JPH0756380B2 - Combustion type combustion device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a compulsory blower type combustion apparatus that supplies combustion air to a burner by a blower, and in particular, a burner plate is arranged in a combustion chamber to perform high load combustion. , It is effective in the case where the combustion amount is changed as necessary.

[Prior Art] In a forced-blowing combustor, in order to prevent noise generated by high-load combustion, a natural frequency f ₁ (determined by the size and shape of the combustion part that performs combustion Of the combustion resonance noise and noise by matching the natural frequency f ₂ (the minimum natural frequency when there is more than one) determined by the size and shape of the supply part that supplies the combustion air. Can be reduced.

These natural frequencies f ₁ and f ₂ are the equivalent cross-sectional areas S ₁ and S ₂ of the openings with respect to the atmosphere of each part, the passage equivalent lengths l ₁ and l ₂ , and the equivalent volumes.
It is determined based on V ₁ , V ₂ , and sound velocities c ₁ , c ₂ , respectively.

Further, in the forced air blowing type combustion device, since the temperature in the combustion chamber and the exhaust passage and the like are changed and the passage resistance is different between the initial stage of combustion and the steady state combustion, even if the blower is controlled to the same rotation speed,
The supply amount of combustion air changes regardless of the control state of the blower. This change is remarkable especially in a combustor in which a burner plate is arranged in the combustion chamber and which performs all primary air combustion. In response to such changes, the air-heat ratio is normally corrected by detecting the combustion temperature by a thermocouple, and the ratio of the air and fuel supply amounts is appropriately maintained.
Stable combustion can be obtained.

[Problems to be Solved by the Invention] However, in an actual combustion apparatus, for example, as in a gas water heater, the amount of combustion required to heat water changes depending on the temperature of supplied water and the amount of supplied hot water. To do. Therefore, in the combustion section, the temperature inside the combustion changes with the change in the combustion amount, and at the same time, the sound velocity c ₁ in the combustion section changes, so the natural frequency f ₁ of the combustion section changes according to the combustion amount. . On the other hand, in the supply unit, the sound velocity does not change due to the change in the combustion amount,
Depending on the amount of combustion, the natural frequency f ₁ of the combustion section and the natural frequency
There is a problem that noise cannot easily occur because f ₂ cannot be matched.

Further, normally, the air-heat ratio is corrected according to the change in the supplied air amount between the initial stage of combustion and the steady state combustion, but in the combustor of all primary air combustion, the range of the stable combustion region is narrow. further,
The blower is controlled within a certain number of revolutions.For example, when the water supply temperature to the gas supplier is high and the heating amount becomes excessive, the combustion amount is controlled to the minimum combustion amount, and the blower is accordingly adjusted. Since the rotation speed of is kept fixed at the minimum rotation speed,
Even if the air-heat ratio is out of the range of the stable combustion region, the amount of combustion air supplied cannot be corrected by changing the operating state of the blower.

Therefore, in the combustor of all primary air combustion, especially when the blower is controlled to the minimum rotation speed, even if there is a difference in the air flow rate between the initial combustion and the steady combustion, the air-heat ratio is from the stable combustion region. It is necessary to ensure that the air flow rate is maintained in the stable combustion region so as not to make a large deviation.

INDUSTRIAL APPLICABILITY The present invention can reduce the generation of noise even when the combustion amount is changed in the forced air blowing type combustion device that supplies combustion air by a blower, and even when the combustion amount is changed, The purpose is to maintain a proper air-heat ratio regardless of temperature and to obtain stable combustion.

[Means for Solving the Problem] The present invention includes a blower that is controlled from a minimum rotation speed to a maximum rotation speed in accordance with a target combustion amount, and a supply unit provided with an air supply duct on the suction side of the blower, In a forced-blowing combustor comprising a combustion section having a burner, the equivalent cross-sectional area of the opening of the air supply duct, which corresponds to the passage, so that the natural frequency of the supply section substantially matches the natural frequency of the combustion section. While setting the length and equivalent volume, in the air supply duct,
A damper that is swingably supported to change the equivalent cross-sectional area is provided, and the damper minimizes the equivalent cross-sectional area when the rotation speed of the blower is the minimum rotation speed, and the rotation speed of the blower. Is greater than the first predetermined number of revolutions greater than the lowest number of revolutions, the corresponding cross-sectional area is increased in accordance with the air flow generated by the operation of the blower, and the first predetermined number of revolutions or more and the highest number of revolutions The technical means is to maximize the equivalent cross-sectional area when the rotational speed is equal to or higher than the second predetermined rotation speed smaller than the predetermined number.

[Operation] In the forced ventilation combustion device of the present invention, since the blower is provided with the air supply duct, the natural frequency of the supply unit can be made close to the natural frequency of the combustion unit. Further, in the air supply duct, a damper that is swingably supported and that changes the equivalent cross-sectional area of the air supply duct in accordance with the airflow generated by the operation of the blower is installed, so the combustion amount If it changes, the damper opening changes according to the blower volume of the blower, which is changed according to the change in the combustion amount, so the natural frequency of the supply unit is changed in accordance with the natural frequency of the combustion unit. can do. Here, since the damper is set so as to largely change the equivalent cross-sectional area of the air supply duct only when the rotational speed is equal to or higher than the first predetermined rotational speed, the minimum rotational speed of the blower is smaller than the first rotational speed. In the case of the rotational speed, the damper is always positioned so that the equivalent cross-sectional area becomes the minimum regardless of whether the temperature of the combustion section is low at the beginning of combustion or at the time of steady combustion where the temperature is high.

Further, when the rotation speed of the blower is equal to or higher than the second predetermined rotation speed, the damper is positioned so that the equivalent sectional area of the air supply duct becomes maximum.

[Advantages of the Invention] In the present invention, even if the natural frequency of the combustion part changes due to the change in the combustion amount, the blower rotates from the first rotation speed to the second rotation speed.
In the combustion amount controlled by the rotation speed of, the equivalent cross-sectional area is changed by the damper swinging in the air supply duct and the natural frequency of the supply part is changed. Can be matched. Therefore, it is possible to reduce the generation of noise even if the combustion amount changes.

Further, when the rotation speed of the blower is controlled to the minimum rotation speed, the damper is always positioned so as to have the smallest equivalent cross-sectional area. At this time, since the damper is in contact with the air supply duct, Even if the passage resistance differs due to the difference, the equivalent cross-sectional area is not changed by the damper and the equivalent cross-sectional area in the air supply duct is constant. Only minimal changes due to differences in.

Therefore, the size and arrangement of the dampers are adjusted so that stable combustion can be obtained both during the initial combustion and during steady combustion at the minimum combustion amount where the stable combustion region is narrow and the rotation speed of the blower is at the minimum rotation speed. Then, even in each combustion amount within the operation range of the blower controlled within the fixed rotation speed range from the minimum rotation speed to the maximum rotation speed, the combustion is performed in the stable combustion region both at the initial combustion and at the steady combustion.

EXAMPLES Next, the present invention will be described based on examples.

The gas supply device 1 shown in FIG. 2 is equipped with a highly efficient combustor 2 that is small in size and realizes low noise by all primary air combustion. The combustor 2 supplies fuel to the combustion part 10 and the combustion part 10. And a supply unit 20 for supplying a mixture of gas and air.
20 is provided with an air supply case 31 for guiding air and fuel gas, a heat exchanger 50 is provided in the combustion section 10, the combustor 2 is controlled by a control device 70, and the entire gas water heater 1 is illustrated. Not stored in the water heater casing.

In the combustion section 10, a ceramic flat burner plate 12 having a large number of flame openings is arranged in the opening at the lower end of a cylindrical combustion case 11, and the opening at the upper end of the combustion case 11 is an exhaust pan 13. Combustion chamber 14 covered by combustion case 11
However, the exhaust passages 15 are formed by the exhaust pans 13, respectively.

The exhaust pan 13 is formed with an exhaust port 16 for discharging the combustion gas generated in the combustion chamber 14 to the outside. Further, an inclined surface 13b is formed by glass wool 13a on the opposing surface inside the exhaust pan 13 in order to prevent repeated reflection of air vibrations, and its reflection direction is changed.

Here, several layers of glass wool 13a are fixed with an inorganic binder to form the inclined surface 13b.

A water pipe type heat exchanger 50 connected to a water supply source such as water supply is provided above the inside of the combustion case 11 to heat water passing through the inside.

Further, in the vicinity of the burner plate 12 in the combustion case 11, two sparker electrodes 17 for ignition, a frame rod 18 for detecting ignition, and a thermocouple 19 for detecting combustion temperature for correcting the air-fuel ratio. Are provided respectively.

The supply unit 20 includes a mixing case 21 provided below the combustion case 11 so as to cover 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 inflow port 21a and guides it to the combustion unit 10. A rectifying plate 24 is provided in the mixing case 21, and the air-fuel mixture is formed by a plurality of holes 24a of the rectifying plate 24. Disperse and rectify.

The blower case 22 is, as shown in FIG. 1 and FIG.
A scroll casing 22a having a substantially short cylindrical shape with one bottom surface opened, and a flat plate portion 23 provided so as to close the opening of the scroll casing 22a.
22 is equipped with a blower 25.

On the outer peripheral portion of the scroll casing 22a, the mixing case 21
An air outlet 22b is provided which communicates with the inflow port 21a and forms a constant angle with the center direction of the scroll casing 22a.

The flat plate portion 23 is provided at its center with a bellmouth-shaped suction port 23a protruding toward the scroll casing 22a side, and sucks air and fuel gas from the suction port 23a according to the rotation state of the blower 25, and blows it out. Blow out from 22b.

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

Here, the blower 25 out of the ejection ports 23c arranged in a line
At the time of the operation of the blower case 22, the diameter of the ejection port 23c1 which is the most upstream side with respect to the blowout port 22b of the blower case 22 is larger than the diameters of the other ejection ports 23c, and the fuel gas is supplied into the fuel ejection pipe 23b at the same pressure Therefore, the amount of fuel gas ejected from the ejection port 23c1 is larger than that of the other ejection ports 23c.

The blower 25 includes an impeller 25a inside the blower case 22, a motor 25b provided outside the blower case 22 rotationally drives the impeller 25a, sucks air and fuel gas from the suction port 23a, and blows the blowout port 22b. The air-fuel mixture is blown out from and supplied to the combustion unit 10 via the mixing case 21.

Here, the motor 25b is controlled according to the required combustion amount,
The impeller 25a is rotated counterclockwise in FIG. 2 at a rotation speed according to the control state.

The blower case 22 is provided with an air supply case 31 so as to cover the suction port 23a and the fuel ejection pipe 23b.

The air supply case 31 has an equivalent volume V ₂ , a passage equivalent length l _2, and an equivalent length l ₂ in order to match the natural frequency f ₂ of the supply unit 20 with the natural frequency f ₁ based on the acoustic characteristics of the combustion unit 10. It is provided to secure the cross-sectional area S ₁ .

The air supply case 31 has a substantially rectangular parallelepiped shape with two directions open.
One of the open portions faces the flat plate portion 23 of the blower case 22, and the other open portion opens downward in the drawing as an air supply port 31a, which is airtightly joined to the blower case 22 and is sucked from the air supply port 31a. An air supply path 32 for guiding the air for use and the fuel gas ejected into the air supply case 31 to the suction port 23a is formed.

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

Inside the air supply case 31, as shown in FIG.
A fuel distribution plate 33 is arranged so as to be inclined so as to cover a part of the inside of 31c and the air supply case 31.

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

The fuel distribution plate 33 is provided with a plurality of fuel jet ports 33a dispersed in one row. Further, several fuel jet ports 33a are provided on the most upstream side of the blower port 22b of the blower case 22 separately from the fuel jet port 33a. The fuel injection port 33b is provided.

As a result, the fuel gas supplied into the fuel distribution chamber 35 is
Since more fuel is jetted from the fuel jet port 33b toward the upstream side of the air supply passage 32, efficient mixing is performed.

In the upstream air supply passage 32 in the air supply case 31, the width of the air supply passage 32 is gradually reduced to the fuel ejection pipe 23b so that turbulence does not occur with respect to the passing air. A diaphragm plate 36 is provided.

Therefore, the throttle plate 36 forms a venturi that reduces the cross-sectional area of the air supply passage 32 and temporarily squeezes the air passing through the air supply passage 32. It is possible to improve the mixing of the fuel gas ejected from each fuel ejection port 33a of the plate 33 and the air.

A damper 38, which is swingably supported by a shaft 37, is provided near the air supply port 31a in the air supply case 31. damper
38 is provided in order to change the equivalent cross-sectional area S ₂ of the supply unit 20 by its swinging, the damper 38 according to the wind pressure of the air sucked from the air supply port 31a with the operation of the blower 25. Operate and change the equivalent cross-sectional area S ₂ . As a result, when the combustion amount of the combustor 2 is large and the blast amount is large,
The damper 38 opens and the equivalent cross-sectional area S ₂ increases, and when the combustion amount is small and the blown air amount is small, the opening degree of the damper 38 decreases and the equivalent cross-sectional area S ₂ decreases.

When the damper 38 swings, a part of the distal end portion 38a on the outer peripheral side has a minimum equivalent cross-sectional area S ₂ of the supply portion 20, and when the minimum opening degree is exhibited, the wall portion 31d of the air supply case 31 is provided. Abutment 3
8b is formed.

As a result, the damper 38 has the first opening when it exhibits the minimum opening.
As shown in the figure, this protrusion 38b is the wall portion 31d of the air supply case 31.
The front end 38a of the damper 38 and the wall 3 of the air supply case 31.
A proper gap is formed between 1d and 1d so that a required amount of air can be supplied.

At this time, the damper 38 is urged in the closed state direction by its own weight, and with respect to the rotation speed of the blower 25 controlled according to the required combustion amount, as shown in FIG. The opening degree according to the temperature is shown. Here, the solid line A shows a case where the temperature of the burner plate 12 and the like in the combustor 2 is low (when cold), and the broken line B shows a case where the temperature of the combustor 2 has sufficiently risen (when hot).

As shown here, in the present embodiment, when the blower 25 is controlled to the minimum rotation speed Nmin, whether it is cold or hot, always has the minimum opening θmin for supply air, The length of the protrusion 38b or the width of the damper 38 is set, and for example, when cold, the blower 25 has a minimum rotation speed Nmin.
When the rotational speed Na is decreased to a higher rotational speed Na, the damper 38 exhibits the minimum opening degree θmin, and at all rotational speeds up to the minimum rotational speed Nmin, the damper 38 exhibits the minimum opening degree θmin.

Further, at the time of hot, the damper 38 has a rotational speed Nb that is even greater than the rotational speed Na at which the damper 38 exhibits the minimum opening θmin during cold.
Exhibits the minimum opening θmin, and all exhibit the minimum opening θmin below the rotation speed Nb.

Therefore, in the small combustion amount where the stable combustion region is narrow, cold
When the rotational speed is Na and the rotational speed is Nb or less, the damper 38 is fixed to the minimum opening θmin.
As in the case where 8 is not provided, the supply amount of combustion air can be appropriately controlled only by the control state of the blower 25,
The air-fuel ratio can be set within the stable combustion region.

On the contrary, the equivalent cross-sectional area S ₂ of the supply unit 20 becomes maximum and the maximum opening θ
When exhibiting max, the damper 38 is stabilized with a proper distance from the diaphragm plate 36, as shown by the chain double-dashed line in FIG.

In addition, both ends of the damper 38 in the axial
Curved parts 38c, 3 to guide the air that pushes up 38 inward
8d is formed. The curved portions 38c and 38d prevent the air hitting the damper 38 from escaping to the outside of the curved portions 38c and 38d, and dust and the like are less likely to adhere to the inner wall surface of the air supply case 31.

Further, since the bearing portions 38e and 38f of the damper 38 are provided on the flat plate portion 23 side of the blower case 22 with respect to the damper 38 that receives the wind pressure, the horizontal distance between the center of gravity of the damper 38 and the shaft 37 can be secured, and the damper 38 The moment of rotation of the damper 38 can always urge the damper 38 to the closed state, and the damper 38
Since the air flow can pass between the damper 38 and the diaphragm plate 36 even when the maximum opening is maximized, the damper 38 can be stabilized in each case.

A protrusion 39 that protrudes inward of the air supply case 31 is provided upstream of the wall portion 31d of the air supply case 31 with which the protrusion 38b of the damper 38 abuts, in order to change the direction of the air flow to be sucked. . When the damper 38 is in the closed state due to the protruding portion 39, the air supply port 31b is provided at a portion 1/3 from the tip end portion 38a of the damper 38.
If the air from the
Since the air hits the whole, the opening degree of the damper 38 can be made proportional to the combustion amount.

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

The air supply port 31a is provided with a filter 41 made of a metal net.

The fuel pipe 60a that guides the fuel to the fuel supply port 31c is
The fuel injection pipe 23b is connected to the fuel pipe 60.

Upstream of the fuel pipe 60, a solenoid valve that is opened / closed according to the control state and a controller 70 together with the blower 25 according to the required combustion amount are provided.
A proportional control valve 61 controlled by the proportional control valve 61 is supplied to the fuel injection pipe 23b and the fuel supply port 31c.

The heat exchanger 50 is connected to a water pipe (not shown) that guides water from the water supply, and the water pipe upstream of the heat exchanger 50 is equipped with a water amount control valve for adjusting the amount of inflow water, a water flow sensor, and an incoming water temperature thermistor. A hot water outlet temperature thermistor is provided downstream of the heat exchanger 50, and a water tap (not shown) operated by the user is provided at the downstream end.

The control device 70 opens the solenoid valve in response to the water flow signal from the water flow sensor, performs spark discharge on the sparker electrode 17 to perform ignition control, and controls the water flow control valve based on the inflow temperature to control the maximum inflow. Limit the amount.

After a certain period of time has passed since ignition was detected by the frame rod 18, the hot water temperature set by the user, the amount of inflow water detected by the water flow sensor, the inflow water temperature detected by the inflow water temperature thermistor, and the outflow water temperature thermistor are detected. Blower 25 and proportional control valve based on the tap water temperature
By controlling 61, the combustion amount of the combustor 2 is adjusted. At this time, the blower 25 and the proportional control valve 61 have their respective control states corrected based on the combustion temperature detected by the thermocouple 19, and are maintained at an air-fuel ratio such that combustion is performed in the stable combustion region.

The gas water heater 1 having the above configuration operates as follows.

When the user sets the hot water temperature by the controller and operates the faucet to start hot water supply, the combustor 2 starts combustion in a predetermined sequence, and the water quantity control valve causes water to enter the heat exchanger 50. The inflow of is regulated.

By the operation of the blower 25, air is sucked in from the hot water supply port 31a.

On the other hand, the fuel gas whose supply amount is adjusted by the proportional control valve 61 is ejected from the ejection port 23c of the fuel ejection pipe 23b and the fuel ejection ports 33a and 33b to the fuel distribution plate 33.

Therefore, the fuel gas is ejected in a wide range and thus mixes well with the air.

On the other hand, the damper 38 swings to the following respective positions, as shown in FIG. 5, depending on the amount of air taken in.

A) Cold time When the combustion amount of the combustor 2 is small and the rotation speed of the blower 25 is between the minimum rotation speed Nmin and the rotation speed Na, the damper 38 has the wall portion 31.
It comes into contact with b and exhibits the minimum opening θmin as shown by the solid line A.

When the combustion amount is increased and the rotation number of the blower 25 is between the rotation number Na and the rotation number Nc, the damper 38 exhibits an opening degree according to the blow amount, and the combustion amount is further increased, and the rotation number of the blower 25 is increased. Is between Nc and Nmax, the damper 38 has a maximum opening θma.
present x.

The relationship between the number of revolutions of the blower 25 and the combustion amount (blowing amount) at this time is shown by the solid line C in FIG.

A) At the time of hot In this case, as shown by the broken line B, the damper 38 contacts the wall portion 31b and exhibits the minimum opening θmin until the rotation speed of the blower 25 is higher than the rotation speed Nb. , The rotation speed of the blower 25 is between the rotation speed Nb and the rotation speed Nd (> Nc),
The damper 38 exhibits an opening degree according to the blown air amount, the combustion amount is further increased, and the damper 38 exhibits the maximum opening degree θmax between the rotation speeds Nd and Nmax of the blower 25.

The relationship between the number of revolutions of the blower 25 and the combustion amount (blowing amount) at this time is shown by a broken line D in FIG.

Therefore, during cold and hot, the equivalent cross-sectional area S of the supply unit 20 is between the minimum opening θmin and the maximum opening θmax.
_{Since 2} changes according to the combustion amount, the supply unit changes according to the change of the natural frequency f ₁ of the combustion unit 10 that changes according to the combustion amount.
The natural frequency f _{2 of} 20 also changes in the same manner, and noise can be reduced even if the combustion amount changes.

Further, at a small combustion amount where the stable combustion region is narrow and the rotation speed of the blower 25 is small, the opening degree of the damper 38 is the minimum opening degree θm regardless of cold time and hot time.
Since the air flow rate is in and the blown air amount can be controlled only by controlling the blower 25, an appropriate air-fuel ratio is obtained and stable combustion is performed.

As described above, according to the present invention, even if the combustion amount changes,
Since the equivalent cross-sectional area of the supply unit changes accordingly, it is possible to suppress the generation of noise. Further, when the blower is controlled to the minimum rotation speed according to the change in the combustion amount, the damper always exhibits the minimum opening regardless of the temperature of the combustor, so that a stable combustion state can be obtained.

In this example, the blower rotates at a rotation speed Na during cold.
Therefore, the damper exhibits the minimum opening degree θmin during the rotation speed Nmin. However, the damper may exhibit the minimum opening degree θmin at least at the rotation speed Nmin during cold.

In the present embodiment, the damper is operated according to the wind pressure of the air sucked from the air supply port, but a motor for driving the damper is separately provided, and the damper is used for the required combustion amount, the blower rotation speed or the proportional control valve. The opening degree may be controlled on the basis of the value of the energization current to the.

[Brief description of drawings]

1 to 4 show a gas water heater according to an embodiment of the present invention, FIG. 1 is a side sectional view of a supply unit, FIG. 2 is a front view showing a schematic configuration of the gas water heater, and FIG. FIG. 4 is an exploded perspective view showing the configuration of the supply unit, and FIG. 4 is an exploded perspective view showing the inside of the air supply case. FIG. 5 is a characteristic diagram showing the opening degree of the damper with respect to the rotation speed of the blower in this embodiment, and FIG. 6 is a characteristic chart showing the combustion amount (blowing amount) with respect to the rotation speed of the blower in this embodiment. In the figure, 2 ... Combustor (compulsory blower type combustor), 10 ... Combustion part, 12 ... Burner plate (burner), 20 ... Supply part, 25 ... Blower, 31 ... Air supply case (supply) Air duct),
38 …… Damper.

Claims (1)

[Claims] 1. A blower which is controlled from a minimum rotation speed to a maximum rotation speed in accordance with a target combustion amount, and comprises a supply section provided with an air supply duct on the suction side of the blower, and a combustion section having a burner. In the forced air blowing combustion device, the equivalent cross-sectional area of the opening of the air supply duct, the equivalent passage length, and the equivalent volume are set so that the natural frequency of the supply section is substantially matched with the natural frequency of the combustion section. , A damper that is swingably supported to change the equivalent cross-sectional area is provided in the air supply duct, and the damper includes
When the rotation speed of the blower is the minimum rotation speed, the equivalent cross-sectional area is minimized, and the rotation speed of the blower is a first predetermined rotation speed greater than the minimum rotation speed or more and air generated in association with the operation of the blower. The equivalent sectional area is increased according to the flow, and the equivalent sectional area is maximized when the rotational speed is equal to or higher than the first predetermined rotational speed and equal to or higher than a second predetermined rotational speed smaller than the maximum rotational speed. Forced air blow type combustion device.