JPH09203502A - Method for arranging vibrationproof board for pipe group - Google Patents

Abstract

PROBLEM TO BE SOLVED: To sharply reduce the uncomfortable sound caused by resonance phenomena by preventing the resonance of the columnar vibration and heat conductive pipe vibration covering the whole range of the load of a boiler, without using many vibration-proof boards. SOLUTION: In a boiler equipped with a group of pipes 12 consisting of many pipes arranged in parallel in rectangular direction to the glass flow and a passage 14 with a group of built-in pipes, a plurality of vibration boards parallel with the pipe are installed along the gas flow, and they are arranged unequally in the direction (right and left in figure) orthogonal to the gas flow and the pipes and besides unequally in the adjacent positions (up and down in the figure) along the gas flow. Moreover, the interval L between the vibration-proof boards is decided so that the natural frequency of the plural adjacent air columns divided by the vibration boards may differ from each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration damping plate arranging method for a tube group in a boiler.

[0002]

2. Description of the Related Art FIG. 3 is an overall configuration diagram of a boiler comprising a furnace 1 and a rear heat transfer section 2 which are surrounded by a heat transfer tube. In the boiler, heavy oil or pulverized coal is burned in the furnace 1 to generate combustion gas, and the reheater 3 arranged in the rear heat transfer section 2 is used.
a, the superheater 3b, the economizer 3c (economizer), and the like, the heat of the combustion gas is recovered by the heat transfer pipes, and then the exhaust gas passage 4 is introduced to an exhaust gas treatment facility (not shown) or the like. .

The heat transfer tube 3 of the reheater 3a, the superheater 3b, the economizer 3c, etc. is a horizontal loop tube in which both ends of a large number of horizontal tubes are connected as shown in FIG. Form a vertical heat transfer tube group as a whole, and the intervals between the horizontal tubes are closely arranged so as to have a sufficient heat transfer area.

[0004]

FIG. 4 is a sectional view of FIG.
It is sectional drawing in a line. In this figure, when the combustion gas 5 flows from the top to the bottom, so-called Karman vortices are periodically generated on the downstream side of the heat transfer tube 3, and a horizontal lift is applied to the heat transfer tube 3 to cause the heat transfer tube 3 to move. Vibrate at the separation frequency f _k . This separation frequency f _k can be expressed by Equation 1. Here, S is the Strouhal number, V is the gas flow velocity (m /
s) and D are outer diameters (m) of the pipe.

(Formula 1) f _k = S × V / D On the other hand, in FIG. 4, the air column formed between the furnace walls 6 is
It has a certain natural frequency, and when this natural frequency matches the frequency of the heat transfer tube, a resonance phenomenon occurs, which causes unpleasant noise at low frequencies, and in extreme cases, a member that constitutes the furnace wall. However, there is a problem in that it may be damaged by vibration. Hereinafter, this problem will be referred to as "air column vibration problem".

The noise level due to the air column vibration changes periodically along the wall surface of the boiler, but reaches a level of about 90 dB even at a low portion, which is a very serious problem. In order to solve this problem, conventionally, the vibration isolator 7 is inserted between the furnace walls 6 at a constant interval, and the natural frequency f of the air column formed between the vibration isolator plates or between the oven wall and the vibration isolator is f. increase _g ,
It has been attempted that the separation frequency f _k of the heat transfer tube does not match. The natural frequency f _g of this air column can be expressed by Equation 2. Here, T is the gas temperature (K), and L is the maximum dimension of the part partitioned by the vibration-proof plates, that is, the distance between the vibration-proof plates (m).

(Formula 2) f _g = 9.67 × T ^1/2 / L

FIG. 5 is a diagram showing the relationship between the load (horizontal axis) and the frequency (vertical axis) of the boiler. As shown in this figure, the natural frequency f _g of the air column is, in addition to the primary frequency shown in Equation 2, the secondary, tertiary, and quaternary frequencies that are two times, three times, four times, and so on. There are frequencies f _g1, f _g2, f _{g3, and} f _g4 . Further, as is clear from the equation 1, the separation frequency f _k is proportional to the gas flow rate, and when the boiler load is changed, the combustion gas amount changes and the separation frequency f _k also increases with the load. Therefore, in the above-described conventional method, even if the vibration isolator is inserted to some extent, the natural frequencies f _{g1 to} f _g4 of the air column and the separation frequency f _k are equal to or close to each other as shown by the dashed circle in the figure. It was thought that it would be almost impossible to completely solve the air column vibration problem in the boiler.

In principle, the air column vibration problem can be avoided by setting the primary natural frequency f _g1 of the air column shown in Equation 2 to be larger than the separation frequency f _k at the maximum load. In this case, it is necessary to insert a large number of anti-vibration plates 7, which raises the manufacturing cost of the boiler and makes maintenance difficult.

The present invention was created to solve such problems. That is, the object of the present invention is to prevent resonance of air column vibration and heat transfer tube vibration over the entire load range of the boiler without using a large number of vibration damping plates, and to significantly reduce unpleasant noise due to the resonance phenomenon. An object of the present invention is to provide a method of arranging a vibration isolation plate for a tube group.

[0011]

According to the present invention, there is provided a tube group consisting of a large number of tubes arranged in parallel to each other in a direction orthogonal to the gas flow, and a flow path containing the tube group. In the boiler, a plurality of vibration isolation plates parallel to the pipe along the gas flow are provided, and the vibration isolation plates are unevenly arranged in the direction orthogonal to the gas flow and the adjacent positions along the gas flow. A non-vibrating plate arranging method is provided for the pipe group. That is, in the case where a gas flow flows downward from top to bottom, in a boiler provided with a tube group composed of a large number of tubes arranged horizontally and in parallel with each other, and a flow path containing the tube group, A group of tubes comprising a plurality of vertical vibration-isolating plates parallel to the pipe, the vibration-isolating plates being unevenly arranged in a direction orthogonal to the pipe, and being unevenly arranged at vertically adjacent positions. A method for arranging a vibration proof plate is provided.

According to the above-mentioned method of the present invention, the width of the air column formed between the vibration isolator plates (distance between the vibration isolator plates) is along the gas flow and the direction orthogonal to the pipe (for example, horizontal direction) and the gas flow. Since they are arranged unevenly in adjacent positions (for example, in the vertical position), the natural frequencies of adjacent air columns are different, and the natural frequency of a certain air column resonates with the separation frequency in the boiler load at a certain frequency. However, since the natural frequency of the air column around it is different, the air column around it attenuates its resonance, and the unpleasant sound due to the resonance phenomenon can be greatly reduced. Therefore, the resonance of the air column vibration and the heat transfer tube vibration can be almost completely prevented over the entire load range of the boiler without using a large number of vibration isolation plates.

According to a preferred embodiment of the present invention, the distance between the vibration isolation plates is determined so that the natural frequencies of a plurality of adjacent air columns partitioned by the vibration isolation plates are different. That is, effective damping of the air column resonance is performed by setting the interval between the vibration isolation plates so that the natural frequencies of the adjacent air columns including the second and higher order natural frequencies are different. You can

Further, it is preferable that the vibration isolation plates are arranged at different positions alternately at adjacent positions along the gas flow. That is, since the gas temperature changes along the gas flow, if the vibration isolation plates are alternately arranged at different positions adjacent to each other along the gas flow (for example, above and below), the air columns at the same intervals are separated from each other. However, since the gas temperature is different, the natural frequency f _{g of the} air column shown in Equation 2 is different. Therefore, according to this method, the number of types of arrangement of the vibration-proof plate can be reduced (for example, two types), and the design and maintenance can be facilitated.

Furthermore, it is preferred that the ends of the vibration isolator overlap each other at adjacent locations along the gas stream. By this method, air column vibration generated in a certain air column can be made difficult to propagate to the adjacent air column, and the vibration isolation effect of the vibration isolator can be further enhanced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In the drawings, common parts are denoted by the same reference numerals. FIG. 1 is a view similar to FIG. 4 showing a method of arranging a vibration isolation plate for a tube group according to the present invention. In FIG. 1, 2 is a rear heat transfer part of a boiler, 3 is a heat transfer tube, 5 is a gas flow, 6 is a furnace wall, and 7 is a vibration isolator. That is, this boiler has a tube group 12 composed of a large number of heat transfer tubes 3 arranged in parallel to each other in a direction orthogonal to the gas flow 5 (direction perpendicular to the paper surface in the figure) and a tube surrounded by a furnace wall 6. And a channel 14 containing the group 12. Further, in this figure, the gas flow flows downward from above, and the heat transfer tubes 3 are horizontally arranged. The tube group 12 is a horizontal loop tube such as a reheater, a superheater, and a economizer.

According to the method of the present invention, a plurality of vibration isolation plates 7 are provided parallel to the heat transfer tubes 3 along the gas flow 5. The anti-vibration plates 7 are arranged non-uniformly in a direction orthogonal to the gas flow 5 and the heat transfer tubes 3, and also non-uniformly arranged at adjacent positions along the gas flow 5. That is, in FIG. 1, a plurality of vertical vibration isolating plates 7 parallel to the heat transfer tubes 3 are provided, and the vibration isolating plates 7 are unevenly arranged in the left-right direction in the drawing, and are also unevenly arranged in vertically adjacent positions. doing.

According to the above-described method of the present invention, air columns (for example, a, b, c, d, e, in the drawing) formed between the vibration damping plates 7 are formed.
The width L (distance between anti-vibration plates) of f) is unevenly arranged in a direction orthogonal to the gas flow 5 and the heat transfer tube 3 (eg, horizontal direction) and at adjacent positions along the gas flow 5 (eg, vertical position). Therefore, even if the natural frequencies of the adjacent air columns a to f are different and the natural frequencies of a certain air column g resonate in accordance with the separation frequency in the boiler load, the air columns a to f around the air columns a to f Since the natural frequencies of the above are different, the surrounding air columns a to f can dampen their resonances, and the unpleasant noise due to the resonance phenomenon can be significantly reduced. Therefore, without using a large number of anti-vibration plates 7,
Resonance between air column vibration and heat transfer tube vibration can be almost completely prevented over the entire load range of the boiler.

Further, in FIG. 1, the vibration-proof plate is so arranged that the natural frequencies of a plurality of adjacent air columns a to f divided by the vibration-proof plate 7 are different, including the natural frequencies of higher than second order. It is preferable to define an interval between seven. With this configuration, the air column resonance can be effectively attenuated.

In addition, at adjacent positions along the gas flow 5 (that is, in the upper and lower portions in the drawing), different intervals (A, B, and
It is preferable to dispose the vibration damping plate 7 in A and B). With this configuration, the gas temperature changes along the gas stream 5,
If the vibration damping plates 7 are alternately arranged at different positions at adjacent positions along the gas flow 5 (for example, above and below), the gas temperature will be different even if the air columns at the same intervals are apart, Two
The natural frequency f _g of the air column shown by is different. Therefore, according to this method, the number of types of arrangement of the vibration-proof plate can be reduced (for example, two types), and the design and maintenance can be facilitated.

Furthermore, it is preferable that the ends of the vibration isolator 7 overlap each other at adjacent positions along the gas flow 5 (ie, at the top and bottom in the figure). By this method, the air column vibration generated in a certain air column g can be made difficult to propagate to the adjacent air columns a to f, and the vibration isolation effect of the vibration isolation plate 7 can be further enhanced.

FIG. 2 shows an actual application example of the present invention in comparison with the noise level of the conventional boiler in which the air column vibration problem occurs. In this figure, the solid line shows the conventional noise level, the broken line shows the noise level after applying the vibration damping plate arranging method of the present invention, and the horizontal axis shows the width direction of the boiler. As is clear from this figure, before the application of the present invention, a noise level of at least about 90 dB was reached, but by applying the present invention, the noise level can be reduced by 10 dB or more on average, and the maximum noise level can be reduced. The level could be suppressed to about 85 dB or less.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0024]

As described above, according to the method of arranging the vibration isolator of the tube group of the present invention, the resonance of the air column vibration and the heat transfer tube vibration is prevented over the entire load range of the boiler without using many vibration isolators. However, it has an excellent effect that unpleasant noise due to the resonance phenomenon can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of arranging a vibration isolation plate for a tube group according to the present invention.

FIG. 2 is an example of measurement data showing an application result of the present invention.

FIG. 3 is an overall configuration diagram of a boiler.

FIG. 4 is a cross-sectional view taken along line AA of FIG.

FIG. 5 is a relationship diagram between a load of a boiler and a frequency.

[Explanation of symbols]

 1 Furnace 2 Rear Heat Transfer Section 3 Heat Transfer Tube 4 Exhaust Gas Passage 5 Gas Flow (Combustion Gas) 6 Furnace Wall 7 Vibration Isolator 12 Tube Group 14 Flow Path

Claims (5)

[Claims] 1. A boiler having a tube group including a plurality of tubes arranged in parallel to each other in a direction orthogonal to a gas flow, and a flow path containing the tube group, wherein the tubes are arranged along the gas flow. A plurality of anti-vibration plates parallel to each other, the anti-vibration plates being unevenly arranged in the direction orthogonal to the gas flow and the pipe, and also being unevenly arranged at adjacent positions along the gas flow. The method of arranging the vibration isolator for the tube group. 2. A boiler provided with a tube group composed of a plurality of tubes arranged horizontally and in parallel to a gas flow flowing downward, and a flow path containing the tube group, wherein A plurality of vertical vibration-proof plates that are parallel to each other, the vibration-proof plates are unevenly arranged in a direction orthogonal to the pipes, and the vibration-proof plates are unevenly arranged at vertically adjacent positions. How to arrange the vibration plate. 3. The pipe according to claim 1, wherein the distance between the vibration isolation plates is determined so that the natural frequencies of a plurality of adjacent air columns partitioned by the vibration isolation plate are different. Arrangement method of anti-vibration plate for group. 4. The vibration damping plate arranging method according to claim 1, wherein the vibration damping plates are arranged alternately at different positions at adjacent positions along the gas flow. 5. The method of arranging a vibration isolation plate for a tube group according to claim 1, wherein the ends of the vibration isolation plate are overlapped with each other at adjacent positions along the gas flow.