JP3726327B2 - Damping plate placement method for tube group - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vibration isolation plate arrangement method for a tube group in a boiler.
[0002]
[Prior art]
FIG. 3 is an overall configuration diagram of a boiler including a furnace 1 and a rear heat transfer section 2 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 heat transfer tubes such as a reheater 3a, a superheater 3b, and a economizer 3c (economizer) disposed in the rear heat transfer section 2 are used. After recovering the heat of the combustion gas, it is led to an exhaust gas treatment facility (not shown) through the exhaust gas passage 4.
[0003]
The heat transfer tubes 3 such as the reheater 3a, the superheater 3b, and the economizer 3c are horizontal loop tubes in which both ends of a large number of horizontal tubes are connected as illustrated in FIG. A vertical heat transfer tube group is configured, and the intervals between the horizontal tubes are closely arranged so as to have a sufficient heat transfer area.
[0004]
[Problems to be solved by the invention]
4 is a cross-sectional view taken along line AA in FIG. 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 acts on the heat transfer tube 3. Vibrates at the peeling frequency f _k . This peeling 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 is the pipe outer diameter (m).
[0005]
(Formula 1) f _k = S × V / D
On the other hand, in FIG. 4, the air column formed between the furnace walls 6 has a certain natural frequency. When this natural frequency matches the frequency of the heat transfer tube, a resonance phenomenon occurs, When an unpleasant noise of a frequency is generated and severe, there is a problem that a member constituting the furnace wall may be damaged by vibration. This problem is hereinafter referred to as “air column vibration problem”.
[0006]
The noise level due to such air column vibrations periodically changes along the wall surface of the boiler, but it reaches about 90 dB even at a low part, which is a very big problem.
In order to solve this problem, conventionally, the vibration isolator plates 7 are 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 furnace wall and the vibration isolator plate. _g has been increased so as not to coincide with the peeling frequency f _k of the heat transfer tube. The natural frequency f _g of the air column can be expressed by Equation 2. Here, T is the gas temperature (K), and L is the maximum dimension of the portion partitioned by the vibration isolating plates, that is, the distance (m) between the vibration isolating plates.
[0007]
(Formula 2) f _g = 9.67 × T ^1/2 / L
[0008]
FIG. 5 is a relationship diagram between the boiler load (horizontal axis) and the frequency (vertical axis). As shown in this figure, in addition to the natural frequency f _g of the air column of the primary frequency indicated by Equation 2, twice its three times, second-order frequency of four times such, cubic, quartic There are frequencies f _g1, f _g2, f _{g3, and} f _g4 . As is clear from Equation 1, the separation frequency f _k is proportional to the gas flow rate, and when the boiler load is changed, the amount of combustion gas changes and the separation frequency f _k 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 coincide with or are close to each other as shown by broken circles in the figure. It was thought that it was almost impossible to completely solve the air column vibration problem in the boiler.
[0009]
In principle, the air column vibration problem can be avoided if the primary natural frequency f _g1 of the air column shown in Equation 2 is made larger than the separation frequency f _k at the maximum load. In this case, it is necessary to insert a large number of vibration isolating plates 7, which causes problems such as an increase in boiler manufacturing costs and difficulty in maintenance, and thus cannot be applied practically.
[0010]
The present invention has been made to solve such problems. That is, an 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 isolation plates, and can greatly reduce unpleasant noise due to the resonance phenomenon. An object of the present invention is to provide a vibration isolation plate arrangement method for a tube group.
[0011]
[Means for Solving the Problems]
According to the present invention, in a boiler including a tube group including a plurality of tubes arranged in parallel to each other in a direction orthogonal to the gas flow, and a flow path incorporating the tube group, along the gas flow. A plurality of vibration isolating plates parallel to the pipe, the vibration isolating plates being non-uniformly arranged in a direction perpendicular to the gas flow and the pipe, and non-uniformly arranging at adjacent positions along the gas flow; A featured vibration isolation plate arrangement method for a tube group is provided. That is, when a gas flow flows from top to bottom, a boiler having a tube group consisting of a large number of tubes arranged horizontally and parallel to each other, and a flow path containing the tube group, A plurality of vertical vibration isolating plates parallel to the pipe, the vibration isolating plates being non-uniformly arranged in a direction perpendicular to the pipe, and non-uniformly arranged at positions adjacent to each other in the vertical direction; There is provided a vibration damping plate arrangement method.
[0012]
According to the method of the present invention, the width of the air column formed between the vibration isolating plates (distance between the vibration isolating plates) is adjacent to the gas flow and the direction perpendicular to the pipe (for example, the horizontal direction) along the gas flow. Even if the natural frequencies of adjacent air columns are different and resonate in line with the separation frequency of a boiler load with a certain natural column frequency Since the natural frequency of the surrounding air column is different, the surrounding air column attenuates the resonance, and an unpleasant sound due to the resonance phenomenon can be greatly reduced. Therefore, resonance between the air column vibration and the heat transfer tube vibration can be prevented almost completely over the entire load range of the boiler without using a large number of vibration isolation plates.
[0013]
According to a preferred embodiment of the present invention, the interval between the vibration isolating plates is determined so that the natural frequencies of a plurality of adjacent air columns partitioned by the vibration isolating plate are different. In other words, the air column resonance can be effectively attenuated by setting the spacing between the vibration isolating plates so that the natural frequencies of adjacent air columns, including the second and higher order natural frequencies, are different. Can do.
[0014]
In addition, it is preferable to arrange the vibration isolating plates alternately at different intervals at adjacent positions along the gas flow. In other words, since the gas temperature changes along the gas flow, if the vibration isolation plates are alternately arranged at different intervals at adjacent positions along the gas flow (for example, up and down), the air columns at the same interval are separated from each other. Even if it exists, since the gas temperature is different, the natural frequency f _{g of the} air column shown in Equation 2 is different. Therefore, this method can reduce the number of types of vibration damping plates (for example, two types), and can facilitate design and maintenance.
[0015]
Furthermore, it is preferable that the ends of the vibration isolation plates overlap each other at adjacent positions along the gas flow. By this method, it is possible to make it difficult for air column vibration generated in a certain air column to propagate to an adjacent air column, and the vibration isolation effect of the vibration isolation plate can be further enhanced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and used for the common part in each figure.
FIG. 1 is a view similar to FIG. 4 showing a vibration isolation plate arranging method for a tube group according to the present invention. In FIG. 1, 2 is a rear heat transfer section of the boiler, 3 is a heat transfer tube, 5 is a gas flow, 6 is a furnace wall, and 7 is a vibration isolating plate. That is, this boiler is surrounded by 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 furnace wall 6. And a flow path 14 containing the group 12. Moreover, in this figure, the gas flow flows downward from the top to the bottom, and the heat transfer tubes 3 are arranged horizontally. The tube group 12 is a horizontal loop tube such as a reheater, a superheater, or a economizer.
[0017]
According to the method of the present invention, a plurality of vibration isolating plates 7 are provided along the gas flow 5 and parallel to the heat transfer tubes 3. The vibration isolating plate 7 is non-uniformly arranged in the direction perpendicular to the gas flow 5 and the heat transfer tube 3, and is 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 unevenly arranged at positions adjacent to each other in the vertical direction. are doing.
[0018]
By the above-described method of the present invention, the width L (distance between the vibration isolating plates) of the air columns (for example, a, b, c, d, e, f in the figure) formed between the vibration isolating plates 7 is the gas flow. 5 and a direction orthogonal to the heat transfer tube 3 (for example, a horizontal direction) and an adjacent position (for example, a vertical position) along the gas flow 5, the natural frequencies of the adjacent air columns a to f are Differently, even if the natural frequency of a certain air column g resonates in accordance with the separation frequency in a boiler load, the natural frequencies of the surrounding air columns a to f are different. The resonance can be attenuated, and unpleasant noise due to the resonance phenomenon can be greatly reduced. Therefore, the resonance between 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 isolating plates 7.
[0019]
Further, in FIG. 1, the natural frequencies of a plurality of adjacent air columns a to f partitioned by the vibration isolating plate 7 are different between the vibration isolating plates 7 so that the natural frequencies including second and higher order natural frequencies are different. It is preferable to determine the interval. With this configuration, the air column resonance can be effectively attenuated.
[0020]
Moreover, it is preferable to arrange the vibration isolator plates 7 at different intervals (A, B, A, B in the drawing) at adjacent positions along the gas flow 5 (that is, up and down in the drawing). With this configuration, since the gas temperature changes along the gas flow 5, if the vibration isolation plates 7 are alternately arranged at adjacent intervals along the gas flow 5 (for example, up and down), air columns with the same interval are provided. Since the gas temperatures are different even at positions away from each other, the natural frequency f _{g of the} air column shown in Equation 2 is different. Therefore, this method can reduce the number of types of vibration damping plates (for example, two types), and can facilitate design and maintenance.
[0021]
Furthermore, it is preferable that the ends of the vibration isolating plate 7 overlap each other at adjacent positions along the gas flow 5 (that is, up and down in the drawing). By this method, it is possible to make it difficult for the air column vibration generated in a certain air column g 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.
[0022]
FIG. 2 shows an actual application example of the present invention in comparison with the noise level of a boiler in which a conventional air column vibration problem has occurred. In this figure, the solid line is the conventional noise level, the broken line is the noise level after applying the vibration isolation plate placement method of the tube group of the present invention, and the horizontal axis indicates the width direction of the boiler. As is apparent from this figure, the noise level that had reached a minimum noise level of about 90 dB before the application of the present invention can be reduced by an average of 10 dB or more by the application of the present invention. The level could be suppressed to about 85 dB or less.
[0023]
In addition, this invention is not limited to embodiment mentioned above, Of course, it can change variously in the range which does not deviate from the summary of this invention.
[0024]
【The invention's effect】
As described above, the vibration isolation plate arrangement method of the tube group of the present invention prevents 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 isolation plates, and is based on a resonance phenomenon. It has excellent effects such as being able to significantly reduce unpleasant sounds.
[Brief description of the drawings]
FIG. 1 is a view showing a method of arranging vibration isolating plates for a tube group according to the present invention.
FIG. 2 is an example of measurement data indicating an application result of the present invention.
FIG. 3 is an overall configuration diagram of a boiler.
4 is a cross-sectional view taken along line AA in FIG.
FIG. 5 is a relationship diagram between boiler load and 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)

In a boiler comprising a tube group consisting of a large number of tubes arranged in parallel to each other in a direction perpendicular to the gas flow, and a flow path containing the tube group,
A plurality of vibration isolating plates parallel to the pipe are provided along the gas flow, the vibration isolating plates are non-uniformly arranged in a direction perpendicular to the gas flow and the pipe, and non-uniform at adjacent positions along the gas flow. A method of arranging a vibration isolating plate for a tube group, characterized in that it is arranged. In a boiler comprising a tube group consisting of a large number of tubes arranged horizontally and parallel to the gas flow flowing downward, and a flow path containing the tube group,
A plurality of vertical vibration isolating plates parallel to the pipe, the vibration isolating plates being non-uniformly arranged in a direction perpendicular to the pipe, and non-uniformly arranged at positions adjacent to each other in the vertical direction; Vibration isolation plate placement method. 3. The vibration isolating plate for a tube group according to claim 1 or 2, wherein an interval between the vibration isolating plates is determined so that natural frequencies of a plurality of adjacent air columns divided by the vibration isolating plate are different from each other. Placement method. The method of arranging a vibration isolating plate for a tube group according to claim 1 or 2, wherein the vibration isolating plates are alternately arranged at different intervals at adjacent positions along the gas flow. 3. The vibration isolation plate arrangement method according to claim 1, wherein the ends of the vibration isolation plates overlap each other at adjacent positions along the gas flow.

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