JP2000170688A - Axial flow fan - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the difference of pressure between the inside of an rear inner cylinder and an oil tank, and to reduce the height of a U-seal by providing a drain pipe connecting the rear inner cylinder and the oil tank, and a pressure uniforming pipe communicating between a front inner cylinder and the rear inner cylinder in an axial flow fan comprising the front inner cylinder and the rear inner cylinder in front and rear of a blade-wheel. SOLUTION: In an axial flow fan having a front inner cylinder 2 and a rear inner cylinder 3 in front and rear of a blade-wheel 1, pressure in the rear inner cylinder 3 tend to be increased by leaking-in of a fluid body from a seal part 4 on the rear flow side, because pressure in the rear flow side is higher than that of the blade-wheel 1. For that reason, a pressure uniforming pipe 13 communicating between the front inner cylinder 2 and the rear inner cylinder 3 is provided. The fluid body is sucked out from an upper stream side seal part 7 to decrease pressure in the front inner cylinder 2, and inner pressure of both inner cylinders 2, 3 is uniformed to decrease pressure in the rear inner cylinder 3, so that a difference in pressure with an oil tank is reduced. Therefore, the U-seal height U of an U-seal 11 of a drain pipe 11 is allowed to be small to simplify a piping adjustment and a piping structure of the drain pipe 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow fan which is used, for example, for a boiler of a thermal power plant, and has a front inner cylinder and a rear inner cylinder before and after an impeller.

[0002]

2. Description of the Related Art As shown in FIG. 2, in an axial fan having a front inner cylinder 2 and a rear inner cylinder 3 before and after an impeller 1,
Since the pressure on the downstream side of the impeller 1 becomes higher, the pressure inside the rear inner cylinder 3 also increases due to leakage of fluid from the seal portion 4 on the downstream side. In the drawings, 5 is a main shaft, 6 is a main bearing, 7 is an upstream seal portion, 8 is a casing, and 9 is a flow direction of a fluid.

In the above-described axial fan, hydraulic oil for controlling the pitch of the blades leaks into the rear inner cylinder 3, and this oil is drained through a drain pipe 10 into an oil tank (not shown) of an oil supply device. Zu). At this time, the pressure inside the rear inner cylinder 3 is high as described above, while the oil tank is at atmospheric pressure. Therefore, the U-seal 11 is interposed in the middle of the drain pipe 10 to Prevents leaks. In particular, when the fluid is a combustion gas, since SO _X and NO _X are contained, it is necessary to securely seal to prevent air pollution. In addition, 12 indicates a foundation, H indicates a foundation height, h indicates a digging depth, and U indicates a U seal height.

[0004]

However, in recent years, the size and pressure of the power generation plant have been increased, and the size of the axial flow fan has also been increased and the pressure has been increased. Therefore, the inside of the rear inner cylinder 3 and the oil tank (atmospheric pressure) ) Becomes large, and in order to obtain a sufficient sealing effect, the U seal height U must be increased, and the height H of the foundation 12 is increased and the digging depth h is increased. This necessitates a great deal of cost for civil engineering work when installing an axial fan at the site.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an axial flow fan having a front inner cylinder and a rear inner cylinder before and after an impeller. An axial flow fan comprising: a drain pipe connected to an oil tank; a U-seal interposed in the drain pipe; and a pressure equalizing pipe communicating the front inner cylinder and the rear inner cylinder. I do.

[0006] By the above means, the pressure difference between the inside of the rear inner cylinder and the oil tank (atmospheric pressure) is reduced, and therefore, the U seal height is reduced.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Explanation will be made based on 1. Components having the same functions as those in FIG. 2 are denoted by the same reference numerals, and description thereof will be omitted. In the figure, 1
Reference numeral 3 denotes a pressure equalizing pipe that connects the front inner cylinder 2 and the rear inner cylinder 3. As a result, the pressure in the front inner cylinder 2 is reduced so that the fluid is sucked out from the upstream-side seal portion 7. As a result, the pressure in the rear inner cylinder 3 is reduced, so that the pressure difference between the rear inner cylinder 3 and the oil tank is reduced. Thereby, the U seal height U of the U seal 11 of the drain pipe 10 can be reduced.

[0008]

According to the present invention, the pressure in the rear inner cylinder can be reduced by equalizing the front inner cylinder and the rear inner cylinder by the pressure equalizing pipe. (Atmospheric pressure). Therefore, the height of the U seal is reduced (about one half of the conventional one), the piping adjustment and the piping structure of the drain pipe are simplified, the required height of the foundation is reduced, and the U seal height is secured. No digging is required. As a result, enormous costs for civil engineering work can be suppressed, and costs can be reduced without impairing the performance of the axial fan and the effect of the U seal.

[Brief description of the drawings]

FIG. 1 is a front view showing an axial fan according to an embodiment of the present invention.

FIG. 2 is a front view showing a conventional axial fan.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 impeller 2 front inner cylinder 3 rear inner cylinder 4 downstream seal section 5 main shaft 6 main bearing 7 upstream seal section 8 casing 9 fluid flow direction 10 drain pipe 11 U seal 12 foundation 13 pressure equalizing pipe

Claims (1)

[Claims] 1. An axial fan having a front inner cylinder and a rear inner cylinder before and after an impeller, wherein a drain pipe connecting the rear inner cylinder and an oil tank of an oil supply device is provided, and the drain pipe is interposed in the drain pipe. An axial flow fan comprising: a U-seal provided; and a pressure equalizing pipe communicating the front inner cylinder and the rear inner cylinder.