JPS61132798A - Operation of variable dynamic vane axial fan for boiler - Google Patents

Abstract

PURPOSE:To lower the minimum air flow by arranging a flow regulation unit for opening/closing a bypath and regulating the opening of bypath through flow regulation unit upon full-close of dynamic vane. CONSTITUTION:A bypath 2 coupling between suction and delivery sides of axial fan 1 is arranged through a recirculation control damper 2. When the dynamic vane is not fully closed, the damper 3 is fully closed to operate like a conventional axial fan while when the dynamic vane is fully closed, the recirculation control damper 3 is regulated to lower the minimum air flow. Consequently, the minimum air flow can be lowered without modifying the fan itself.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention finds application in the technical field of reducing the minimum air flow rate of an axial fan of an entire boiler with a variable blade axial fan.

BACKGROUND OF THE INVENTION In order to cope with the difference in power demand between day and night, electric power companies implement minimum load operation late at night, shut down at night, and start up early in the morning (DSS).

With the adoption of such an operation pattern, there are demands on the boiler side such as ``maintaining high efficiency in low load ranges'' and ``reducing startup and shutdown losses.

The best way to meet these demands is to reduce the minimum boiler air flow rate. However, in recent years F
As a DP (forced draft fan), the centrifugal fan is large, and although it can still be reduced from the boiler side, the minimum air flow rate is restricted from the fan side. On the other hand, in the balanced ventilation system, when the IDF (induction fan) starts up, the furnace pressure drops too much, causing damage to various colors, but it does not come within the control range from the fan side.

As an example, FIG. 3 shows a performance curve for an axial flow of 7 am.

On the boiler side, if there is no combustion problem, it is possible to reduce the minimum air flow rate to 25% MOR, but as in the example of an axial flow of 7 amps, it is possible to fully close the FDP rotor blade opening (open the middle operating room). degree θ
%), the minimum air flow rate is 40% MCR, and the minimum air flow rate may not be reduced.

The reason why the minimum air flow rate of the rotor blade variable axial flow fan does not become zero will be briefly described.

The relationship between the rotor blades and the central control room opening display is as follows.

Fully open display - m - The rotor blade angle is at a position of -25° compared to the reference opening (or -30° in some cases). At this time, the arc of the blade tip is approximately perpendicular to the airflow direction (on the contrary, the rotor blade angle is determined so that it is approximately perpendicular).

Fully open display -m - The rotor blade angle is at a position of +20° from the reference opening.

By the way, the blade base and blade tip of the rotor blade are twisted, and their reference axes are on the same plane (・(The circumferential speed is different in the radial direction.

Therefore, the wing must be twisted to achieve the optimum angle of attack.) Therefore, as mentioned above, when the rotor blade disclosure display is fully closed, the blade at the tip of the rotor blade is almost perpendicular to the airflow and does not blow air, but the container from the tip of the blade to the blade is at an angle of less than 90 degrees to the airflow and does not blow air. I will do it.

Therefore, even when the rotor blade opening degree display is fully closed, the air flow rate of the axial fan does not become zero.

Problems to be Solved by the Invention The present invention is directed to reducing the minimum air flow rate of a variable blade axial flow fan.

Means for Solving the Problems The present invention takes the following measures in order to solve the above-mentioned problems. That is, a bypass passage is formed between the discharge side passage and the suction side passage of a rotor blade variable axial flow fan that can adjust the amount of air supplied to the boiler, and a flow rate adjustment device is provided to open and close the bypass passage. When the rotor blade opening is fully open, the minimum air flow rate is reduced by adjusting the opening degree of the bypass passage using the flow rate adjustment device.

Effect According to the means described above, when the rotor blade opening is not fully closed, the damper is fully closed and the operation is performed like a normal axial flow fan, and when the rotor blade opening is fully closed, the control damper is closed. By adjusting, the minimum air flow rate can be reduced.

Embodiment Next, an embodiment of the present invention will be described with reference to FIG.

The conventional axial flow fan 1 shown in FIG. 2 is installed with the roll damper 3 shown in FIG. 1 interposed therebetween.

When the rotor blade opening is not fully closed, the recirculation amount control damper 3 is fully closed and the fan operates like a normal axial flow fan.

When the rotor blade opening is fully closed, recirculation amount control damper 3
Reduce the minimum air flow rate by adjusting.

That is, in FIG. 1, QS+QR=QO+QR is constant because the rotor blades are fully closed. However, since QR can be changed by adjusting the recirculation amount control damper 3, Q
s=Qo (boiler supply air amount) can be adjusted.

Effects of the Invention By adopting the operating method of the present invention, the following effects can be achieved.

(al) Even with existing axial fans, it is possible to reduce the minimum air flow rate without modifying the fan itself.

('bl Also, the minimum air flow rate can be lowered as much as you like.

(C) In the low air volume region, the power consumption is lower compared to other control methods. I would like to add an additional comment regarding this.

In the method of controlling the minimum air flow rate by providing a damper,
As the damper is throttled to reduce the air volume, the power of the fixed-blade axial fan tends to increase, reaching its maximum near the cut-off point.

Therefore, in a variable rotor blade axial flow fan, if the rotor blades are fixed (central control fully closed) and the flow rate is adjusted by providing a damper on the discharge side, the power consumption will increase compared to the recirculation method.

On the other hand, even if a damper is installed on the suction side, the air volume is essentially adjusted using the resistance loss of the damper, and power is not saved.

In addition, the method of installing vanes on the suction side to adjust the air volume saves axial power more than the damper method, but the damper method tends to increase the power of fixed-blade axial fans as the air volume decreases. are the same, and again the recirculation method is advantageous.

For reference, the advantages of reducing the minimum air flow rate of the boiler are shown below.

B] Boiler efficiency increases due to the reduction in exhaust gas volume.

(Reduction of mouth + NOx

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the configuration of an axial fan for carrying out the operating method according to the present invention, Fig. 2 is a cross-sectional view of a conventional axial fan, and Fig. 3 is a chart showing the axial fan performance curve. be. 1. Axial flow fan, 2. Bypass flow path, 3. Control damper. C1,C;Q-

Claims (1)

[Claims] A bypass passage is formed between the discharge side passage and the suction side passage of a rotor blade variable axial flow fan that can adjust the amount of air supplied to the boiler, and a flow rate adjustment device is provided to open and close the bypass passage. A method of operating a variable rotor blade axial flow fan for a boiler in which the minimum air flow rate is reduced by adjusting the opening degree of a bypass passage using a flow rate adjustment device when the blade opening degree is fully closed.