JP2019045076A - Gas flow rate controller - Google Patents

Abstract

To provide a gas flow controller capable of determining deviation of an opening of a flow regulating valve.SOLUTION: A gas flow rate controller comprises a flow regulating valve 2 provided in a gas flow passage 1 to a burner, and determination means of determining deviation of an opening of the flow regulating valve 2. The determination means is configured to compare a capacity coefficient in an actual opening of the flow regulating valve 2, with a preset reference value, to determine the deviation of the opening of the flow regulating valve 2. The reference value of a capacity coefficient is preferably evaluated as flow characteristics by using an approximate expression, from two different openings and capacity coefficients at these openings.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a gas flow control device capable of determining an opening deviation of a flow control valve.

  Heretofore, as disclosed in Patent Document 1 below, there is known a gas flow rate control device in which a flow rate adjustment valve is provided in a gas flow path to a burner to adjust the gas flow rate. The flow control valve is provided with an orifice in the middle of the flow path, and by moving the valve body to and from the orifice hole by a motor, the gap between the orifice hole and the valve body can be increased or decreased to adjust the flow rate .

JP, 2015-218950, A (paragraph 0024, FIG. 1)

  In the conventional gas flow control device, although the origin of the flow control valve can be confirmed, there is no means for confirming the opening degree other than the origin. Therefore, for example, with respect to the instruction opening degree from the controller of the boiler, it is unclear whether or not the opening degree is actually as instructed. Therefore, for example, when the opening deviation occurs due to malfunction due to electrical noise, step out of stepper motor, wear due to aging, etc., the expected amount of gas can not be sent to the burner, which may cause combustion failure. is there.

  Therefore, the problem to be solved by the present invention is to provide a gas flow control device capable of determining the opening deviation of the flow control valve.

  The present invention has been made to solve the above-mentioned problems, and the invention according to claim 1 relates to a flow control valve provided in a gas flow path to a burner and an actual opening of the flow control valve. Gas flow rate control characterized by further comprising: determination means for comparing the capacity coefficient with a reference value of the capacity coefficient at the opening degree, which is set in advance, to determine the opening deviation of the flow adjustment valve. It is an apparatus.

  According to the first aspect of the present invention, the displacement coefficient of the flow control valve can be determined by comparing the capacity coefficient at the actual opening of the flow control valve with a preset reference value. In this way, it is possible to monitor whether or not the desired amount of gas is being supplied to the burner and to prevent combustion failure in advance.

  The invention according to claim 2 is characterized in that the reference value of the capacity coefficient at the opening of the flow rate adjusting valve is an approximate expression in advance as a flow characteristic from the two or more different openings and the capacity coefficient at these openings. It is a gas flow rate control device according to claim 1, characterized in that it is determined.

  According to the second aspect of the present invention, the reference value of the capacity coefficient can be obtained from an approximate expression based on two or more different opening degrees and the capacity coefficient at the opening degree. Thus, the reference value to be compared with the capacity coefficient at the opening can be easily obtained.

  The invention according to claim 3 adjusts the opening degree based on the pressure on the primary side of the flow rate adjustment valve and the air flow rate to the burner, and the capacity after the adjustment is calculated according to the approximate expression. The gas flow control device according to claim 2, wherein a reference value of the coefficient is obtained.

  According to the third aspect of the present invention, a desired amount of gas is supplied to the burner by adjusting the opening of the flow control valve based on the pressure on the primary side of the flow control valve and the air flow to the burner. Can. Moreover, with respect to the adjusted opening degree, it is possible to monitor the presence or absence of the opening degree deviation by comparison with the reference value by the approximate expression.

  Furthermore, in the invention according to claim 4, the burners are controlled by at least a first combustion, a second combustion and a third combustion in the order of increasing combustion stages, and correspond to the first combustion and the second combustion, respectively. The capacity coefficient at the opening of the flow control valve is determined by an approximate expression as a reference value, and the capacity coefficient at the opening of the flow control valve corresponding to each of the second combustion and the third combustion is used as a reference It is a gas flow rate control device according to claim 2 or claim 3 characterized by being obtained by an approximation formula.

  According to the invention described in claim 4, in the burner in which the amount of combustion is adjusted in a plurality of stages, it is possible to easily obtain the reference value in each amount of combustion by an approximate expression.

  According to the present invention, it is possible to realize a gas flow control device capable of determining the opening deviation of the flow control valve.

It is the schematic which shows the gas flow path where the gas flow control apparatus of one Example of this invention was applied. It is the schematic which shows an example of the relationship between the opening degree of a flow regulating valve, and a capacity coefficient.

Hereinafter, specific embodiments of the present invention will be described in detail based on the drawings.
FIG. 1 is a schematic view showing a gas flow path 1 to which a gas flow control device according to an embodiment of the present invention is applied. The gas flow rate control device of the present embodiment is applied to the gas flow path 1 to a burner (not shown) of a boiler, and the gas flow rate can be adjusted by the flow rate adjustment valve 2. It is possible to determine the deviation between the opening degree indicated by the controller and the actual opening degree.

  In the gas flow path 1, a first shutoff valve 3, a second shutoff valve 4 and a flow control valve 2 are provided in order from the gas supply source to the burner. The first shutoff valve 3 and the second shutoff valve 4 are solenoid valves whose opening and closing are controlled, and switch the presence or absence of gas supply to the burner. Gas can be supplied to the burner by opening the shutoff valves 3 and 4, and gas supply to the burner can be stopped by closing the shutoff valves 3 and 4. Then, while the shutoff valves 3 and 4 are open, the gas flow rate to the burner can be adjusted by adjusting the opening degree of the flow rate adjustment valve 2.

  Although the flow control valve 2 is not shown to a specific configuration, it has a body with a flow path formed, an orifice provided in the middle of the flow path in the body, and a shaft with a valve body moving back and forth with respect to this orifice And a motor for advancing and retracting the shaft. The orifice is formed of a plate in which an orifice hole is formed. The valve body is formed such that the outer peripheral surface is tapered (e.g., a tapered shape whose diameter decreases toward the axial proximal end of the shaft), and can be advanced and retracted by the shaft. The motor for advancing and retracting the shaft is typically a stepping motor. By moving the valve body to and from the orifice hole by the motor, the gap between the valve body and the orifice hole can be increased or decreased to adjust the flow rate through the orifice hole.

  In the gas flow path 1, a first pressure sensor 5 is provided on the primary side (inlet side) of the flow rate adjustment valve 2, and a second pressure sensor 6 is provided on the secondary side (outlet side) of the flow rate adjustment valve 2. Be Further, a temperature sensor 7 is provided, for example, on the secondary side of the flow control valve 2 to monitor the temperature of the gas. Furthermore, a flow sensor 8 is provided, for example, on the primary side of the first shut-off valve 3 in order to monitor the gas supply flow rate to the burner.

  The first pressure sensor 5, the second pressure sensor 6, the temperature sensor 7, the flow sensor 8, etc. in addition to the first shut-off valve 3, the second shut-off valve 4 and the flow control valve 2 are connected to a controller (not shown) Ru. Then, as described below, the controller controls each of the valves 2 to 4 to change the presence or absence and amount of gas supply to the burner, and adjust the flow rate based on the detection signals of each of the sensors 5 to 8 and the like. The opening degree deviation of the valve 2 is determined. That is, the controller also functions as a determination unit of the opening deviation of the flow rate adjustment valve 2. The gas flow rate control device of this embodiment comprises at least the flow rate adjustment valve 2 in the configuration of FIG.

  Hereinafter, the control method of each of the valves 2 to 4 by the controller and the determination method of the opening deviation of the flow control valve 2 will be described. The controller can be identified by a sensor (not shown) with the specific position (typically, the maximum closing position, ie, the opening degree 0%) of the flow rate adjustment valve 2 as the origin.

  In the present embodiment, gas fuel is supplied to the burner of the boiler via the first shutoff valve 3, the second shutoff valve 4 and the flow rate adjustment valve 2. The amount of combustion of the boiler is adjusted according to the load of use of steam. For example, the working load of steam is monitored based on the steam pressure at the outlet side of the boiler, and as the working load of steam increases (in other words, the steam pressure decreases), the gas flow rate to the burner is increased to increase the combustion amount As the working load of steam decreases (in other words, the steam pressure increases), the gas flow rate to the burner decreases to reduce the amount of fuel. In the present embodiment, for example, the amount of combustion is switched stepwise at four positions of high combustion, medium combustion, low combustion and stop. While the flow rate of the gas is changed by the flow control valve 2 according to the change of the amount of combustion, the flow rate of the combustion air from the blower to the burner is also changed. These controls are also performed by the controller.

  During operation of the boiler, the pressure on the primary side of the flow control valve 2 can be detected by the first pressure sensor 5, the pressure on the secondary side of the flow control valve 2 can be detected by the second pressure sensor 6, and the temperature sensor 7 The temperature of the gas can be detected, and the flow rate sensor 8 can detect the flow rate of the gas.

  The boiler is previously adjusted for combustion so as to obtain an appropriate air ratio. For example, at the time of boiler installation (field test run), annual inspection after installation, etc., the combustion stage (high combustion in the above example) so that the ratio of gas to combustion air becomes the set value. The opening degree of the flow rate adjustment valve 2 is set (registered) in the controller as a combustion adjustment value (for creating a reference value to be described later) for each position of middle combustion, low combustion. Under the present circumstances, the capacity coefficient with respect to the opening degree of the flow control valve 2 in each combustion stage is also calculated | required as a combustion adjustment value (for reference value creation mentioned later). Specifically, at each combustion stage, the capacity coefficient at the time of combustion adjustment is determined by [Equation 1] described later based on the detection values of each of the sensors 5 to 8 and the like, and is set (registered) in the controller. .

  There are various types of capacity coefficients of the flow rate adjustment valve 2, and for example, a Cv value is used. Cv value is calculated | required by Cv = Qx (root) (G / (DELTA) p) as well-known. Here, Q is the flow rate of the gas, G is the specific gravity of the gas, and Δp is the differential pressure before and after the flow control valve 2. More specifically, in the present embodiment, the Cv value is determined by the following equation.

  [Equation 1] Cv = Q / 4140 × √ {(Gg × (273 + t)) / ((P1−P2) × P2)}

However, each symbol in the formula is as follows.
Q [m ³ / hr] indicates a standard flow rate of gas, and is obtained by the flow rate sensor 8.
Gg is the specific gravity of gas (when air is 1), and is 0.64 when using, for example, city gas 13A.
t [° C.] is the temperature of the gas, which is determined by the temperature sensor 7.
P1 [MPa] is the gas pressure (absolute pressure) on the primary side of the flow control valve 2 and is determined by the first pressure sensor 5.
P2 [MPa] is the gas pressure (absolute pressure) on the secondary side of the flow control valve 2 and is determined by the second pressure sensor 6.

  FIG. 2 is a schematic view showing an example of the relationship between the opening degree Op [%] of the flow control valve 2 (0% fully closed and 100% fully open) and the capacity coefficient Cv. In the figure, points L, M and H are values (opening degree, Cv value) at each combustion stage obtained at the time of the combustion adjustment described above. Specifically, at the time of combustion adjustment, the opening degree at low combustion and the Cv value are indicated by point L, and the opening degree at medium combustion and the Cv value are indicated by point M, and the opening degree at high combustion and Cv The value is shown at point H.

  The controller can obtain a Cv value at an arbitrary opening degree by using an approximate expression as a flow rate characteristic from two or more different opening degrees and the Cv values at these opening degrees, and the obtained Cv value is used as a reference value I assume. In the illustrated example, based on the combustion adjustment value of the point L and the point M, the Cv value for an arbitrary opening degree between these points (point L to point M) can be obtained as a reference value by linear approximation (linear interpolation) . Further, based on the combustion adjustment value of the point M and the point H, the Cv value for an arbitrary opening degree in the period (point M to point H) can be obtained as a reference value by linear approximation (linear interpolation).

  The linear approximate straight line between the point M and the point H is extended to the high opening side with respect to the point H with the same inclination, and the Cv value for any opening degree larger than the point H can also be obtained. Similarly, the linear approximate straight line between the point L and the point M may be extended to the lower opening side than the point L with the same inclination, and the Cv value for any opening degree smaller than the point L may be obtained . Furthermore, if desired, similarly, the linear approximate straight line between point M and point H may be extended to a lower opening side than point M, or the linear approximate straight line between point L and point M may be higher than point M It may be extended to the opening side to make it possible to obtain the Cv value at any opening degree. The Cv values obtained in this manner are all used as reference values at the time of opening deviation determination, as described later.

  During the operation of the boiler, as described above, in the present embodiment, the amount of combustion is adjusted stepwise at four positions of high combustion, medium combustion, low combustion and stop based on the steam load. At this time, the controller instructs the flow rate adjusting valve 2 to an opening degree corresponding to each combustion stage. Specifically, the high combustion opening degree at high combustion, the middle combustion opening degree at medium combustion, and the low combustion opening degree at low combustion, basically, the opening degree at the time of combustion adjustment (point H, The flow control valve 2 may be instructed as the opening degree of M, L). Alternatively, the air flow rate may be changed in accordance with the combustion stage, and the flow adjustment valve 2 may be instructed with an opening degree that provides a predetermined air ratio accordingly. On the other hand, when the combustion is stopped (standby), each shutoff valve may be closed.

  In each state of high combustion, medium combustion, and low combustion, the air flow rate changes according to the combustion stage (also adjusted depending on the outside air temperature if necessary), and gas supply pressure etc. also changes even in the same combustion stage. It is preferable to adjust the degree of opening at the time of combustion adjustment based on the gas pressure on the primary side of the flow rate adjustment valve 2 and the air flow rate to the burner in consideration of obtaining. For example, as the gas supply pressure (the pressure detected by the first pressure sensor 5) is lower, control may be performed so as to have an opening degree larger than the opening degree of the combustion adjustment value. The gas pressure on the primary side of the flow rate adjustment valve 2 is determined by the pressure detected by the first pressure sensor 5. Further, the air flow rate to the burner may be determined by the rotational speed of the blower, the opening degree of the damper, or the like, or may be determined by the differential pressure before and after the orifice provided in the combustion air supply system.

  During operation of the boiler, the controller determines the deviation of the flow rate adjustment valve 2 at set timing (for example, every set time, every transition of the combustion stage, etc.). However, after the transition of the combustion stage, the flow rate detected by the flow rate sensor 8 becomes stable (for example, the variation rate falls within a predetermined range, or a predetermined time elapses after the transition) without immediately making a decision. It is preferable to determine the deviation of the opening degree.

  In order to determine the opening deviation, the controller determines a Cv value at the actual opening of the flow control valve 2. That is, at the determination timing, the Cv value may be obtained based on the above [Equation 1] based on the detection signal of each of the sensors 5-8. Then, the deviation of the flow rate adjusting valve 2 is determined by comparing the Cv value at the actual opening degree with a reference value (reference Cv value) set in advance.

  Here, the reference value is obtained based on the indicated opening degree from the controller to the flow rate adjustment valve 2. That is, the opening degree corresponding to the combustion stage, and preferably the Cv value for the opening degree adjusted based on the gas pressure on the primary side of the flow rate adjusting valve 2 as described above, is based on FIG. Based on the described approximate expression, it is acquired as a reference value. Then, based on whether or not the actual Cv value is separated by a predetermined distance or more from the reference value by the approximate expression, it is determined whether or not the flow rate adjustment valve 2 has an opening deviation. For example, if the actual Cv value is within “reference value ± 10%”, it is determined that there is no opening deviation, and if it exceeds “reference value ± 10%”, it is determined that there is opening deviation. Then, when it is determined that there is an opening deviation, for example, a notification may be given to the user by displaying on a buzzer or a touch panel, or the operation of the boiler may be stopped.

For example, at the time of high combustion at the time of combustion adjustment, Cv value 5.34 and gas flow rate 179 [m ³ N / hr] at opening degree 59% indicate failure of flow control valve 2 and open degree instructed from controller Assuming that the degree of opening is only about 54% open to 59% and only the gas flow rate of 160 [m ³ N / hr] flows, the Cv value calculated at the time of opening degree deviation determination is about 4.77 and the Cv value is It will be about 10% off. In such a case, it is determined that there is a possibility that the opening of the flow control valve 2 is out of alignment. However, since there is a possibility that displacement of the flow rate sensor 8 occurs, it is preferable to confirm whether or not the flow rate sensor 8 is used at the time of determination.

  According to the gas flow rate control device of this embodiment, during the gas supply to the burner, the Cv value (actual value) at the actual opening of the flow rate adjustment valve 2 is determined as appropriate, and the flow rate is adjusted from the controller at that time. The Cv value (reference value) for the indicated opening to the valve 2 is obtained from the relationship between the opening degree previously obtained at the time of combustion adjustment and the like and the ideal state of the Cv value (approximated expression in FIG. 2) It is possible to determine the opening deviation of the flow rate adjusting valve 2 depending on how far it is from the reference value. In this way, it is possible to monitor whether or not the desired amount of gas is being supplied to the burner and to prevent combustion failure in advance.

  The gas flow rate control device of the present invention is not limited to the configuration of the above embodiment, and can be appropriately changed. In particular, (a) the flow control valve 2 provided in the gas flow path to the burner, (b) the capacity coefficient at the actual opening of the flow control valve 2, and a reference value of the capacity coefficient set in advance And the other configuration can be changed as appropriate as long as it includes determination means for determining the opening deviation of the flow rate adjustment valve 2 by comparing the above.

  For example, in the above embodiment, the boiler is controlled at four positions of high combustion, medium combustion, low combustion and stop, but controlled at three positions of high combustion, low combustion and stop, or conversely at four positions or more It may be controlled. Alternatively, the present invention is similarly applicable to a boiler that continuously adjusts the opening degree of the flow control valve 2, such as proportionally increasing or decreasing the combustion amount based on the steam pressure.

  In any case, at the time of combustion adjustment and the like, the opening degree of at least two points or more and the Cv value at the opening degree are obtained beforehand, and based on that, the Cv corresponding to the indicated opening degree from the controller The reference value of the value may be determined and compared with the actual Cv value. In that case, the opening degree of the flow control valve 2 corresponding to each of the first combustion and the second combustion when controlled by at least the first combustion, the second combustion and the third combustion in the increasing order of the combustion phase (from the controller The volume coefficient at the commanded opening degree of is calculated by the approximate expression as a reference value, and the capacity coefficient at the opening degree of the flow control valve 2 (commanded opening degree from the controller) corresponding to the second combustion and the third combustion is The reference value may be obtained by an approximate expression.

  Further, although the Cv value is used as the capacity coefficient in the above embodiment, other than the Cv value (for example, the Kv value or the Av value) may be used. Furthermore, in the above embodiment, the approximation formula for obtaining the reference value of the capacity coefficient uses linear approximation, but polynomial approximation or the like may be used.

  Moreover, although the example applied to the steam boiler was shown in the said Example, it is applicable also to a hot-water boiler etc. FIG. Furthermore, it is applicable similarly to the gas channel to various apparatuses other than a boiler.

1 gas flow path 2 flow control valve 3 first shut-off valve 4 second shut-off valve 5 first pressure sensor 6 second pressure sensor 7 temperature sensor 8 flow sensor

Claims (4)

A flow control valve provided in the gas flow path to the burner,
Determining means for comparing the capacity coefficient at the actual opening of the flow control valve with a reference value of the capacity coefficient at the opening, which has been set in advance, to determine the deviation in the opening of the flow control valve A gas flow control device comprising: The reference value of the capacity coefficient at the opening degree of the flow rate adjustment valve can be obtained in advance by an approximate expression as a flow rate characteristic from two or more different opening degrees and the capacity coefficient at these opening degrees. The gas flow rate control device according to 1. Adjusting the opening degree based on the pressure on the primary side of the flow rate adjustment valve and the air flow rate to the burner;
The gas flow rate control device according to claim 2, wherein the reference value of the capacity coefficient is determined by the approximate expression for the adjusted opening degree. The burners are controlled by at least a first combustion, a second combustion and a third combustion in the order of increasing combustion stages,
The capacity coefficient at the opening of the flow control valve corresponding to each of the first combustion and the second combustion is determined by an approximate expression as a reference value, and the flow rate corresponding to each of the second combustion and the third combustion The gas flow rate control device according to claim 2 or 3, wherein the capacity coefficient at the opening degree of the adjustment valve is determined by an approximate expression as a reference value.

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