JP4256928B2 - Combustion air supply control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion air supply amount adjusting device.
[0002]
[Prior art]
The combustion apparatus of a boiler sends combustion air by a blower. When adjusting the combustion amount, such as high combustion, low combustion, or stop, the combustion amount is adjusted by increasing or decreasing the combustion air supply amount and the fuel supply amount. As a means for adjusting the combustion air supply amount, a rotational speed control device such as an inverter device is provided in the blower, and the rotational speed of the blower is increased or decreased.
[0003]
When air volume adjustment is performed using the rotation speed control device, it is possible to reduce power consumption and noise by reducing the rotation speed of the blower. However, if ignition is performed with the rotational speed of the blower lowered, an ignition shock generated in the combustion section will spread to the blower. In a state where the discharge static pressure is secured by increasing the flow area, the flow passage area of the air passage is reduced by the damper device, and the air volume is adjusted by the damper device to prevent the ignition shock from spreading. Thereafter, the opening of the damper is fully opened, and the combustion air supply amount is adjusted by controlling the rotational speed.
[0004]
FIG. 3 shows the state of adjustment of the combustion state and the combustion air supply amount when the combustion amount is controlled at three positions of high combustion, low combustion, and stop. A fully open position, an ignition position, and a fully closed position are determined as the damper opening, and the blower frequency is set to a high combustion frequency and a low combustion frequency. When starting combustion, it is necessary to perform a pre-purge to ventilate the furnace before the start of combustion. First, a pre-purge process is performed. Since the pre-purge is for ventilating the inside of the furnace by sending a constant amount of air into the furnace, the implementation time can be shortened as the air volume is increased. Therefore, the supply air volume is increased by setting the damper opening to the fully open position and setting the blower frequency for high combustion. When ignition is performed after completion of pre-purge, it is necessary to close the damper opening to the ignition position in order to prevent the ignition shock from spreading to the blower during the ignition process. After that, the damper opening is fixed at the fully open position, and the frequency of the blower is switched between the high combustion frequency and the low combustion frequency in accordance with the change in the combustion amount so as to obtain an air blowing amount that matches the combustion amount.
[0005]
By controlling the rotational speed of the blower, it is possible to supply the amount of combustion air that matches the amount of combustion, but in order to perform low combustion, if the rotational speed of the blower is reduced to reduce the air volume, Combustion sometimes became unstable, such as vibration combustion. As a result of research, it was found that reducing the amount of air generated by reducing the rotational speed of the blower reduced the static pressure of the combustion air, which made the combustion unstable.
[0006]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to prevent instability of combustion when the air volume is reduced in a combustion apparatus that adjusts the supply amount of combustion air supplied by increasing or decreasing the rotational speed of the blower. .
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided a blower for adjusting the amount of combustion air to be supplied by increasing or decreasing the rotation speed of the blower, and a fuel supply amount adjusting means for increasing or decreasing the amount of fuel to be supplied. By adjusting the supply amount, the combustion amount can be adjusted at three positions: high combustion, low combustion, and stop . In the combustion device, the flow passage area is adjusted to the air passage that passes the combustion air generated by the blower. The flow rate adjusting device is set for high combustion and low combustion, and the flow rate adjustment device is set for high combustion, low combustion, and ignition, When the combustion device is ignited, the rotation speed of the blower is for high combustion, and the flow area of the flow control device is for ignition. When the combustion is low, the rotation speed of the blower is for low combustion, and the flow control device is for low combustion. For high combustion, set the rotation speed of the blower for high combustion and the flow control device. The road area is for high combustion, the rotation speed of the blower is low combustion <ignition time and low combustion <high combustion time, and the flow control device flow path area is ignition <low combustion <high combustion time and said that you are. The invention according to claim 2 is characterized in that the flow path adjusting device is a damper device for preventing ignition shock spreading provided in the middle of the air passage.
[0008]
According to the invention of claim 1, when the rotational speed of the blower is changed and the flow passage area of the ventilation path is reduced, the amount of combustion air passing through the ventilation path is small, but the flow passage area of the ventilation path is reduced The static pressure of the combustion air can be kept high by adding a pressure loss when passing through. Therefore, even if it is a case where the rotation speed of a blower is reduced and an air volume is reduced, combustion can be performed without becoming unstable. According to the invention of claim 2, the use of the damper necessary for preventing the spreading of the ignition shock makes the combustion unstable without newly providing a device for limiting the flow passage area of the ventilation path. Combustion can be performed without any problems. According to the invention of claim 3, since the flow passage area is further reduced compared with the case where the combustion amount is reduced at the time of ignition, the air volume is reduced while the rotation speed of the blower remains high, and the spread of the ignition impact is prevented. be able to.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a time chart showing the state of combustion and air volume adjustment in one embodiment of the present invention, and FIG. 2 is a configuration diagram of one embodiment of the present invention. The boiler 1 is provided with a burner 2 at the top, and performs combustion with fuel sent through the fuel supply pipe 3 and combustion air sent through the blower passage 11 connected to the blower 6. The combustion amount is controlled at three positions of high combustion, low combustion, and stop, and the combustion amount is changed by adjusting the fuel supply amount and the combustion air supply amount. The amount of fuel supplied is controlled by a first electromagnetic valve 4 and a second electromagnetic valve 5 provided in the middle of the fuel supply pipe 3. Combustion stops when both the first solenoid valve 4 and the second solenoid valve 5 are closed, low combustion when only the first solenoid valve 4 is opened, and both the first solenoid valve 4 and the second solenoid valve 5 are opened. High combustion.
[0010]
An inverter device 8 that sets a high combustion frequency and a low combustion frequency is connected to the blower 6. The rotational speed of the blower 6 is changed according to the operating frequency output from the inverter device 8 that is the rotational speed control device. A damper device 9 is provided in the air passage 11 connecting the blower 6 and the burner 2, and the opening degree of the damper device 9 is set to a high combustion position, a low combustion position, an ignition position, and a fully closed position, respectively. The boiler is operated by the control device 10, and the control device 10 sends commands to the burner 2, the first electromagnetic valve 4, the second electromagnetic valve 5, the inverter device 8, and the damper device 9.
[0011]
When the combustion is stopped, the damper opening is set to the fully closed position, the blower is stopped, and the supply of combustion air to the burner 2 is stopped. When starting combustion, a pre-purge process is first performed. In the pre-purge, the damper opening is set to a high combustion position, and the blower frequency is set to a high combustion frequency to increase the supply air volume. When the pre-purge is performed for a predetermined time, the pre-purge is finished and the ignition process is started. At the time of ignition, the blower frequency remains at the high combustion frequency, and the damper opening is set to an ignition position that is smaller than the low combustion position in order to prevent the ignition shock from spreading to the blower. When ignition ends, the damper opening is set to the low combustion position and the blower frequency is set to the low combustion frequency.
[0012]
When changing the combustion amount between low combustion and high combustion, the rotation speed of the blower 6 is changed by the inverter device 8 and the opening degree of the damper device 9 is changed. When performing low combustion, let the damper opening be the low combustion position and the blower frequency be the low combustion frequency. In this case, although the amount of combustion air passing through the ventilation path 7 is small, the flow passage area of the ventilation path 7 is reduced by the damper device 9, so that the pressure loss when the combustion air passes through the damper device 9 portion is increased. The static pressure of the combustion air can be kept high. Therefore, even if it is a case where the rotation speed of a blower is reduced and an air volume is reduced, combustion can be performed without becoming unstable. When performing high combustion, let the damper opening be the high combustion position and the blower frequency be the high combustion frequency. In this case, since the amount of combustion air passing through the ventilation path 7 increases, the static pressure of the combustion air can be kept high without reducing the flow passage area of the ventilation path 7 by the damper device 9, and combustion does not occur. It will never be stable.
[0013]
In order to perform low combustion, if the air supply amount for combustion is reduced only by controlling the blower rotation speed by the inverter device 8, vibration noise may be generated at an air ratio of about 1.2 to 1.3. The air ratio could not be lowered any more. However, when the amount of combustion air supply is reduced using both the inverter device 8 and the damper device 9, stable combustion can be obtained with a low air ratio setting of 1.2 or less.
[0014]
Note that means other than the damper device 9 may be used as means for reducing the flow path area of the ventilation path 7. However, the damper device 9 is originally necessary to prevent the impact of the ignition shock, and if the damper device 9 is used as a means for reducing the flow passage area of the ventilation path 7, it is necessary to provide a special device separately. It is preferable to use the damper device 9 for preventing the ignition shock from spreading.
[0015]
【The invention's effect】
By implementing the present invention, it is possible to prevent instability of combustion even if the amount of supply of combustion air is reduced by reducing the number of revolutions of the blower when the combustion amount is reduced. The air ratio can be set. Further, by using a damper for restricting the flow path area of the ventilation path, it is possible to prevent the combustion from becoming unstable without providing a special device.
[Brief description of the drawings]
FIG. 1 is a time chart of an air volume adjustment situation in one embodiment of the present invention. FIG. 2 is a block diagram of an embodiment of the invention. FIG. 3 is a time chart of a conventional air volume adjustment situation.
DESCRIPTION OF SYMBOLS 1 Boiler 2 Burner 3 Fuel supply piping 4 1st solenoid valve 5 2nd solenoid valve 6 Blower 7 Ventilation path 8 Inverter apparatus 9 Damper apparatus 10 Control apparatus

Claims (2)

By having a blower that adjusts the amount of combustion air supplied by increasing or decreasing the rotation speed of the blower, and a fuel supply amount adjusting means that increases or decreases the amount of fuel supplied, by adjusting the supply amount of combustion air and fuel In the combustion apparatus that enables adjustment of the combustion amount at three positions of high combustion, low combustion, and stop , a flow path adjustment device that adjusts the flow area is provided in the air passage through which combustion air generated by the blower passes. The fan speed is set for high combustion and low combustion, and the flow area of the flow control device is set for high combustion, low combustion, and ignition, and when the combustion device is ignited, The rotation speed is for high combustion, the flow area of the flow control device is for ignition, the rotation speed of the blower is for low combustion at low combustion, the flow passage area of the flow control device is for low combustion, and the blower's flow area is at high combustion The rotation speed is for high combustion, and the flow area of the flow control device is for high combustion. And the rotation speed of the blower is set to the time of the low combustion state <time of ignition, and low combustion at <high combustion flow passage area of the flow rate adjusting device is characterized in that as the time of ignition at <time of low combustion <high fire Combustion air supply control device.  2. The combustion air supply amount adjustment device according to claim 1, wherein the flow passage adjustment device is a damper device for preventing an ignition shock spread provided in the air passage.

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