JPH02150614A - Forced draft type combustion apparatus - Google Patents

Abstract

PURPOSE:To prevent the occurrence of noise even when the amount of combustion is changed and to prevent the occurrence of an extraordinary sound at the time of ignition by a construction wherein a damper for changing the degree of opening of a supply port of a supply duct in accordance with a stream generated with an operation of a fan is disposed in the supply duct and a ventilation hole piercing the supply duct is provided on the downstream side of the damper. CONSTITUTION:When a spark discharge is conducted as an igniting operation by a sparker electrode 17, a fuel-air mixing supplied into a combustion chamber 14 is ignited. Although a force of actuating a damper 38 of a supply element 20 in the direction of closure is generated by an ignition pressure, the ignition pressure can be released by a through hole 31e (31f) provided in a supply case 31 and the degree of opening of the damper 38 can be maintained practically at that corresponding to the amount of combustion. Therefore no extraordinary sound occurs at the time of ignition. The corresponding cross-sectional area of the supply element 20 varies in accordance with the amount of combustion between the minimum and maximum degrees of opening. Therefore the natural frequency of the supply element 20 changes in accordance with a change in the natural frequency of a combustion element 10 varying in accordance with the amount of combustion, in the same way as the latter, and thus noise can be reduced even when the amount of combustion is changed.

Description

[Detailed Description of the Invention] Industrial Application Field 1 The present invention relates to a forced air combustion device equipped with an air blower.
In particular, the present invention relates to improvements that reduce noise for each combustion amount that is changed during steady combustion, and also prevent noise from occurring 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, noise may be generated due to resonance within the combustor casing. is likely to occur.

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 that The basic means of solving this problem and the means of solving the problem when the amount of combustion changes are proposed in the patent application filed in 1983.
It has already been introduced in No. 38030 and Japanese Patent Application No. 63-138031.

One way to do this is to connect an air supply duct to the casing of a blower for supplying combustion air in order to increase the volume of the supply section, which conventionally had a small volume compared 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, each combustor uses a relatively large amount of gas within the range in which the combustion amount can be changed, in order to ignite reliably and safely. 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 due to ignition, the damper is biased in the closing direction, and the natural frequency of the supply section becomes equal to the natural frequency of the combustion section. It will be lower than that.

In addition, in combustion equipment, the initial stage of ignition (cold
Since the flame stability and natural frequency of the combustion equipment are different during steady combustion (hot time) and steady combustion (hot time), even if combustion is performed with the same amount of combustion, the natural frequency of the combustion part will differ between the initial ignition period and the steady combustion time. is not constant.

Therefore, in order to prevent the generation of noise mainly during steady combustion which is used for a long time, even if the damper opening characteristics are set to match the natural frequencies of the combustion section and the supply section, In the early stages of ignition, especially in cold conditions, if the damper opening is biased in the closing direction by the ignition pressure, the natural frequency of the supply section and the natural frequency of the combustion section will deviate greatly, causing abnormal noise. The problem is that there are cases where this happens.

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

[Means for Solving the Problems] The present invention connects an air supply duct corresponding to the combustion chamber to a blower cooling unit that supplies combustion air to a combustion chamber equipped with a burner using a blower, and A damper that changes the opening degree of the air supply port of the air supply duct according to the airflow generated by the operation of the air blower is disposed in the air supply duct, and a ventilation hole passing through the air supply duct is provided downstream of the damper. technical means.

[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 inside 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 supply The natural frequency of the combustion section can be made to match the natural frequency of the combustion section.

Therefore, no noise is generated during normal steady combustion.

In addition, if ignition is performed, for example, at a slow ignition combustion amount within the range in which the combustion amount can be changed, the damper will open according to the combustion amount in accordance with 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 reducing the damper opening to steady combustion. It is possible to maintain the opening almost at the same time.

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 ensured 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 total air combustion. The supply section 20 is equipped with an air supply case 31 that guides the air and the fuel gas, and a heat exchanger 50 is provided in the combustion section 10. The whole is housed in a water heater casing (not shown).

In the combustion section 10, a burner plate 12 in the shape of a flat ceramic plate having a large number of flame ports is disposed in an opening at the lower end of a cylindrical combustion case 11, and an opening at one end of the combustion case 11 is arranged in an exhaust pan 13. The combustion chamber 14 is covered by the combustion case 11, and the exhaust passage 15 is covered by the exhaust pan 13.
are formed respectively.

The exhaust pan 13 contains combustion gas generated in the combustion chamber 14.
An exhaust gas 16 is formed to exhaust the air to the outside. In addition, glass wool 13 is installed on the opposing surfaces inside the exhaust pan] 3 to prevent repeated reflections of air vibrations.
A sloped surface], 3b is formed by a, and the reflection direction is changed. Here, several layers of glass wool], 3
A is fixed with an inorganic binder to form an inclined surface 13b.

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

In addition, near the burner plates 1 to 2 in the combustion case 11, there are two sparker electrodes 7 for ignition, a flame rod 18 for detecting ignition, and a combustion temperature detection for correcting the air-fuel ratio. A thermocouple 19 is provided for each.

The supply section 20 has a burner plate l below the combustion coupe 11.
- Consists of a mixing case 21 provided to cover the mixing case 12, and a blower case 22 provided in communication with the inlet 21a at the lower end of the mixing case 21.

The mixing case 21 disperses the mixed valley air supplied from the inlet 21a and guides it to the combustion section 10.
A rectifying plate 24 is provided inside, and a plurality of holes 2 of the rectifying plate 24
4a performs dispersion and rectification of the air-fuel mixture.

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

The scroll casing 22 is connected to the inlet 21a of the mixing case 21 on the outer circumference of the scroll casing 22a.
An air outlet 22b is provided which forms a certain angle with the center direction of the air outlet 22b.

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

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

Here, in order to improve the mixing, when the blower 25 is operated, the blower case 2 is
The outlet 2 which is the most upstream side with respect to the outlet 22b of the outlet 2
The diameter of the spout 3c1 is larger than the diameter of the other jet ports 23c.

The blower 25 has an impeller 25a inside the blower case 22.
A motor 2 provided on the outside of the blower case 22
5b rotates the impeller 25a, sucks in air and fuel gas from the inlet 23a, blows it out from the outlet 22b, and sends the air-fuel mixture to the combustion section 1 via the mixing case 21.
Supply to 0.

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

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

The air supply case 31 has an equivalent volume 2, an equivalent passage length 1 □, and an equivalent cross-sectional area in order to match the natural frequency f2 of the supply section 20 with the natural frequency f1 based on the acoustic characteristics of the combustion section 10. This is provided 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 opening downward in the figure as an air supply port 31a. Air-tightly joined to the blower coupe 22, and the air supply port 31a
An air supply path 32 is formed that guides the combustion air sucked in from the air supply case 31 and the fuel gas ejected into the air supply case 31 to the suction port 23a.

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.

Further, each side wall 31b, 31d of the air supply case 31 has a first
As shown in the figure, a plurality of through holes 31e and 31f are provided in a distributed manner through the inside and outside of the air supply case 31, respectively.

These through holes 31e and 31f are formed so that a damper 38, which will be described later, is difficult to close when ignition occurs in the combustion section 10.
The air supply path 3 is provided to release the ignition pressure in the combustion chamber 14 that is applied to the supply section 20, and through which air sucked from the intake port 23a of the blower case 22 passes.
It is provided in such a way that it has less influence on the aperture performance of No. 2.

A fuel distribution plate 33 is provided inside the air supply case 31 so as to cover the fuel supply port 31c and a part of the inside of the air supply case 31.
are arranged at an angle.

The fuel distribution plate 33 has a stepped portion in the middle, and the backing 3
4 is airtightly fixed to the inside of the air supply case 31 to form an inclined surface for smoothly guiding the air-fuel mixture to the intake port 23a, and a fuel distribution chamber 35 is formed by the air supply case 31 and the fuel distribution plate 33. do.

The fuel dispersion plate 33 is provided with a plurality of fuel injection ports 33a distributed in a row, and the fuel injection ports 22 of the blower case 22 are provided with a plurality of fuel injection ports 33a.
Several fuel jet ports 33b are provided on the most upstream side with respect to b, separated from the fuel jet port 33a.

As a result, the fuel gas supplied into the fuel distribution chamber 35 is ejected from the fuel injection port 33b as much as possible on the upstream side of the air supply path 32, so that efficient mixing is performed.

This fuel dispersion plate 33 has fuel injection 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 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.

A fuel injection port 3 is provided on the fuel distribution chamber 35 side of the fuel distribution plate 33.
Along the edge of the fuel gas outlet 33,
A fuel guiding plate 33c for guiding the fuel to a is 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 remains in the fuel injection port 33a.
The fuel gas is ejected smoothly, and the fuel gas does not generate abnormal sounds such as resonance when passing through.

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, since the throttle plate 36 forms a venturi that reduces the cross-sectional area of the air supply passage 32 and once restricts the air passing through the air supply passage 32, the throttle plate 36 reduces the cross-sectional area of the air supply passage 32 and once restricts the air passing through the air supply passage 32. Each fuel jet port 33a, 3 of the plate 33
The fuel gas ejected from 3b 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 S2 of the supply section 20 by its swinging.
8 operates according to the wind pressure of the air sucked in from the air supply port 31a as the blower 25 operates, and the corresponding cross section MS2
change. 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. becomes smaller, and the equivalent cross-sectional area S
Decrease 2.

When the damper 38 swings, a portion of the tip 38a on the outer circumferential side comes into contact with the inner wall 31g of the air supply case 31 when the equivalent cross-sectional area S2 of the supply section 20 becomes the minimum and exhibits the minimum opening degree. A protrusion 38b is formed. As a result, even when the equivalent cross-sectional area 82 of the supply section 20 is minimized, an appropriate gap is formed between the tip 38a of the damper 38 and the inner wall 31g of the air supply case 31, and the required amount of air is can be supplied.

When the equivalent cross-sectional area S2 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 area S2 becomes the maximum and exhibits the maximum opening degree, the damper 38 moves toward the diaphragm plate 36 as shown by the two-dot chain line.
It stabilizes after a moderate interval.

Further, at both ends of the damper 38 in the axial direction, there are curved portions 3 for guiding the air sucked in and pushing up the damper 38 inward.
8c and 38d are formed.

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.

Furthermore, since the bearing parts 38e and 38f of the damper 38 are provided on the flat plate part 23 side of the blower case 22 with respect to the damper 38 which receives wind pressure, the horizontal distance between the center of gravity of the damper 38 and the shaft 37 can be secured, and the damper 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,
Since the air flow can pass between the damper 38 and the diaphragm plate 36, the damper 38 can be stabilized in each case.

The inner wall 31g of the air supply case 31 that the protrusion 38b of the damper 38 comes into contact with is provided with a protrusion 39 that protrudes toward the inside of the air supply case 31 in order to change the direction of the sucked air flow. There is. Due to this protrusion 39, when the damper 38 is in the closed state, air from the air supply port 31a hits the portion 173 from the tip 38a of the damper 38.
When the damper 38 is fully opened, air hits the entire damper 38, so 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, and the bearing member 40 is connected to the flat plate portion 2.
3 and a fitting groove formed in the air supply case 31.

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

A fuel pipe 60a that guides fuel to the fuel supply port 31c is connected to a fuel jet pipe 23b, and the fuel jet pipe 23b is connected to the fuel pipe 60.
is connected to.

A blower 2 is installed in the 1st stream of the fuel pipe 60 depending on the required combustion amount.
A proportional control valve (not shown) that is controlled together with the fuel injection pipe 23b and the fuel supply port 31c is provided, and fuel gas whose supply amount is adjusted by the proportional control valve is supplied to the fuel injection pipe 23b and the fuel supply port 31c.

The heat exchanger 50 is connected to a wood 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 combustor 2 starts combustion in a predetermined sequence, and the water flow control valve starts supplying water into the heat exchanger 50. The amount of inflow is adjusted.

When the blower 25 is controlled to a slow ignition speed and air is sucked in from the air supply port 31a by its operation, the damper 3
8 changes the 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 ejection port 23c of the fuel injection pipe 23b and the fuel ejection ports 33a and 33b of the fuel distribution plate 33, and the fuel gas is wide. It is sprayed 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, the ignition pressure generates a force that urges the damper 38 of the supply section 20 in the closing direction, but the ignition pressure can be released through the through holes 31e and 31f provided in the air supply case 31. Since the opening degree of the damper 38 can be maintained approximately at the opening degree corresponding to the combustion amount, no abnormal noise is generated at the time of ignition.

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

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

The combustion amount is increased, and the rotation speed of the blower 25 is increased from N2 to N2.
3, the damper 38 exhibits an opening degree that corresponds to the amount of air blown.

The combustion amount is further increased, and the rotation speed of the blower 25 is increased to N.
Between 3 and N4, the damper 38 is fully open.

Therefore, between the minimum opening degree and the maximum opening degree, the equivalent cross-sectional area S2 of the supply section 20 changes depending on the combustion amount, so the natural frequency f1 of the combustion section 10 changes depending on the combustion amount. Accordingly, the natural frequency f2 of the supply section 20 changes in the same way, and 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 the drawing]

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, and 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, 2
2...Blower case (blower casing), 25...
・Blower, 31...Air supply case (air supply duct), 31
e, 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 an airflow is generated in the air supply duct as the blower operates. A forced air combustion device 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 condition, and a ventilation hole passing through the air supply duct is provided downstream of the damper. .