KR20120133732A

KR20120133732A - Noise reduction device to improve performance in airflow by using Helmholtz resonator

Info

Publication number: KR20120133732A
Application number: KR1020110052542A
Authority: KR
Inventors: 남경훈; 김원진
Original assignee: 엔알텍주식회사
Priority date: 2011-06-01
Filing date: 2011-06-01
Publication date: 2012-12-11

Abstract

The present invention relates to a noise reduction device that improves the flow performance by using a Helmholtz resonator, and more particularly, to a noise reduction device using a Helmholtz resonator that can increase the noise reduction effect even when the exhaust gas flow rate is high. .
Noise reduction device to improve the flow performance using the Helmholtz resonator according to an aspect of the present invention includes an exhaust pipe, the body and the projection membrane. The exhaust pipe is formed with a plurality of through holes along the circumferential direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out through the through hole of the exhaust pipe. The projection membrane protrudes in front of the respective through holes in the exhaust pipe.
Noise reduction device to improve the flow performance using the Helmholtz resonator according to another aspect of the present invention includes an exhaust pipe, the body. The exhaust pipe is formed with a plurality of rectangular through-holes in the longitudinal direction and short in the circumferential direction along the circumferential direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out through the through hole of the exhaust pipe.

Description

Noise reduction device to improve performance in airflow by using Helmholtz resonator}

The present invention relates to a noise reduction device that improves the flow performance by using a Helmholtz resonator, and more particularly, to a noise reduction device using a Helmholtz resonator that can increase the noise reduction effect even when the exhaust gas flow rate is high. .

In general, silencers have been widely used in gas turbines of industrial plants and diesel engines of ships, including internal combustion engine cars. Exhaust noise emitted from the engine exhaust port is being studied as one of the important noise sources of the main machinery.In the case of ships, diesel engines are installed in the engine room and surrounding residential areas due to exhaust noise emitted from the diesel engine exhaust ports at the top of the ship funnel. The environmental noise problem is also emerging, and the need for exhaust noise control is increasing. Helmholtz resonators are known to be effective in noise control in low frequency bands.

Helmholtz resonators absorb sound waves of a certain frequency, or resonance frequency, and a high sound absorption effect appears in the region centered on this specific frequency. Therefore, in order to reduce exhaust noise of diesel engine of ship, silencer using Helmholtz resonator is installed at exhaust stage. However, in the case of a diesel engine of a real ship, a silencer using a Helmholtz resonator when mounted has a problem of reducing noise reduction effect. This phenomenon is presumed to be caused by the performance of the silencer deteriorated by the flow of exhaust gas of about 35 m / s emitted from the engine inside the silencer mounted on the ship. That is, in the case of the conventional muffler using the Helmholtz resonator, there is a problem that the performance of the muffler is lowered when the flow rate of the exhaust gas flowing through the neck of the resonator is high.

The present invention is intended to solve the above problems. An object of the present invention is to provide a noise reduction device using a Helmholtz resonator that can increase the noise reduction effect even if the speed of the fluid passing through the neck of the resonator is high.

Noise reduction device to improve the flow performance using the Helmholtz resonator according to an aspect of the present invention includes an exhaust pipe, the body and the projection membrane. The exhaust pipe is formed with a plurality of through holes along the circumferential direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out through the through hole of the exhaust pipe. The projection membrane protrudes in front of the respective through holes in the exhaust pipe.

Noise reduction device to improve the flow performance using the Helmholtz resonator according to another aspect of the present invention includes an exhaust pipe, the body. The exhaust pipe is formed with a plurality of rectangular through-holes in the longitudinal direction and short in the circumferential direction along the circumferential direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out through the through hole of the exhaust pipe.

Noise reduction device to improve the flow performance using the Helmholtz resonator according to another aspect of the present invention includes an exhaust pipe, the body. The exhaust pipe is separated and formed to be spaced at regular intervals along the longitudinal direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out at the interval of the exhaust pipe. And the body is coupled to the exhaust pipe so that one end is in contact with the gap.

Noise reduction device to improve the flow performance using the Helmholtz resonator according to another aspect of the present invention includes an exhaust pipe, a body and a net. A plurality of through holes is formed along the circumferential direction. The body is coupled to the exhaust pipe by wrapping the exhaust pipe so as to accommodate the fluid flowing out through the through hole of the exhaust pipe. The mesh is located in each of the through holes.

According to the present invention, by providing a noise reduction device using a Helmholtz resonator provided with a projection membrane, a net, etc. inside the exhaust pipe, the noise reduction effect of the noise reduction device can be improved even if the flow velocity of the exhaust gas is high.

1 is a perspective view of an embodiment of a noise reduction device using a conventional Helmholtz resonator,
2 is a perspective view of the exhaust pipe of the embodiment shown in FIG. 1;
Figure 3 is an embodiment of the noise reduction device to improve the flow performance using the Helmholtz resonator according to the present invention,
Figure 4 is another embodiment of the noise reduction device to improve the flow performance using the Helmholtz resonator according to the present invention,
Figure 5 is another embodiment of the noise reduction device to improve the flow performance using the Helmholtz resonator according to the present invention,
Figure 6 is another embodiment of the noise reduction device to improve the flow performance using the Helmholtz resonator according to the present invention,
7 is a graph of insertion loss through the performance test apparatus of the embodiment shown in FIG.
8 is a graph of insertion loss through the performance test apparatus of the embodiment shown in FIG.
9 is a graph of insertion loss through the performance test apparatus of the embodiment shown in FIG.
10 is a graph of insertion loss through the performance test apparatus of the embodiment shown in FIG.
11 is a graph of insertion loss through the performance test apparatus of the embodiment shown in FIG.
12 is a graph comparing insertion loss of each embodiment.

Helmholtz resonators, which are generally used to reduce engine exhaust noise in low frequency bands, are known as one of the noise control elements that can reduce noise at specific frequencies. It is known as one of the possible noise control elements. Helmholtz resonators can be analogized to a one-degree-of-freedom mechanical system, which makes it easier to characterize the resonator.

The transmission loss (TL) of a Helmholtz resonator is the transfer matrix using the relationship between pressure and volume velocity when a resonator is attached to the duct through which the wave passes. method). The basic assumption is that there is an anechoic termination condition in which the plane wave propagates in the duct and there is no reflected wave at the exit.

1 and 2 is an embodiment of a noise reduction device using a conventional Helmholtz resonator. The conventional noise reduction device includes an exhaust pipe 10 and a body 20.

The exhaust pipe 10 is formed with a plurality of circular through holes 11 along the circumferential direction. 1 and 2, four through holes 11 are formed in the circumferential direction. Thus, the exhaust gas passing through the exhaust pipe 10 flows out into the through hole 11.

The body 20 is coupled to the exhaust pipe 10 so as to surround the exhaust pipe 10 so as to accommodate the exhaust gas when the exhaust gas flowing into the exhaust pipe 10 flows out through the through hole 11.

In this case, the exhaust gas discharged to the exhaust pipe 10 is accommodated in the body 20 by the through hole 11 and then exits to the outside of the exhaust pipe 10. At this time, since the noise of a specific frequency is canceled by the body 20, the noise is reduced and flows out. However, when the exhaust gas velocity is high, the effect of reducing noise is significantly lowered.

Thus, FIGS. 3 to 5 are embodiments of a noise reduction device in which performance is improved at an internal flow rate of about 30 m / s for a Helmholtz resonator controlling a 1/3 octave band center frequency 250 Hz band.

Figure 3 is an embodiment using a projection membrane to improve the performance at an internal flow rate condition of about 30m / s. The noise reduction device using the Helmholtz resonator according to FIG. 3 further includes a projection film 25 in the embodiment shown in FIG. 1. That is, the SOE reduction apparatus illustrated in FIG. 3 includes an exhaust pipe 10, a body 20, and a projection membrane 25.

The projection film 25 is projected in front of each through hole 11 in the exhaust pipe 10.

4 is another embodiment for improving performance at internal flow velocity conditions of about 30 m / s. The embodiment according to FIG. 4 has an exhaust pipe 10 and a body 20. In addition, a plurality of rectangular through-holes 13 are formed in the exhaust pipe 10 in the circumferential direction. That is, in the embodiment shown in FIG. 1, the through hole 11 is formed in a circular shape. In the embodiment shown in FIG. 4, the through hole 13 is formed in a long rectangle in the longitudinal direction and a short rectangle in the circumferential direction.

5 is another embodiment for improving performance at internal flow velocity conditions of about 30 m / s. The embodiment according to FIG. 5 has an exhaust pipe 10 and a body 20. In this case, the exhaust pipe 10 is separated and formed to be spaced apart at regular intervals 15 along the longitudinal direction. And the body 20 is coupled to the exhaust pipe 10 by wrapping the exhaust pipe 10 to accommodate the fluid flow out at the separated interval (15). Thus, the exhaust gas flowing through the exhaust pipe 10 is discharged to the separated interval 15 is received in the body 20 and is discharged through the exhaust pipe 10. At this time, the body 20 is formed so as to contact the interval 15 is separated front or rear end. In the present embodiment, the rear end of the body 20 was formed to contact the separated interval 15.

6 is another embodiment for improving performance at internal flow velocity conditions of about 30 m / s. The noise reduction device using the Helmholtz resonator according to FIG. 6 further includes a mesh 30 in the embodiment shown in FIG. 1. In other words, the present embodiment includes an exhaust pipe 10, a body 20, and a mesh 30. The mesh 30 is located in each through hole 11.

In order to determine the flow rate in the neck of the resonator for the above embodiments, the flow analysis was performed using FLUENT, a CFD commercial code. In the embodiment of Figure 6 is difficult to implement the shape is not possible because the flow analysis is omitted. From the analysis results it can be seen that the embodiment of Figures 3 to 5 has a lower flow rate in the neck than in FIG.

Example 1 3 4 5 Flow rate in the neck (m / s) 10.22 5.84 6.55 5.67

7 to 11 are graphs showing insertion loss with respect to FIGS. 1 and 3 to 6 using a performance test apparatus. 7 is an insertion loss graph of FIG. 1, and FIG. 8 is an insertion loss graph of FIG. 3. 9 is an insertion loss graph of FIG. 4, FIG. 10 is an insertion loss graph of FIG. 5, and FIG. 11 is an insertion loss graph of FIG. 6. 7 to 11 show the insertion loss according to the flow rate 1/3 octave band spectrum. FIG. 12 shows the insertion loss of each example in a 1/3 octave band spectrum at a flow rate of 30 m / s. 7 to 12, the vertical axis of the graph represents a dynamic insertion loss (DIL) level. And 7 to 11 'speaker' is a graph when there is only a noise source without flow, 'speaker + 10m / s' is a graph when there is a flow and noise source of 10m / s,' speaker + 20m / s 'Is a graph when there is a flow and noise source of 20 m / s, and' speaker + 30 m / s' is a graph when there is a flow and noise source of 30 m / s. In FIG. 12, 'basic model' is a graph of the embodiment of FIG. 1, 'improved model 1' is a graph of the embodiment of FIG. 3, 'improved model 2' is a graph of the embodiment of FIG. 4, and 'improved model 3' is FIG. 5. 'Improved model 4' is a graph of the embodiment of FIG.

Performance evaluation of each embodiment to obtain the insertion loss by 1/3 octave band spectrum, as shown in Table 2 when comparing the insertion loss level of the center frequency 250Hz band and the total insertion loss level of 160 ~ 400 Hz band.

Insertion loss [dB] 1 3 4 5 6 30 m / s
250 Hz 1.90 8.0 7.14 9.31 9.11 160-400 Hz 2.04 4.79 4.67 5.05 5.47

Through the performance test results, it can be seen that the embodiments of FIGS. And comparing the degree of performance improvement of the flow analysis, it can be seen that it is similar to the test result.

As shown in the graph of Figures 7 to 12, Figure 3 is based on the region of interest (160 ~ 400 Hz) at 30 m / s flow rate compared to the conventional noise reduction device using the Helmholtz resonator of Figure 1 is 2.75 dB insertion loss 4 shows the improvement of performance of 2.63 dB, the insertion loss of 3.01 dB, and the insertion loss of 3.43 dB.

10 exhaust pipe 11: through hole
13 through hole 15 gap
20: torso 25: projection
30: netting

Claims

An exhaust pipe formed with a plurality of through holes along the circumferential direction,
A body coupled to the exhaust pipe by surrounding the exhaust pipe so as to receive the fluid leaked into the through hole of the exhaust pipe;
Noise reduction device to improve the flow performance using the Helmholtz resonator, characterized in that it comprises a plurality of projections protruding in front of the respective through holes in the exhaust pipe.

An exhaust pipe formed with a plurality of rectangular through-holes long in the longitudinal direction and short in the circumferential direction along the circumferential direction,
Noise reduction device to improve the flow performance using the Helmholtz resonator characterized in that it comprises a body coupled to the exhaust pipe surrounding the exhaust pipe so as to accommodate the fluid leaked through the through-hole of the exhaust pipe.

An exhaust pipe separated and formed to be spaced at regular intervals along the longitudinal direction,
A body coupled to the exhaust pipe by surrounding the exhaust pipe so as to receive the fluid leaked out at intervals of the exhaust pipe,
The body is noise reduction device to improve the flow performance using the Helmholtz resonator, characterized in that the one end is coupled to the exhaust pipe so as to contact the gap.

An exhaust pipe formed with a plurality of through holes along the circumferential direction,
A body coupled to the exhaust pipe by surrounding the exhaust pipe so as to receive the fluid leaked into the through hole of the exhaust pipe;
Noise reduction device to improve the flow performance using the Helmholtz resonator, characterized in that it comprises a plurality of mesh located in each through hole.