JPH05195893A - Variable passage sectional area type silencer - Google Patents

Abstract

PURPOSE:To provide a silencer construction which can deal with the case of variation of frequency corresponding to the highest sound pressure level of noise. CONSTITUTION:This silencer 1 is constituted so that a plurality of swirl vanes 3, constituting members having changing sectional area from (d1) to (d4), are annularly arranged, and a conical block 8 to change the width of the passage in the center space from C1 to C3 is provided, in a main body 1 of cylindrical or polygonal columnar shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silencer, and more particularly to the structure of a silencer provided at a compressor air intake port of an exhaust turbine supercharger used in a large diesel engine.

[0002]

2. Description of the Related Art A conventional compressor 3'for an exhaust turbine supercharger.
FIG. 5 shows the structure of the silencer provided at the air suction port of the above. Air is sucked from the atmosphere outside the device through the path indicated by the white arrow in the drawing. On the contrary, noise is propagated to the outside of the device through the route indicated by the black arrow. A plurality of sound absorbing cells 5'having an air passage in the axis are positioned as a sound absorbing cell group 5a of a plate-like block with the axes thereof parallel to the intake side of the apparatus as shown in the figure. Air filter 8'and wire mesh on the air suction side end surface of the sound absorbing cell set
3/99 9'is for dust protection, and the wire mesh 9'on the opposite surface
Is provided. In addition, the sound absorbing cell of the unit framed the inner cylinder and the outer cylinder of the punching plate (perforated plate) to be coaxial,
The annular space is filled with a porous sound absorbing material. As the porous sound absorbing material, plant fiber materials such as cotton, linen and panya, animal fibers such as felts, mineral fibers such as glass wool and rock wool are used.
FIG. 6A is a cross-sectional view taken along the line AA of the figure (a wire mesh is partially shown in an E view). In this case, the air passage 5b 'of the sound absorbing cell has a cylindrical shape as shown in FIG. 6B and its diameter does not change. The rotor 3a ', which is the rotating body of the compressor for the exhaust turbine supercharger, is provided with a plurality of blades, and the rotor has a rotor shaft 2'of 16000 rpm to 20000r.
Since the motor rotates at pm, the air flow is cut off every minute at "the number of revolutions x the number of blades", and therefore noise of high frequency such as 4 KHz is generated and its treatment is necessary. An example of the measurement result of the noise generated from the exhaust turbine supercharger compressor of this type is shown in FIG. 7 as a frequency vs. sound pressure diagram (noise spectrum). Further, since it has a rotor with blades as a compressor device, it is inevitable to generate high frequency noise, and it is strongly desired to propose a device structure for preventing this noise from being emitted outside the device. However, in the conventional sound deadening device, since the air passage has the same diameter in the cylindrical sound absorbing cell, as shown in FIG. 4A, the sound pressure level of a specific frequency can be lowered. . This is because 1/2 of the frequency of the silenced sound corresponds to the diameter of the air passage of the sound absorbing cell, which has been confirmed by experiments. (Journal of Acoustical Society of Japan, Vol. 31, No. 8, Obata, Hirata, Onaka, Nishiwaki, "Attenuation Characteristics of Sound Absorption Duct")

[0003]

In the conventional sound absorbing cell, since the gas passage has a cylindrical shape with the same diameter, noise corresponding to one frequency is mainly silenced, and it is necessary to muffle noise by changing the load of the diesel engine. Whenever the frequency of the highest sound pressure level fluctuates within a certain range, the highest reference number P205G
4/9 Means to mute the sound within the high level frequency fluctuation range,
A device is needed and its solution is desired.

[0004]

A noise absorbing device provided at an air inlet of a compressor or the like of an exhaust turbine supercharger is a unit sound absorbing member that forms a gas passage and changes the cross-sectional area of the gas passage along a gas passage. Providing a plurality of units, and providing a structure using a plurality of pillar-shaped unit silencers in which a plurality of trapezoidal sound absorbing partition plates are arranged at intervals in the axial direction, such as a swirl vane Is.

[0005]

Embodiment 1 FIG. 1 (A) is a front view of a partial cutout of a silencer 1 according to the first embodiment of the present invention, and FIG. 1 (B) is FIG.
It is a partially cutaway plan view of the BB section of (A). In the body frame 2, a plurality of swirl vanes (unit sound absorbing members) 3 are arranged between the lower sound absorbing material disk 7a and the upper sound absorbing material annular plate 7b, and a gas passage formed by two swirling blades is illustrated. By varying d _{1 to} d ₄ and the cross-sectional area of the passage, a muffling device in which the plurality of passages are arranged annularly is configured. In the present invention, as shown in FIG. 1 (A), after the air passes through the plurality of blades, the sound absorption at the center of the lower sound absorbing material disk is further made so that the passage sectional area changes from c _{1 to} c _{3 in the} central space of the device. A conical block 8 made of material is provided. The surface of the conical block is covered with a wire net or a perforated punching plate to prevent the sound absorbing material from scattering. A metal net 5, a sound absorbing material 6, and a filter 6a are provided on the cylindrical outer surface side of the muffler 1. With such a configuration, even if the maximum sound pressure level of noise varies with the load variation of the equipment connected to the device, the width corresponding to the frequency to be muted corresponding to this can be provided. Effective muffling can be achieved by changing the cross-sectional area of the passage, eliminating the need for special operations.

[Example 2] Reference number P205G
5/9 FIG. 2 (A) is a partially cutaway front view of the silencer 1a according to the second embodiment, and FIG. 2 (B) is a sectional view taken along line CC of FIG. 2 (A). In this case, if the height h of the swirl vane 3 is made smaller than the outer peripheral pitch p of the swirl vane, the passage cross-sectional area becomes smaller than in the case of the first embodiment, and noise of higher frequency can be silenced. However, this increases the resistance to gas suction, so
As shown in (A), the standard unit muffler 3a has a plurality of stages (three stages in the illustrated example) to reduce the gas flow velocity and reduce the gas passage resistance. In this case, the swirl vane 3 is provided with a bent portion 4 and the cross-sectional area of the gas passage is changed along the gas flow so as to have a certain frequency range with a width, and the illustrated sound wave S is as shown in FIG. 2 (B). A plurality of reflections are made between the two swirl blades to increase the sound deadening effect. Furthermore the cross-sectional area aims to divide the cone block gas passage is provided a plurality of partition plates 10 connecting to 8 C ₁ -C ₃
The corresponding muting corresponding to and may be made more effective. In this way, the unit silencer 3 stacked in a plurality of stages
When a is used as a standard part, the manufacturing cost is reduced, the assembling is easy, and the manufacturing effect is remarkable.

Third Embodiment FIGS. 3A and 3B show a third embodiment. As shown in FIG. 3B, a trapezoidal sound absorbing partition plate 12 is arranged in a columnar frame 11b having a trapezoidal cross section with a plurality of intervals in the axial direction of the columnar frame to form a unit silencer 11a.
A polygonal body frame (octagon in the illustrated example) 14 is arranged along the frame so that one side of the ring is in contact with each other to form a columnar unit muffler set, and a void 15 is provided in the center thereof. Since the unit muffler 11a has a trapezoidal shape as shown in the figure, the cross-sectional area of the gas passage changes with the flow of gas. The degree of change in the passage cross-sectional area can be designed in advance by adjusting the number of sides of the polygon (also the length of the side). Further, it is easy to manufacture a unit silencer formed with a straight peripheral edge, and it is convenient that the height of the columnar frame can be selected to correspond to the amount of processing gas and the flow resistance. Reference number P205G
6/9

[0006]

By carrying out the present invention, as shown in FIG.
In the conventional device as shown in (A), the diamond-shaped gaps between the cylindrical outer surfaces of the cells in plan view are eliminated, and on the other hand, the cross-sectional shape can be all straight lines, which makes the manufacture and assembly of the members extremely easy. By measuring the noise spectrum of the target device in advance, the frequency corresponding to the highest sound pressure level of the noise to be silenced is clarified, and the condition of the change of the gas passage cross-sectional area can be calculated to design the device. By providing the device according to the present invention, it is possible to deal with muffling when the frequencies corresponding to a plurality of high-pitched sound levels fluctuate, which greatly contributes to noise prevention. The device according to the present invention can be used not only for muffling the compressor of the supercharger, but also for a blower, a compressor, etc. as a device that emits a wide range of noise.

[Brief description of drawings]

FIG. 1A is a partially cutaway front view of an apparatus according to a first embodiment of the present invention.

FIG. 1 (B) is a partially cutaway BB cross section of FIG. 1 (A).

FIG. 2A is a partially cutaway front view of an apparatus according to a second embodiment of the present invention.

2 (B) is a partially cutaway CC sectional view of FIG. 2 (A).

FIG. 3 (A) is a partially cutaway front view of an apparatus according to a third embodiment of the present invention.

FIG. 3B is a partially cutaway DD sectional view of FIG.

FIG. 4 (A) is a diagram showing the sound deadening performance of a conventional sound absorbing cell. Reference number P205G
7/9

FIG. 4 (B) is a diagram showing the effect of being able to mute a wide range of frequencies, showing the effect of implementing the present invention.

FIG. 5 is a vertical cross-sectional view of a conventional silencer.

6 (A) is a cross-sectional view taken along the line AA of FIG.

FIG. 6B is a perspective view of a conventional sound absorbing cell having a tubular gas passage.

FIG. 7 is a noise spectrum diagram when there is no silencer at the compressor air suction port of the exhaust turbine supercharger.

[Explanation of symbols]

1 silencer 1a silencer 2 main frame 3 swivel blade 3a unit silencer 4 bent part 5 wire mesh 6 sound absorbing material 6a filter 7a lower sound absorbing material disk 7b upper sound absorbing material annular plate 8 conical block 9 flange 10 partition plate 11 sound absorbing device Reference number P205G
8/9 11a Unit silencer 12 Trapezoidal sound absorbing partition plate

Claims (3)

[Claims] 1. A muffler connected to a gas suction port of a device that emits noise, comprising a plurality of unit sound-absorbing members that form a gas passage and change the cross-sectional area of the gas passage along the gas passage. Muffler with variable passage cross-section. 2. The unit sound absorbing member is a swirl vane, the back length of the swirl vane is set to be equal to or less than the pitch of the end of the swirl vane on the outer circumference of the circular bottom plate, and a plurality of unit silencers composed of the circular bottom plate and a plurality of swirl vanes are stacked. The passage cross-sectional area change type silencer according to claim 1, which is mounted in one body frame. 3. A unit silencer is formed by arranging a plurality of trapezoidal sound absorbing partition plates at intervals in the axial direction of the columnar frame in a columnar frame having a trapezoidal cross section. 2. The passage cross-sectional area change type silencer according to claim 1, wherein the silencers are arranged so as to face each other around the periphery of the rectangular main body frame and are arranged in an integral ring shape.