JP2019203668A - Premixing device - Google Patents

Abstract

To provide a premixing device for mixing a fuel gas to air and supplying an air-fuel mixture to a burner through a fan, in which a butterfly valve 7 rotated by a motor through a valve shaft 71 is disposed on a part of an air supply passage at an upstream side with respect to a gas suction portion disposed on the air supply passage at an upstream side of the fan, and a clearance formed between a butterfly valve outer peripheral edge and a peripheral wall surface 32 of the air supply passage in a closing attitude of the butterfly valve 7, is made uniform over the whole periphery.SOLUTION: Projecting portions 7a of a height same as a clearance formed between an outer peripheral edge of a butterfly valve 7 and a peripheral wall surface 32 of an air supply passage in a state that the butterfly valve 7 has a closed attitude, are formed on at least three places in the circumferential direction of an outer peripheral edge of the butterfly valve 7 or a peripheral wall surface 32 of the part of the air supply passage provided with the butterfly valve 7. Further the valve shaft 71 or the butterfly valve 7 are connected to a motor or the valve shaft 71 with play.SELECTED DRAWING: Figure 4

Description

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

  Conventionally, as a premixing device of this type, the downstream end of the gas supply path is connected to a gas suction portion provided in the air supply path upstream of the fan, and in the portion of the air supply path upstream of the gas suction section, There has been known one provided with a butterfly valve that is rotatable in an opening posture parallel to the longitudinal direction of the air supply passage and in a closing posture orthogonal to the longitudinal direction of the air supply passage (see, for example, Patent Document 1). The butterfly valve is connected to a motor via a valve shaft orthogonal to the longitudinal direction of the air supply path, and the butterfly valve is rotated by the motor.

  By the way, in a state where the butterfly valve is in the closed position, a clearance is generated between the outer peripheral edge of the butterfly valve and the peripheral wall surface of the air supply path. Here, the clearance should be uniform over the entire circumference of the butterfly valve. However, when the butterfly valve is assembled in an eccentric state with respect to the air supply path, the clearance is narrowed in part in the circumferential direction of the butterfly valve, and noise may be generated due to the air flowing in the narrowed portion of the clearance.

JP 2017-181011 A

  This invention makes it the subject to provide the pre-mixing apparatus which made the said clearance uniform over the perimeter of a butterfly valve in view of the above point.

  In order to solve the above-described problems, the present invention provides a premixing device that mixes fuel gas with air and supplies the air-fuel mixture to a burner via a fan, wherein the downstream end of the gas supply path is on the upstream side of the fan. Connected to the gas suction section provided in the air supply path, and closed in the air supply path portion upstream of the gas suction section in the opening posture parallel to the longitudinal direction of the air supply path and perpendicular to the longitudinal direction of the air supply path A butterfly valve that can freely rotate in a posture is provided, and the butterfly valve is connected to a motor via a valve shaft that is orthogonal to the longitudinal direction of the air supply path, and the butterfly valve is rotated by the motor. The outer peripheral edge of the butterfly valve and the peripheral wall surface of the air supply path in at least three places in the circumferential direction of the peripheral wall surface of the air supply path portion where the butterfly valve is disposed, with the butterfly valve in a closed position of A projecting portion having a height equivalent to the clearance generated in the valve shaft, so that the butterfly valve can move in any direction along a plane perpendicular to the longitudinal direction of the air supply path in the closed posture of the butterfly valve. The butterfly valve is connected to the motor or the valve shaft with play.

  According to the present invention, when the butterfly valve is rotated to the closed position, the butterfly valve is guided by the convex portions at a plurality of positions and positioned so as to be concentric with the air supply path by the movement due to the play. Therefore, the clearance generated between the outer peripheral edge of the butterfly valve and the peripheral wall surface of the air supply path in a state where the butterfly valve is in the closed posture is uniform over the entire circumference of the butterfly valve. As a result, it is possible to prevent abnormal noise from being generated by the air flowing through the narrowed portion of the clearance.

  Further, in the present invention, it is desirable that a convex portion protrudes from the outer peripheral edge of the butterfly valve, and the convex portion is formed in a shape that makes point contact with the peripheral wall surface of the air supply path when the butterfly valve is closed. According to this, even if the convex part bites on the peripheral wall surface of the air supply path, this can be easily released, and the butterfly valve can be prevented from being locked in the closed posture.

The cut side view which shows the premixing apparatus of embodiment of this invention. Sectional drawing cut | disconnected by the II-II line | wire of FIG. Sectional drawing cut | disconnected by the III-III line | wire of FIG. The expanded cutting top view cut | disconnected by the IV-IV line of FIG.

  Referring to FIG. 1, B is a burner composed of an all-primary combustion burner having a combustion surface Ba on which an air-fuel mixture is ejected and burned. A fan F is connected to the burner B. The premixing device 1 according to the embodiment of the present invention mixes fuel gas with air and supplies the mixture to the burner B via the fan F. .

  The premixing device 1 includes an air supply path 3 on the upstream side of the fan F and a gas supply path 4 for supplying fuel gas, which are provided in a casing 2 as a main body of the apparatus. As shown in FIG. 3, fuel gas is supplied to the gas supply path 4 via an upstream gas supply path 4a provided with an on-off valve 5 and a flow rate control valve 6 including a proportional valve and a zero governor. Further, the downstream end of the gas supply path 4 is connected to a gas suction part 31 provided in the air supply path 3, and fuel gas is sucked into the air supply path 3 from the gas suction part 31. Further, the premixing device 1 includes an air resistance switching means for switching the ventilation resistance of the portion of the air supply passage 3 upstream of the gas suction unit 31 to a large and small portion, and a portion of the gas supply passage 4 downstream of the flow rate control valve 6. Gas resistance switching means for switching the ventilation resistance of the gas to large or small.

  Here, when a proportional valve is used as the flow control valve 6, the proportional valve is controlled so that an amount of fuel gas corresponding to the required combustion amount is supplied, and the air-fuel ratio of the air-fuel mixture supplied to the burner B is further controlled. Is controlled in accordance with the required combustion amount. However, the required combustion amount becomes less than the predetermined value, the fan rotation speed becomes lower than the lower limit rotation speed at which the proportional characteristic of the blown air volume can be maintained, or the proportional valve current (energization current to the proportional valve) is proportional to the gas supply amount. When the current becomes lower than the lower limit current at which the characteristics can be maintained, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount.

  When a zero governor that maintains the secondary gas pressure at atmospheric pressure is used as the flow control valve 6, the supply amount of the fuel gas is the difference between the atmospheric pressure that is the secondary gas pressure and the negative pressure in the air supply path 3. Varies with pressure. And since the negative pressure in the air supply path 3 changes according to a fan rotation speed, the supply amount of fuel gas changes according to a fan rotation speed, ie, the supply amount of air. Therefore, by controlling the fan rotation speed according to the required combustion amount, air and fuel gas in an amount corresponding to the required combustion amount are supplied to the burner B. Even in this case, when the fan rotation speed is equal to or lower than the lower limit rotation speed at which the proportional characteristic of the blown air amount can be maintained, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount. For this reason, when the required combustion amount becomes a predetermined value or less, the air resistance switching means increases the ventilation resistance of the air supply path 3 so that the fan rotation speed is not lower than the lower limit rotation speed, and the request value is lower than the predetermined value. It is necessary to be able to supply an amount of air corresponding to the amount of combustion. Further, simply increasing the airflow resistance of the air supply path 3 causes the fuel gas supply amount to exceed the amount corresponding to the required combustion amount due to an increase in the negative pressure in the air supply path 3. It is necessary to increase the ventilation resistance of the gas supply path 4 as the ventilation resistance is increased.

  Therefore, when the required combustion amount becomes a predetermined value or less, the air resistance switching means increases the ventilation resistance of the air supply path 3 and the gas resistance switching means increases the ventilation resistance of the gas supply path 4 to a predetermined value or less. The amount of air and fuel gas corresponding to the required combustion amount can be supplied.

  Referring also to FIGS. 2 and 3, the air resistance switching means has an opening posture parallel to the longitudinal direction of the air supply path 3 in the portion of the air supply path 3 upstream from the gas suction portion 31 (the phantom line in FIG. 2). ) And a butterfly valve 7 made of a disc that is rotatably provided in a closed posture (posture indicated by a solid line in FIG. 2) orthogonal to the longitudinal direction of the air supply path 3. The butterfly valve 7 is connected to a motor 72 via a valve shaft 71 orthogonal to the longitudinal direction of the air supply path 3. When the required combustion amount becomes equal to or less than a predetermined value, the butterfly valve 7 is rotated from the open position to the closed position by the operation of the motor 72.

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

  The switching valve 8 is opened / closed via the interlocking mechanism 9 as the butterfly valve 7 rotates. As shown in FIGS. 1 and 3, the interlocking mechanism 9 includes a cam 91 connected to the valve shaft 71 and a rod 92 connected to the switching valve 8 and having one end that can contact the cam 91. . When the butterfly valve 7 is rotated to the open position, the rod 92 is pushed up by the cam 91, the switching valve 8 is opened against the urging force of the valve spring 84, and the butterfly valve 7 is rotated to the closed position. As a result, the push-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.

  The portion of the air supply path 3 where the butterfly valve 7 is disposed is surrounded by a cylindrical body 32 provided in the casing 2. An annular gap surrounding the cylinder 32 is provided in the casing 2, and the auxiliary passage 33 parallel to the butterfly valve 7 is configured by this gap. When the butterfly valve 7 is rotated to the closed position, the peripheral wall surface of the portion of the air supply path 3 where the butterfly valve 7 is disposed, that is, between the inner peripheral surface of the cylindrical body 32 and the outer peripheral edge of the butterfly valve 7. Thus, air flows only through the clearance and the sub-passage 33, and the airflow resistance of the air supply passage 3 is increased.

  A venturi portion 34 is provided in a portion of the air supply path 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 cylindrical portion 35 having a diameter larger than that of the venturi portion 34. The downstream end portion of the venturi portion 34 is inserted into the upstream end portion of the cylindrical portion 35 with an annular gap, and the gas suction portion 31 communicating with the gas chamber 41 is constituted by this gap. An annular space surrounding the cylindrical portion 35 is provided in the casing 2, and the gas chamber 41 is configured by this space.

  By the way, if the clearance is not uniform over the entire circumference of the butterfly valve 7 and the clearance becomes narrow in a part of the circumferential direction, abnormal noise may be generated by the air flowing through the narrowed portion. Therefore, in the present embodiment, as shown in FIG. 4, the outer peripheral edge of the butterfly valve 7 and the inner peripheral surface of the cylindrical body 32 in a state where the butterfly valve 7 is closed at three positions in the peripheral direction of the outer peripheral edge of the butterfly valve 7. A protruding portion 7a having a height equivalent to the clearance generated between the protruding portion 7 and the protruding portion 7 is provided. Further, the valve shaft 71 is connected to the motor 72 with play so that the butterfly valve 7 can move in any direction along the plane orthogonal to the longitudinal direction of the air supply path 3 in the closed posture of the butterfly valve 7. doing. As a matter of course, the valve shaft 71 is inserted through the insertion hole 21 for the valve shaft 71 formed in the casing 2 with play. It is also possible to project the convex portions 7a at four or more locations in the circumferential direction of the outer peripheral edge of the butterfly valve 7.

  According to this, when the butterfly valve 7 is rotated to the closed position, the butterfly valve 7 is guided by the convex portions 7a at a plurality of locations and positioned so as to be concentric with the cylindrical body 32 by the movement due to the play. Therefore, the clearance generated between the outer peripheral edge of the butterfly valve 7 and the inner peripheral surface of the cylindrical body 32 in a state where the butterfly valve 7 is in the closed posture is uniform over the entire circumference of the butterfly valve 7. As a result, it is possible to prevent abnormal noise from being generated by the air flowing through the narrowed portion of the clearance.

  Each convex portion 7 a is hemispherical, and makes point contact with the inner peripheral surface of the cylindrical body 32 when the butterfly valve 7 is closed. According to this, even if the protrusion 7a bites against the inner peripheral surface of the cylindrical body 32, this can be easily released, and the butterfly valve 7 can be prevented from being locked in the closed posture.

As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, in the above-described embodiment, the shape of the convex portion 7a is hemispherical. The shape may be other than a hemispherical shape such as a conical shape. It is also possible to form a protrusion that is long in the direction of the generatrix on the peripheral wall surface of the portion of the air supply passage 3 where the butterfly valve 7 is arranged, and to form a protrusion by this protrusion. Further, the butterfly valve 7 is connected to the valve shaft 71 with play so that the butterfly valve 7 can move in any direction along the plane perpendicular to the longitudinal direction of the air supply path 3 when the butterfly valve 7 is closed. It may be made to become.
In the above embodiment, the air supply passage 3 is provided with the sub-passage 33 parallel to the butterfly valve 7. However, the sub-passage 33 may be omitted.

  B ... burner, F ... fan, 1 ... premixing device, 3 ... air supply path, 31 ... gas suction part, 4 ... gas supply path, 7 ... butterfly valve, 7a ... convex part, 71 ... valve shaft, 72 ... motor .

Claims (2)

A premixing device that mixes fuel gas with air and supplies the air-fuel mixture to the burner via a fan, with the downstream end of the gas supply path connected to a gas suction section provided in the air supply path upstream of the fan A butterfly valve that is rotatable in an opening posture parallel to the longitudinal direction of the air supply passage and a closing posture orthogonal to the longitudinal direction of the air supply passage is provided in a portion of the air supply passage upstream of the gas suction unit. The butterfly valve is connected to a motor via a valve shaft orthogonal to the longitudinal direction of the air supply path, and the butterfly valve is rotated by the motor.
The outer peripheral edge of the butterfly valve and the peripheral wall surface of the air supply passage are in at least three positions in the circumferential direction of the outer peripheral edge of the butterfly valve or the peripheral wall surface of the part of the air supply passage where the butterfly valve is disposed in a state where the butterfly valve is closed. A convex part with the same height as the clearance generated between
The valve shaft or butterfly valve is connected with play to the motor or valve shaft so that the butterfly valve can move in any direction along the plane perpendicular to the longitudinal direction of the air supply path when the butterfly valve is closed. A premixing device.   The premixing according to claim 1, wherein a convex portion is provided on the outer peripheral edge of the butterfly valve, and the convex portion is formed in a shape that makes point contact with the peripheral wall surface of the air supply path when the butterfly valve is closed. apparatus.

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