
to 9e, the pressures of fuel gas flowing in the branched channels
9f and 9g, in which the respective shutoff valves 21f and 21g are
opened, are regulated to be constant in accordance with the signal
pressure, thus remaining unchanged. Consequently, regardless of the
control of either opening or closing of the shutoff valves 21a to
21e, the same amount of fuel gas flows in the branched channels 9f
and 9g, in which the respective shutoff valves 21f and 21g are
opened. Herein, it is preferable to usually open the shutoff valve
21g of the branched channel 9g provided with the secondary-pressure
outlet 28 in either increasing or decreasing the combustion amount
during combustion.
[0100] The above-mentioned example illustrates the case in which
five of the shutoff valves among the seven valves 21a to 21g are
closed, but the similar effect is achieved and the ratio of the
amounts of air and fuel gas supplied to the burners to be used for
combustion remains unchanged even when less than or more than five
of the valves are closed. That avoids an unstable combustion even
when the shutoff valves 21a to 21g are used to control the
combustion amount.
[0101] The above-mentioned embodiment illustrates a configuration
in which the secondary-pressure outlet 28 is disposed in the
branched channel 9g of the fuel supply channel 9, but the present
invention is not limited thereto and may have a configuration in
which the outlet 28 is disposed in any of the branched channels 9a
to 9f, for example. In this case, it is preferable to dispose in
one of those where a flow of fuel gas is not obstructed during
combustion. In other words, it is preferable to select one having
the shutoff valve never closed during combustion. By this
configuration, an accurate air-fuel ratio is maintained even when
any of the shutoff valves 21a to 21g is closed.
[0102] Further, the above-mentioned embodiment illustrates a
configuration in which the shutoff valves 21a to 21g is provided at
all the branched channels 9a to 9g respectively and the
secondary-pressure outlet 28 is disposed in the branched channel 9g
provided with the shutoff valve 21g, but the present invention is
not limited thereto and may have a configuration in which shutoff
valves are provided in some of the branched channels 9a to 9g and a
secondary-pressure outlet is disposed in one of branched channels
without the shutoff valve. The similar effect as the
above-mentioned embodiment is also achieved by this
configuration.
[0103] Further, the above-mentioned embodiment has a configuration
in which the secondary-pressure outlet 28 is disposed in one of the
branched channels 9a to 9g, but the present invention is not
limited thereto and may have a configuration, as in a combustion
apparatus 1' shown in FIG. 2, in which the outlet 28 is disposed in
the common channel 9y. In this case, it is preferable to dispose at
downstream (in the fuel-gas flowing direction) of the common
channel 9y and adjacent to the boundary with the branched channels
9a to 9g. That regulates a pressure adjacent to the boundary
between the common channel 9y and the branched channels 9a to 9g to
a pressure equal to the signal pressure. Therefore, the similar
effect as the above-mentioned embodiment is achieved.
[0104] Further, the above-mentioned embodiment has a configuration
in which one branched channel is arranged in each of the seven
groups 19a to 19g each consisting of the different number of
burners 8a to 8t, but the present invention is not limited thereto
and may have a configuration, as in a combustion apparatus 1''
shown in FIG. 3, in which the number of burners 8a to 8d is equal
to that of the branched channels 9a to 9d, for example.
[0105] Further, the above-mentioned embodiment has a configuration
in which only one secondary-pressure outlet 28 is provided in the
fuel supply channel 9, but the present invention is not limited
thereto and may have a configuration in which a plurality of
secondary-pressure outlets 28 are provided in the fuel supply
channel 9. As in a combustion apparatus 40 shown in FIG. 4, for
example, secondary-pressure outlets 28a to 28c are respectively
arranged in the branched channel 9g, a downstream portion of the
common channel 9y, and a middle portion of the common channel 9y.
Further, the pressure regulator 6 is connected to a
secondary-pressure conducting pipe 38 via the secondary-pressure
inlet 29. The pipe 38 has three branch pipes 39a to 39c, an end of
each pipes 39a to 39c being communicated with one of the outlets
28a to 28c. In this embodiment, the outlet 28a is communicated with
the pipe 39a, the outlet 28b is communicated with the pipe 39b, and
the outlet 28c is communicated with the pipe 39c. The branch pipes
39a to 39c are respectively provided with shutoff valves
(electromagnetic valves) 41a to 41c. This configuration allows a
more practical control than the combustion apparatus 1 in the
above-mentioned embodiment.
[0106] In the fuel supply channel 9, fuel gas is subjected to
pressure loss because of a pipe resistance, having a pressure
reduced toward downstream. Specifically, in a stable combustion (in
the normal combustion) after the elapse of a certain period of time
after ignition, an actual pressure is decreasing toward downstream
in this way: pressure at the branch pipe 39c>pressure at the
branch pipe 39b>pressure at the branch pipe 39a.
[0107] Thus, a configuration in which the secondary pressure can be
detected at various positions and the positions can be changed
helps slight change in pressure of fuel gas discharged from the
pressure regulator 6. That allows change in the air-fuel ratio
depending on a period of combustion. For example, a ratio of fuel
gas may be increased upon ignition than that in the normal
combustion, the ratio may be kept lower than that in the normal
combustion for a certain period of time after ignition, and the
ratio may be back in a normal state when combustion is stabled.
[0108] Generally, it is said to be preferable to give a higher
ratio of fuel gas than the air-fuel ratio in the normal combustion
so as to improve ignition performance upon ignition. In contrast,
until a certain period of time passes after ignition, it is said to
be preferable to give a lower ratio of fuel gas than the air-fuel
ratio in the normal combustion in case of a combustion state
involving oscillating combustion.
[0109] A modified embodiment shown in FIG. 4 is a combustion
apparatus improving ignition performance upon ignition and a
combustion state until a certain period of time passes after
ignition.
[0110] The combustion apparatus in this embodiment opens only the
shutoff valve 41b provided in the branch pipe 39b in the normal
combustion, so as to control either increase or decrease of fuel
gas based on a secondary pressure detected at the branch pipe
39b.
[0111] Alternatively, the secondary pressure is to be detected at
more downstream so as to have a higher concentration of fuel gas
than that in the normal combustion like upon ignition of the
burners 8.
[0112] Specifically, only the shutoff valve 41a provided at the
branch pipe 39a is opened. Such a control is executed so as to
improve ignition performance more than the combustion apparatus 1
in the foregoing embodiment. This embodiment facilitates ignition
by a higher ratio of fuel gas in ignition than the air-fuel ratio
in the normal combustion.
[0113] Further, an unstable combustion (oscillating combustion)
might be readily generated until a certain period of time passes
after ignition. Specifically, the air feeder 3 is designed to feed
air by driving a motor not shown to rotate fans. Generally, it
takes time to drive the air feeder 3 until reaching a certain air
feeding amount. In contrast, fuel gas flows at a constant flow rate
immediately after opening of the valves. That may require some time
to reach the air-fuel ratio in the normal combustion, resulting in
being subject to oscillating combustion. Consequently, during an
early period of ignition, only the shutoff valve 41c disposed at
the upstream branch pipe 39c is opened to control either increase
or decrease of fuel gas based on a secondary pressure at the valve
41c, so as to make the fuel gas leaner. That reduces oscillating
combustion in an unstable combustion.
[0114] A further modified embodiment described below is recommended
so as to modify the air-fuel ratio with even more flexibility.
[0115] A combustion apparatus 50 shown in FIG. 5 is provided with a
pressure modification board (pressure modification means) 12
adjacent to the signal-pressure outlet 33 and at a position
opposite the outlet 33. The pressure modification board 12 is
designed to either increase or decrease a signal pressure detected
at the outlet 33.
[0116] The pressure modification board 12 is a rectangular thin
plate and rotates so that ends of the board 12 in a longitudinal
direction come close to or move apart from the outlet 33 around its
center in a longitudinal direction. The board 12 controls to change
an angle formed by the intersection with an air flowing direction
of the air supply passage 37, thereby either increasing or
decreasing a signal pressure to be introduced into the pressure
regulator 6. Further, the board 12 is powered by a known stepping
motor (pressure modification means or actuator) not shown. Driving
of the stepping motor rotates the pressure modification board 12.
Herein, the stepping motor is controlled by a controller not shown
and is driven upon reception of a signal from the controller.
[0117] The combustion apparatus 50 in this embodiment is designed
to detect a signal pressure in the pressure regulator 6 at the
outlet of the air feeder 3 and regulates a secondary pressure in
the common channel 9y connected to the pressure regulator 6 in
accordance with the detected signal pressure. Further, in the
combustion apparatus 50, the pressure modification board 12 is
disposed at the air supply passage 37, so as to modify the signal
pressure detected at the signal-pressure outlet 33.
[0118] In this embodiment, as shown in FIG. 6A, one end (downstream
side in the air feeding direction) of the board 12 is arranged to
move slightly close to the signal-pressure outlet 33 (position in a
stable combustion), so as to slightly direct an air flow to the
outlet 33, thereby controlling the air-fuel ratio in the normal
combustion by the action of a slight dynamic pressure. In order to
increase the signal pressure detected at the outlet 33, as shown in
FIG. 6B, the board 12 is controlled to rotate in a direction closer
to the outlet 33 (direction with a larger angle formed by the
intersection of the board 12 with the air flowing direction in the
air supply passage 37), so that more air flows to the outlet 33
(position in an increased dynamic pressure). That increases a
dynamic pressure acting to the position where the pressure is
detected. In contrast, in order to decrease the signal pressure
detected at the outlet 33, as shown in FIG. 6C, the board 12 is
controlled to rotate in a direction away from the outlet 33
(direction with a smaller angle formed by the intersection of the
board 12 with the air flowing direction in the air supply passage
37), so that less air flows toward the outlet 33 (position in a
decreased dynamic pressure). That decreases a dynamic pressure
acting to the position where the pressure is detected.
[0119] Therefore, the pressure modification board 12 is designed to
modify an original signal pressure having been detected at the air
feeder 3 so as to introduce the modified signal pressure into the
pressure regulator 6. More specifically, as shown in FIG. 6B, a
control of the board 12 so as to direct air to the signal-pressure
outlet 33 increases a signal pressure to be introduced into the
signal-pressure inlet 32 without increasing the number of rotations
of the air feeder 3, thereby supplying fuel gas in an amount in
response to the increased signal pressure to the fuel supply
channel 9. That enables a control to have a higher ratio of fuel
gas than the air-fuel ratio in the normal combustion. Consequently,
the combustion apparatus 50 in this embodiment improves ignition
performance in ignition and reduces an oscillating combustion that
is possibly generated within a certain period of time after
ignition and an unstable combustion that is possibly generated in
increasing the combustion amount in the normal combustion by
opening of some of the shutoff valves 21a to 21g.
[0120] Further, as shown in FIG. 6C, a control of the board 12 so
that less air flows toward the outlet 33 than that in the normal
combustion allows an original signal pressure (static pressure) in
response to the number of rotations of the air feeder 3 to be
introduced into the pressure regulator 6, thereby supplying fuel
gas in an amount in response to the signal pressure (static
pressure) to the fuel supply channel 9. That enables a control to
have a lower ratio of fuel gas than the air-fuel ratio in the
normal combustion. Consequently, the combustion apparatus 50 in
this embodiment reduces an oscillating combustion that is possibly
generated within a certain period of time after ignition and an
unstable combustion that is possibly generated in decreasing the
combustion amount in the normal combustion by closing of some of
the shutoff valves 21a to 21g.
[0121] Still further, this embodiment allows either pseudo increase
or decrease of a signal pressure introduced into the
signal-pressure inlet 32 by a control of the board 12.
Consequently, the amount of fuel gas flowing in the fuel supply
channel 9 is either increased or decreased by the pseudo signal
pressure, whereby the air-fuel ratio is modified. The combustion
apparatus 50 in this embodiment not only maintains a constant
air-fuel ratio but also performs practical combustion as described
above by modifying the air-fuel ratio as needed.
[0122] The above-mentioned embodiment illustrates a configuration
in which the pressure modification board 12 is provided adjacent to
the signal-pressure outlet 33 so as to modify a signal pressure,
but the present invention is not limited thereto and may have a
configuration in which the pressure modification board 12 is
provided in the fuel flowing channel.
[0123] As shown in a combustion apparatus 70 in FIG. 7, for
example, in a case where a secondary pressure to be introduced into
the pressure regulator 6 is detected at the secondary-pressure
outlet 28 provided adjacent to the fuel common channel 9, the
pressure modification board 12 is arranged adjacent to the outlet
28. The board 12 is arranged in the substantially same manner as
that in the above-mentioned embodiment. Specifically, the board 12
is arranged so as to slightly direct a flow of fuel gas to the
secondary-pressure outlet 28 for making a dynamic pressure to be
detected. The way to control of either increase or decrease of the
amount of fuel gas is slightly different from that in the
above-mentioned embodiment, being described in detail below.
[0124] In the case of arrangement of the pressure modification
board 12 near a position where the secondary pressure is detected,
a control of the board 12 to direct a flow of fuel gas to the
secondary-pressure outlet 28 makes the secondary pressure detected
at the outlet 28 higher than an original secondary pressure of fuel
gas actually flowing in the fuel supply channel 9. The pseudo
secondary pressure (dynamic pressure) introduced into the pressure
regulator 6 is regulated in accordance with the signal pressure
from the air feeder 3, so that fuel gas supplied to the combustion
space 14e has a lower ratio than the air-fuel ratio in the normal
combustion. Such a control provides an effect similar to that
obtained by detecting the static pressure by controlling the board
12 to rotate so that less air flows to the signal-pressure outlet
33 as described in the above-mentioned embodiment.
[0125] Further, the control of the board 12 so that less fuel gas
flows toward the secondary-pressure outlet 28 allows the secondary
pressure detected at the outlet 28 to be the original secondary
pressure of fuel gas having been discharged in accordance with the
signal pressure. Specifically, the pseudo secondary pressure
(static pressure) introduced into the pressure regulator 6 is
regulated in accordance with the signal pressure from the air
feeder 3, and whereby fuel gas supplied to the combustion space 14
has a higher ratio than the air-fuel ratio in the normal
combustion. Such a control provides an effect similar to that
obtained by detecting the dynamic pressure by controlling the board
12 to rotate so as to direct an air flow to the signal-pressure
outlet 33 as described in the above-mentioned embodiment.
[0126] Consequently, by this configuration, the control of the
pressure modification board 12 regulates fuel gas having a ratio
shifted from the air-fuel ratio in the normal combustion, as
needed, thereby providing an effect similar to that obtained by the
above-mentioned embodiment.
[0127] The above-mentioned embodiment illustrates a configuration
in which the pressure modification board 12 is powered by the
stepping motor as the actuator not shown, but the present invention
is not limited thereto and may have a configuration in which the
board 12 is powered by a servomotor or a motor with a limit
switch.
[0128] The above-mentioned embodiment illustrates a configuration
in which the pressure modification board 12 is controlled in three
steps: the position in the stable combustion; the position in the
increased dynamic pressure; and the position in the decreased
dynamic pressure, but the present invention is not limited thereto
and may have a configuration having at least one additional step
between the positions in the increased dynamic pressure and the
decreased dynamic pressure.
[0129] The above-mentioned embodiment illustrates a configuration
in which the pressure modification board 12 is controlled to be at
the position in the decreased dynamic pressure until a certain
period of time passes after ignition, but the present invention is
not limited thereto and may have a configuration in which the board
12 is controlled to be at the position in the increased dynamic
pressure. Shortly, it is enough only to reduce an unstable
combustion such as an oscillating combustion that is possibly
generated until the combustion is stabilized after ignition.
[0130] By the above-mentioned embodiment, a change of the number of
burners to be used for combustion provides no change of the ratio
of air and fuel supplied to the burners and achieves a stable
combustion. Yet, the combustion might be temporally unstable
immediately after the change of the numbers of burners to be used
for combustion.
[0131] The reason for such a case would be as follows. The pressure
regulators 6 employed in the combustion apparatuses 1 and 50
described above each regulate a secondary pressure of fuel gas so
that a pressure introduced through the signal-pressure inlet 32
becomes substantially equal to a discharge pressure of the fuel gas
from the pressure regulator 6. However, when the combusting area is
decreased by closing of some of the shutoff valves 21a to 21g, the
secondary pressure in the common channel 9y in the fuel supply
channel 9 is temporally increased, resulting in temporally
increasing of the amount of the fuel gas flowing in the remaining
branched channels 9a to 9g having the remaining opened shutoff
valves 21a to 21g. As described above, in each of the combustion
apparatuses 1 and 50, the pressure regulator 6 regulates the
increased secondary pressure in accordance with the signal
pressure, but it takes a certain period of time to regulate the
secondary pressure in accordance with the signal pressure. As a
result, the fuel gas has excessively high concentration in the
combustion space 14 until regulated, resulting in an unstable
combustion.
[0132] Research and studies of the above-mentioned problem revealed
that it is because the slow movement of a main valve of a pressure
regulator to a closed side (in a direction to narrow an open area),
the movement being performed in accordance with pressure increase
of fuel gas within a fuel supply channel.
[0133] Specifically, the pressure regulator has the main valve,
which is operated so as to either increase or decrease an effective
area in which fuel gas flows in the fuel gas passage, thereby
regulating a pressure at the outlet to a predetermined
pressure.
[0134] More specifically, the main valve of the pressure regulator
is operated by a diaphragm or a bellows, each of which has a
predetermined working-fluid chamber. A pressure in the chamber is
either increased or decreased by a working fluid flowing into the
chamber, thereby expanding or contracting the diaphragm or the
bellows so as to operate the main valve. The working fluid is
normally a gas, especially air in a pressure regulator of a direct
acting type and fuel gas in a pressure regulator of a pilot
type.
[0135] Upon pressure increase of fuel gas in the fuel supply
channel, the main valve is moved to the closed side so as to
decrease the pressure of fuel gas discharged from the pressure
regulator, so that the pressure in the fuel supply channel is
returned to a normal level. For doing that, it is necessary to
eliminate a part of the working fluid within the working-fluid
chamber so as to contract the diaphragm or the bellows. However,
the previously produced combustion apparatus could not smoothly
eliminate the working fluid from the chamber, resulting in taking
time to contract that. As a result, excessively high pressure in
the fuel supply channel persisted over a period of time, causing an
unstable combustion.
[0136] Therefore, with a configuration in which a working-fluid
supply part (air supply part) is temporally closed to close a
passage for supplying the fluid to the chamber so as to facilitate
the elimination of the fluid from the chamber when the combusting
area is decreased by closing of shutoff valves, a stable combustion
is maintained even immediately after changing of the number of
burners.
[0137] A further modified combustion apparatus in an embodiment
described below has a pressure regulator provided with a main valve
for either increasing or decreasing an open area in a main passage
of fuel gas and a main-valve drive mechanism for operating the main
valve. The main-valve drive mechanism includes a working-fluid
chamber, a working-fluid supply part, and a leak channel, so as to
operate the main valve by supplying a working fluid to the
working-fluid chamber having passed through the supply part. The
supply part is temporally closed simultaneously with closing the
shutoff valves so as to reduce the combusting area, thereby
stopping supply of the working fluid to the chamber.
[0138] The leak channel is designed to leak the working fluid,
which is supplied from the supply part, from the working-fluid
chamber. Closing of the supply part stops supply of the working
fluid to the chamber and further allows the working fluid within
the chamber to be leaked through the leak channel, thereby
decreasing a pressure in the chamber. That makes the main valve to
move to decrease the open area, so as to rapidly decrease a
secondary pressure of fuel gas. Thus, by the combustion apparatus
in this embodiment, temporally closing of the working-fluid supply
part blocks the working fluid from flowing into the working-fluid
chamber and further allows the working fluid within the chamber to
leak via the leak channel, thereby rapidly decreasing the secondary
pressure. Consequently, even when some of the shutoff valves are
closed so as to decrease the combusting area, the time to regulate
the secondary pressure in the fuel supply channel to an appropriate
secondary channel is shortened.
[0139] The combustion apparatus in this embodiment is designed only
to temporally increase the leak amount of the working fluid so as
to shorten the time required for returning the secondary pressure
within the fuel supply channel to a normal level. Thus, the
working-fluid supply part is opened immediately after the closing,
so that the secondary pressure is regulated to an appropriate
secondary pressure in accordance with a signal pressure.
Consequently, even when the combusting area is reduced by closing
of the shutoff valves, the combustion apparatus in this embodiment
shortens the time to regulate the secondary pressure to an
appropriate secondary pressure and maintains an appropriate
air-fuel ratio, thereby reducing an unstable combustion.
[0140] FIG. 8 is a configuration diagram showing a combustion
apparatus having the above-mentioned embodiment.
[0141] The combustion apparatus 80 shown in FIG. 8 has a
configuration in which a secondary-pressure conducting pipe
(working-fluid supply part) 35 for conducting a signal pressure
from the air feeder 3 is provided with a three-way valve 43. The
three-way valve 43 has connecting ports 43a and 43b in two
directions, the ports 43a and 43b forming a part of the conducting
pipe 35, and a connecting port 43c in the rest one direction, the
port 43c being connected to a temporary leak channel 42. The
working fluid is air from the air feeder 3.
[0142] In order to reduce the combusting area by closing of some of
the shutoff valves 21a to 21g, the three-way valve 43 is temporally
switched at the same time of the closing of the shutoff valves.
Specifically, the three-way valve 43 is switched so as to make the
connecting port 43b to be communicated with the connecting port
43c, thereby leaking the working fluid within a working-fluid
chamber 6i in the pressure regulator 6. That stops introducing the
signal pressure into the working-fluid chamber 6i, thus moving a
diaphragm 6b in the pressure regulator 6 downwardly and also a main
valve 6a downwardly. That narrows an area through which fuel gas
flows, thereby decreasing the secondary pressure. Consequently, by
this configuration, forcible stop to introduce the signal pressure
into the pressure regulator 6 shortens the time to temporally
increase the secondary pressure, thereby reducing an unstable
combustion even when the combusting area is reduced using the
shutoff valves 21.
* * * * *