JPS6172919A - Air-fuel ratio controlling method - Google Patents

Abstract

PURPOSE:To always realize the most appropriate air-fuel ratio by a method wherein the degree of opening of the auxiliary damper which is the most appropriate air-fuel ratio in response to the load of a combustion device and the degree of opening of the auxiliary damper is determined by processing signals from the stored data. CONSTITUTION:A trial operation is performed and data are collected and these are inputted to RAM of an air-fuel ratio control device 27 from the console part 28. CPU processes these inputted data and gets a degree of opening of the auxiliary damper 18 providing the most appropriate air-fuel ratio control and a degree of opening of the auxiliary damper 18 for performing a control over an air-fuel ratio with a low concentration of O2 in the discharged gas under their calculation and then stores them in RAM. CPU transmits an electrical signal to the support motor 19 through I/O port and a degree of opening of the auxiliary damper 18 is realized and the most appropriate air-fuel ratio control is operated. In this way, once a trial operation is carried out with a tester 26 of concentration of O2 and the required data are collected, the tester 26 of a concentration of O2 is not required in the subsequent real combustion and thus it is possible to control the most appropriate air-fuel ratio in response to the variation of load.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to an air-fuel ratio control method for a combustion device such as a boiler, and in particular, the present invention relates to an air-fuel ratio control method for a combustion device such as a boiler. The present invention relates to an air-fuel ratio control method that achieves an appropriate air-fuel ratio without using an exhaust gas sensor or a complicated cam mechanism.

[Prior art and its problems]

Conventionally, the air-fuel ratio control of combustion equipment such as boilers has been based on the valve opening of a fuel control valve that is linked to a motor driven by a detected value of a sensor that responds to the load, and the air supply that is operated in synchronization with this. The adjustment was performed depending on the opening of the damper. This mechanical air-fuel ratio control requires complex correction of the movement of either the control valve or the damper opening in order to achieve the optimal air-fuel ratio in response to load fluctuations, so a complex cam mechanism is required. The disadvantage was that it required Moreover, since this movement is unique to the combustion device, it is necessary to provide the cam mechanism with an adjustment function, which also has the drawback of requiring extremely laborious adjustment.

[Summary of the invention]

The present invention has been made in view of the above circumstances, and includes an auxiliary damper in place of the cam mechanism of the conventional technology, and further includes memory for the opening degree of the auxiliary damper that provides the optimum air-fuel ratio according to the load of the combustion device. In actual operation, the opening of the auxiliary damper is determined by signal processing from this memorized data without using an exhaust gas sensor, making it possible to always achieve the optimum air-fuel ratio. . below,
The present invention will be explained in detail based on examples.

[Detailed explanation of examples]

In FIG. 5, the air-fuel ratio control device according to the present invention is applied.
For example, an overall configuration diagram of boiler combustion control is shown.

1 is a boiler, the inside of which is filled with water 2,
Steam 5 generated by the heat of the flame 4 burned in the combustion chamber 3 is supplied to a load (not shown) through a pipe 6. 7 is the combustion flue. The combustion of the burner 8 of the boiler 1 is started and stopped in a fail-safe manner using an igniter, a main valve, and a flame sensor (not shown) after a combustion safety control device (not shown) performs a pre-purge using a fan motor 9. Here, the fan motor 9 supplies air for combustion after ignition.

Reference numeral 10 denotes a pressure converter, which converts the vapor pressure of the steam 5 into, for example, a corresponding electrical resistance value by mechanical displacement or the like. Reference numeral 11 denotes a control motor, which is, for example, a drive device based on the principle that changes in the electrical resistance value of the pressure transducer 10 are operated by balancing a bridge circuit.
The rotating shaft will be driven in response to the vapor pressure detected by the sensor.

This control motor 11 has a manual setting section 12 that can be electrically separated from the pressure transducer 10 and driven manually, and also has a feedback resistor 13 that detects the rotation angle of the rotation shaft of the control motor 11.

The rotation of the rotation shaft of the control motor 11 determines the opening degree of the proportional valve 15 for fuel supply via the linkage 14, and also determines the opening degree of the main damper 17 for regulating the amount of fuel via the linkage 16. . In this way, air-fuel ratio control is realized by proportionally controlling the valve opening of the proportional valve 15 and the opening of the main damper 17 in synchronization with one control motor 11 that responds to the steam pressure of the boiler. However, as is often said, complete air-fuel ratio control cannot be achieved unless corrections are made in synchronization with variations in the boiler load.

Therefore, conventionally, either the linkage 14 or the linkage 16 has been provided with a complicated cam mechanism that can be adjusted to achieve this correction.

Reference numeral 18 denotes an auxiliary damper according to the present invention, the opening degree of which is determined by the drive of a servo motor 19, and corrects the amount of supplied air. This servo motor 19, like the control motor 11, is driven by a manual setting section 2 that can be driven manually.
0 and a feed bank resistor 21 for detecting the rotation angle of the rotation shaft of the servo motor 19.

22 is a fuel temperature regulator, and a fuel temperature sensor 23
The fuel heater 2
4. Reference numeral 25 denotes an air temperature sensor that detects the temperature of the air supplied to the burner 8 by the fan motor 9, and the detected value is sent to an air-fuel ratio control device 27, which will be described later. 26 is an ot concentration tester,
This is used when determining the opening degree of the auxiliary damper.

27 is an air-fuel ratio control device according to the present invention, and includes a console section 28+! for data setting. : It has a display section 29 with a %7-ta display. FIG. 6 shows the relationship between the hardware configuration of the air-fuel ratio control device 27 and the connected external devices such as the control motor 11, the engine motor 19, and the nitrogen temperature sensor 25. Air-fuel ratio control device 2
The signal processing unit of 7 is CPU30, ROM31, RAM32
A program for controlling the CPU 30 is written in the ROM 31, and the CPU 30 executes the flowchart of FIG. 1, which will be described later, in accordance with this program. The RAM 32 is a temporary storage memory and has a function of storing data in the middle of calculation and various setting values.

Next, the operation of the present invention will be explained in detail.

The invention consists of two stages. The first stage is data sampling and arithmetic processing for executing air-fuel ratio control, and is executed during test operation, and the second stage is during actual operation, in which air-fuel ratio control is executed based on this data. This is the process.

First, the first stage will be explained. At this stage, the operator switches the control motor 11 and servo motor 19 to manual mode, and uses the manual setting section 12 and manual setting section 20 to operate the valve opening degree of the proportional valve 15 and the opening degree of the auxiliary damper 18. Become. Further, at this stage, a 0° concentration tester 26 is placed in the flue 7 so as to be able to detect the oxygen concentration in the exhaust gas. In this state, the operator operates the combustion safety side leg device (not shown) and turns burner 8.
Boiler 1 is operated by burning. By manually operating the control motor 11, the valve opening degree of the proportional valve 15 can be adjusted to, for example, 0, 25, 50%, 7.
5%, 10 (1%, 1st shift).

However, the minimum air supply is ensured even when the valve opening is O. The value of the valve opening of the proportional valve 15, the control motor 11
Since the value of the feedback resistor 13 is determined by the angle of the rotation axis of It can be easily set by operating 12.

In the present invention, the air-fuel ratio based on the valve opening degree of the proportional valve 15 and the opening degree of the main damper 17 determined by the linkage 14 and the linkage 16 is configured to be sufficiently air rich. That is, the valve opening degree of the proportional valve 15 is set to 5, for example.
When set to a predetermined value of 0%, the air richness becomes sufficient when the auxiliary damper 18 is fully opened. Therefore, the operator drives the servo motor 19 using the manual setting section 20 while checking the detected value of the O1 concentration tester 26.
0 in exhaust gas! The auxiliary damper 1 is adjusted so that the concentration is at a value that provides conventionally known appropriate air-fuel ratio control, for example, 3%.
This determines the opening degree of No.8. Here, this opening degree is also determined by the value of the feedback resistor 21, and
9 will be displayed.

In this first stage test operation, which determines the opening degree of the auxiliary damper 18 that will provide an appropriate air-fuel ratio for boiler combustion in accordance with the valve opening degree of the proportional valve 15, at the same time, an air temperature sensor is The air temperature detected by 25 is also determined. The configuration is such that this value can also be displayed on the display section 29. An example of the data obtained in this way is shown in FIG. The horizontal axis indicates the opening degree of the proportional valve 15, for example, 0, 25, 50%,
75chi, 100%. The vertical axis is the opening degree of the auxiliary damper 18. For further explanation, 0chi → 1.25% → 2.50% → 3.75% → 4.10
0% → 5 is symbolized as i, and the opening degree of the auxiliary damper 18 at this time is represented by SMI (i), the air temperature at this time is represented by T (i), and the air ratio is represented by M 1 (i). do. This air ratio M 1 (i) is determined as follows, where the exhaust gas O1 concentration of the O2 concentration tester 26 is expressed as P(i)%. Here, 21 indicates oxygen in the air, P
(i) is approximately 3chi in this example.

Furthermore, in the present invention, it is necessary to compensate for the difference in air density caused by the difference in air temperature T(i) at the time of data collection (,5M1(i)
When collecting data, the opening degree S of the auxiliary damper 18 that gives a slightly smaller oxygen concentration in the exhaust gas, for example 2.
M 2 (i) is also determined at the same time. The air ratio at this time is expressed as M2(i). This air ratio M2
(i) is 0! The 01 concentration of the concentration tester 26 is q (i)
When expressed as , it is determined by . q(i) is approximately 2chi in this example. The ratio α(i) of the change in the air ratio to the change in the opening degree of the auxiliary damper in S M 1 (i) can be found by calculating the following equation from these data. In order to absorb the difference in air temperature T(i) in each experiment, it is necessary to correct it so that SMI(i) becomes S M 1*(i), which is the value at air temperature T(1). However, this correction requires T(1) and T
The ratio C(i) of the air density ρ in (i) is as follows, and the difference ΔQ in air amount to make the amount of oxygen contained in T(i) the same as the amount of oxygen contained in T(1) is: Therefore, the difference ΔSM(i) in the opening degree of the auxiliary damper 18 to obtain ΔQ can be found as α(i) considering that the air amount corresponds to the air ratio.

That is, SMI*(i) is calculated as Ml(i) Ml(i)-M2(i). Similarly, S M 2*(i), which is the value of 5M2(i) at T(1), is calculated as Ml(i) Ml(i)-M2(dish).

This is the first step of the present invention. In other words, a trial run was performed and 8M1 (1), ・5M2 (i), Ml (i),
The data of M2(i) and T(i> are collected and input into the RAM 32 of the air-fuel ratio control device 27 from the console section 28.The CPU 30 uses these input data to adjust the valve of the proportional valve 15. Opening degree SMI of the auxiliary damper 18 that provides appropriate air-fuel ratio control at opening degree i and air temperature T(1)
(i) and the opening degree S M 2*(i
) is calculated and stored in the RAM 32. These data will be used in the second stage to perform appropriate air-fuel proportional control in actual boiler combustion. At this first stage, SMI(i) alone (8
The reason why we also collected data on M2(i) is that, in general, when the opening degree of the main damper 17 is constant, the relationship between the opening degree of the auxiliary damper 18 and the O1 concentration in the exhaust gas is a non-linear relationship. Therefore, an attempt was made to absorb this nonlinearity by performing temperature correction using the slope of the tangent at SM(i). FIG. 2 summarizes the steps of the first step of the present invention in a flowchart. Although this embodiment shows an example in which all data is collected manually, it is also possible to automatically sample data using an automatic scanning method.

Next, the second stage of the present invention will be explained.

This second stage relates to a control method that uses the data obtained in the first stage to achieve an optimal air-fuel ratio in actual combustion. FIG. 1 shows a flowchart of this second stage executed by CPU 30.

In normal combustion, the control motor 11 is driven by the pressure transducer 10 that responds to the steam pressure of the steam 5 of the boiler, regardless of the manual setting section 12, and this changes the valve opening of the proportional valve 15 and the main damper 17. The opening degree is determined,
Combustion control is performed to achieve the desired vapor pressure.

At a predetermined control cycle, the CPU 30 reads the resistance value of the feedback resistor 13 via the I10 port, and detects the valve opening X of the proportional valve 15. And CPU3
0, a known judgment program is used to determine which zone of the discrete valve openings (i, i+1) that this valve opening degree X belongs to in the first stage.

The RAM 32 stores the experimental data S M obtained in the first step.
1”(i), 8M2*(i), Ml(i), M2(i
) are stored in a table. This data is schematically shown in FIG. Next, the CPU 30 uses this data to calculate 8M1*(x) and 8M2", which are the values at the valve opening degree X of the proportional valve 15, according to a known linear interpolation program.
(x), M 1 (x), and M 2 (x). Here, 8M1*(X) is the opening degree of the auxiliary damper 18 that executes optimal air-fuel ratio combustion when the so-called air temperature is T(1), and the air-fuel ratio control device 27 sends an electric signal corresponding to the height-bo motor 19. It will be decided by sending . Since this SMI*(x) is the value when the air temperature is T(1), it is converted to the value at the current temperature T(X) detected by the air temperature sensor 25 read through the I10 boat. There is a need.

This conversion is performed in a similar manner to the conversion performed in the first stage. That is, at the valve opening degree X, the auxiliary damper 1
8. The ratio α(X) of the change in air ratio to the change in opening degree is determined as follows. Since the temperature T(1) and the air density ρ at T (xl), SMI**(X) is the air temperature T
Assuming that it is the converted value of S M 1”fX) at
-1) -(SMI*(x).Here, C(i) in the first stage is multiplied by the reciprocal 1/C(i), while C(i) in the second stage is The difference in that (x) is not a reciprocal and is directly applied to C(x) is that the first step normalizes to the temperature T(1) of the molecule of C(i), while the second step normalizes it to the temperature T(1) of the molecule of C(i). This is due to the difference in that the step is converted to the temperature T(x) of the denominator of C(x).

That is, the CPU 30 is 8M1*(x), S M 2
*(x) After calculating υ of SM 1 (x) and M2 (x), the detected value T (x) of the air temperature sensor 25 is calculated.
After reading C(x) through the I10 port and calculating C(x), use these data to calculate 8M1 according to the above formula.
** Find (x). Since this S Ni 1''(x) is the opening degree of the auxiliary damper 18 that executes the optimum air-fuel ratio combustion at the valve opening degree X of the proportional valve 15 and the air temperature T(x), the CPU 30 By sending an electrical signal corresponding to this S M 1** (x) to the servo motor 19 via the port, the opening degree of the auxiliary damper 18 is increased to 8 M 1
**(x) is realized, and optimal air-fuel ratio control is executed.

In other words, the present invention is advantageous in that, once a test run is performed using the Ox concentration tester 26 and the necessary data is collected, the O1 concentration tester 26 is not required in subsequent actual combustion, and the O1 concentration tester 26 is not required. In response, optimal air-fuel ratio control can be executed.

In the embodiment shown in FIG. 5, the fuel temperature regulator 22 is
The fuel heater 24 is controlled so that the fuel temperature detected by the fuel temperature sensor 23 becomes a predetermined value. For example, if fuel with high viscosity such as heavy oil is used, even if the opening degree of the proportional valve 15 is the same, the amount of fuel supplied to the burner 8 will differ and optimal air-fuel ratio control may not be achieved. Because there is. From now on, by keeping the fuel temperature constant, it will be possible to keep the viscosity constant and further improve the accuracy on the air-fuel ratio side.

In explaining this example, in the first step,
For a predetermined valve opening degree of the proportional valve 15, there is a concentration of 02 in the exhaust gas that provides optimal air-fuel ratio control, and a concentration of 00. An example has been shown in which optimal air-fuel ratio control is achieved by determining the opening degree of the auxiliary damper 18 that provides concentration.
The present invention is not limited to this. For example, in the first stage, O7 in the exhaust gas that has the optimum air-fuel ratio
The optimum air-fuel ratio control may be achieved in a similar manner by determining the opening degree of the auxiliary damper 18 that gives a slightly larger O1 concentration in the exhaust gas. The Ot concentration in the exhaust gas is sandwiched between the Ot concentration in the exhaust gas, which is a little higher than that, and the O2 concentration in the exhaust gas, which is a little smaller than the Ot concentration in the exhaust gas. The opening degree of the auxiliary damper 18 that provides the concentration may be determined and the optimum air-fuel ratio control may be achieved in a similar manner.

In the embodiment shown in FIG. 5, the auxiliary damper 18
Although an example has been shown in which the auxiliary damper 18 is arranged in series in the same air supply pipe as the main damper 17, the present invention is not limited to this, and the auxiliary damper 18 may be arranged by providing a bypass air supply pipe. It's okay.

Alternatively, as shown in FIG. 7, the main damper 17 can also have the function of an auxiliary damper. In this case, a servo motor 41 is provided as means for driving the main damper 17. This servo motor 41 is arranged so that its rotation axis 42 is parallel to the rotation center of the main damper 17,
Furthermore, it is rotatably supported by a suitable support mechanism (not shown) about a common axis with this rotating shaft 42. The arm 43 supported by the rotating shaft 42 is connected via a suitable link mechanism 44 so that the rotation angle about the centroid of the rotating shaft 42 is reflected in the rotation angle of the main damper 17. Therefore, the rotation angle of the main damper 17 is regulated by both the rotation angle of the servo motor 41 itself and the rotation angle of the arm 43 with respect to the length-port motor 41.

The mechanism for rotating the motor 41 itself consists of a lever 46 that rotates around a shaft 45 in accordance with the output of the linkage 16, and a rotating body 4 that rotates the lever 46.
With a link mechanism 48 that reaches @7.

It consists of a transmission mechanism 49 that transmits the rotation of the rotating body 47 to the servo motor 41.

In such a configuration, the control amount applied via the linkage 16 is transmitted to the main damper 17 as rotation of the servo motor 41 itself, and the control amount from the air-fuel ratio control device 27 shown in FIG. This is transmitted to the main damper 17 as a rotation angle of 42.

[Effects of the present invention]

According to the present invention, air-fuel ratio control can be realized without using a 0° sensor during normal combustion operation. Conventional air-fuel ratio control methods using O,sensors such as zirconia, etc. Since the sensor is used in exhaust gas, it is impossible to prevent errors due to excessive dirt during long-term use, making it impractical and impractical. In contrast, the present invention provides O! Senna is necessary for collecting data during a test run, but is not needed during actual operation, so it is extremely practical.
It is also practical as it does not require expensive sensors.

In addition, in other conventional technologies that control the air-fuel ratio using a cam mechanism or the like without using an O, Senna, the movement of the cam is complicated, resulting in a complicated cam structure and extremely difficult adjustment. Ta. On the other hand, the present invention does not require a complicated cam mechanism and handles the problem through signal processing, so it does not require any adjustment by the operator, and furthermore, it is possible to control the air temperature density, which could not be achieved with conventional mechanical air-fuel ratio control. Since errors due to changes are corrected, the accuracy of air-fuel ratio control can be made extremely high.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a combustion device showing one embodiment of the air-fuel ratio control method of the present invention, FIG. 2 is a block diagram of the air-fuel ratio control device of the combustion device shown in FIG. 1, and FIGS. The figure is a flowchart of the process executed by the combustion device shown in Figure 1,
5 and 6 are diagrams showing the combustion characteristics of the combustion device shown in FIG. 1, and FIG. 7 is a schematic side view showing a modification of the damper control mechanism. 1...Boiler, 5...Steam, 8...Burner, 10
... Pressure transducer, 13.21 ... Angle detector, 15
... Proportional valve, 17 ... Main damper, 18 ... Auxiliary damper, 25 ... Temperature sensor, 26 ... O1a degree tester, 27 ... Air-fuel ratio side (foundation) device, 30 ...・CPU
, 31...ROM, 32...RAM 0

Claims (2)

[Claims] (1) The fuel supplied to the burner through the proportional valve and the air pumped through the main damper are mixed and combusted in the combustion chamber of the combustion device, and the steam pressure generated by the heat from the combustion chamber Accordingly, in the air-fuel ratio control method of controlling the proportional valve and the main damper to obtain an optimum air-fuel ratio, the valve opening of the proportional valve and the above-mentioned Data indicating the opening degree of the auxiliary damper, which is installed to control the amount of air pumped into the combustion chamber together with the main damper, is read, and various combustion parameters including the air-fuel ratio are calculated using this data, and the calculated results are stored in memory. A control amount is calculated to obtain the optimum air-fuel ratio based on the data stored in the memory and the valve opening of the proportional valve read every predetermined period. and a second process of controlling the opening degree of the auxiliary damper according to the amount of the auxiliary damper. (2) The fuel supplied to the burner via the proportional valve and the air pumped via the main damper are mixed and combusted in the combustion chamber of the combustion device, and the steam pressure generated by the heat from the combustion chamber Accordingly, in the air-fuel ratio control method for controlling the proportional valve and the main damper to obtain an optimum air-fuel ratio, the valve opening of the proportional valve and the above-mentioned Data indicating the opening degree of the auxiliary damper, which is installed to control the amount of air pumped into the combustion chamber together with the main damper, and the temperature of the air pumped into the combustion chamber is read, and this data is used to control the combustion including the air-fuel ratio. The first part calculates various parameters and stores the calculated results in memory.
A control amount is calculated to obtain the optimum air-fuel ratio based on the data stored in the memory stored in the first process, the valve opening of the proportional valve read every predetermined period, and the temperature of the air. and a second process of controlling the opening degree of the auxiliary damper according to the amount of the auxiliary damper.