SU1353900A1 - Noise muffler - Google Patents

Abstract

The invention relates to the design of noise suppressors, mainly for pre-installed installations and power installations. The purpose of the invention is to increase the efficiency of the silencer. The perforated insert (PV) 3, coaxial with the body (K), is made in the form of a cylindrical shell of a honeycomb structure. In cell cells PV 3, there is a sound-absorbing filler (ZPN) 10, made of capillary-porous material. The outer surface of PV 3 is provided with a winding 1I in the form of strands placed in layers and crosswise. To 1 m. Also implemented in the form of a cellular structure. Cell cells of insert 3 and K 1 are filled with a transverse size not exceeding the wavelength of the largest component of the spectrum of the muffled noise. ZPN 10 separates the gas flow into separate streams when passing through the ZPN IO capillaries and actively absorbs energy (L somal co r)

Description

This means that sound vibrations propagate in the gas stream due to friction on the walls of the capillaries. This provides a significant reduction in hydraulic resistance.

I

The invention relates to mechanical engineering, in particular, to power and papermaking engineering, in particular to a silencer m. Mainly pneumatic installations and power installations,

The purpose of the invention is to increase the efficiency of the silencer.

FIG. 1 shows a muffler, a longitudinal section; figure 2 is the same, the variant with the perforation of the housing in the form of holes and the winding of the housing and the insert of the grid; on fig.Z - the same version of the cellular structure of the housing; figure 4 - section aa on figi; fig.Z - section BB on fig.Z; figure 6 is a view In figure 3; figure 7 is a view of G in figure 2; in Fig.8 is an element of the cellular structure of the housing (split ring); figure 9 - element of the cellular structure of the insert (ring); figure 10 is an element of the cellular structure of the housing, (edge); figure 11 is an element of the cellular structure of the insert (edge); Fig. - diagram of the interaction of sound waves with the design elements of a silencer; Figure 13 shows the velocity distribution diagrams in the gas stream; Fig. 14 shows pressure distribution diagrams in a gas stream.

The silencer includes a housing 1, an inlet pipe 2 with a front skirt, one having an inner diameter d, a perforated insert 3 with an inner diameter dg ,, coaxial with the body 1 and a blind front wall 4. The front shaft chuck 2, body I and the end wall 4 bolted connections. The centering of the insert 3 in the housing 1 during assembly is provided by a circular outflow on the end wall 4 with a diameter d equal to the inner diameter

a silencer and a significant degradation of its sound-absorbing ability. In addition, the danger of excessive moisture in ZPN 10 and frost in the silencer is eliminated, 6 h, n, f-ly, 14 ill.

insert 3, made in the form of a cylindrical shell honeycomb structure. The honeycomb structure of the insert 3 is formed by a system of rings 5 with an inner diameter d and ribs 6 of length H, respectively, perpendicular and parallel to the axis of the device and having the same width h ,. Rings 5 along the outer perimeter are provided with radial slits 7 with a step of 1, and ribs 6 along one side are provided with slots 9 perpendicular to it with a step of Ij. The depth of the slots 7 and 8 1, and width - respectively

S, and. When assembling the insert 3, its rings 5, the number M of which is equal to the number of slots 8 on the edges 6, are combined with their slots 7 with the slots 8 in the edges 6. At the same time, the number of edges

N is equal to the number of cuts 7 on the rings 5.

Between the indicated sizes and the numbers there are the following relations:

h 2 (2b)

NT H.

 m;

The width of the slots 7 on the rings 5 S is equal to the thickness of the ribs 6, and the width of the slots 8 on the ribs 65, the thickness of the rings 5. The edges of the ring 5 along the inner perimeter (facing the axis) and the corresponding edges of the ribs 6 can be made pointed. The ribs 6 and the rings 5 are bonded to each other after assembly, for example, by welding. Welding or otherwise may be

I are fastened to the edges 6 only the most

upper and lower rings 5, which provides sufficient strength soto-.

 one

B, :: -;

i;

1 i- - - -7 -.

(1) (2) (3)

313

The design of the insert is out of place. It is possible to place the slots 7 along the inner perimeters of the rings 5. This somewhat complicates the ringing of the rings 5, the assembly of the insert 3 and the body 1, but increases their strength.

As a result of the assembly, an insert 3 of cylindrical shape with an inner

more than 3 cm, if „11500 Hz. At that

The same diameter d, the outer diameter at the same time by the structural consideration d and height H of the honeycomb structure. The height of the cell is 9 h, i.e. equal to the width of the rings 7 and the edges 8, and the transverse dimensions of the cells 9 have a height of 1 and a maximum width of 1, respectively, and the smallest h, satisfying relations

1, 11 -S. ;

(4) (5) (6)

For example, with the overall small overall dimensions of the designed silencer, dimensions 1 and 1 of the cellular structure of the insert 3 can be selected15 less than A ;, defined by formula (7), since the magnitude of the sound attenuation effect does not decrease and 7 without reducing the efficiency of the silencer can

g,

 - da

W,

-S,

1, i; -§2

(4) (5) (6)

The lateral dimensions 1 and 2 of the cells 9 of the insert 3 when designing a silencer are not exceeding

The dpins of the waveform of the largest frequency-25 pillary-porous material, which influences the spectrum of the muffled exhaust noise.

The length of the sound wave 7 is determined by the formula

measures ultra-super-thin fiberglass. The outer cylindrical surface of the insert 3 is provided with a winding 11 formed by layered or cross-section.

-

C is the speed of sound propagation in the gas stream emitted through the inlet pipe 2 into the internal cavity of the silencer, m / s;

f - upper bound of frequency

m

exhaust noise spectrum silenced by a silencer, Hz.

35 is held on the outer surface of the insert 3 by a pinch formed by the cords (Lig.7), crosswise through the holes in the edges of the mesh 12. The diameters of the threads or wire,

The magnitude of the speed of sound C, of which 40 is made, is winding 1I,

It is based on reference data, based on the known temperature, pressure and composition of the gas stream. The frequency f is either taken equal to the highest frequency in the spectrum of the muffled noise, at which the level of the specified exhaust noise exceeds the maximum permissible point (at the workplace, in the working area) set by GOST, or takes 50 with an equal to 11,500 Hz - upper bound frequency the noise spectrum, normalized by the state standard specification, if the upper limit of the spectrum of the silenced noise is not precisely defined (for example, when designing a silencing device intended for serial production and using it to silence and noise of various machines, spektlezhat in the range 0.3-3.0 mm, the packing density of the fillers on the sound absorption in the cells 9, 10 of the insert 3 in the range 10-200 kg / m, so that x

The 45 cross section of the capillary filler 10 is 0.995-0.95. The bulk density of the winding threads of the winding 11 and the living section of the grid 12 lie in cases 0.7-0.95.

Winding filaments or wire winding II (or mesh 12) on the outer surface of the insert 3 characterizes with an average bulk density B, the value of which with uniform

55 winding is calculated by the formula

AT.

Ob-rv L

H

(eight)

where t is the mass of the winding I1 of the insert 3, kg;

which muted noise are of high frequency nature).

Thus, “it is practically limited to 3 cm at m / s (the speed of sound in air at 20 ° C and normal atmospheric pressure). Values 1 and 1i can be

more than 3 cm, if „11500 Hz. At that

same time on constructive considerations

- but by constructive consideration

For example, with the overall small overall dimensions of the designed silencer, dimensions 1 and 1 of the cellular structure of the insert 3 can be selected15 less than A ;, defined by formula (7), since the magnitude of the sound attenuation effect does not decrease and 7 without reducing the efficiency of the silencer can

20 be reduced to 2 mm (mesh with 2x2 mm cells and more acoustically transparent).

The cells 9 of the insert 3 are filled with sound absorbing filler 10 of capillary-porous material, for example

measures ultra-super-thin fiberglass. The outer cylindrical surface of the insert 3 is provided with a winding 11 formed by layered or cross-section.

30 winding cotton or synthetic yarn, or winding metal wire. The winding 11 may be made of one or more layers of the grid 12, the latter

35 is held on the outer surface of the insert with 3 holes formed by cords (Lig. 7), crosswise threaded through holes in the edges of the mesh 12. The diameters of the threads or wire,

40 of which winding 1I is performed,

0

lie in the range of 0.3-3.0 mm, the packing density of the sound-absorbing filler 10 in the cells 9 of the insert 3 is in the range of 10-200 kg / m, so that the living section of the filler capillary 10 is 0,995-0, 95 The bulk density of the winding threads of the winding 11 and the living section of the grid 12 are in the range of 0.7-0.95.

Winding filaments or wires of winding II (or grid 12) onto the outer surface of the insert 3 is characterized by an average bulk density B, the value of which at uniform

5 winding is calculated by the formula

AT.

Ob-rv L

H

(eight)

where t is the mass of the winding I1 of the insert 3, kg;

outer diameter of the insert 3, m;

specific mass of winding material 11, kg / m

winding thickness

where s

(9)

at,

If the winding II is unevenly wound — its density increases along the silencer axis away from the inlet 2, for example, according to a linear law, the average volumetric winding density is calculated by the formula

D .р; (,

i 6g - winding thickness 11

insert 3, respectively, at the front cover of the inlet pipe 2 and the end wall 4.

The winding of a given density of the winding 1 1 and the uneven density of its winding are provided by the use of threads and wires of different diameters or nets of different numbers.

The iguma silencer housing 1 is made in the form of a thin-walled cylindrical shell with a diameter of wall thickness 8 with flanges for connecting the front cover of the socket 2 and the end wall 4, respectively, with diameters P and D |. The side surface of the housing 1 is perforated with holes in the form of longitudinal slits 13 of length 1p. and width S or in the form of perforation holes 14 having diameters d. The coefficient of the living section (the ratio of the total area of the longitudinal slits 13 or perforation holes 14 to the side surface area) of the housing 1 is in the range of 25-0.9. The length of the longitudinal slots 13 is 1-0.7-0.95 N, where H is the height of the body. The width of the 13 "slots and the hole diameters for increasing the noise damping effect and reducing the hydraulic resistance of the body 1 can be accomplished by assembling a honeycomb structure similar to the design of the insert 3. In this case, the honeycomb structure of the body 1 is formed by systems of mutually perpendicular rings 5 (Fig.8) of width h with the notch mi 16 along the outer perimeter going in increments of 1h, depth bj and width o, and ribs 17 (figure 10) of length Hj, width h and with slits 18 on one side, going in increments of 1 „depth b and width & 4 - 5 points by adjacent rings 15 and Brahmi 16 cell cells 19 have a height If, and the greatest width is 1, and the smallest n ,. Between the indicated dimensions of the honeycomb-housing structure 1, the following size relations (1) to (6) are the same as for the honeycomb structure of the insert 3

1 P2.

2 2

T (N7

Mi

M.

20

25

P

four

.2Ы.

(12) (13) (14)

thirty

35

g

1, 1 1

2

 IT De N7

. -S

four ,

(15)

(16) (17)

where Mj and N

the number of combs 19 in the housing I, respectively, along the axis and along the circumference.

The lateral dimensions of the cells 19 of the cellular to-design housing 1 1 and 1, as well as the cells 9 of the insert 3; made not exceeding the longest wavelength D frequency component

Stage 14 of the perforation d lies within the spectrum of the noise suppressed, determined to be 3–20 mm.

Thus, the pitch between the longitudinal slits 13 along the circumference 1 ,, and the distance between adjacent perforation holes 14 around the circumference and along the axis in the case of a square arrangement of the holes 14 a are determined from the ratios

formula (7).

The inner diameter d, of the housing 1 of the honeycomb structure is determined by the ratio

dK DK - 2h.

The inner diameter of the housing 1 d C is greater than the outer diameter of the insert d by twice the thickness of the winding 11 of the insert 3.

a, hl ;;

(10) (11)

In order to increase the noise suppression effect and decrease the hydraulic resistance, the body 1 can be made by assembling a cellular structure similar to the structure of the insert 3. At the same time, the cellular structure of the body 1 forms systems of mutually perpendicular rings 5 (Fig. 8) of width h with slots 16 along the outer perimeter, going with step 1h, depth bj and width o, and edges 17 (figure 10) of length Hj, width h and with slots 18 on one side, going with step 1, depth Ъ wide & 4 limited by neighboring by rings 15 and edges 16, cellular cells 19 are high that If, and the greatest width is 1, and the smallest n ,. Between the indicated dimensions of the honeycomb-housing structure 1, the following ratios of dimensions (1) to (6) are the same as for the honeycomb structure of the insert 3

1 P2.

2 2

T (N7

Mi

M.

0

five

P

four

.2Ы.

(12) (13) (14)

0

five

g

1, 1 1

2

 IT De N7

. -S

four ,

(15)

(16) (17)

where Mj and N

the number of combs 19 in the housing I, respectively, along the axis and along the circumference.

The lateral dimensions of the cells 19 of the cellular to-design housing 1 1 and 1, as well as the cells 9 of the insert 3; made not exceeding the longest wavelength D frequency component

noise spectrum,

formula (7).

The inner diameter d, of the housing 1 of the honeycomb structure is determined by the ratio

dK DK - 2h.

The inner diameter of the housing 1 d C is greater than the outer diameter of the insert d by twice the thickness of the winding 11 of the insert 3.

The width, j of the slits 16 on the rings 15 corresponds to the thickness of the ribs 17, and the width of the 4 slits on the ribs 18 to the thickness of the rings 15.

The outer cylindrical surface of the housing 1 is covered by a filament or wire winding 20, similar in purpose and execution to the winding 11 of the insert 3, or a grid 21 similar to the grid 12, held on the housing 1 by lacing (not shown). In this case, as in the case of the insert. 3, the density of winding 20 on housing I is the same or increasing away from inlet 2.

To simplify the assembly of the silencer and to ensure that the inner surface of the housing 1 fits snugly to the outer surface of the insert 3 with a winding 11, whose thickness is of an indefinite value, depending largely on chance, especially when winding threads or wire, the rings 15 of the housing 1 are provided with a through radial slot 22 (Fig. 8) and the assembly of the housing 1 is carried out in such a way that the slots 22 lie in the same plane. As a result, the body 1 of the honeycomb structure is cut through the axially through slot, and when assembling the entire device, the body 1 is put on the insert 3, and then the compression of the case 1 on the insert 3 is carried out with the help of screws with nuts threaded through the holes in the ribs 17, located on both sides of the through slot, and then the front cap of the nipple 2, the end wall 4 is attached to the housing 1, and the outer winding 20 is applied.

The flanges of the case 1 of the honeycomb structure are made in one piece with the upper and lowermost rings 15, the outer diameters of which are increased compared with the outer diameter of the case D to the values of the diameters of the front joint of 2 Dy and the end wall 4 D. To reduce the dimensions of the silencer, the diameters of the cap of the nozzle 2 and the walls 4 can be equal to the diameter of the housing 1, and then the diameters of the flanges of the housing 1 are also chosen to be equal to its diameter: the inner diameter of the inlet 2 d. when designing a silencer

.

-

is chosen to be equal to the internal diameter of the outlet of the pneumatic (energy) machine, which is intended for damping noise, the remaining main structural dimensions are determined by

performance characteristics and features of the operating cycle of the machine being loaded.

The muffler works as follows.

The gas flowing out of the mechanism with a speed usually close to sound is continuously or periodically supplied through the inlet 2 attached to it into the internal cavity of the silencer, from which, under the pressure difference, pass through the pores of the sound-absorbing filler 10 filling the cell 9 of insert 3. external winding II insert1 with „

 - ki 3, through the annular space and

then between the insert 3 and the housing 1 and through the holes 14 of the perforations and the capillaries of the winding 20 of the housing 1 or through the cells 19 and the capillaries of the winding 20 20 of the housing 1 flow into the atmosphere. In this case, the outflow of a jet of gas into the internal cavity of the silencer is accompanied by noise, the sound power of which

is determined by the formula 25 p.

Р Y 1-1О-Г РО -0

where X is the proportionality coefficient:

t.

(18)

thirty

35

40

-

P is the density of the gas in the jet;

V is the jet velocity at the shear e of the inlet 2;

PQ is the density of the gaseous medium at the inlet nozzle 2;

 the speed of sound in a gas environment. The frequency spectrum of exhaust noise is usually continuous with a weakly expressed maximum and with weakly expressed discrete components at frequencies equal to and multiple to the Strouhal frequency, as well as the frequency of the mechanism's response, if the exhaust gas at the exhaust is periodic in nature and is determined by calculation. reference books or as a result of direct measurements.

The front of the exhaust noise sound waves has the shape of a hemisphere with its center in the outlet nozzle 2, so that the sound waves of exhaust noise propagate mainly along the surface of the sound-absorbing filler 10, the fill cells 9 of the insert 3 and are reflected from the end wall 4 according to the diagram (Fig. 12) . The calculation of the values of s-absorption absorption of exhaust noise by frequency bands can be carried out according to the method of calculating the channel

50

(active) silencers. The calculated values of the sound absorption values in the frequency bands JK have the dimension dB / m, and from them in the corresponding bands the sound absorption values are determined by the formula

(nineteen)

TO,

n

uKi, - Lip n where H is the size of the body along the axis

silencer M,

The efficiency of the silencer is maintained on. as high as possible in a wide range of frequencies and when using cellular koHCTpyKUHH insert 3, as well as housing 1, with limited transverse

cell size

9 and 19 1

i

1-, 1, and 1 due to the fact that it eliminates the possibility of the propagation of sound waves in the volume of sound. co-filler filler 10 filling the insert 3, and in the annular space between the windings I1 and 20 of the insert 3 and the housing 1 in the same case, if it is required to ensure uniform, i.e. by approximately the same amount, reducing the noise level in the range of low, medium and high frequencies from 100 to 10,000 Hz, the design of housing I in the form of a shell perforated with holes 14 or longitudinal slots 13 is selected, and if noise reduction is required the exhaust by an amount that increases with increasing frequency, then the honeycomb structure of the housing 1- is selected, and the relative thickness of the air sublayer, 9. If it is required to reduce exhaust noise by 10 - 30 dB, then the total thickness of the insert 3 and the annular cavity or body 1 of the honeycomb structure is chosen within h, + hj 40-150 mm, and the relative thickness of the air sublayer is 0.1-0.3 or h ,, 0.7-0.9.

Case size 1 along the H axis and the direction along the silencer axis, in combination with

  The inner diameter of the insert 3d., by the transducer, propagates sound waves inside the insert 3, emitted by the inlet pipe 2. Possible interaction of the sound waves with the material of the sound-absorbing filler, windings 11 and 20 of the insert 3 and the housing 1 only in the radial direction, at which the greatest effect of sound absorption of the noise energy emitted through the inlet 2 is ensured.

thirty

at

they are made, firstly, on the basis of providing the required average speed Vj. the flow of the emitted gas through the walls of the insert 3 and the housing 1 in cases where the gas flow through the inlet pipe is continuous, with little variation in performance. In this case, the average speed for a given silencer

35 is selected in the range of V. 10–40 m / s. At m / s, the oversized are usually oversized. measures and material consumption of the noise silencer, and at VCP 40 m / s, hydraulic losses of the noise silencer have an excessive amount, and secondary noise generation of power is also possible when the gas flow interacts with the structural elements given the same longitudinal cell sizes 9 and 19, i.e. insert thickness h and the transverse size of the ring 15 h; j between insert 3 and case 1 or the thickness of the cellular structure of the case 1 h, are determined based on the required efficiency and the reduction spectrum of the sound power levels of exhaust noise in standard octave bands in accordance with GOST. If, for example, the exhaust noise level is required to be reduced by 20-40 dB and preferably at low and medium frequencies (up to 500 Hz), then the total thickness h (h, + h or h, h,) must be taken within 100 - 200 mm, and if it is required to reduce the exhaust noise mainly at high frequencies (500 Hz), then the total area should be taken from the limits of h 40–150 mm. The relative thickness should be chosen.

air sublayer h

., + h in pre

affairs h Oh, 1-0,9.

If it is necessary to ensure uniform, i.e. by approximately the same amount, reducing the noise level in the range of low, medium and high frequencies from 100 to 10,000 Hz, the design of housing I in the form of a shell perforated with holes 14 or longitudinal slots 13 is selected, and if noise reduction is required exhaust by an amount that increases with increasing frequency, then the honeycomb structure of the housing 5- 1 is selected, and the relative thickness of the air sublayer, 9. If it is required to reduce exhaust noise by 10 - 30 dB, then the total thickness of the insert 3 and the annular cavity or body 1 of the honeycomb structure is chosen within h, + hj 40-150 mm, and the relative thickness of the air sublayer is 0.1-0.3 or h ,, 0.7-0.9.

inner diameter of the insert 3d., defined

at

they are made, firstly, on the basis of providing the required average speed Vj. the flow of the emitted gas through the walls of the insert 3 and the housing 1 in cases where the gas flow through the inlet pipe is continuous, with little variation in performance. In this case, the average speed for a given silencer

selectable within V. 10–40 m / s. At m / s, the oversized are usually oversized. measures and material consumption of the noise silencer, and with a VCP of 40 m / s, hydraulic losses of the noise silencer are of excessive magnitude, and secondary noise may also form a lower power when the gas flow interacts with the structural elements of this device at high speeds. The calculated average gas flow rate through the filling cells 9 of the insert 3, sound-absorbing filler 10 is determined by the formula

Vcp. . ot, Q (20)

where Q is the gas flow rate through the inlet

pipe 2, m / s; OS - the volume density of the filling with the sound-absorbing filler of 10 cells 9 of the insert 3 lying in this case is in the range of about; ,, 95-0, 995,

or the average volume density of the winding 1 G of the insert 3 Na (or the hull of the body) in this case lies within the limits of ° C, 0.8-0.95; oil, 0.5-0.9. (a value of about is substituted, corresponding to the minimum of

with;

1and 5

ci

and about.,, ) .

The choice of a comparatively higher average density of the winding 20 of the outer cover of the housing 5 in comparison with the winding density I1 of the coating of the insert 3 is due to the fact that for efficiently absorbing the energy of the sound wave propagating along the surface of the layer of sound-absorbing filler 10, behind which there is an air underlayer, it is required higher acoustic permeability of the coatings on both sides of it and at the same time a good ability of the surface limiting the air sublayer to reflect sound vibrations and.

In turn, the acoustic permeability is thin: d; of coatings the higher, the greater their air permeability, therefore, it is possible to regulate the value of acoustic permeability of coatings of a given silencer by the density of their windings 11 and 20.

The outer cover of the housing 1 and insert 3, in addition, additionally absorbs the energy of the exhaust sound, has a microporous structure similar to that of sound-absorbing filler 10. However, the magnitude of this sound absorption is relatively small: it is 1-3 dB at low and medium frequencies (up to 500 Hz) and 3-10 dB - at higher frequencies. However, this sound absorption effect should be taken into account in the acoustic calculation of the intended device.

Additional conditions, in accordance with which the values of dg and H are specified by the formula (17), are the observance of the inequality

dfi d ",

and also, in some cases, the condition for adjusting the cavity of the silencer, bounded by the inner surface of the insert 3 and the roof strip 2 and the end wall 4, resonates to the fundamental frequency of the silenced exhaust noise d (- of which the value H is taken equal to a quarter of the length

the sound waves at the main frequency of the muffled noise - by the formula

 axes

 --fl

(21)

five

0

five

0

five

0

five

0

five

where C is the speed of sound propagation in the gas filling the silencer cavity, m / s.

The choice of the size H according to the formula (16) gives a particularly large effect of noise-damping in cases when the tonal spectrum of the exhaust noise occurs, i.e. such a spectrum, which contains one or several frequency components, not less than 10 dB above the levels of the other frequency components of the spectrum. At the same time, the internal diameter dg of the insert 3 should be as small as possible, which ensures the most efficient noise absorption by this device. Moreover, the larger the H / dg ratio, the greater the sound absorption effect of this device.

The role of the windings 11 and 20 of the insert 3 and the housing 1 is not limited to their participation in the active absorption of sound energy together with sound-absorbing filler 10, but it is more significant and ultimately contributing to the total effect of reducing the sound power of exhaust noise, comparable to the acoustic efficiency of the sound-absorbing filler

10 and the air sublayer behind it, since the windings indicated

11 and 20 have a significant effect on the gas-dynamic processes in the silencer, on which, in turn, depends both its total efficiency and the emissivity of the inlet pipe 2, which can be reduced to some extent by choosing the winding density of the windings 11 and 20.

The gas jet flowing through the inlet 2, having its initial velocity at its cut, is then braked inside the insert 3 to zero at the end wall 4, for example, according to a linear law, if the air permeability of the walls of the insert 3 and the housing 1 together with the coatings is constant along the height of the device (curve 1 on Fig). By the same linear law (curve 3 in Fig. 14), for example, the pressure increases over the height of the body 1 from the value of PO (pressure at the inlet section

.tube 2) to the value of P defined by Lormule

-M p.-d,

(22)

where p is the density of the gas in the jet; M is the coefficient of deceleration of the jet to the approach to the end wall 4; g - free fall acceleration.

The pressure differential between atmospheric and inside the silencer causes the outflow of the ejected gas through the device walls in the radial direction with a flow height that is proportional to the pressure differential.

With an uneven density of the windings 1 1 and 20 on the outer surface of the insert 3 and the housing 1, increasing from the front hatch of the inlet pipe 2, but such that the full hydraulic resistance of the silencer is maintained at the same level, the velocity of the gas stream inside the silencer decreases from V to Zero (curve 2 in Fig. 13), according to a nonlinear law, also increases the pressure, however, already up to P ,, smaller P, since the areas limited by curves 4 and 3, 1 and 2 must be the same due to that remains unchanged in both cases The reason for the hydraulic resistance of the device and the amount of mechanical energy of the outgoing gas jet. As a result of reducing the maximum pressure drop between atmospheric pressure and pressure P inside the silencer at the end wall 4, as well as equalizing the pressure drop over the height of the device, the maximum of local (per unit area) flow is reduced the ejected gas at the end wall 4, as well as the overall alignment of the gas flow through the walls along the height of the cylinder. Moreover, since the hydraulic losses are proportional to the 2nd degree of speed, and the sound power of the secondary sound formation is proportional to the 6-8th degree of the flow velocity, the overall hydraulic resistance of this device decreases accordingly (and therefore it becomes possible to increase the average density of the winding 20 of the housing 1 and the average density of the winding 1 of the insert 3 at a given value of hydraulic resistance and thereby increase the acoustic efficiency of this

353900 14

- devices) If sound is reduced

power of the secondary noise in the gas-dynamic interaction of the outgoing jet with structural elements

5 silencer.

This also reduces the danger of wetting and frosting, and the risk of loss of efficiency or complete withdrawal from it.

10 pgum silencer, especially with a high moisture content of the emitted gas. It is known that liquid vapors contained in the ejected gas can condense into liquid wipes if the temperature of the gas jet decreases due to a decrease in pressure at the cut-off outlet 2 below the dew point. These droplets are delayed, deposited in

20 capillaries of sound-absorbing filler 10 and reduce its sound-absorbing ability. In addition, they can freeze and destroy the capillary structure of the filler 10 at negative temperatures of the surrounding atmosphere and even at room temperature with deep supercooling of the gas jet and poor heat exchange with the environment. Hazard 25

thirty

The excessive moisture of the sound-absorbing filler 10 and the frosting of the silencer 9 is eliminated or reduced to a minimum, and the possibility of using the silencer silencer c. sv ei s

5 this greatly expands due to the fact that when equalizing the differential pressure and flow along the axis of the device due to the uneven winding of the yachts 11 and 20, local

 pressure drops in the gas flow, which means that it is easier to organize the discharge of gas into the atmosphere through the muffler at temperatures above the dew point throughout its volume. This is also largely due to the air permeability of the SGOO% living cross-section) of the cellular structure of the insert 3 and the housing 1, which is almost completely filled with air;

The sound-absorbing filler 10 filling the cells 9 of the insert 3 plays a double role in reducing the sound power of the gas flow emitted through the outlet 2: separates the gas flow into separate streams passing through the capillary ry filler 10, which in itself contributes- 0

It reduces the noise of the gas flow and actively absorbs the energy of the sound vibrations propagating in the gas flow due to friction on the walls of the capillaries. At the same time feature 5 clap muffled cars. At t; T,

the calculated maximum value of the excess pressure P in the cavity of the pressure device, created at each successive exhaust, is calculated by the formula

p .. / 01

 --v, p, d (dl .p c,. V) -

foot device, m; dg — insert inner diameter, m; d is the internal diameter of the inlet pipe 2; - critical (maximum) gas outflow rate through the inlet 2, m / s (for approximate calculations it can be taken equal to 300 m / s) (- dimensionless coefficient of the exhaust gas pulse shape, showing what part of the mass of gas passed through the inlet 2 in the subcritical flow regime (usually lies within the limits (0.7–1.0 and, in approximate calculations, it is assumed (jf 0.95); T, is the duration of the exhaust gas in the supercritical mode.

The duration of the exhaust into the atmosphere, increasing due to the attachment to the outlet of the silenced machine of the proposed muffler, is increased to

25

The noise silencer is that the cells 9 of the insert 3 have limited transverse dimensions, and their cross-sectional area increases in the direction of the outer surface of the housing 1, and that the gas flow flows from the inside to the outside of the device. This provides the conditions for reliable retention of the filler, where E is atmospheric pressure. Pa; 10 in cells 9 with external only — H — height of the working cavity of the silencer — covering winding II, and there is no need for additional application for this purpose of any devices, for example, a design like a perforated cylinder adjacent to the inner surface of the insert 3. As a result, the cylindrical surface of the insert is formed practically only by the porous surface of the sound-absorbing filler 10, which, with the same overall dimensions of the device, provides a significant reduction in hydraulic resistance to the silencer and at the same time a significant (10-20 dB) increase in its sound-absorbing ability. This is facilitated by the use of the tapered edges of the rings 5 and the ribs 6, forming the honeycomb structure of the insert 3 and facing the axis of the housing 1. I

When using a noise silencer to reduce the noise of machines operating in a periodic (with a period T) gas release for a period of time T, moreover T (on the exhaust of a pneumatic cylinder, a plate compressor, etc.), the recommended recommendations for its design and calculation efficiencies are generally maintained, with the exception that the estimated average speed V.,., in this case can be taken on a much larger value. In addition, in this case, there is the possibility of additional use for damping the noise of the internal cavity of the device as a buffer, pressure equalizer. Hydraulic resistance30

35

40

 G, g-p-C-, (24)

 dg

where 1Х, „is the dimensionless linear coefficient of the living cross section permeable to the structural elements of the damping device;

"- the dimensionless reduced coefficient of local resistance of the silencer.

When approximate calculations choose

50

such values oi-n and „, in which their product for the same structural element (sound-absorbing filler 10, windings II and 20 of insert 3 or housing 1) gives the minimum value, by the contribution of the remaining permeable elements to hydrated values of oi- n and „, in which their product for the same structural element (sound attenuating filler 10, windings II and 20 of insert 3 or housing 1) gives a minimum value, while the contribution of the remaining permeable elements to the device's control and average speed

gas flow Vj. can be significant resistance device

relatively increased compared to this is neglected.

In this case, it is only important that the pressure in the cavity of the silencing device, within the period of its response, T be compared with the atmospheric pressure, until the next batch of gas arrives at the next equalized maximum excess pressure P in the cavity of the damping device, which is generated at each next, exhaust, calculated by the formula

p .. / 01

 --v, p, d (dl .p c,. V) -

where E is atmospheric pressure. Pa; H - the height of the working cavity silencer-

foot device, m; dg — insert inner diameter, m; d is the internal diameter of the inlet pipe 2; - critical (maximum) gas outflow rate through the inlet 2, m / s (for approximate calculations it can be taken equal to 300 m / s) (- dimensionless coefficient of the exhaust gas pulse shape, showing what part of the mass of gas passed through the inlet 2 in the subcritical flow regime (usually lies within the limits (0.7–1.0 and, in approximate calculations, it is assumed (jf 0.95); T, is the duration of the exhaust gas in the supercritical mode.

The duration of the exhaust into the atmosphere, which increases due to the attachment to the outlet of the silenced machine of the proposed muffler, is increased to

where E is atmospheric pressure. Pa; H - the height of the working cavity silencer-

0

 G, g-p-C-, (24)

 dg

where 1Х, „is the dimensionless linear coefficient of the living cross section permeable to the structural elements of the damping device;

"- the dimensionless reduced coefficient of local resistance of the silencer.

When approximate calculations choose

0

such values oi-n and „, in which their product for the same structural element (sound-absorbing filler 10, windings II and 20 of insert 3 or housing 1) gives the minimum value, by the contribution of the remaining permeable elements to the guide

The calculated value j must satisfy the condition

 ii

(25)

where T is the frequency of emissions.

. Strength calculation using formula (16) and hydraulic calculation using formulas (24) and (25) ensure high efficiency and reliability of the noise silencer in the periodic wipe mode of the silenced machine.

Claims (7)

1. A noise suppressor comprising a cylindrical body, an inlet pipe, a blind end wall and an outer winding, a coaxial perforated insert and a sound absorbing element, the side surface of the case is perforated, characterized in that, to improve efficiency, the perforated insert is wired in the form of a cylindrical shell of a honeycomb structure, soundproofed; the drive is placed in the cell cells of the insert and made of a capillary-porous material, and the outer surface l insert is equipped with a winding in the form placed in layers five 0 five 0 and cross-filaments, the cells being made transverse in size, not exceeding lig-cm wavelength of the largest component of the spectrum of the muffled noise. 2. A silencer pop. 1, distinguished by the fact that the body is made in the form of a honeycomb structure, moreover, the cell cells of the body are made of a transverse size not exceeding the wavelength of the largest component of the spectrum of the muffled noise. 3. The silencer in accordance with claims 1 and 2, which is characterized in that the insert winding is made of a grid. 4. The silencer according to claims 1–3, of which is the winding of the body from the grid, 5. The silencer according to claims 1-4, of which is due to the fact that the winding of the housing is made with a density exceeding the density of the winding of the insert. 6. The silencer of Claims 1-5, which is based on the fact that the density of the body winding and the insert is fulfilled with densities increasing away from the inlet manifold. 7. The silencer according to claims 1-6, which is readable. the fact that the edges of the cell cells of the insert, facing the axis, are made pointed. Vuz. 6 ig.7  B sixteen FIG. eight "about 9g.9 9u2. iO 9iie. eleven . 9.12 h, jH H P, ffa Editor A. Kozoriz Compiled by V. SlavNIKOE Tehred A. Kravchuk Proofreader m.Maksimishiyiets Order 5677/29 Circulation 482Subscription VNIIPI: USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 p p About (NIC fpa. one