JP3534865B2 - Air-fuel ratio control device for combustor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a burner and a combustion fan for supplying and exhausting air, and makes it possible to adjust the amount of air and gas supplied to the burner so that the air-fuel ratio becomes a predetermined value. The present invention relates to an air-fuel ratio control device for a combustor.

[0002]

2. Description of the Related Art As a conventional air-fuel ratio control device for a combustor, a proportional valve provided in a gas pipe is current value controlled, and the current value is detected and the air amount to a burner is detected by an air flow sensor. It is common to detect and adjust the gas amount and the air amount based on the current value and the output value of the air amount sensor to control the air-fuel ratio which is the ratio of the gas amount and the air amount.

[0003]

However, in such a conventional air-fuel ratio control device for a combustor, since there is no proportional relationship between the current value of the proportional valve and the gas amount, linearity cannot be obtained. If the amount of gas is adjusted based on the current value, the amount of gas will be insufficient with respect to the amount of air, or on the contrary, it will be excessive, and the ideal air-fuel ratio cannot be obtained, resulting in non-combustion. There was a point. Also, as a method to solve this,
Japanese Unexamined Patent Publication No. 61-72920 discloses that the amount of gas and the amount of air are controlled by operating their respective control valves based on the output values of the gas amount sensor and the air amount sensor. Since the gas amount sensor and the air amount sensor are arranged on the upstream side of the control valve, and each sensor cannot accurately grasp the situation of the gas amount and the air amount immediately before being used for combustion, the ideal air gap The fuel ratio could not be obtained. The present invention has been made in view of such conventional problems, and a combustor capable of accurately adjusting the amount of gas supplied to the burner to obtain an ideal air-fuel ratio. It is an object of the present invention to provide an air-fuel ratio control device of

[0004]

The gist of the present invention for achieving the above object is to provide a burner (13) and a combustion fan (1) for supplying and exhausting air.
2) and an air-fuel ratio control device for a combustor, in which the amount of air and the amount of gas supplied to the burner (13) are adjustable and the air-fuel ratio becomes a predetermined value,
A gas amount sensor (28) is provided during rectification of the gas flow passage (26) for supplying the gas to the burner (13) in the downstream of the valve (24, 25) for controlling the gas flow. An air-fuel ratio control device for a combustor, which adjusts a gas amount based on an output value of a sensor (28).

A burner (12) for supplying and exhausting two burners (13) is provided, and the amount of air and the amount of gas supplied to the burner (13) can be adjusted respectively, and the air-fuel ratio becomes a predetermined value. In the air-fuel ratio control device for a combustor, the gas amount sensor (28) is provided during the rectification of the nozzle holder (23) for supplying gas to the burner, and the output value of the gas amount sensor (28) is set. An air-fuel ratio control device for a combustor that adjusts the amount of gas based on the above.

A burner (3) and a combustion fan for supplying and exhausting air are provided, and the amount of air and the amount of gas supplied to the burner (13) can be adjusted so that the air-fuel ratio becomes a predetermined value. In the air-fuel ratio control device for the combustor, the bypass passage (17) for air is formed along the air supply flow path for supplying air to the burner (13),
An air amount sensor (18) provided in the air bypass passage (17) and a nozzle holder (23) at the tip of a gas pipe (26) for supplying gas to the burner (13).
The gas nozzle (22) is connected through the gas nozzle (22), and the gas amount sensor (28) provided in the nozzle holder (23) and the ideal air-fuel ratio, which is the ideal ratio between the air amount and the gas amount, are recorded. When the storage unit (31) and the output value of the air amount sensor (18) and the output value of the gas amount sensor (28) are read, one of the both output values is used as a reference, and the other An arithmetic unit (32) that compares one of the air amount and the gas amount at the ideal air-fuel ratio corresponding to the output value with the other amount and calculates the difference between the two.
When the difference signal between the two is output from the calculation unit (32), a drive circuit (an electric value based on the difference signal is output to the supply amount adjustment unit (27, 37) for one of the air amount and the gas amount. 33, 34) and an air-fuel ratio control device for a combustor.

[0007]

Since the gas amount sensor (28) is provided during the rectification of the gas supply passage (26) for supplying the gas to the burner (13), the output value of the gas amount sensor (28) and the gas amount are A proportional relationship is established between them, and the gas amount can be accurately adjusted based on the output value of the gas amount sensor (28), whereby an ideal air-fuel ratio can be obtained.

A gas bypass passage (2) is provided along a gas supply passage (26) for supplying gas to the burner (13).
9) is formed, the gas amount sensor (28) provided in the bypass passage (29) for the gas, and the storage unit (on which the ideal air-fuel ratio, which is the ideal ratio between the air amount and the gas amount, is recorded. Three
1), and when the output value of the air amount sensor (18) and the output value of the gas amount sensor (28) are read, one of the both output values is used as a reference and the other output value is set as the reference. An arithmetic unit (32) for comparing one of the air amount or the gas amount at the corresponding ideal air-fuel ratio with the other amount, and calculating the difference between the two, and the arithmetic unit (32).
And a drive circuit (33, 34) for outputting an electric value based on the difference signal to the supply amount adjusting unit (27, 37) for one of the air amount and the gas amount when the difference signal between the both is output. As for the equipped one, the output value of the air amount sensor (18) provided in the air bypass passage (17) and the gas amount sensor (28) provided in the gas bypass passage (29).
The output value of is read by the calculation unit (32).

When the output value of the air amount sensor (18) and the output value of the gas amount sensor (28) are read, the arithmetic unit (32) uses one of the output values as a reference and outputs the other output. The value is compared with one of the air amount and the gas amount in the ideal air-fuel ratio corresponding to the other output value, and the difference between the two is calculated.

The drive circuit (33, 34) is connected to the arithmetic unit (3
When the difference signal between the two is output from 2), the electric value based on the difference signal is output to the supply amount adjusting unit (27, 37) for one of the air amount and the gas amount. Air amount sensor (18)
A proportional relationship is established between the output value and the air amount, and similarly, a proportional relationship is established between the gas amount sensor (28) and the gas amount, which is accurately grasped by the air amount sensor (18). Based on the gas amount also accurately grasped by the air amount and gas amount sensor (28), the supply amount adjusting unit (27,
37) is controlled, the air-fuel ratio can be adjusted to a predetermined value.

An air bypass passage (17) is formed along an air supply passage for supplying air to the burner (13), and an air amount sensor (provided in the air bypass passage (17) is provided. 18) and a gas nozzle (22) is connected to the tip of a gas pipe (26) for supplying gas to the burner (13) via a nozzle holder (23), and is provided in the nozzle holder (23). Gas sensor (2
8) and 8), the air amount and the gas amount can be supplied to the burner (13) under precise numerical values, and the air-fuel ratio can be adjusted to a predetermined numerical value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Each drawing shows an embodiment of the present invention. As shown in FIG. 1, a burner 13 is installed on the lower side of the combustion chamber 11, and a combustion fan 12 for supplying and exhausting air is provided below the burner 13. The combustion fan 12 is provided with a rotation detection sensor (not shown). A hot water supply heat exchanger 14 is provided above the combustion chamber 11, and the hot water supply heat exchanger 1
A water supply pipe (not shown) is connected to the inlet side of 4, and a hot water supply pipe (not shown) is also connected to the outlet side of the hot water heat exchanger.

A gas pipe 26 is connected to the burner 13 via a gas nozzle 22, a nozzle holder 23, a proportional valve 24 and a solenoid valve 25. The tip of the gas nozzle 22 is directed toward the gas inlet of the burner 13, and a gap is formed between the gas inlet of the burner 13 and the tip of the gas nozzle 22 so as to take in combustion air. Proportional valve 24
The valve opening can be adjusted by the actuator 27, which is a supply amount adjusting unit. A lower side of the burner 13 and an upper side of the burner 13 communicate with each other through a bypass passage 17. The air amount sensor 1 is provided in the middle of the bypass passage 17.
8 are provided. As the air amount sensor 18, a hot-wire type wind velocity sensor or a diaphragm type differential pressure sensor is used. The hot-wire anemometer measures the wind speed by the amount of heat taken from a wire such as a platinum wire, which is output as a change in the flow speed of the current, and some of them are provided on a silicon substrate. The diaphragm type differential pressure sensor outputs a difference between the pressure on the combustion fan 12 side of the burner 13 and the pressure on the combustion chamber 11 side as a change in current. Generally, the relationship between the air amount and the pressure difference is Qa when the air amount Qa, the pressure difference Δp and the coefficient Fa are Qa.
= Fa√ (Δp)

Inside the nozzle holder 23, a gas amount sensor 28 is provided. The same type of sensor is used for the gas amount sensor 28 and the air amount sensor 18. For example, if the air amount sensor 18 is a hot-wire wind speed sensor, the gas amount sensor 28 is also a hot-wire wind speed sensor. If the air amount sensor 18 is a diaphragm type differential pressure sensor, the gas amount sensor 28 is also a diaphragm type differential pressure sensor. Similar to the calculation formula of the air amount, generally, the relationship between the gas amount and the pressure difference can be expressed by Qg = Fg · √ (Δp), where the gas amount Qg, the pressure difference Δp and the coefficient Fg. . The gas amount sensor 28 is not limited to this, and may be provided in the middle of a bypass passage 29 formed along the gas pipe 26 as shown in FIG. 2, for example.

FIG. 3 shows a block diagram of the present control device. The control device includes a control unit 30 which is an MPU. The control unit 30 includes a power supply circuit (not shown) and
A clock (not shown) for connecting the output signal of the air amount sensor 18 is connected. The output signal of the air amount sensor 18 is input as a digital value to a memory 31 described later via a sample hold circuit, an AD conversion circuit, and a control unit 30 which are not shown.
Similarly, the output signal of the gas amount sensor 28 is output from a sample hold circuit, an A / D conversion circuit, and a control unit 3 which are not shown.
It is inputted as a digital value to the memory 31 described later via 0.

The control device includes a RAM as an internal storage unit.
Alternatively, a storage unit memory 31 including a rewritable EEPROM is provided. In the memory 31,
The control program, the correlation coefficient between the air amount and the gas amount, the correlation coefficient between the gas amount and the output signal for proportional valve control, and the like are recorded.

The arithmetic unit 32 reads the output value of the air amount sensor 18 recorded in the memory 31 according to the control signal of the control unit 30, and calculates the gas amount from the read output value of the air amount sensor 18. A numerical value is calculated, and the calculated numerical value of the gas amount is compared with the output value of the gas amount fetched from the memory 31 to calculate the difference between the two. The difference signal between the two is output to a power amplifier 33, which is a drive circuit. The power amplifier 33 converts the difference signal between the two into an electric value such as a current value and outputs the actuator 27. The actuator 27 outputs the electric value. Based on this, the proportional valve 24 is driven to adjust the valve opening degree. Proportional valve 24
After the adjustment of the valve opening of the memory 3, the memory 3 is operated by the same method as described above based on the gas amount detected by the gas amount sensor 28.
The output value of the gas amount taken in from 1 is compared to calculate the difference between the two. If there is no difference between the two, the valve opening of the proportional valve 24 is not adjusted, and if there is a difference between the two, the same. Thus, the valve opening of the proportional valve 24 is adjusted. That is, the supply amount of the gas amount is adjusted based on the detection value of the gas amount sensor 28, and is not adjusted based on the electric value for driving the proportional valve 24.

The control unit 30 also outputs a fan control signal to the power amplifier 34, which is a drive circuit, based on the output value of the air amount sensor 18, and the power amplifier 34 supplies a current value corresponding to the fan control signal. The actuator 37, which is a quantity adjusting unit, sends the actuator 37.
Supplies the required current to the combustion fan 12 based on the current value.

Next, the operation will be described. The control unit 30 obtains the timing of receiving the output value of the air amount sensor 18 from an oscillation circuit (not shown). By the control signal of the control unit 30,
The output value of the air amount sensor 18 is output to the control unit 30 as a digital value via a sample hold circuit and an AD conversion circuit, which are not shown. The output value of the air amount sensor 18 is written in the memory 31.

Similarly, the output value of the gas amount sensor 28 is output to the control unit 30 as a digital value, and the output value of the gas amount sensor 28 is written in the memory 31. The following method is used to adjust the gas amount based on the air amount to obtain a predetermined air-fuel ratio.

That is, by the control signal of the control unit 30,
The output value of the air amount sensor 18 written in the memory 31 is read by the calculation unit 32, and the calculation unit 32 reads the correlation coefficient between the air amount and the gas amount recorded in the memory 31 and the read value. A numerical value of the gas amount is calculated from the output value of the air amount sensor 18. Further, the calculation unit 32 compares the calculated numerical value of the gas amount with the output value of the gas amount read from the memory 31, and calculates the difference between the two. The difference signal between the two is controlled by the control signal from the control unit 30.
3, the power amplifier 33 converts the difference signal between the two into an electric value such as a current value and outputs the electric value to the actuator 27, and the actuator 27 outputs the proportional valve 2 based on the electric value.
4 is driven to adjust the valve opening.

The above method is continued until the air-fuel ratio of the air amount and the gas amount reaches a predetermined value. On the other hand, in order to adjust the air amount based on the gas amount and obtain a predetermined air-fuel ratio, the following method is used.

That is, by the control signal of the control unit 30,
The output value of the gas amount sensor 28 written in the memory 31 is read by the calculation unit 32, and the calculation unit 32 reads the correlation coefficient between the air amount and the gas amount recorded in the memory 31 and the read value. The numerical value of the air amount is calculated from the output value of the gas amount sensor 28. Further, the calculation unit 32 compares the calculated numerical value of the air amount with the output value of the air amount read from the memory 31, and calculates the difference between the two. The difference signal between the two is controlled by the control signal from the control unit 30.
4, the power amplifier 34 converts the difference signal between the two into an electric value such as a current value and outputs the electric value to the actuator 37. Based on the electric value, the actuator 37 drives, for example, a DC motor of the combustion fan 12. Then, adjust the rotation speed.

This method is also continued until the air-fuel ratio between the air amount and the gas amount reaches a predetermined value. Although the method of controlling the gas amount based on the air amount has been described in the above embodiment, a method of controlling the air amount based on the gas amount may be used.

That is, when the user starts to use the hot water, the flow rate [X (l / min)] of the hot water is measured by the flow sensor in the instrument, and the supply water temperature (t1 ° C.) is measured by the thermistor. Required heat amount [(t2-t1) .60X / 0.8 (kcal / h)] from desired hot water temperature (t2 ° C)
To calculate. Calculate the required gas amount from the required heat amount,
The opening of the proportional valve is controlled so that the measured value of the gas amount sensor becomes the gas amount, and then the air amount is adjusted based on the gas amount. On the other hand, when adjusting the amount of gas based on the amount of air, the amount of gas can change almost instantaneously between its minimum and maximum values when the amount of gas changes significantly, such as during ignition or when capacity changes. However, the air volume changes relatively slowly between the minimum rotation speed and the maximum rotation speed of the fan,
It cannot be changed instantaneously, there is a difference in the speed of adjusting the amount of gas and the amount of air, and the air-fuel ratio collapses as it is.
In order to prevent the air-fuel ratio from collapsing, there is one that adjusts the gas amount by corresponding to the change in the air amount whose adjustment speed is slow, that is, calculating the numerical value of the gas amount according to the output value of the air amount sensor. .

Further, in the above-mentioned embodiment, although it is not shown that the respective temperatures of the air and gas to be supplied are taken in as correction data when adjusting the air amount and the like, the air amount is measured by the mass sensor (hot wire anemometer). When controlling using a measured value, the measured amount is output as a numerical value converted to 0 ° C., for example. With respect to this numerical value, it is also necessary to calculate the accurate air-fuel ratio by using the numerical value obtained by converting the gas amount into 0 ° C. instead of the flow velocity. Therefore, it is necessary to make a correction based on the gas temperature, but the temperature of the gas discharged from the nozzle is affected by the heat (radiation heat transfer) from the combustion chamber depending on the combustion amount of the burner. Therefore, by disposing a sensor in the nozzle holder, data close to the temperature of the gas discharged from the nozzle can be given, and as a result, a value very close to the mass flow rate can be obtained. When the diaphragm type differential pressure sensor is used, the mass flow rate is not obtained, and therefore it is necessary to correct the temperature by using a thermistor or the like. In addition, pressure correction may be performed to accurately perform temperature correction.

Further, a concrete description will be given. At the point A, the temperature is 0 ° C., and the gas flow rate is 1 liter / unit time. Since the temperature is 82 ° C. at point B in the middle of the gas flow path, the gas flow rate is 1.3 liters / unit time gas flow rate, and the volume increases. As a result, at point C at the tip of the nozzle, a gas of 1.3 liters / unit time flows at a temperature of 82 ° C.

Under these circumstances, the heat transfer temperature at point B is 8
If the temperature drops from 2 ° C to 41 ° C, 1.
Since gas of 3 liters / unit time is flowing out, at point B, 1.3 liters of gas moves at a temperature of 41 ° C., and at point A, 1.15 liters / at a temperature of 0 ° C. The gas per unit time moves, and the difference in mass flow rate becomes 15%. Actually, the point C and the point B are very close to each other, and the specific gravity of the gas changes due to the volume change due to heat transfer, and the amount of gas from the nozzle tip changes. However, when the heat transfer amount changes, C
It is clear that there is a difference in the measured values between the point A and the point A, and in order to perform accurate air-fuel ratio control, it is not point A but C
It is necessary to correct the temperature based on the measurement results at the points.
In the above-mentioned embodiment, since the gas amount sensor is provided during the rectification of the nozzle holder, the mass flow rate can be accurately measured. On the other hand, when a gas amount sensor is simply provided in the gas flow path and the place where it is provided is turbulent, the flow rate cannot be accurately measured, and especially in low calorie gas (6B4C etc.) Since the flow rate is large relative to the quantity, the measured value will vary greatly depending on the measurement location. Further, by providing a bypass flow path to form a rectifying path in which turbulent flow is unlikely to occur, and by providing a gas amount sensor downstream of the proportional valve in the rectifying path, the mass flow rate can also be measured accurately. .

[0029]

According to the air-fuel ratio control device for a combustor according to the present invention, the gas amount sensor is provided during the rectification of the gas supply passage for supplying the gas to the burner. From the proportional relationship established between the amount of gas supplied to the burner and the amount of gas supplied to the burner, it becomes possible to supply a predetermined amount of gas to the burner based on the output value of the gas amount sensor. It is possible to obtain an ideal air-fuel ratio necessary for controlling NOX and the like.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a combustor showing an embodiment of the present invention.

FIG. 2 is a partial conceptual diagram of a combustor showing a modified example of the present invention.

FIG. 3 is a block diagram of an air-fuel ratio control device for a combustor showing an embodiment of the present invention.

[Explanation of symbols]

10 ... Combustor 11 ... Combustion chamber 12 ... Combustion fan 13 ... Burner 14 ... Hot water heat exchanger 17 ... Bypass passage for air 18 ... Air amount sensor 22 ... Gas nozzle 23 ... Nozzle holder 24 ... Proportional valve 26 ... Gas piping 27 ... Actuator (supply amount adjusting unit) 28 ... Gas amount sensor 29 ... Bypass passage for gas 30 ... Control unit 31 ... Memory (storage unit) 32 ... Calculation unit 33, 34 ... Power amplifier (driving circuit) 37 ... Actuator (supply amount adjusting unit)

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F23N 1/02 F23N 1/02 101 F23N 5/20

Claims (3)

(57) [Claims] 1. An air-fuel ratio of a combustor, comprising a burner and a combustion fan for supplying and exhausting air, and adjusting the amount of air and gas supplied to the burner so that the air-fuel ratio becomes a predetermined value. In the fuel ratio control device, a gas amount sensor is provided during the rectification of the wake of the valve that controls the gas flow in the gas supply passage for supplying gas to the burner, and the gas amount is adjusted based on the output value of the gas amount sensor. An air-fuel ratio controller for a combustor that is adjusted. 2. An air-fuel ratio of a combustor, comprising a burner and a combustion fan for supplying and exhausting air, and adjusting the amount of air and gas supplied to the burner so that the air-fuel ratio becomes a predetermined value. In a fuel ratio control device, a gas amount sensor is provided during rectification of a nozzle holder for supplying gas to a burner, and the gas amount is adjusted based on the output value of the gas amount sensor. 3. An air of a combustor comprising a burner and a combustion fan for supplying and exhausting air, and adjusting the amount of air and gas supplied to the burner so that the air-fuel ratio becomes a predetermined value. In a fuel ratio control device, an air bypass passage is formed along an air supply passage for supplying air to the burner, and an air amount sensor provided in the air bypass passage and gas are supplied to the burner. A gas nozzle is connected to the tip of the gas pipe via a nozzle holder for recording the gas amount sensor installed in the nozzle holder and the ideal air-fuel ratio, which is the ideal ratio of air amount to gas amount. When the output value of the air amount sensor and the output value of the gas amount sensor are read out, one of the both output values is used as a reference, and the ideal value corresponding to the other output value. At air-fuel ratio When one of the air amount or the gas amount is compared with the other amount and the difference between the two is calculated, and the difference signal between the both is output from the calculation unit, the difference signal is output. And a drive circuit that outputs an electric value based on the above to a supply amount adjusting unit for one of an air amount and a gas amount.