CN107218108A - A kind of wideband high frequency silencing noise unit - Google Patents

Abstract

The invention discloses a wide-band high-frequency noise muffler unit, which comprises an air intake pipe, a bellows pipe and an air outlet pipe. The inlet pipe and the outlet pipe are straight pipes with equal cross-section, which are respectively connected to the two ends of the bellows to form an independent muffler unit. The corrugated pipe is a U-shaped corrugated pipe composed of a plurality of corrugated corrugations with different corrugation heights, and the height of each corrugated pipe increases or decreases linearly. The invention has a reasonable structure, can work in a high-temperature environment, and has independent noise elimination characteristics of wide-band high-frequency noise. The invention provides a wide-band high-frequency noise silencing unit. The internal-combustion engine muffler is provided with a bellows, and through reasonable design, the silencing bandwidth and silencing capacity of the high-frequency exhaust noise are effectively improved.

Description

A Broadband High Frequency Noise Muffling Unit

technical field

The invention relates to the technical field of vehicle mufflers, in particular to a wide-band high-frequency noise muffler unit.

Background technique

The muffler is a device installed on the airflow channel of aerodynamic equipment or in the intake and exhaust systems to reduce noise. It can not only allow airflow to pass through, but also effectively reduce noise. The most widely used noise reduction equipment.

Taking internal combustion engines as an example, the exhaust mufflers currently used in internal combustion engines are mainly resistant mufflers. The inlet pipe and outlet pipe of this type of muffler are connected to the expansion chamber, and the gas enters the muffler from the inlet pipe and is discharged from the outlet pipe. This kind of resistant muffler uses the reflection and interference effects of sound waves, etc., to prevent the outward propagation of sound wave energy by changing the propagation characteristics of sound waves.

However, due to the existence of the inherent upper cut-off frequency of the resistive muffler, it is difficult for the resistive muffler to obtain ideal noise reduction performance in the frequency band above the cut-off frequency. Usually, perforated tubes and sound-absorbing materials are used to improve the noise reduction performance of the resistant muffler in the frequency band above the cut-off frequency. However, the use of these two methods will significantly increase the volume of the muffler, which in turn will affect the overall design of the muffler. How to improve the noise reduction performance of the resistant muffler over a wide frequency band without changing or reducing the volume of the muffler and without significantly increasing the pressure loss of the muffler has become a difficult point in the design of the resistant muffler.

In view of this, how to improve the internal structure of the internal combustion engine muffler and structurally improve the noise reduction effect on broadband high-frequency noise is a technical problem to be solved urgently by those skilled in the art.

Contents of the invention

In order to solve the above-mentioned existing problems, the present invention provides a wide-band high-frequency noise muffler unit. The muffler for an internal combustion engine is provided with a bellows. Through reasonable design, the muffler bandwidth and muffler volume of high-frequency exhaust noise are effectively improved. To achieve this purpose, the present invention provides a wide-band high-frequency noise silencing unit, including an air intake pipe, a bellows, a fixed plate and an air outlet pipe, the air inlet pipe and the air outlet pipe are respectively connected to the two ends of the bellows to form a An independent noise reduction unit, the bellows includes at least 2 bellows units, each bellows unit is fixed by fixing plates on both sides to form a bellows, the corrugation height of each bellows unit linearly increases or decreases other structural dimensions The same or the corrugation width increases or decreases linearly and the other structure dimensions are the same.

As a further improvement of the present invention, the upper and lower limit frequencies and bandwidth formulas of the effective noise reduction frequency band of the noise reduction unit are as follows:

Where d _cmax is the maximum corrugation height of the bellows unit, d _cmin is the minimum corrugation height of the bellows unit, l _c is the width of the corrugation of the bellows unit, w _c is the corrugation interval, c ₀ is the speed of sound, f _L is the effective noise reduction The lower limit frequency of the frequency band, f _H is the upper limit cut-off frequency, and B _w is the anechoic bandwidth.

As a further improvement of the present invention, the bellows unit is U-shaped, and U-shaped bellows units are commonly used in the present invention.

As a further improvement of the present invention, the bandwidth of the broadband high-frequency noise silencing unit with a transmission loss of 20db(A) reaches more than 2000 Hz, and the bandwidth of the broadband high-frequency noise silencing unit of the present invention can reach more than 2000 Hz.

Compared with the prior art, a wide-band high-frequency noise silencing unit of the present invention has the following beneficial effects: the present invention uses a plurality of U-shaped corrugations to be combined according to specific rules, so that the silencing frequency bands of each corrugation form a complementary and silencing amount Superposition is formed, which can effectively improve the noise reduction bandwidth and the noise reduction amount of high-frequency noise. Compared with the way of using sound-absorbing materials and perforated pipes in the prior art to improve the silencing of high-frequency noise, the present invention does not increase the volume of the muffler. In addition, the present invention will not be affected by the blockage of oil dirt and carbon particles in the engine exhaust to affect the noise reduction bandwidth and noise reduction amount. However, perforated pipes and sound-absorbing materials are sensitive to oil and carbon particles, which may easily lead to reduced noise reduction or even failure. The present invention does not have a similar situation, so the service life is longer and the use environment is wider. The invention is particularly important for the design of the muffler under the conditions of high-power large-displacement engines and limited installation space.

Description of drawings

Fig. 1 is a front view of the present invention;

Fig. 2 is the right view of the present invention;

Fig. 3 is a schematic diagram of parameters of the present invention;

Fig. 4 is a transmission loss curve diagram 1 of an embodiment of the present invention;

Fig. 5 is the transmission loss curve figure 2 of the embodiment of the present invention;

Graphical description:

Among them, 1 intake pipe, 2 bellows unit, 3 fixed plate, 4 air outlet pipe.

detailed description

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

The invention provides a wide-band high-frequency noise silencing unit. The internal-combustion engine muffler is provided with a bellows. Through reasonable design, the silencing bandwidth and silencing capacity of high-frequency exhaust noise are effectively improved.

Please refer to Figures 1-3, Figures 1-3 are structural schematic diagrams of a specific embodiment of the broadband high-frequency noise silencing unit provided by the present invention.

The wide-band high-frequency noise muffler unit in this embodiment has an air inlet pipe 1 , a corrugated pipe, a fixed plate 3 and an air outlet pipe 4 . The inlet pipe 1 and the outlet pipe 4 are respectively connected to two ends of the bellows; the fixing plate 3 is used to fix the bellows unit 2 to prevent its structural deformation from affecting the noise reduction performance. The corrugation height of the bellows unit 2 increases or decreases linearly, and other structural dimensions are the same.

Specifically, the inner diameter of the inlet pipe 1 and the outlet pipe 4 shown in FIG. 1 is 55mm, and the bellows unit 2 is a U-surface bellows, which is composed of 8 corrugations with different corrugation heights. The corrugations of the bellows unit 2 are uniformly arranged along the axial direction of the bellows unit 2 by four fixing plates 3 for fixing the positions of the corrugations. The maximum corrugation height dcmax and the minimum corrugation height dcmin of the bellows unit 2 are 50mm and 15mm respectively, and the corrugation height difference between adjacent corrugations is 5mm. The corrugation width lc of the bellows is 12.5 mm, and the corrugation interval wc is 8 mm. According to these structural dimensions and the formulas (1) and (2), the upper and lower limit frequencies and the bandwidth of the effective anechoic frequency band of the embodiment shown in FIG. 1 can be estimated.

According to formula (1), getting sound velocity c0 is 340m/s, and the lower limit frequency fL of the effective anechoic frequency band of the embodiment shown in Figure 1 is about 1292Hz, and the upper limit cut-off frequency fH is about 4271Hz, so the effective The noise cancellation frequency band is 1292Hz-4271Hz, and the noise cancellation bandwidth Bw is 2979Hz, which can realize the noise cancellation performance of the embodiment shown in FIG. 1 for broadband high frequency noise. Although the formula (1) is an empirical formula proposed by the inventor and applicable to the present invention, there is a certain prediction error, but it can provide a design basis for the design of other specific embodiments of the present invention.

In use, the inlet pipe 1 and the outlet pipe 4 can be interchanged, depending on the installation method of the noise reduction unit in the muffler, without affecting the noise reduction performance of the present invention. Taking the implementation shown in Figure 1 as an example, the noise signal enters from the intake pipe 1 and passes through the corrugations of the corrugated pipe from left to right, realizing broadband noise reduction from the lower limit frequency of the anechoic frequency band to the upper limit frequency of the anechoic frequency band. In the following, a simulation experiment is used to demonstrate that a noise-absorbing unit of the present invention has good noise-absorbing performance of wide-band high-frequency noise. The simulation experiment uses the commercial LMS Virtual.Lab simulation software. FIG. 4 is a transmission loss curve of the embodiment shown in FIG. 1 . It can be seen from FIG. 4 that the effective noise reduction frequency band of the noise reduction unit in the embodiment shown in FIG. 1 is 1039.49 Hz-4004.185 Hz, and the effective noise reduction bandwidth Bw is about 2965 Hz. Taking the transmission loss of 20dB(A) as an example, as shown in FIG. 5, the noise reduction bandwidth Bw of the embodiment shown in FIG. Therefore, it can be concluded from the simulation experiment that the sound-absorbing unit adopting the structure of the present invention can realize the sound-absorbing performance of wide-band high-frequency noise.

During design, the anechoic frequency band of the designed anechoic unit can be estimated according to formula (1), and then the structural size of the designed anechoic unit can be adjusted in combination with the simulation experiment results to achieve the required anechoic capacity and anechoic frequency. bandwidth.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any other form, and any modification or equivalent change made according to the technical essence of the present invention still belongs to the scope of protection required by the present invention .

Claims (4)

1. a kind of wideband high frequency silencing noise unit, including air inlet pipe (1), bellows, fixed plate (3) and escape pipe (4), It is characterized in that：The two ends that the air inlet pipe (1) and escape pipe (4) are connected to bellows form an independent noise elimination list Member, the bellows includes at least two ripple pipe unit (2), and each ripple pipe unit (2) is entered by the fixation plate (3) of both sides Row is fixed to form bellows, the linear increasing or decreasing other structures size of wave height of each ripple pipe unit (2) it is identical or The linear increasing or decreasing other structures size of waviness width is identical.

2. a kind of wideband high frequency silencing noise unit according to claim 1, it is characterised in that：The muffling unit The bound frequency and its bandwidth formula of effective noise elimination frequency band are as follows：

<mrow> <msub> <mi>f</mi> <mi>L</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mn>0.103</mn> <msub> <mi>c</mi> <mn>0</mn> </msub> </mrow> <mrow> <msubsup> <mi>d</mi> <mrow> <mi>c</mi> <mi>max</mi> </mrow> <mn>0.71</mn> </msubsup> <msubsup> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> <mrow> <mo>-</mo> <mn>0.13</mn> </mrow> </msubsup> <msubsup> <mi>l</mi> <mi>c</mi> <mn>0.38</mn> </msubsup> <msubsup> <mi>w</mi> <mi>c</mi> <mn>0.04</mn> </msubsup> </mrow> </mfrac> <mo>,</mo> <msub> <mi>f</mi> <mi>H</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mn>0.331</mn> <msub> <mi>c</mi> <mn>0</mn> </msub> </mrow> <mrow> <msubsup> <mi>d</mi> <mrow> <mi>c</mi> <mi>min</mi> </mrow> <mn>0.40</mn> </msubsup> <msubsup> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> <mn>0.46</mn> </msubsup> <msubsup> <mi>l</mi> <mi>c</mi> <mn>0.12</mn> </msubsup> <msubsup> <mi>w</mi> <mi>c</mi> <mn>0.02</mn> </msubsup> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> <mo>;</mo> </mrow>

<mrow> <msub> <mi>B</mi> <mi>w</mi> </msub> <mo>=</mo> <msub> <mi>f</mi> <mi>H</mi> </msub> <mo>-</mo> <msub> <mi>f</mi> <mi>L</mi> </msub> <mo>=</mo> <mfrac> <mrow> <mn>0.331</mn> <msub> <mi>c</mi> <mn>0</mn> </msub> </mrow> <mrow> <msubsup> <mi>d</mi> <mrow> <mi>c</mi> <mi>min</mi> </mrow> <mn>0.40</mn> </msubsup> <msubsup> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> <mn>0.46</mn> </msubsup> <msubsup> <mi>l</mi> <mi>c</mi> <mn>0.12</mn> </msubsup> <msubsup> <mi>w</mi> <mi>c</mi> <mn>0.02</mn> </msubsup> </mrow> </mfrac> <mo>-</mo> <mfrac> <mrow> <mn>0.103</mn> <msub> <mi>c</mi> <mn>0</mn> </msub> </mrow> <mrow> <msubsup> <mi>d</mi> <mrow> <mi>c</mi> <mi>max</mi> </mrow> <mn>0.71</mn> </msubsup> <msubsup> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> </mrow> <mrow> <mo>-</mo> <mn>0.13</mn> </mrow> </msubsup> <msubsup> <mi>l</mi> <mi>c</mi> <mn>0.38</mn> </msubsup> <msubsup> <mi>w</mi> <mi>c</mi> <mn>0.04</mn> </msubsup> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> <mo>;</mo> </mrow>

Wherein d_cmaxFor the maximum wave height of ripple pipe unit, d_cminFor the minimal ripple height of ripple pipe unit, l_cFor ripple The width of pipe unit ripple, w_cFor ripple interval, c₀For the velocity of sound, f_LFor the lower frequency limit of effective noise elimination frequency band, f_HEnd for the upper limit Frequency, B_wFor noise elimination bandwidth.

3. a kind of wideband high frequency silencing noise unit according to claim 1, it is characterised in that：The ripple pipe unit (2) to be U-shaped.

4. a kind of wideband high frequency silencing noise unit according to claim 1 or 2 or 3, it is characterised in that：Described width Frequency band high-frequency noise muffling unit transmission loss 20db (A) bandwidth reaches more than 2000Hz.