RU2367807C2 - Multi-section cellular silencer to be mounted on gas turbine intake - Google Patents

Abstract

FIELD: engines and pumps.

SUBSTANCE: invention relates to power plant silencers and can be used at axial compressors of power drive for gas-compressor turbine plants. Multi-section cellular silencer fitted on gas turbine plant intake consists of separate jointed sections, each comprising consecutively arranged subsections accommodating noise-absorbing elements made from perforated enclosure that houses noise-absorbing material. Sections are made from metal carcass. Section lateral, bottom and top walls are covered with a layer of noise-absorbing material coated, inside the section, with perforated plate. Aforesaid rhomb-like noise-absorbing elements are integrated into modules arranged along subsection cross section to make vertical diagonal of each noise-absorbing element parallel to lateral walls of the section. Subsections are formed by vertical posts fitted on top and bottom walls of each section and furnished with cuts for noise-absorbing module to be attached.

EFFECT: expanded spectrum of sound vibration absorption, higher efficiency of absorption on unit length of noise absorber.

2 cl, 6 dwg

Description

The invention relates to silencers of power plants and can be used in axial compressors of energy and drive (gas pumping) gas turbines of small, medium and partially high power, as well as in high-speed axial and centrifugal air turbochargers operating in various climatic zones in metallurgy, chemistry, energy and other industries.

Such designs are active type silencers. They use the principle of spatially uniform distribution of sound-absorbing material over the passage section of the silencer. This principle is used in plate silencers, which are most widely used in the practice of both domestic and foreign turbocompressor engineering. The plate silencer is a series of parallel shields of sound-absorbing material inserted into a rectangular box, dividing the interior of the silencer casing into a series of parallel channels. The thickness of the plates and the distance between them are the same throughout the channel section. The sound attenuation in the silencer is resonant in nature. The absorption maximum is observed at a frequency satisfying the equality:

where δ is the plate thickness, m; C _p - the speed of sound in sound-absorbing material, m / s; f _max - the frequency at which the maximum absorption, Hz.

The value of sound attenuation depends not only on the thickness of the plates, but also on the distance between them. To effectively reduce noise, the distance between the plates should be no more than half the wavelength λ of the muffled sound.

where C is the speed of sound, m / s; f is the frequency of sound vibrations, 1 / s.

When the compressor is operating, due to air pulsation, a broadband noise is emitted during suction with a peak of siren noise superimposed on it reaching 140 dB.

Discrete maxima correspond to blade frequencies:

where n is the number of revolutions of the rotor per minute,

z _i - the number of blades of the i-th stage.

Converted gas turbine engines having high compressor shaft speeds and a maximum of noise radiation shifted to the high frequency region are finding increasing use in modern energy. To effectively reduce noise in the frequency range 4000-8000 Hz, the thickness of the plates and the distance between them should be about 40 mm, which at high air flow rates and, accordingly, with large sizes of plates causes known technological difficulties. The use of thicker plates with high-frequency radiation, installed at intervals greater than half the sound wavelength, violates the diffuseness of the field. The sound field becomes uneven in cross section and a "radiation effect" occurs, consisting in the formation of an axial beam of sound energy, on which the lining of the plates and the walls of the body has a weak effect. In this case, the attenuation per unit length of the muffler decreases, and its dimensions, respectively, grow.

A sound-absorbing structure is known in which the casing of the sound attenuation unit is mounted directly on the horizontal support beams of the CVOU, and the output vertical flange of the sound attenuation unit is connected to the vertical flange of the vertical shaft, in which the air flow is rotated 90 ° twice and the inner walls of which are lined with sound-absorbing material, and in the block a plate silencer was installed with a plate thickness of 30-100 mm, a plate height (size along the air) of 1.00 ÷ 2.00 m, and plate lengths of up to 3 m (see Ter Hove AL "Combating noise at compressor stations." - L .: Nedra, 1985. - s.s.105-113).

Known silencer has several disadvantages. With a plate thickness of 80-100 mm, silencers have a relatively low efficiency in the high-frequency range, which complicates their use in modern high-speed turbomachines. At smaller thicknesses, the plates lose their rigidity, which complicates the provision during assembly of equal gaps between the plates over the entire cross-sectional area of the muffler. Serious technological difficulties are caused by the task of ensuring a uniform arrangement of sound-absorbing material on the surface of the plate, as well as preventing caking of the material during long-term operation. A serious disadvantage of this method of forming absorbing structures is a sharp decrease in the efficiency of sound absorption at low frequencies. With plate thicknesses of 30–50 mm, an additional low-frequency silencer may be required in the intake duct.

In addition, the manufacturing process of the plates is very time-consuming, because requires the use of mainly manual labor.

Cellular silencers are widely known as an active silencer with a uniform spatial distribution of a sound absorber in the air duct (see, for example, Fig. 12.23. Monographs: “Noise Reduction in Buildings and Residential Areas” / G.L. Osipov, E.Ya. Yudin, G.Hyubner et al .; - M .: Stroyizdat, 1987.- 558 p.). This muffler can be considered as a series of parallel tubular mufflers of rectangular shape, laid close to each other and to the walls of the duct in the place of its expansion under the muffler. Absorber packing is performed in the gaps between the inner and outer perforated or mesh walls of the tubular silencers. In tubular and cellular silencers, cyclic air flows through the central channels and noise energy is distributed in the air, at the same time, sound-absorbing material is located on the periphery of each channel and sound energy is distributed in the sound-absorbing material in one plane.

Although the effectiveness of cellular silencers is significantly higher than plate-type silencers, especially in the high-frequency region, cellular silencers have not been widely used due to the great structural complexity and poor technological preparation of the production proposed by developers for use in the industry of cellular silencers.

The closest technical solution to the proposed invention is a multi-section silencer, consisting of separate, series-connected sections, each of which is made of sound-absorbing material (ZPM), lined with a perforated shell from the inside, each section consisting of subsections in which single sound absorbers are made made of spherical forms from hemispheres from the perforated material in which ZPM is enclosed. The subsection is made in the form of a rectangular pipe covered with perforated walls covered with sound-absorbing material, in the center of its section there are single sound-absorbing elements forming a square, the sides of which are parallel to the walls of the subsections.

The hemispheres are fixed to each other and in subsections by means of fasteners in the form of rods and rings (RF Patent No. 2280176).

This invention improves the efficiency of sound attenuation by increasing the contact area of the intake air and sound-absorbing material, achieved by filling the casing of the sound attenuation block with rectangular tubular silencers, the walls of which are parallel to the walls of the sound attenuation block. Rectangular tubular silencers inserted into the body of the noise attenuation unit communicate with each other and form a honeycomb array.

However, this muffler does not fully implement the basic principle of the optimum sound attenuation - the uniform distribution of sound-absorbing material and channels for air passage, so that the area occupied by sound-absorbing material is equal to the area of the passage channels.

Making a single perforated half-shell, stuffing it with ZPM and connecting each element and fastening them together and with the subsection housing due to the rod does not provide structural rigidity and is rather non-technological when executed.

The technical task of the invention is the creation of such a design of a cellular silencer suction GTU, which would consist of separate universal modules, including several sound-absorbing elements suitable for use in mufflers of different sizes, and sound-absorbing elements are arranged in such a way that increases the efficiency of noise reduction at low, and at high frequencies, and also facilitates the work of their manufacture and the work of staff.

The technical result that will be obtained by carrying out the invention is to expand the frequency spectrum of the intense absorption of sound vibrations and increase the sound absorption efficiency in a single section of the length of the silencer.

The technical result is achieved due to the fact that in the well-known multi-sectional cellular silencer, consisting of separately connected sections made of a metal frame, each of the side, upper and lower walls of which are covered with a layer of sound-absorbing material (ZPM), lined from the inside of the section with a perforated plate, each of the sections contains successively placed subsections in which sound-absorbing elements are installed made of a perforated shell in which sound-absorbing is placed material made design changes, namely:

- single sound-absorbing elements (rods) having a rhombic cross-sectional shape are combined into modules installed along the entire cross-section of the subsection, so that the vertical diagonal of each sound-absorbing element is parallel to the side walls of the section;

- vertical racks with horizontal slots are attached to the upper and lower walls of each section, forming subsections and used to set the height of the cross section of the subsection, each sound-absorbing module;

- the number of individual sound-absorbing elements in the module and the number of modules correspond to the condition of equality of the areas of sound-absorbing elements and through channels for the passage of air in each subsection.

The accepted arrangement of sound-absorbing elements ensures the uniformity of their placement along the entire transverse channel of the subsections. The combination of several sound-absorbing elements into modules simplifies the assembly of the unit by increasing the manufacturability of their manufacture and simplifies the assembly of the sound attenuation unit.

The rhombic shape of the sound-absorbing element is selected from the condition of ensuring the equality of the areas occupied by the air channels and sound-absorbing elements in the cross section of the block, the technological simplicity of ensuring the uniform arrangement of all sound-absorbing elements relative to the block walls (parallelism of the vertical diagonal to the side walls of the sections), and also providing volumetric (in two mutually perpendicular planes) penetration of sound vibrations in the ZPM of sound-absorbing elements (rods). Such an arrangement of sound-absorbing elements makes it possible to increase the energy dissipation efficiency of sound vibrations, especially at high frequencies.

In addition, the thickness of the sound-absorbing material reinforcing the walls of the section depends on the intensity of the low-frequency components of sound vibrations propagating in the air passing through the sound attenuation unit, i.e. from the power of the low-frequency components of the noise coming from the gas turbine engine to the integrated air preparation device (CVO). The thickness of the layer of sound-absorbing material (wall thickness) of the sections is taken to be equal to or close to equal to half the wavelength corresponding to the average frequency of an octave, at which the sound pressure level exceeds its standard value by a maximum value, compared with the values of excess sound pressure on other low-frequency octaves.

The design of the noise reduction unit and its individual elements is shown in figures 1-6.

Figure 1 shows a General view of the block silencing suction GTU; figure 2 shows a breakout in arrow A; figure 3 - mounting sections of the silencer between themselves; figure 4 shows the design of the noise reduction module; in Fig.5 - a device for installing a sound-absorbing element in a sound attenuation module; and Fig.6 - fastening of a sound attenuation module in a subsection.

Figure 1 shows a copy of a photograph of a prototype of a multi-section cellular noise blocking unit 1 of the gas turbine engine. The frame of the sections of the block is welded from rectangular pipes 2 with a cross section of 140 × 80 × 3 mm and sheathed on the outside with sheet steel with a thickness equal to (depending on the dimensions of the block) d = 3.0 ÷ 5.00 mm. To the upper and lower walls of the housing at the inlet and outlet of each section is welded by n _v uprights 3 forming the sub-section. Sound-absorbing elements are installed in the longitudinal guides of the racks 3 evenly over the cross section, forming sound attenuation modules 4, between which channels 5 for air passage are formed, and the total area of the sound attenuation elements and the total area of the channels in each subsection are approximately equal.

On the breakout along arrow A (Fig. 2), it is evident that the outer sheets of the noise suppression block 6 and 7 are covered with sound-absorbing material (ZPM) 8. From the inside, along the side walls, floor and ceiling, the block is sheathed with perforated steel sheet 9 with a thickness of d = 0.8 mm

If it is necessary to intensify the absorption by the walls of the casing of the low-frequency part of the spectrum, the thickness of the walls of the block and, therefore, the layer of sound-absorbing material can be increased to 200 mm or more due to the use of larger rectangular sections for the manufacture of the frame sections and vertical flanges.

The body of the cellular silencer consists of two sections 10 and 11, tightened with each other by bolt connections 13, and between the sections when assembling the body, in order to reduce transmission of structural noise through the body of the unit, a rubber frost-resistant rubber gasket 12 is installed (Fig. 3).

Figure 4 shows the proposed universal module 4 noise attenuation assembly.

Its body consists of two corrugated sheets 14, which, when connected, form square or generally (at an angle α ≠ 90 °) rhombic openings 15 filled with sound-absorbing material 16, which is wrapped with fiberglass 16a. Each module consists of three elements equipped with covers 17, and in the second section 10 each element has two covers 17, and in section 11 (front) instead of cover 17 a fairing 18 is installed outside to reduce resistance to the air entering the silencer.

Filling the openings of each rhombus with sound-absorbing material is carried out using a special, but rather simple device, the design of which is presented in Fig.5.

The device is a metal tray 19 made of a sheet with a thickness of 0.6-0.8 mm, having a diamond-shaped cross section identical to the cross-section of the opening of the universal module, but having dimensions 1-2 mm smaller than the opening, and the length "L _p " 20-50 mm larger than the length of the corrugated sheet 14 (see figure 4). On one side of the tray, a thrust plate 20 and a handle-rod 21 are welded into it. Fiberglass 22 and sound-absorbing material 16 are successively stacked in the tray 19 along its entire length.

Figure 6 shows the mounting of the universal modules 4 to the racks 3, forming a subsection through the corners 23. The design does not require additional explanation.

Figure 1 (General view) of the prototype of a multi-sectional cellular silencer, in which the bar sound absorbing elements are installed. Block 1 noise reduction is designed to reduce sound pressure, providing the greatest reduction in high and medium frequencies, to a sanitary norm of 80 dBA.

The height of the passage section of the silencer block is taken as a multiple of the height of the universal module 4 (see figures 1 and 4). The width of the passage section of the silencer block is taken to be a multiple of the width of the module housing 4. The area F _{w of the} passage section of the silencer block is determined by the equation:

,

,

where k is the area overlap coefficient for not very small sizes of the sides of the sound-absorbing element and the angles α ° at the vertices of rhombuses, not very different from 90 °, k≈2.0,

Q _ok - volumetric air flow through the noise attenuation unit at the nominal operation mode of the gas turbine engine,

W _W - the average cross-section of the block flow rate in the air channels, m / s; depending on the design features, it is selected in the range from 12 m / s to 30 m / s. The lower values are limited by the cost of the silencer and overall dimensions, the upper ones - by increased hydraulic losses and secondary noise formation in the channels of the silencer.

Sound-absorbing material 16 should be non-combustible, non-toxic, non-explosive, soft to the touch, vibration-resistant material with high soundproof and sound-absorbing properties, protected from blowing by a shell 18 of fiberglass, for example, with a blow resistance of not more than 300 N s / m ² .

Corrugated sheet 14 is obtained by stamping from a perforated workpiece (to ensure acoustic transparency, the perforation coefficient should be at least 0.22) made of steel or stainless steel sheet. Due to the presence of two axes of symmetry on the corrugated sheet (x-x and y-y axes), the second sheet is obtained from the first by 180 ° rotation around the x-axis. The sheets 14 are welded to each other at the points of contact by spot or roller contact welding. Fairings 18 and covers 17 can be made both from metal by stamping, and from frost-resistant plastic or polyethylene on specialized, but widespread and often used equipment.

Using the proposed design of the rod silencer and new sound-absorbing elements, actually combining n rod sound absorbers into one module (three in the considered version), it allows to solve the problem posed in the invention and to obtain a new technical result. Since there is currently no exact method for calculating a rod silencer, its effectiveness has been tested on an acoustic bench on full-scale models of rod-shaped rhombic sound-absorbing elements. The table shows the results of measurements on models with cell sizes: 40 × 40 mm, 60 × 60 mm and 80 × 80 mm, filled with sound-absorbing material ATM-1.

No. p / p Type of muffler, Main characteristics Decrease in sound power levels, dB, at geometric mean frequencies of octave bands, Hz and working part length 1 m 31 63 125 250 500 1000 2000 4000 8000 one d × e = 40 × 40 mm, honeycomb silencer with openings for sound absorbers - - twenty 24 27 42 44 70 80 2 * Honeycomb silencer with openings for sound absorbers d × e = 60 × 60 mm - - 21 19.5 31 37 40 47 fifty 3 Honeycomb silencer with openings for sound absorbers d × e = 80 × 80 mm - - 23 fifteen 34 34 35 35 43 four Plate silencer design NTT ZAO, plates 80 mm, pitch 80 mm - 2.0 3,5 4,5 9.5 14.5 22 26 26.5 5 Plate silencer according to SNiP II-12-77 Appendix 3 Table 3, plates 100, pitch - 200 mm, ZPM - superthin basalt fiber - 2 5 13 twenty 29th 31 25 fifteen 6 Excessive efficiency of silencer line 3 compared with silencer line 4,% - - 557 233 257 134 59 35 62 * Note: the values of the reduction in sound power levels for rods of size 60 × 60 mm were obtained by approximating the data in poses 1 and 3.

Examination of the data in the table shows that using the proposed design of the noise suppression unit allows achieving the claimed result - increasing the sound absorption efficiency at the base length of the active part of the sound absorption element of module 4 both at low and at high frequencies.

As noted in the specialized literature (see Noise Reduction in Buildings and Residential Areas / G.L. Osipov, E.Ya. Yudin, G.Hyubner et al .: Edited by G.L. Osipov, E.Ya. Yudin. - M .: Stroyizdat, 1987, p. 478 and Fig. 12.23), “attenuation in plate mufflers is one caliber slightly less (by 20–40%) attenuation in tubular” mufflers, which form the corresponding cellular muffler.

The table shows that instead of a plate muffler with a plate thickness of 80 mm (row 4 of the table), a honeycomb (honeycomb) muffler with openings for rod sound absorbers 80 × 80 mm (row 3 of the table), attenuation in most octave bands for the proposed muffler significantly higher than in the well-known cellular silencer (see page 6 of the table).

The greater sound absorption efficiency obtained in the experiment for the proposed option is explained by the provision of a larger contact surface for the ZPM-air, as well as the fact that here the dissipation and propagation of sound energy in the ZPM occurs in two mutually perpendicular planes, while in the plate and cellular silencers these the processes are on the same plane. It should be noted that the area of contact of air with ZPM, and hence the sound absorption intensity, can be further increased by a deviation of ± Δα ° of angles at the vertices of rhombuses from the base value α = 90 °. The impact of these changes is not currently calculated and should be determined experimentally. Based on design considerations, it is advisable for gas turbine engines with a flow rate of 100 ÷ 55.0 kg / s through an axial compressor to use sound absorbing elements of size 80 × 80, at a flow rate of 54.9 ÷ 25.0 kg / s - size 60 × 60, with a flow rate of less 25 kg / s - size 40 × 40 mm.

If there is a developed demand for the proposed high-performance sound-absorbing elements, the process of their creation can be fully automated and the cost of manufacturing silencing blocks is significantly reduced.

Using the proposed design of sound-absorbing elements and a silencer case instead of a prototype allows you to solve the problem and get a new technical result - simplify and automate manufacturing, ensure geometry stability and sound-absorbing properties of elements, increase noise reduction efficiency by increasing the contact area of air and sound-absorbing material, which As a result, it will allow solving the problem of noise reduction with maximum efficiency.

Currently, the design of the proposed multi-section silencer for the gas turbine engine has been fully developed, universal models have passed bench tests, and at the end of 2007 similar gas turbine silencing units will be equipped with gas turbines of various capacities.

Claims (2)

1. A multi-section honeycomb silencer for the exhaust gas turbine installation, consisting of separately connected sections made of a metal frame, each of the side, lower and upper walls of which are covered with a layer of sound-absorbing material, lined from the inside of the section with a perforated plate, each of the sections contains successively placed subsections in which are installed sound-absorbing elements made of a perforated shell, which is placed sound-absorbing material, characterized in that the sound absorption The clamping elements are made in the form of a rhombus and combined into modules that are installed along the entire cross-section of the subsection, so that the vertical diagonal of each sound-absorbing element is parallel to the side walls of the section, while the subsections are formed by vertical posts mounted on the upper and lower walls of each section and having slots for attaching a sound-absorbing module. 2. The multi-sectional cellular noise muffler according to claim 1, characterized in that the number of individual sound-absorbing elements in the module and the number of modules correspond to the condition of equal areas of sound-absorbing elements and through channels for air passage in each subsection.

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