JPH0444165B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a forced air combustion device equipped with an air blower, and in particular aims at reducing noise for each combustion amount that is changed during steady combustion. This invention relates to an improvement for preventing the generation of noise even during ignition.

[Prior Art] In forced-air combustion devices, such as small gas water heaters, in which combustion air is supplied by a blower and combustion occurs within a narrow combustion chamber, resonance within the combustor casing, etc. noise is likely to be generated.

The inventors of the present application have discovered that such noise is caused by a mismatch in the natural frequencies of the combustion section, which consists of a combustion chamber and exhaust path, and the supply section, which consists of a mixing chamber, blower casing, etc., and have found that noise Basic means for this purpose and solutions for cases where the combustion amount changes are described in Japanese Patent Application No. 1983-138030, (Japanese Patent Application Laid-open No. 29505-1983), Japanese Patent Application No. 138031-1982, (Japanese Patent Application Laid-open No. 1997-1998). It was already introduced in Publication No. 306713).

One way to do this is to connect an air supply duct to a blower casing for supplying combustion air to increase the volume of the supply section, which conventionally had a small volume relative to the combustion section. In addition, even if the natural frequency of the combustion section changes due to a change in the combustion amount, the combustion amount is set in the supply air duct as a means of matching the natural frequency of the supply section. A damper is installed to change the opening degree of the air intake port of the air supply duct according to the change in the amount of combustion, and the natural frequency of the supply section is changed in accordance with the change in the amount of combustion to prevent noise caused by changes in the amount of combustion. ing.

[Problem to be Solved by the Invention] However, in general, when igniting combustion equipment, in order to ignite reliably and safely, each combustor uses a relatively large amount of gas within the range in which the combustion amount can be changed. Ignition is performed with a slow ignition combustion amount in the middle of a variable range, for example, and with a large proportion of fuel to the supplied combustion air.

Therefore, in a forced air combustion device equipped with the damper described above, when ignition pressure is generated by ignition, the damper is biased in the closing direction.
The natural frequency of the supply section is lower than the natural frequency of the fuel section.

In addition, in combustion equipment, the flame stability and natural frequency of the combustion equipment differ between the initial stage of ignition (cold time) and steady combustion (hot time), excluding re-ignition, so even if combustion is performed with the same amount of combustion, In the combustion section, the natural frequencies during the initial stage of ignition and steady combustion are not constant.

Follow. Even if the damper opening characteristics are set to match the natural frequencies of the combustion section and the supply section in order to prevent the generation of noise mainly during steady combustion, which is used for a long period of time, When the damper is open in the closed direction due to the ignition pressure during cold operation, the natural frequency of the supply section and the natural frequency of the combustion section will deviate greatly, causing abnormal noise. There is a problem that occurs.

The present invention features forced air combustion that does not generate noise even when the combustion amount is changed during steady combustion (hot), ignites reliably during ignition, and does not generate abnormal noise even when ignited during cold conditions. The purpose is to provide equipment.

[Means for Solving the Problems] The present invention provides a blower casing that supplies combustion air to a combustion chamber equipped with a burner by a blower,
An air supply duct corresponding to the combustion chamber is connected, and a damper is arranged in the air supply duct to change the opening degree of the air supply port of the air supply duct in accordance with the airflow generated with the operation of the blower. At the same time, it is a technical measure that a ventilation hole passing through the air supply duct is provided downstream of the damper.

[Operation and Effects of the Invention] In the present invention, since the blower casing is provided with the air supply duct corresponding to the combustion chamber, the natural frequency of the supply section consisting of the blower casing, the air supply duct, etc. is adjusted to the combustion chamber, etc. Basically, the natural frequency of the combustion section can be approximated.

In addition, a damper is installed in the air supply duct, and the opening degree of the air supply port of the air supply duct is changed by the airflow generated by the operation of the blower, so even if the combustion amount is changed. , the natural frequency of the supply section can be made to match the natural frequency of the combustion section.

Therefore, no noise is generated during normal steady combustion.

In addition, when ignition is performed, for example, at an intermediate warm ignition combustion amount within the range in which the combustion amount can be changed, the damper will open according to the combustion amount in response to the operation of the blower, and at the time of ignition, the damper will open in accordance with the combustion amount. When the internal pressure increases due to the ignition pressure, it acts to bias the damper in the closing direction. However, the air supply duct has a ventilation hole downstream of the damper, which allows the ignition pressure to escape, weakening the force that biases the damper in the closing direction and keeping the damper open at a steady state. The opening can be maintained at approximately the same opening as during combustion.

Therefore, a sudden change in the acoustic natural frequency can be prevented, a considerable cross-sectional area of the opening of the supply section can be secured in terms of acoustic characteristics, and noise such as combustion resonance noise is not generated.

[Example] Next, the present invention will be explained based on examples.

The gas water heater 1 shown in Fig. 2 is equipped with a high-efficiency combustor 2 that is compact and achieves low noise through all primary air combustion.
0, and a supply section 20 that supplies a mixture of fuel gas and air to the combustion section 10.The supply section 20 is equipped with an air supply case 31 that guides air and fuel gas. A heat exchanger 50 is provided, and the entire heat exchanger 50 is housed in a water heater casing (not shown).

In the combustion section 10, a burner plate 12 in the shape of a flat plate made of ceramics and having a large number of flame ports is disposed at the opening at the lower end of a cylindrical combustion case 11, and an exhaust damper 13 is arranged at the opening at the upper end of the combustion case 11. The combustion chamber 14 is covered by the combustion case 11.
Furthermore, exhaust passages 15 are formed by the exhaust pans 13, respectively.

An exhaust port 16 is formed in the exhaust pan 13 to exhaust combustion gas generated in the combustion chamber 14 to the outside. In addition, glass wool 13a is provided on the opposing surfaces inside the exhaust pan 13 to prevent repeated reflections of air vibrations.
is formed and changes its reflection direction. Here, the inclined surface 13b is formed by fixing several layers of glass wool 13a with an inorganic binder.

A water tube type heat exchanger 50 connected to a water supply source such as a water supply is provided above the combustion case 11, and heats water passing through the interior.

In addition, two sparker electrodes 1 for ignition are provided near the burner plate 12 in the combustion case 11.
7. Flame rod 18 for detecting ignition;
A thermocouple 19 is provided for detecting combustion temperature for correcting the air-fuel ratio.

The supply unit 20 includes a mixing case 21 provided below the combustion case 11 and covering the burner plate 12.
and a blower case 22 provided in communication with an inlet 21a at the lower end of the mixing case 21.

The mixing case 21 disperses the air-fuel mixture supplied from the inlet 21a and guides it to the combustion section 10.
A rectifying plate 24 is provided inside the mixing case 21, and the plurality of holes 24a of the rectifying plate 24 disperse and rectify the air-fuel mixture.

As shown in FIGS. 3 and 4, the blower case 22 includes a scroll casing 22a having a substantially short cylindrical shape with one bottom open, and a flat plate portion 23 provided so as to close the opening of the scroll casing 22a. The blower case 22 is equipped with a blower 25.

An air outlet 22b is provided on the outer periphery of the scroll casing 22a, communicating with the inlet 21a of the mixing case 21 and forming a constant angle with respect to the center of the scroll casing 22a.

The flat plate part 23 is provided with a bellmouth-shaped suction port 23a that protrudes toward the scroll casing 22a side at the center thereof, and according to the rotational state of the blower 25, air and fuel gas are sucked in from the suction port 23a, and the air and fuel gas are sucked in from the suction port 23a. It blows out from 22b.

A fuel ejection pipe 23b for ejecting fuel gas supplied from the fuel pipe 60 is formed integrally with the flat plate part 23 on the surface of the flat plate part 23, which is the outside of the blower case 22. The spout ports 23c are provided in one row.

Here, in order to improve the mixing, among the jet ports 23c arranged in a row, the diameter of the jet port 23c1, which is the most upstream side with respect to the blow port 22b of the blower case 22 when the blower 25 is activated, is different from that of the other jet ports 23c. It is made larger than the diameter of the spout 23c.

The blower 25 includes an impeller 25a inside the blower case 22, and rotates the impeller 25a by a motor 25b provided outside the blower case 22, sucks air and fuel gas through the intake port 23a, and blows the air and fuel gas. The air-fuel mixture is blown out from the outlet 22b and is supplied to the combustion section 10 via the mixing case 21.

Here, the motor 25b is controlled according to the required combustion amount, and the impeller 25b is rotated at a rotation speed according to the control state.
Rotate a.

An air supply case 31 is installed in the blower case 22 so as to cover the intake port 23a and the fuel injection pipe 23b.
is provided.

The air supply case 31 has an equivalent volume V ₂ , a passage equivalent length l _{2 , and an equivalent cross-sectional area in order to match the natural frequency 2 of} the supply section 20 with the natural frequency 1 based on the acoustic characteristics of the combustion section ₁₀ . This was established to ensure _S2 .

The air supply case 31 has a substantially rectangular parallelepiped shape that is open in two directions, with one open part facing the flat plate part 23 of the blower case 22 and the other open part facing the air supply port 31a.
An air supply path 32 that opens downward in the figure and is hermetically joined to the blower case 22 and guides combustion air sucked in from the air supply port 31a and fuel gas ejected into the air supply case 31 to the suction port 23a. Form.

A fuel supply port 31c is provided through one side wall 31b of the air supply case 31 to be connected to the fuel pipe 60a.

In addition, each side wall 31b, 31d of the air supply case 31 has a plurality of through holes 31e, 31, which pass through the inside and outside of the air supply case 31, as shown in FIG.
f are provided separately.

These through holes 31e and 31f are connected to the combustion section 10.
The combustion chamber 1 is added to the supply section 20 so that a damper 38 (described later) is difficult to close during ignition.
This is provided to release the ignition pressure in the blower case 22, and is designed to reduce the effect on the throttle performance of the air supply path 32 through which air sucked from the intake port 23a of the blower case 22 passes. It is provided.

Inside the air supply case 31, a fuel distribution plate 33 is disposed at an angle so as to cover the fuel supply port 31c and a part of the inside of the air supply case 31.

The fuel distribution plate 33 has a step in the middle, is airtightly fixed to the inside of the air supply case 31 by packing 34, and forms an inclined surface for smoothly guiding the air-fuel mixture to the intake port 23a. air case 31
and the fuel distribution plate 33 form a fuel distribution chamber 35.

The fuel distribution plate 33 is provided with a plurality of fuel injection ports 33a distributed in a row, and the blower case 2
On the most upstream side of the second outlet 22b, there are several fuel outlets 33b separated from the fuel outlet 33a.
is provided.

As a result, more fuel gas supplied into the fuel distribution chamber 35 is ejected from the fuel ejection port 33b toward the upstream side of the air supply path 32, so that efficient mixing is performed.

This fuel dispersion plate 33 has fuel jet ports 33a, 33b that have different sizes and numbers depending on the type of gas used, and can easily handle different gas types, and can control the fuel supply amount and the fuel gas. and air are mixed properly. Note that when the fuel distribution plate 33 is replaced depending on the type of gas, the flat plate portion 23 integrated with the fuel injection pipe 23b is also replaced at the same time.

On the fuel distribution chamber 35 side of the fuel distribution plate 33, there is a fuel guide plate 33c along the end of the fuel nozzle 33a for smoothly guiding the fuel gas to the fuel nozzle 33a.
are fixed by spot welding.

As a result, even if the amount of fuel gas supplied into the fuel distribution chamber 35 or the gas pressure changes, the fuel gas can be smoothly ejected from the fuel injection port 33a, and the fuel gas can avoid abnormalities such as resonance when passing through the fuel injection port 33a. No sound is produced.

In the air supply passage 32 on the upstream side of the air supply case 31, the width of the air supply passage 32 is gradually reduced toward the fuel injection pipe 23b so that the air passing therethrough is not disturbed. An arranged aperture plate 36 is provided.

Therefore, the throttle plate 36 forms a ventilate that reduces the cross-sectional area of the air supply passage 32 and once restricts the air passing through the air supply passage 32, so that each injection port 23c of the fuel injection pipe 23b and the fuel Dispersion plate 3
The fuel gas ejected from the three fuel ejection ports 33a, 33b can be mixed well with air.

A damper 38 swingably supported by a shaft 37 is provided in the air supply case 31 near the air supply port 31a. The damper 38 is provided to change the equivalent cross-sectional area S ₂ of the supply section 20 by its swinging motion. , and changes the equivalent cross-sectional area S ₂ .
As a result, when the combustion amount of the combustor 2 is large and the amount of air blown is large, the damper 38 is opened and the equivalent cross-sectional area _S2 becomes large, and when the amount of combustion is small and the amount of air blown is small, the damper 38 is opened. The opening degree of is reduced, reducing the equivalent cross-sectional area _S2 .

The tip 38 on the outer circumferential side when the damper 38 swings
In a part of a, when the equivalent cross-sectional area S ₂ of the supply section 20 becomes the minimum and exhibits the minimum opening degree, the air supply case 3
A protrusion 38b that abuts on the inner wall 31g of 1 is formed. As a result, the equivalent cross-sectional area S ₂ of the supply section 20
Even when the tip 3 of the damper 38
A suitable gap is formed between the air supply case 8a and the inner wall 31g of the air supply case 31, so that the necessary amount of air can be supplied.

When the equivalent cross-sectional area S ₂ of the supply section 20 is the minimum, the damper 38 has this protrusion 38b in contact with the inner wall 31g of the air supply case 31, as shown in FIG. When the cross-sectional area S ₂ becomes the maximum and exhibits the maximum opening, the damper 38
As shown by the two-dot chain line, it is stabilized with an appropriate distance from the diaphragm plate 36.

Further, curved portions 38c and 38d are formed at both ends of the damper 38 in the axial direction to guide the air sucked in and pushing up the damper 38 inward.
These curved portions 38c and 38d prevent the air hitting the damper 38 from escaping to the outside of the curved portions 38c and 38d, making it difficult for dust and the like to adhere to the inner wall surface of the air supply case 31.

Further, bearing portions 38e and 38f of the damper 38
is provided on the flat plate portion 23 side of the blower case 22 with respect to the damper 38 that receives wind pressure, so that a horizontal distance between the center of gravity of the damper 38 and the shaft 37 can be secured;
The rotational moment due to the weight of the damper 38 can always bias the damper 38 in the closed state, and even when the damper 38 is at its maximum opening, airflow can pass between the damper 38 and the throttle plate 36. Therefore, the damper 38 can be stabilized in each case.

Upstream of the inner wall 31g of the air supply case 31 against which the projection 38b of the damper 38 comes into contact, a protrusion 39 that protrudes toward the inside of the air supply case 31 is provided to change the direction of the sucked air flow. Due to this protrusion 39, when the damper 38 is in the closed state, air from the air supply port 31a is difficult to hit the 1/3 part from the tip 38a of the damper 38, and when it is fully open, the entire damper 38 is Because of the air,
The opening degree of the damper 38 can be made proportional to the combustion amount.

The shaft 37 is loosely supported at both ends by a cylindrical bearing member 40 made of fluororesin.
0 is fitted and supported within a fitting groove formed in the flat plate portion 23 and the air supply case 31.

A filter 41 made of a metal mesh is provided in the air supply port 31a.

Fuel pipe 60a that guides fuel to fuel supply port 31c
is connected to the fuel injection pipe 23b, and is connected to the fuel injection pipe 23b.
3b is connected to a fuel pipe 60.

A proportional control valve (not shown) is provided upstream of the fuel pipe 60 and is controlled together with the blower 25 according to the required amount of fuel. A regulated fuel gas is provided.

The heat exchanger 50 is connected to a water pipe (not shown) that leads water from the water supply, and the water pipe upstream of the heat exchanger 50 is equipped with a water flow control valve, a water flow sensor, and an inlet water temperature thermistor from the upstream side. A hot water temperature thermistor is provided downstream of the heat exchanger 50, and a water faucet (not shown) that is operated by the user is provided at the downstream end.

The gas water heater 1 having the above configuration is controlled by a control device and operates as follows.

When the user sets the hot water temperature using the controller and operates the faucet to start hot water supply, the fuel device 2 starts combustion in a predetermined sequence, and the water flows into the heat exchanger 50 using the water flow control valve. The inflow of water is adjusted.

When the blower 25 is controlled to a slow ignition rotational speed and air is sucked in from the air supply port 31a by its operation, the damper 38 changes its opening degree to the opening degree for ignition according to the amount of air supply.

On the other hand, fuel gas whose supply amount is adjusted for slow ignition by the proportional control valve is ejected from the injection port 23c of the fuel injection pipe 23b and the fuel injection ports 33a, 33b of the fuel distribution plate 33. is ejected over a wide area and mixes well with the air.

When spark discharge is performed at the sparker electrode 17 as an ignition operation, the air-fuel mixture supplied into the combustion chamber 14 is ignited. At this time, depending on the ignition pressure, the supply part 2
A force that urges the damper 38 in the closing direction is generated, but the through hole 3 provided in the air supply case 31
Since the ignition pressure can be released by 1e and 31f, the opening degree of the damper 38 can be maintained approximately at the opening degree corresponding to the combustion amount, so that no abnormal noise is generated during ignition.

Thereafter, the damper 38 swings to each position as follows depending on the amount of air sucked in.

When the combustion amount of the combustor 2 is small and the rotation speed of the blower 25 is between N1 and N2 in FIG.
The damper 38 comes into contact with the inner wall 31g and exhibits an opening state with the minimum opening area as shown by the broken line A.

The combustion amount is increased and the rotation speed of the blower 25 is increased to N.
Between 2 and N3, the damper 38 exhibits an opening degree that corresponds to the amount of air blown.

When the combustion amount is further increased and the rotational speed of the blower 25 is between N3 and N4, the damper 38 is fully opened.

Therefore, between the minimum opening degree and the maximum opening degree, the equivalent cross-sectional area S ₂ of the supply section 20 changes depending on the combustion amount, so the natural frequency f of the combustion section 10 changes depending on the combustion amount. ₁ , the natural frequency f ₂ of the supply section 20 changes in the same way, so that even if the combustion amount changes, noise can be reduced. Note that at this time, the combustion amount of the combustor 2 changes as shown by the solid line B.

As described above, according to the present invention, no abnormal sound or noise is generated during ignition or steady combustion, and a low-noise combustion device can be achieved.

[Brief explanation of drawings]

1 to 4 show a gas water heater according to an embodiment of the present invention, FIG. 1 is an exploded perspective view showing the inside of the air supply case, and FIG. 2 is a front view showing the schematic configuration of the gas water heater. FIG. 3 is an exploded perspective view showing the configuration of the supply section;
FIG. 4 is a side sectional view of the supply section. FIG. 5 is a characteristic diagram showing the amount of combustion air supplied by the supply section of this embodiment and the opening degree of the damper. In the figure, 2... combustor (forced air combustion device),
12...Burner plate (burner), 14...Combustion chamber, 22...Blower case (blower casing) 25...Blower, 31...Air supply case (air supply duct), 31e, 31f...Through hole (ventilation) hole),
38...Damper.

Claims (1)

[Claims] 1. An air supply duct corresponding to the combustion chamber is connected to a blower casing that supplies combustion air by a blower to a combustion chamber equipped with a burner, and air generated in the air supply duct as the blower operates. Forced air combustion characterized in that a damper is arranged to change the opening degree of the air supply port of the air supply duct according to the airflow, and a ventilation hole passing through the air supply duct is provided downstream of the damper. Device.