JP2018179447A - Pre-mixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pre-mixing device which requires a low cost and which prevents a control failure by inclusion of foreign substance, the pre-mixing device including: a butterfly valve 7 connected to a gas suction part 31 in which a downstream end of a gas supply path 4 is provided to an air supply path 3 at an upstream side of a fan 2, the butterfly valve serving as an air resistance switching means for switching a ventilation resistance at the air supply path 3 at an upstream side of the gas suction part 31; and a gas resistance switching means for switching the ventilation resistance of the gas supply path between large and small.SOLUTION: A gas resistance switching means is composed of a gas butterfly valve 8 rotatably provided in a gas supply path 4. An air butterfly valve 7 and the gas butterfly valve 8 are connected to a common valve shaft 91 which is rotatably driven by a single actuator 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a premixing device which mixes fuel gas with air and supplies a 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 passage provided with a flow rate control valve for supplying a fuel gas is provided to a gas suction portion provided in an air supply passage on the upstream side of a fan. Air resistance switching means connected for switching the ventilation resistance of the portion of the air supply passage upstream from the gas suction part large and small, and the gas resistance switching the ventilation resistance of the portion of the gas supply passage downstream of the flow control valve large and small It is known to provide 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 the amount of fuel gas corresponding to the required combustion amount is supplied, and the air-fuel ratio of the mixture supplied to the burner is made constant. Thus, the fan rotational speed is controlled in accordance with the required combustion amount. However, the required amount of combustion becomes equal to or less than a predetermined value, and the fan rotation speed becomes equal to or less than the lower limit rotation speed at which the proportional characteristic of the air flow can be maintained, or the proportional valve current (current supplied to the proportional valve) If the current falls below the lower limit current at which the characteristics can be maintained, the amount of air or fuel gas can not be supplied according to the required combustion amount.

  Moreover, as a flow control valve, zero governor which maintains a secondary gas pressure at atmospheric pressure may be used. In this case, the amount of fuel gas supplied changes in accordance with the differential pressure between the atmospheric pressure, which is the secondary gas pressure, and the negative pressure in the air supply passage. Then, since the negative pressure in the air supply path changes in accordance with the fan rotational speed, the fuel gas supply amount changes in accordance with the fan rotational speed, that is, the air supply amount. Therefore, by controlling the fan rotational speed according to the required amount of combustion, air and fuel gas in amounts corresponding to the required amount of combustion are supplied to the burner.

  Even in this case, when the fan rotation speed becomes lower than the lower limit rotation speed at which the proportional characteristic of the air blowing amount can be maintained, it is not possible to supply the amount of air or fuel gas according to the required combustion amount. Therefore, when the required amount of combustion becomes equal to or less than the predetermined value, the air resistance switching means increases the ventilation resistance of the air supply passage, and the required number of combustions equal to or less than the predetermined value without making the fan rotational speed equal to or lower than the lower limit rotational speed. It is necessary to be able to supply an amount of air according to the amount. In addition, if the air flow resistance in the air supply path is increased simply by increasing the negative pressure in the air supply path, the amount of fuel gas supplied will exceed the amount according to the required combustion amount. It is necessary to increase the air flow resistance of the gas supply path as the size is increased.

  Therefore, in the above conventional example, when the required combustion amount becomes equal to or less than the predetermined value, the air resistance switching means increases the air flow resistance of the air supply path and the gas resistance switching means increases the air flow resistance of the gas supply path. As the capacity state, it is possible to supply air or fuel gas in an amount according to the required amount of combustion below a predetermined value, and when the required amount of combustion exceeds the predetermined value, the air resistance switching means At the same time, the gas resistance switching means restores the large capacity state in which the gas flow resistance of the gas supply path is reduced.

  Here, in the one described in Patent Document 1, the air resistance switching means is provided in the portion of the air supply passage on the upstream side of the gas suction portion, and has an open posture parallel to the longitudinal direction of the air supply passage and the air supply passage. And a butterfly valve that is pivoted to a closed position orthogonal to the longitudinal direction of the valve. Further, the gas resistance switching means is constituted by a switching valve provided so as to be able to open and close in the gas supply passage. And in the thing of patent document 1, the interlocking mechanism which opens and closes the switching valve interlockingly with the opening attitude | position of a butterfly valve, and rotation to a closing attitude | position becomes required. Therefore, the structure is complicated and the cost is high. Further, foreign matter flowing in the gas supply path may bite between the valve seat of the switching valve and the valve body, resulting in a closing failure of the switching valve, and the gas amount may not be properly controlled in the small capacity state.

Unexamined-Japanese-Patent No. 2015-230113

  SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a premixing device which is low in cost and in which control defects due to biting of foreign matter do not occur.

  In order to solve the above problems, the present invention is a premixing device which mixes a fuel gas with air and supplies a mixture to a burner through a fan, and is provided with a flow control valve for supplying the fuel gas. A downstream end of the gas supply passage is connected to a gas suction unit provided in an air supply passage on the upstream side of the fan, and the air resistance switching unit switches the flow resistance of the portion of the air supply passage on the upstream side from the gas suction unit And a gas resistance switching means for switching the gas flow resistance of the portion of the gas supply path downstream of the flow rate control valve to a greater or lesser degree, and the air resistance switching means is an air butterfly rotatably provided in the air supply path. In the one constituted by the valve, the gas resistance switching means is constituted by the butterfly valve for gas rotatably provided in the gas supply passage, and the butterfly valve for air and the butterfly valve for gas are operated by a single actuator. rotation Characterized in that it is connected to a common valve shaft which is dynamic.

  According to the present invention, since the gas resistance switching means is constituted by the butterfly valve for gas connected to the same valve shaft as the butterfly valve for air, a complicated interlocking mechanism becomes unnecessary, and the cost can be reduced. Further, unlike the switching valve of the above-described conventional example, the gas butterfly valve can appropriately control the amount of gas without causing a valve closing failure due to the biting of foreign matter flowing in the gas supply passage.

  Further, in the present invention, the opening angle of the valve shaft at which the opening area of the air butterfly valve arrangement portion of the air supply passage is minimized is the minimum angle, and the opening area of the air butterfly valve arrangement portion of the air supply passage is largest. The rotation angle of the valve shaft is the maximum angle, and the ratio of the opening area of the gas butterfly valve arrangement portion of the gas supply passage to the opening area of the air butterfly valve arrangement portion of the air supply passage is the opening area ratio. Although the opening area ratio when the movement angle is at the minimum angle and the opening area ratio when the rotation angle of the valve shaft is at the maximum angle is made equal to a predetermined value, the rotation angle of the valve shaft is The opening area ratio at a predetermined intermediate angle to the maximum angle may be different from a predetermined value. For example, the opening area ratio may be larger than a predetermined value when the rotation angle of the valve stem is at an intermediate angle, and in this case, the burner may be ignited with the rotation angle of the valve stem at an intermediate angle. desirable. According to this, at the time of ignition in which the rotation angle of the valve shaft is at the middle angle, the gas concentration of the mixture is higher than when the rotation angle of the valve shaft is at the minimum angle or the maximum angle, and the ignition operation is stable. Can prevent ignition mistakes.

  Further, in the present invention, the minimum angle, the maximum angle, and the opening area ratio are defined in the same manner as described above, and the opening area ratio when the valve shaft rotation angle is the minimum angle is the maximum. The opening area ratio when making an angle is both equal to a predetermined value, and the opening area ratio also has a predetermined value when the turning angle of the valve stem is made an arbitrary angle between the minimum angle and the maximum angle. And may be maintained equal to According to this, the excess air ratio of the mixture does not change regardless of the angle of rotation of the valve shaft between the minimum angle and the maximum angle. Therefore, in addition to the control in the small capacity state where the rotational angle of the valve stem is the minimum angle and the control in the large capacity state where the rotational angle of the valve stem is the large angle, the rotational angle of the valve stem is the smallest Control in medium power state can be performed with an angle between the angle and the maximum angle. Then, by the control in the medium capacity state, the fan rotational speed can be reduced compared to the small capacity state, and noise reduction and power saving can be achieved.

FIG. 1 is a cutaway side view of a premixing device of a first embodiment of the present invention. Sectional drawing cut | disconnected by the II-II line of FIG. Sectional drawing cut | disconnected by the III-III line of FIG. The graph which shows the relationship between the fan rotation speed and the amount of combustion in each large and small capacity state. FIG. 7A is a cross-sectional view of the placement portion of the air butterfly valve of the premixing device of the second embodiment, where FIG. 7A is a view when the valve axis is at a minimum angle, FIG. (C) is a figure when a valve axis is the largest angle. FIG. 7A is a cross-sectional view of the arrangement portion of the gas butterfly valve of the premixing device of the second embodiment, where FIG. 7A is a view when the valve axis is at a minimum angle, FIG. (C) is a figure when a valve axis is the largest angle. The graph which shows the relationship between the rotation angle of the valve stem in the premixing device of a 2nd embodiment, and the excess air ratio of air-fuel mixture.

  Referring to FIG. 1, reference numeral 1 denotes a burner comprising an all primary combustion type burner or the like having a combustion surface 1a on which an air-fuel mixture jets and burns. A fan 2 is connected to the burner 1 and the fuel gas is mixed with air by the premixing device A of the embodiment of the present invention so that the air-fuel mixture is supplied 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 a fuel gas. An open / close valve 5 and a flow control valve 6 including a proportional valve and a zero governor are interposed upstream of the gas supply passage 4. Furthermore, the downstream end of the gas supply passage 4 is connected to a gas suction unit 31 provided in the air supply passage 3.

  Further, the premixing device A is an air resistance switching means for switching the air flow resistance of the portion of the air supply passage 3 upstream of the gas suction portion 31 to a greater or lesser degree, and of the gas supply passage 4 downstream of the flow control valve 6. And a gas resistance switching means for switching the ventilation resistance of the portion to large and small. When the required combustion amount is relatively small, the air resistance switching means increases the air flow resistance of the air supply passage 3 and the gas resistance switching means increases the air flow resistance of the gas supply passage 4 as a small capacity state. The air or fuel gas can be supplied according to a small required combustion amount, and when the required combustion amount becomes relatively large, the air resistance switching means reduces the air flow resistance of the air supply path 3 and the gas resistance switching. It is made to return to the high capacity state which made the ventilation resistance of gas supply way 4 small by means.

  The relationship between the rotational speed of the fan 2 (hereinafter referred to as the fan rotational speed) and the amount of combustion of the burner 1 is as shown by the characteristic line L in FIG. 4 in the small capacity state, and H in FIG. As shown by the characteristic line of. When the required combustion amount falls below the combustion amount Qhmin obtained when the fan rotational speed is set to the lower limit rotational speed Nmin at which the proportional characteristic of the air flow can be maintained in the large capacity state, the large capacity state is changed to the small capacity state When the required combustion amount exceeds the combustion amount Qlmax obtained when the fan rotational speed is set to the predetermined upper limit rotational speed Nmax in the small capacity state, the small capacity state is switched to the large capacity state.

  In the portion of the air supply passage 3 adjacent to the upstream side (lower side in FIG. 1) of the gas suction portion 31, there is a venturi portion 32 having a diameter smaller than that of the air supply passage 3 where the air butterfly valve 7 described later is disposed. It is provided. A portion of the air supply passage 3 adjacent to the downstream side of the venturi portion 32 is surrounded by a cylindrical portion 33 having a diameter larger than that of the venturi portion 32. Then, the downstream end of the venturi portion 32 is inserted into the upstream end of the cylindrical portion 33 with an annular gap, and the gas suction portion 31 is configured by this gap. Further, the peripheral wall surface of the portion of the air supply passage 3 adjacent to the upstream side of the venturi portion 32 is formed as a tapered surface 34 which is reduced in diameter toward the venturi portion 32. Further, a gas chamber 41 communicating with the gas suction unit 31 is provided at the downstream end of the gas supply passage 4 so as to surround the cylindrical portion 33.

  A rotatable air butterfly valve 7 is provided at a portion of the air supply passage 3 on the upstream side of the venturi portion 32, and the butterfly valve 7 constitutes an air resistance switching means. Further, a rotatable gas butterfly valve 8 is provided in a portion of the gas supply passage 4 on the upstream side of the gas chamber 41, and the butterfly valve 8 constitutes a gas resistance switching means. The air butterfly valve 7 and the gas butterfly valve 8 are connected to a common valve shaft 91 which is rotationally driven by a single actuator 9 such as a stepping motor.

  The opening area of the arrangement portion of the air butterfly valve 7 in the air supply passage 3 (the projected area in the longitudinal direction of the air supply passage 3 in the gap between the peripheral wall surface of the air supply passage 3 and the air butterfly valve 7) is minimum. The air flow resistance of the arrangement portion is maximized when the air butterfly valve 7 is in the closed position shown by the solid line in FIG. 2 which is orthogonal to the longitudinal direction of the air supply path 3. 3 that the opening area of the arrangement portion of the air butterfly valve 7 is maximized and the air flow resistance of the arrangement portion is minimized is because the air butterfly valve 7 is parallel to the longitudinal direction of the air supply passage 3 as shown in FIG. It is when it becomes an open posture shown by a virtual line. The opening angle of the valve shaft 91 at which the opening area of the arrangement portion of the air butterfly valve 7 in the air supply passage 3 is minimized is the minimum angle, and the opening area of the arrangement portion of the air butterfly valve 7 in the air supply passage 3 is largest In the present embodiment, the angle difference between the minimum angle and the maximum angle is 90 °, with the rotation angle of the valve stem 91 as the maximum angle.

  Further, when the pivot angle of the valve shaft 91 is a minimum angle, the gas butterfly valve 8 is in a closed position shown by a solid line in FIG. 3 orthogonal to the longitudinal direction of the gas supply passage 4. When the movement angle is the maximum angle, the open posture shown by the phantom line in FIG. 3 parallel to the longitudinal direction of the gas supply passage 4 is obtained. When the small capacity state is set, the rotation angle of the valve shaft 91 is set to the minimum angle. When the large capacity state is set, the rotation angle of the valve shaft 91 is set to the maximum angle.

  Here, the opening area of the arrangement portion of the gas butterfly valve 8 in the gas supply passage 4 with respect to the opening area of the arrangement portion of the air butterfly valve 7 in the air supply passage 3 (the peripheral wall surface of the gas supply passage 4 and the butterfly valve 8 for gas The ratio of the amount of supplied gas to the amount of supplied air decreases when the ratio of the area of the opening to the ratio of the projected area in the longitudinal direction of the gas supply passage 4 in the gap between When the ratio (the amount of air supplied / the amount of theoretical air required for the amount of gas supplied) increases and the opening area ratio increases, the ratio of the amount of supplied gas to the amount of supplied air increases, and the excess air ratio of air-fuel mixture Decrease. In this embodiment, the opening area ratio when the rotation angle of the valve shaft 91 is the minimum angle and the opening area ratio when the rotation angle of the valve shaft 91 is the maximum angle are both equal to predetermined values. I have to. Therefore, the excess air ratio of the air-fuel mixture is maintained at an appropriate value (for example, 1.3) corresponding to the predetermined value in both the small capacity state and the large capacity state. Even if the opening area ratio when the rotation angle of the valve shaft 91 is at the minimum angle and the opening area ratio when the rotation angle of the valve shaft 91 is at the maximum angle is slightly different, the excess air of the mixture is If the rates are not substantially different, they are included in the above "equal to the predetermined value".

  According to this embodiment, since the gas resistance switching means is constituted by the butterfly valve 8 for gas connected to the valve shaft 91 common to the butterfly valve 7 for air, a complicated interlocking mechanism becomes unnecessary, and the cost is reduced. be able to. Further, unlike the switching valve of the above-described conventional example, the gas butterfly valve 8 can appropriately control the amount of gas without causing a valve closing failure due to the biting of foreign matter flowing into the gas supply passage 4.

  By the way, the opening area ratio of the butterfly valve for air 7 and the butterfly valve for gas 8 of the present embodiment has the above-mentioned predetermined opening area ratio even when the rotation angle of the valve shaft 91 is an arbitrary angle between the minimum angle and the maximum angle. It is configured to be maintained equal to the value. Therefore, even when switching to a medium performance state in which the pivot angle of the valve shaft 91 is an angle (for example, 45 °) between the minimum angle and the maximum angle, the excess air ratio of the mixture is appropriate according to the above predetermined value Maintained at the value.

  The relationship between the fan rotational speed and the amount of combustion in the medium capacity state is as shown by the characteristic line M in FIG. When only switching between the small capacity state and the large capacity state, the combustion shown by Qa in FIG. 4 is smaller than Qhmin (the amount of combustion obtained when the fan rotational speed is set to the lower limit rotational speed Nmin in the large capacity state) In order to obtain the amount, it is necessary to set the fan rotational speed to N1 in FIG. 4 in the small capacity state. On the other hand, if it is possible to switch to the medium capacity state in addition to the small capacity state and the large capacity state, the fan rotational speed is set to N2 in FIG. 4 lower than N1 in the medium capacity state to obtain the combustion amount of Qa. By switching to the medium performance state in this manner, it is possible to reduce noise and reduce power consumption by lowering the fan rotational speed compared to the low capacity state.

  Next, a second embodiment shown in FIGS. 5 and 6 will be described. In the second embodiment, when the pivot angle of the valve shaft 91 is set to the minimum angle, the posture shown in FIG. 5 (a) and the gas butterfly valve 8 shown in FIG. 6 (a) are shown. It becomes an attitude. When the pivot angle of the valve shaft 91 is the maximum angle rotated 120 ° from the minimum angle, the posture shown in FIG. 5 (c) for the air butterfly valve 7 and FIG. 6 (c) for the gas butterfly valve 8 It becomes an attitude. The opening area ratio when the rotation angle of the valve stem 91 is the minimum angle and the opening area ratio when the rotation angle of the valve stem 91 is the maximum angle are both equal to predetermined values. On the other hand, when the rotation angle of the valve shaft 91 is set to a predetermined intermediate angle between the minimum angle and the maximum angle (the angle rotated 60 ° from the minimum angle), the posture shown in FIG. The gas butterfly valve 8 is in the attitude shown in FIG. 6 (b), and the opening area ratio is larger than the predetermined value. Thus, the excess air ratio of the mixture changes as shown in FIG. 7 when the valve shaft 91 is rotated from the minimum angle (0 °) to the maximum angle (120 °). That is, the excess air ratio of the mixture is 1.3, which is an appropriate value when the rotation angle of the valve shaft 91 is set to the minimum angle (0 °) or the maximum angle (120 °). When the rotation angle of 91 is an intermediate angle (60 °), it is 1.2.

  So, in 2nd Embodiment, it is made to ignite the burner 1 in the state which made the rotational angle of the valve shaft 91 the middle angle. According to this, the gas concentration of the air-fuel mixture becomes higher than when the rotation angle of the valve shaft 91 is the minimum angle or the maximum angle, the ignition operation is stabilized, and an ignition error can be prevented.

  As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this, A various change can be implemented in the range which does not deviate from the meaning of this invention. For example, in the second embodiment, the opening area ratio when the rotation angle of the valve shaft 91 is an intermediate angle is the opening area ratio when the rotation angle of the valve shaft 91 is a minimum angle or a maximum angle. It is also possible to make it larger than the predetermined value but smaller than the predetermined value.

DESCRIPTION OF SYMBOLS 1 ... Burner, 2 ... Fan, 3 ... Air supply path, 31 ... Gas suction part, 4 ... Gas supply path, 6 ... Flow control valve, 7: ... Air butterfly valve, 8 ... Gas butterfly valve, 9 ... Actuator, 91: Valve shaft.

Claims (4)

A premixing device for mixing fuel gas with air and supplying a mixture to a burner via a fan, wherein the downstream end of a gas supply path provided with a flow control valve for supplying fuel gas is upstream of the fan Air resistance switching means connected to the gas suction unit provided in the air supply passage, for switching the air flow resistance of the portion of the air supply passage upstream from the gas suction unit to large and small, and the gas supply passage downstream of the flow rate control valve And the air resistance switching means is constituted by a butterfly valve for air rotatably provided in the air supply passage.
The gas resistance switching means is composed of a gas butterfly valve rotatably provided in the gas supply passage,
A premixing device characterized in that the butterfly valve for air and the butterfly valve for gas are connected to a common valve shaft rotationally driven by a single actuator.   Minimum rotation angle of the valve shaft where the opening area of the air butterfly valve arrangement portion of the air supply passage is minimum, and rotation angle of the valve shaft where the opening area of the air butterfly valve arrangement portion of the air supply passage is largest The ratio of the opening area of the gas butterfly valve arrangement part of the gas supply passage to the aperture area of the air butterfly valve arrangement part of the air supply passage is the opening area ratio, and the rotation angle of the valve shaft is the minimum angle. The opening area ratio when the opening angle ratio of the valve stem and the opening angle ratio of the valve stem is the maximum angle are both equal to a predetermined value, and the rotation angle of the valve stem is a predetermined angle between the minimum angle and the maximum angle. The premixing device according to claim 1, wherein the opening area ratio at the intermediate angle is different from a predetermined value.   The burner is ignited in a state in which the opening area ratio when the pivot angle of the valve stem is the intermediate angle is larger than the predetermined value and the pivot angle of the valve stem is the intermediate angle. Premixing device. Minimum rotation angle of the valve shaft where the opening area of the air butterfly valve arrangement portion of the air supply passage is minimum, and rotation angle of the valve shaft where the opening area of the air butterfly valve arrangement portion of the air supply passage is largest The ratio of the opening area of the gas butterfly valve arrangement part of the gas supply passage to the aperture area of the air butterfly valve arrangement part of the air supply passage is the opening area ratio, and the rotation angle of the valve shaft is the minimum angle. Both the opening area ratio and the opening area ratio when the rotation angle of the valve shaft is the maximum angle are both equal to a predetermined value, and the rotation angle of the valve shaft is between the minimum angle and the maximum angle. The premixing device according to claim 1, wherein the opening area ratio is maintained equal to a predetermined value even at an arbitrary angle.

Images