JP5820428B2 - Premixing device - Google Patents

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, according to Patent Document 1, the downstream end of a gas supply path provided with a proportional valve as a flow rate adjusting valve for supplying fuel gas is connected to an air supply path on the upstream side of a fan, There is known an air resistance switching means for switching the ventilation resistance of the supply path between large and small, and a gas resistance switching means for switching the ventilation resistance of the portion of the gas supply path downstream of the proportional valve to a large or small.

  By the way, the proportional valve supplies an amount of fuel gas proportional to the energization current (proportional valve current) to the proportional valve, and the proportional valve current is set so that an amount of fuel gas corresponding to the required combustion amount is supplied. Further, the fan rotation speed is controlled in accordance with the required combustion amount so that the air-fuel ratio of the air-fuel mixture supplied to the burner becomes constant. However, the required combustion amount becomes less than the predetermined value, the fan rotation speed becomes less than the lower limit rotation speed that can maintain the proportional characteristic of the blown air amount, or the proportional valve current becomes less than the lower limit current that can maintain the proportional characteristic of the gas supply amount. In such a case, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount.

  Therefore, in the above conventional example, when the required combustion amount becomes a predetermined value or less, the air resistance switching means increases the air supply path ventilation resistance and the gas resistance switching means increases the gas supply path ventilation resistance. Yes. According to this, it is possible to supply an amount of air or fuel gas corresponding to the required combustion amount equal to or less than a predetermined value without setting the fan rotation speed or the proportional valve current below the lower limit rotation speed or the lower limit current.

  Here, in the above-described conventional example, the air supply path is branched into two passages in the middle and then merged, and a valve seat having an opening through which air from one of the passages is formed is provided at the joining portion. Thus, the air resistance switching means is constituted by a valve that closes the opening, and the ventilation resistance of the air supply path is increased by closing the opening. Further, the gas resistance switching means is constituted by a valve which branches the downstream end of the gas supply path into two branch passages connected to the air supply path, and opens and closes the connection port for the air supply path of one branch passage. By closing the mouth, the ventilation resistance of the gas supply path is increased.

  However, in the above-described conventional example, since the valve constituting the air resistance switching means and the valve constituting the gas resistance switching means are arranged in the air supply path, foreign matters such as dust flowing in the air supply path adhere to the valve. There are things to do. Here, when foreign matter adheres to the valve constituting the air resistance switching means, even if the valve is closed, the opening cannot be closed by the foreign matter biting, and the increase in the air resistance of the air supply path is insufficient. As a result, the amount of air becomes excessive compared to the amount of fuel gas, resulting in poor combustion. In addition, when foreign matter adheres to the valve that constitutes the gas resistance switching means, even if the valve is closed, the connection port of the branch passage cannot be closed due to the foreign matter being caught, and the ventilation resistance of the gas supply passage is increased. Becomes insufficient, the amount of fuel gas is excessive compared to the amount of air, and combustion failure occurs.

International Publication No. 2012/134033

  In view of the above points, the present invention provides a premixing device capable of preventing the occurrence of poor combustion when the air resistance switching means and the gas resistance switching means are switched to the side where the ventilation resistance is increased. It is an issue.

In order to solve the above-described problems, the present invention is a premixing device that mixes fuel gas with air and supplies the air-fuel mixture to a burner via a fan, and includes a flow rate control valve that supplies the fuel gas. The downstream end of the gas supply path is connected to the air supply path upstream of the fan, air resistance switching means for switching the ventilation resistance of the air supply path between large and small, and the ventilation of the gas supply path portion downstream of the flow rate control valve The air resistance switching means comprises a butterfly valve rotatably provided in the air supply path, and the gas resistance switching means is connected to the air supply path. Consists of a switching valve that has a valve body in the partitioned valve housing and switches the ventilation resistance between large and small by moving the valve body to and away from the valve seat in the valve housing, and projects from the valve housing of the switching valve into the air supply path Operating rod is provided, When the valve is rotated in a direction to increase the flow resistance, some of the butterfly valve is in contact with the operating rod, the valve body of the changeover valve is pushed through the operating rod in a direction toward the valve seat When the butterfly valve is rotated in the direction to reduce the ventilation resistance, the operation rod follows the butterfly valve together with the valve body until the valve body of the switching valve reaches the stroke end position in the opening direction separated from the valve seat. motion, then, to a position where the smallest ventilation resistance, is rotated in a state in which the butterfly valve away from the operating rod, characterized in Rukoto.

  According to the present invention, since the air resistance switching means is constituted by a butterfly valve, unlike a valve that contacts and separates from the valve seat, there is no valve closing failure due to foreign matter biting, and the butterfly valve is connected to the air supply path. By rotating so as to be in a posture orthogonal to the longitudinal direction, the airflow resistance of the air supply path can be reliably increased. Further, since the valve body of the switching valve constituting the gas resistance switching means is provided in the valve housing partitioned from the air supply path, the valve body does not adhere to the foreign matter flowing in the air supply path. By operating in the direction approaching the valve seat, the ventilation resistance of the gas supply path can be reliably increased. Accordingly, when the air resistance switching means and the gas resistance switching means are switched to the side where the ventilation resistance is increased, the ventilation resistance of the air supply path or the gas supply path is insufficiently increased, resulting in poor combustion due to excessive air or excessive fuel. Can be prevented. Further, since the valve body of the switching valve operates in conjunction with the butterfly valve, no driving means for the switching valve is required, and the ventilation resistance of the air supply path and the gas supply path can be switched simultaneously with a simple structure.

  Further, in the present invention, the portion of the gas supply path on the downstream side of the switching valve is formed in a ring shape surrounding the air supply path, and the downstream end of the ring-shaped portion is opened through the opening on the outer peripheral surface of the air supply path. It is desirable that a tapered portion that is connected to the air supply path and that has a tapered diameter toward the downstream end is formed on the outer peripheral surface of the ring-shaped portion. According to this, the fuel gas supplied from the gas supply path can be efficiently mixed with the air flowing in the air supply path.

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. The graph which shows the relationship between combustion amount and fan rotation speed.

  Referring to FIG. 1, reference numeral 1 denotes a burner including an all-primary combustion burner having a combustion surface 1a on which an air-fuel mixture (a mixed gas of air and fuel gas) is jetted and burned. A fan 2 is connected to the burner 1, and a fuel gas is mixed with air by the premixing device A according to the embodiment of the present invention, and the mixture is supplied to the burner 1 through the fan 2. .

  The premixing device A includes an air supply path 3 on the upstream side of the fan 2 and a gas supply path 4 for supplying fuel gas, and a downstream end of the gas supply path 4 is connected to the air supply path 3. On the upstream side of the gas supply path 4, an on-off valve 5 and a proportional valve 6 serving as a flow rate adjusting valve are interposed. In FIG. 1, the white arrow indicates the air flow, and the black arrow indicates the fuel gas flow.

  The premixing device A further includes an air resistance switching means for switching the ventilation resistance of the air supply path 3 between large and small, and a gas resistance switching means for switching the ventilation resistance of the portion of the gas supply path 4 on the downstream side of the proportional valve 6 between large and small. And.

  During combustion of the burner 1, the energization current (proportional valve current) to the proportional valve 6 is controlled so that an amount of fuel gas corresponding to the required combustion amount is supplied, and the air-fuel mixture supplied to the burner 1 is empty. The rotation speed of the fan 2 (fan rotation speed) is controlled in accordance with the required combustion amount so that the fuel ratio becomes constant. However, the required combustion amount becomes a predetermined value or less, and the fan rotation speed has a proportional characteristic of the air flow rate. When the rotation speed becomes lower than the lower limit rotation speed that can be maintained or the proportional valve current becomes lower than the lower limit current that can maintain the proportional characteristic of the gas supply amount, it becomes impossible to supply air or fuel gas in an amount corresponding to the required combustion amount.

  Therefore, when the required combustion amount becomes a predetermined value or less, the ventilation resistance of the air supply path 3 is increased by the air resistance switching means, and the ventilation resistance of the gas supply path 4 is increased by the gas resistance switching means. According to this, it is possible to supply an amount of air or fuel gas corresponding to the required combustion amount equal to or less than a predetermined value without setting the fan rotation speed or the proportional valve current below the lower limit rotation speed or the lower limit current. FIG. 3 shows the relationship between the combustion amount and the fan rotation speed. In FIG. 3, a is a characteristic line when the ventilation resistance of the air supply path 3 is reduced, and b is the increase of the ventilation resistance of the air supply path 3. It is a characteristic line in the case of.

  Here, in the present embodiment, the air resistance switching means is a butterfly made of a disc having a diameter smaller than the diameter of the air supply path 3 provided in the air supply path 3 so as to be rotatable about the shaft 71. It consists of a valve 7. An actuator 72 is connected to the shaft 71 of the butterfly valve 7 as shown in FIG. When the required combustion amount becomes equal to or less than the predetermined value, the butterfly valve 7 is moved from the open posture shown by the two-dot chain line in FIG. 1 to the closed posture orthogonal to the longitudinal direction of the air supply path 3 by the operation of the actuator 72. Rotate to In the closed posture, air flows only through the gap between the peripheral surface of the air supply path 3 and the outer periphery of the butterfly valve 7, and the ventilation resistance of the air supply path 3 increases.

  Further, the gas resistance switching means is provided with a valve body 82 in a valve casing 81 partitioned from the air supply path 3, and the valve body 82 is switched so as to be movable toward and away from the valve seat 83 in the valve casing 81. It consists of a valve 8. The valve casing 81 is provided with an upstream inlet 81 a and a downstream outlet 81 b of the valve seat 83. Further, the valve seat 83 is formed with a valve hole 83a and a bypass hole 83b as openings for communicating the inflow port 81a and the outflow port 81b. When the valve body 82 is moved in the direction approaching the valve seat 83 and is seated on the valve seat 83, the valve hole 83a is closed, and the fuel gas flows from the inlet 81a to the outlet 81b only through the bypass hole 83b. The ventilation resistance of the gas supply path 4 increases.

  An operation rod 84 is connected to the valve body 82, and a direction in which the valve body 82 is separated from the valve seat 83 by a valve spring 85 contracted between a spring receiver 84 a fixed to the operation rod 84 and the valve seat 83. Is energized. Further, the operation rod 84 projects from the valve housing 81 into the air supply path 3. When the butterfly valve 7 is rotated in a direction to increase the airflow resistance of the air supply path 3, that is, in a closed position, a part of the butterfly valve 7 comes into contact with the operation rod 84 and the valve element 82 is The valve is pushed through the operation rod 84 in a direction approaching the valve seat 83. When the butterfly valve 7 is rotated from the closed position in the opening direction, the operating rod 84 follows the butterfly valve 7 until the spring receiver 84a comes into contact with the end face of the valve casing 81 by the urging force of the valve spring 85 together with the valve body 82. As a result, the ventilation resistance of the gas supply path 4 becomes sufficiently small. Thereafter, since the butterfly valve 7 is separated from the operation rod 84, the butterfly valve 7 is rotated to the open posture along the longitudinal direction of the air supply path 3 without being obstructed by the operation rod 84, and the airflow resistance of the air supply path 3. Can be made sufficiently small.

  The part of the gas supply path 4 on the downstream side of the switching valve 8, that is, the part of the gas supply path 4 communicating with the outlet 81b of the valve casing 81 is formed in a ring shape surrounding the air supply path 3, as shown in FIG. The downstream end of the ring-shaped portion 41 is connected to the air supply path 3 via the opening 31 on the outer peripheral surface of the air supply path 3. In addition, a tapered portion 41 a that is tapered toward the downstream end is formed on the outer peripheral surface of the ring-shaped portion 41.

  According to the present embodiment, since the air resistance switching means is constituted by the butterfly valve 7, unlike the valve that contacts and separates from the valve seat, the valve closing failure occurs due to the biting of foreign matters such as dust flowing in the air supply path 3. Therefore, by rotating the butterfly valve 7 so as to be in a closed posture perpendicular to the longitudinal direction of the air supply path 3, the air resistance of the air supply path 3 can be reliably increased. Further, since the valve body 82 of the switching valve 8 constituting the gas resistance switching means is provided in the valve housing 81 partitioned with respect to the air supply path 3, foreign matters flowing in the air supply path 3 adhere to the valve body 82. By operating the valve body 82 in the direction approaching the valve seat 83 without any problems, the ventilation resistance of the gas supply path 4 can be reliably increased. Therefore, when the air resistance switching means and the gas resistance switching means are switched to the side where the airflow resistance is increased, the airflow resistance of the air supply path 3 or the gas supply path 4 becomes insufficiently increased, resulting in excessive air or excessive fuel. It is possible to prevent the occurrence of defective combustion.

  Further, since the valve body 82 of the switching valve 8 operates in conjunction with the butterfly valve 7, no driving means for the switching valve 8 is required, and the air resistance of the air supply path 3 and the gas supply path 4 with a simple structure. Can be switched simultaneously. Further, by forming a tapered portion 41a on the outer peripheral surface of the ring-shaped portion 41, which is a portion of the gas supply path 4 on the downstream side of the switching valve 8, a speed component in which the fuel gas increases the flow velocity and goes radially inward. And flows into the air supply path 3. Therefore, the fuel gas can be efficiently mixed with the air flowing in the air supply path 3.

  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 embodiment, the valve hole 83a and the bypass hole 83b are formed in the valve seat 83 of the switching valve 8, but when the bypass hole 83b is omitted and the valve body 82 is closest to the valve seat 83, A gap corresponding to a bypass hole may be formed between the valve hole 83a and the valve body 82.

  Moreover, in the said embodiment, although the ring-shaped part 41 surrounding the air supply path 3 is provided in the part of the gas supply path 4 of the downstream of the switching valve 8, the ring-shaped part 41 is abbreviate | omitted and the valve of the switching valve 8 is provided. It is also possible to form an outlet in the casing 81 that directly communicates with the air supply path 3. However, in order to promote the mixing of the fuel gas into the air, the above embodiment is desirable.

  Moreover, in the said embodiment, although the proportional valve 6 is used as a flow control valve interposed in the gas supply path 4, you may use the zero governor which adjusts secondary gas pressure to atmospheric pressure as a flow control valve. When the zero governor is used, the supply amount of the fuel gas changes according to the differential pressure between the atmospheric pressure as the secondary gas pressure and the negative pressure in the air supply path 3. Since the negative pressure in the air supply path 3 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.

  A ... premixing device, 1 ... burner, 2 ... fan, 3 ... air supply path, 31 ... opening of outer peripheral surface of air supply path, 4 ... gas supply path, 41 ... ring-shaped part, 41a ... taper part, 6 ... Proportional valve (flow control valve), 7 ... butterfly valve, 8 ... switching valve, 81 ... valve housing, 82 ... valve body, 83 ... valve seat, 84 ... operating rod.

Claims (2)

A premixing device that mixes fuel gas with air and supplies the air-fuel mixture to a burner via a fan, wherein a downstream end of a gas supply path provided with a flow rate control valve for supplying fuel gas is located upstream of the fan. An air resistance switching means connected to the air supply path for switching the ventilation resistance of the air supply path between large and small, and a gas resistance switching means for switching the ventilation resistance of the portion of the gas supply path on the downstream side of the flow rate control valve to large or small In things,
The air resistance switching means is composed of a butterfly valve rotatably provided in the air supply path,
The gas resistance switching means comprises a switching valve that includes a valve body in a valve housing partitioned from the air supply path, and switches the ventilation resistance between large and small by the contact and separation operation of the valve body with respect to the valve seat in the valve housing,
An operation rod that protrudes from the valve housing of the switching valve into the air supply path is provided, and when the butterfly valve is rotated in the direction that increases the ventilation resistance, a part of the butterfly valve abuts on the operation rod and switches. Opening direction in which the valve body of the switching valve is separated from the valve seat when the valve body is pushed through the operating rod in a direction approaching the valve seat and the butterfly valve is rotated in a direction to reduce the ventilation resistance. operating rod until it reaches the stroke end position moves to follow the butterfly valve together with the valve body, then, to a position where the smallest ventilation resistance, characterized Rukoto is rotated in a state in which the butterfly valve away from the operating rod Premixing device. The portion of the gas supply path on the downstream side of the switching valve is formed in a ring shape surrounding the air supply path, and the downstream end of the ring-shaped portion is connected to the air supply path via an opening on the outer peripheral surface of the air supply path. The premixing device according to claim 1, wherein a tapered portion that is tapered toward the downstream end is formed on the outer peripheral surface of the ring-shaped portion.

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