JP6725339B2 - Premixing device - Google Patents

Description

The present invention relates to a premixing device that mixes fuel gas with air and supplies the mixture to a burner via a fan.

Conventionally, as a premixing device of this type, according to Patent Document 1, a downstream end of a gas supply passage provided with a flow rate control valve for supplying a fuel gas is a gas suction portion provided in an air supply passage on an upstream side of a fan. An air resistance switching unit that is connected and switches the ventilation resistance of the air supply path upstream of the gas suction section between large and small, and a gas resistance that switches the ventilation resistance of the gas supply path downstream of the flow control valve between large and small. It is known to have a switching means.

By the way, when a proportional valve is used as the flow rate control valve, the proportional valve is controlled so that an amount of fuel gas corresponding to the required combustion amount is supplied, and further, the air-fuel ratio of the air-fuel mixture supplied to the burner is kept constant. Therefore, the fan rotation speed is controlled according to the required combustion amount. However, if the required combustion amount falls below a prescribed value, the fan rotation speed falls below the lower limit rotation speed at which proportional characteristics of the air flow can be maintained, or the proportional valve current (current flowing to the proportional valve) is proportional to the gas supply amount. When the current becomes lower than the lower limit current that can maintain the characteristics, it becomes impossible to supply the amount of air or fuel gas corresponding to the required combustion amount.

A zero governor that maintains the secondary gas pressure at atmospheric pressure may be used as the flow rate control valve. In this case, the supply amount of the fuel gas changes according to the pressure difference between the atmospheric pressure, which is the secondary gas pressure, and the negative pressure in the air supply passage. Since the negative pressure in the air supply passage changes according to the fan rotation speed, the fuel gas supply amount changes according to the fan rotation speed, that is, the air supply amount. Therefore, by controlling the fan rotation speed according to the required combustion amount, the amount of air and fuel gas according to the required combustion amount are supplied to the burner.

Even in this case, if the fan rotation speed becomes equal to or lower than the lower limit rotation speed that can maintain the proportional characteristic of the blown air amount, it becomes impossible to supply the air or the fuel gas in the amount corresponding to the required combustion amount. Therefore, when the required combustion amount becomes equal to or less than a predetermined value, the air resistance switching unit increases the ventilation resistance of the air supply path to keep the fan rotation speed from being equal to or lower than the lower limit rotation speed, and being equal to or less than the predetermined combustion value. It is necessary to be able to supply an amount of air according to the amount. In addition, increasing the ventilation resistance of the air supply passage increases the negative pressure in the air supply passage, and the supply amount of fuel gas exceeds the amount corresponding to the required combustion amount. Along with the increase, it is necessary to increase the ventilation resistance of the gas supply passage.

Therefore, in the above-mentioned conventional example, when the required combustion amount becomes equal to or less than a predetermined value, the air resistance switching means increases the ventilation resistance of the air supply path and the gas resistance switching means increases the ventilation resistance of the gas supply path. The amount of air or fuel gas that can be supplied according to the required combustion amount below a predetermined value can be supplied.

Here, in the one described in Patent Document 1, the air resistance switching means is composed of a butterfly valve rotatably provided in a portion of the air supply path upstream of the gas suction portion. However, in this one, when the butterfly valve is rotated to the closed posture orthogonal to the longitudinal direction of the air supply passage, the flow passage in the air supply passage is formed between the peripheral wall surface of the air supply passage and the outer peripheral edge of the butterfly valve. Since the air gap is suddenly narrowed down, the air flow is disturbed, and wind noise is generated in the annular gap portion, which causes noise.

JP, 2005-230113, A

In view of the above points, it is an object of the present invention to provide a premixing device capable of reducing noise due to wind noise even though the air resistance switching unit is configured by a butterfly valve.

In order to solve the above-mentioned problems, the present invention is a premixing device that mixes fuel gas with air and supplies the mixture to a burner through a fan, and a flow control valve that supplies the fuel gas is provided. An air resistance switching means, in which the downstream end of the gas supply path is connected to a gas suction section provided in the air supply path on the upstream side of the fan, and the ventilation resistance of a portion of the air supply path upstream of the gas suction section is switched between large and small. A gas resistance switching means for switching the ventilation resistance of the gas supply passage downstream of the flow rate control valve between large and small, and the air resistance switching means is connected to a portion of the air supply passage upstream of the gas suction portion. With a butterfly valve that is movably installed, a butterfly valve is built in a part of the air supply path upstream of the gas suction part with a gap between it and the peripheral wall surface of the air supply path. Is provided, and a sub passage that is parallel to the main passage in the inner cylinder is configured by the gap between the peripheral wall surface of the air supply passage and the outer peripheral surface of the inner cylinder.

According to the present invention, when the butterfly valve is rotated to the closed posture orthogonal to the longitudinal direction of the main passage, the main passage is almost closed, and the air flow is substantially restricted to the sub passage, and the air supply passage is closed. Increases ventilation resistance. Here, the air flowing in the sub passage is guided inside and outside by the outer peripheral surface of the inner cylinder and the peripheral wall surface of the air supply passage to be in a laminar flow state. Therefore, it is possible to reduce noise due to wind noise generated when the butterfly valve is closed.

By the way, when the butterfly valve is rotated from the closed position to the open position parallel to the longitudinal direction of the main passage, the half part of the butterfly valve which is displaced in the upstream direction of the main passage is moved to the first half part and the downstream direction of the main passage. The half of the displacing butterfly valve is the second half, and the outer peripheral corner of the side of the first half that faces the downstream of the main passage in the closed position and the second half that faces the upstream of the main passage in the closed position. If the outer peripheral corners of the side face of the are angular, the following problems occur. That is, in the initial stage of rotation of the butterfly valve from the closed posture, these outer peripheral corners approach the inner peripheral surface of the inner cylinder, narrowing the gap between the inner peripheral surface of the inner cylinder and the butterfly valve. The flow velocity of the air flowing in the gap increases, and wind noise is likely to occur. Therefore, in the present invention, it is desirable to form the outer peripheral corner portion into a rounded shape. According to this, at the initial stage of the rotation of the butterfly valve from the closed posture, the outer peripheral corner portion does not approach the inner peripheral surface of the inner cylinder, and the above-mentioned problem does not occur.

When the butterfly valve is rotated from the closed position, the first half of the butterfly valve inclines in the upstream direction of the main passage and flows into the gap between the inner peripheral surface of the inner cylinder and the first half. Turbulence is generated in the air flow, and if the flow velocity of this air flow is high, wind noise is likely to occur. Therefore, in the present invention, the inner cylinder is provided with a communication portion that is located upstream of the butterfly valve in the closed posture and on the first half side of the butterfly valve and that communicates the main passage and the sub passage. Is desirable. According to this, a part of the air in the main passage toward the gap between the inner peripheral surface of the inner cylinder and the first half portion is diverted to the sub passage via the communication portion. Therefore, the amount of air flowing into the gap between the inner peripheral surface of the inner cylinder and the first half portion is reduced, the flow velocity of the air flow flowing in this gap is reduced, and wind noise is suppressed.

Further, in the present invention, in the portion of the air supply passage adjacent to the upstream side of the gas suction portion, a venturi portion having a smaller diameter than the portion of the air supply passage in which the inner cylinder is arranged is provided, and the sub passage and the venturi portion are provided. It is desirable that the peripheral wall surface of the portion of the air supply path between the two is formed as a tapered surface whose diameter decreases toward the venturi portion. According to this, even when the butterfly valve is rotated to the closed posture to increase the ventilation resistance of the air supply passage, the air passing through the sub passage smoothly flows to the venturi portion along the taper surface, and Negative pressure is secured. Therefore, the fuel gas is stably sucked from the gas suction portion adjacent to the venturi portion, and the air-fuel ratio of the air-fuel mixture is kept constant.

The cut side view showing the premixing device of the embodiment of the present invention. The cutting top view cut|disconnected by the II-II line of FIG. Sectional drawing cut|disconnected by the III-III line of FIG. Sectional drawing cut|disconnected by the IV-IV line of FIG.

Referring to FIG. 1, reference numeral 1 is a burner including an all-primary combustion type burner having a combustion surface 1a where an air-fuel mixture is jetted and burned. A fan 2 is connected to the burner 1, and the premixing device A according to the embodiment of the present invention mixes fuel gas with air and supplies the mixture to the burner 1 via the fan 2. ..

The premixing device A includes an air supply passage 3 on the upstream side of the fan 2 and a gas supply passage 4 for supplying fuel gas. As shown in FIG. 4, an on-off valve 5 and a flow rate control valve 6 including a proportional valve and a zero governor are provided upstream of the gas supply path 4. Further, the downstream end of the gas supply passage 4 is connected to the gas suction portion 31 provided in the air supply passage 3. In the premixing device A, the air resistance switching means for switching the ventilation resistance of the portion of the air supply passage 3 upstream of the gas suction portion 31 between large and small, and the portion of the gas supply passage 4 downstream of the flow rate control valve 6. And a gas resistance switching means for switching the ventilation resistance of the gas resistance.

Referring also to FIGS. 2 and 3, the air resistance switching means is composed of a butterfly valve 7 formed of a disc provided in the air supply passage 3 so as to be rotatable around a shaft 71. An actuator 72 such as a stepping motor is connected to the shaft 71 of the butterfly valve 7. Then, when the required combustion amount becomes equal to or less than a predetermined value, the actuator 72 is actuated to move the butterfly valve 7 from the open posture along the longitudinal direction of the air supply passage 3 shown by the phantom line in FIG. It is rotated so as to be in a closed posture orthogonal to the longitudinal direction of the air supply passage 3 shown by a solid line in FIG.

The gas supply passage 4 is provided with a valve chamber 81 located upstream of the gas chamber 41 at the downstream end communicating with the gas suction portion 31 and parallel to the passage portion 42 constantly communicating with the gas chamber 41. There is. A switching valve 8 that opens and closes a valve hole 83 formed in the valve seat 82 at the lower end of the valve chamber 81 and communicates with the passage portion 42 is provided in the valve chamber 81, and the switching valve 8 constitutes gas resistance switching means. doing. When the switching valve 8 is closed, the flow of gas through the valve chamber 81 is shut off, and the ventilation resistance of the gas supply passage 4 increases.

The switching valve 8 is opened/closed via the interlocking mechanism 9 as the butterfly valve 7 rotates. As shown in FIGS. 1 and 4, the interlocking mechanism 9 is composed of a cam 91 connected to the shaft 71 of the butterfly valve 7, and a rod 92 connected to the switching valve 8 and having one end abuttable against the cam 91. Has been done. When the butterfly valve 7 is rotated to the open posture, the cam 92 pushes up the rod 92, the switching valve 8 is opened against the biasing force of the valve spring 84, and the butterfly valve 7 is rotated to the closed posture. Then, the pushing up of the rod 92 by the cam 91 is released, and the switching valve 8 is closed by the urging force of the valve spring 84.

Here, in the present embodiment, in the portion of the air supply passage 3 on the upstream side of the gas suction portion 31, there is a gap between the air supply passage 3 and the peripheral wall surface 32 of the air supply passage 3, and the butterfly valve 7 is built in. A cylinder 33 is provided. The gap between the peripheral wall surface 32 of the air supply passage 3 and the outer peripheral surface of the inner cylinder 33 forms a sub passage 3b parallel to the main passage 3a in the inner cylinder 33. A plurality of arc-shaped through holes 33b serving as outlets of the sub passages 3b are formed in the flange portion 33a at the downstream end (upper end in FIGS. 1 and 3) of the inner cylinder 33.

When the butterfly valve 7 is rotated to the closed posture orthogonal to the longitudinal direction of the main passage 3a, the main passage 3a is almost closed, and the air flow is substantially restricted to the sub passage 3b, so that the air supply passage 3 is ventilated. The resistance increases. Here, the air flowing in the sub passage 3b is guided inside and outside by the outer peripheral surface of the inner cylinder 33 and the peripheral wall surface 32 of the air supply passage 3 to be in a laminar flow state. Therefore, the noise due to the wind noise generated when the butterfly valve 7 is closed is reduced.

Further, the butterfly valve 7 from the closed position when rotated to the open posture parallel to the longitudinal direction of the main passage 3a, the butterfly valve halves the first half 7 ₁ 7 displaced in the upstream direction of the main passage 3a, as halves ₂ second half 7 of the butterfly valve 7 which is displaced in the downstream direction of the main passage 3a, closed posture circumference edge ₇₁ a of the first half 7 ₁ side facing the downstream direction of the main passage 3a And the outer peripheral corner portion 7 ₂ a of the side surface of the second half portion 7 ₂ facing the upstream direction of the main passage 3 a in the closed posture is formed in a round shape. In this embodiment, closing the outer peripheral corner portion _{71 b} of the first half 7 ₁ side facing the upstream direction of the main passage 3a in position, a second half facing the downstream direction of the main passage 3a in the closed position 7 ₂ circumference edge 7 _{2 b} side of the also formed into rounded shape, these outer peripheral corner portion 7 _{1 b,} 7 2 _b may have angular.

Here, if the outer peripheral corners 7 ₁ a and 7 ₂ a are angular, the outer peripheral corners 7 ₁ a and 7 ₂ a are located inside the inner cylinder 33 at the initial stage of rotation of the butterfly valve 7 from the closed posture. The gap between the inner peripheral surface of the inner cylinder 33 and the butterfly valve 7 is narrowed by approaching the peripheral surface, and the flow velocity of the air flowing in this clearance increases, which causes a problem that wind noise is likely to occur. .. On the other hand, if the outer peripheral corners 7 ₁ a and 7 ₂ a are formed in the rounded shape as in the present embodiment, the outer peripheral corners 7 ₁ a, 7 a, at the initial stage of rotation of the butterfly valve 7 from the closed posture. 7 2 _a is not close to the inner circumferential surface of the inner cylinder 33, does not cause the above problems.

Also, is rotated from the closed position the butterfly valve 7, the first half 7 ₁ is inclined in the upstream direction of the main passage 3a, the inner peripheral surface and the first half of the inner cylinder 33 7 of the butterfly valve 7 ₁ A turbulent flow is generated in the air flow flowing into the gap between and, and if the flow velocity of this air flow is high, wind noise is likely to occur. Therefore, in this embodiment, the inner cylinder 33, to close than the butterfly valve 7 of posture and is positioned in the first half 7 ₁ of the butterfly valve 7 on the upstream side, communicating the main passage 3a and the sub-passage 3b The communication part 33c is opened. According to this, part of the air in the main passage 3a toward the gap between the inner peripheral surface and the first half 7 ₁ of the inner tube 33 is shunted to the auxiliary passage 3b through the communication unit 33c. Therefore, the amount of air flowing into the gap between the inner peripheral surface and the first half 7 ₁ of the inner cylinder 33 is reduced, the flow velocity of the air stream flowing through the gap becomes slow and the occurrence of wind noise is suppressed It The communication part 33c is formed by a notch extending from a position in the vicinity of the butterfly valve 7 in the closed posture to the upstream end of the inner cylinder 33, but the communication part 33c can be formed by a long hole.

Further, a venturi portion 34 having a smaller diameter than the portion of the air supply passage 3 in which the inner cylinder 33 is arranged is provided in the portion of the air supply passage 3 adjacent to the upstream side of the gas suction portion 31. A portion of the air supply path 3 adjacent to the downstream side of the venturi portion 34 is surrounded by a tubular portion 35 having a diameter larger than that of the venturi portion 34. The downstream end of the venturi portion 34 is inserted into the upstream end of the tubular portion 35 with an annular gap, and the gap forms the gas suction portion 31 communicating with the gas chamber 41. The gas chamber 41 is composed of a gap between the tubular portion 35 and an outer wall surface 41a surrounding the tubular portion 35.

Further, the peripheral wall surface of the portion of the air supply passage 3 between the sub passage 3 b and the venturi portion 34 is formed as a tapered surface 36 having a diameter reduced toward the venturi portion 34. According to this, even when the butterfly valve 7 is turned to the closed posture to increase the ventilation resistance of the air supply passage 3, the air passing through the sub passage 3b smoothly moves to the venturi portion 34 along the tapered surface 36. The flow and the negative pressure in the venturi section 34 are secured. Therefore, the fuel gas is stably sucked from the gas suction portion 31 adjacent to the venturi portion 34, and the air-fuel ratio of the air-fuel mixture is kept constant.

Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited thereto. For example, in the above-described embodiment, the gas resistance switching means is configured by the switching valve 8 that opens and closes the valve hole 83, but a needle valve that changes the opening degree of the valve hole provided in the middle of the gas supply path 4. It is also possible to configure the gas resistance switching means with the above.

A... Premixing device, 1... Burner, 2... Fan, 3... Air supply passage, 3a... Main passage, 3b... Sub passage, 31... Gas suction part, 32... Air supply passage peripheral wall surface, 33... Inner cylinder, 33c... Communication part, 34... Venturi part, 36... Tapered surface, 4... Gas supply path, 6... Flow control valve, 7... Butterfly valve, 7 ₁ ... 1st half part, 7 ₂ ... 2nd half part, 7 ₁ a, 7 ₂ a... Peripheral corner portion, 8... Switching valve (gas resistance switching means).

Claims (4)

A premixing device that mixes fuel gas with air and supplies the mixture to a burner through a fan,
Is connected to the gas suction part downstream end is provided on an air supply passage upstream of the fan of a gas supply passage which is interposed a flow control valve for supplying the fuel gas, the air supply upstream of the gas suction portion includes air resistance switching means for switching the air flow resistance of the portion of the road to the magnitude, and a gas resistance switching means for switching the magnitude of the flow resistance of the portion of the gas supply path on the downstream side of the flow control valve,
The air resistance switching means, in what is consists of a butterfly valve rotatably provided in the portion of the air supply passage upstream of the gas suction portion,
The portion of the air supply passage upstream of the gas suction portion, said to exist a gap between the circumferential wall surface of the air supply passage, the cylinder is provided inside with a built-in said butterfly valve, the air supply passage gap, the premixing device characterized by parallel sub-passage is configured in the main passage in said inner cylinder between the outer peripheral surface of the peripheral wall the inner cylinder of the. When rotating the butterfly valve in the longitudinal direction in the open parallel orientation of the main passage from the closed position perpendicular to the longitudinal direction of the main passage, the halves of the butterfly valve which is displaced in the upstream direction of the main passage the first half, the halves of the butterfly valve which is displaced in the downstream direction of the main passage as the second half, and the outer peripheral corner portion of the side surface of the first half facing the downstream direction of the main passage in the closed position , the premixing device of claim 1 in which the outer peripheral corner portion of the side surface of the second halves in the closed position faces the upstream direction of the main passage, characterized in that it is formed into rounded shapes. When rotating the butterfly valve in the longitudinal direction in the open parallel orientation of the main passage from the closed position perpendicular to the longitudinal direction of the main passage, the halves of the butterfly valve which is displaced in the upstream direction of the main passage the first half, the halves of the butterfly valve which is displaced in the downstream direction of the main passage as the second half, to the inner cylinder, said and said butterfly valve upstream from the butterfly valve closed position the The premixing device according to claim 1 or 2, wherein a communication portion that communicates with the main passage and the sub passage is provided at the first half portion side. The portion of the air supply passage adjacent to the upstream side of the gas suction portion, the small diameter venturi portion is provided than the portion of said air supply passage said inner tube is disposed, and said auxiliary passage and the venturi section the air supply passage peripheral wall surface premixing device of any one of claims 1 to 3, characterized in that it is formed into a tapered surface whose diameter decreases toward the venturi portion of between.

Images