Exhaust silencer of oil-free screw compressor

Abstract

The embodiment of the invention provides an exhaust silencer of an oil-free screw compressor. The exhaust silencer of the oil-free screw compressor comprises a Venturi silencing pipe and / or a small hole diffusion silencing pipe. The venturi hush pipe sequentially comprises a cylindrical inlet section, a conical contraction section, a cylindrical throttling section and a conical diffusion section from the air inlet end to the air outlet end of the venturi hush pipe, and the venturi hush pipe has an obvious muffling effect on medium and low frequency noise below 1000Hz; the small-hole diffusion hush pipe comprises an inner pipe and an outer pipe which are nested inside and outside, an air outlet is formed in the pipe wall of the outer pipe, one end of the inner pipe extends out of one end of the outer pipe to form an air inlet, a plurality of small holes are evenly formed in the pipe wall of the inner pipe, and the small-hole diffusion hush pipe has an obvious muffling effect on high-frequency noise of 1000 Hz or above; the Venturi hush pipe and the small hole diffusion hush pipe can be used independently or in a combined mode according to the actual operation condition of the compressor, and when the two hush pipes are used in a combined mode, a good muffling function can be achieved in a very wide frequency band.

Description

Technical Field

[0001] The invention relates to the technical field of mufflers, and in particular to an exhaust muffler for an oil-free screw compressor. Background Art

[0002] Oil-free screw compressors are often accompanied by loud noises during actual operation, including air flow pulsation noise, mechanical vibration noise, electromagnetic noise, etc. Among them, the air flow pulsation noise at the exhaust port is dominant, so it is the main consideration in the noise reduction design of oil-free screw compressors. Summary of the invention

[0003] In view of this, an embodiment of the present invention provides an exhaust muffler for an oil-free screw compressor, so as to reduce the air flow pulsation noise of the oil-free screw compressor.

[0004] An exhaust silencer for an oil-free screw compressor provided in an embodiment of the present invention comprises a Venturi silencer and / or a small-hole diffuser silencer; the Venturi silencer comprises a cylindrical inlet section, a conical contraction section, a cylindrical throttling section and a conical diffuser section in sequence from its air inlet end to its air outlet end, the maximum diameter end of the contraction section is connected to the inlet section, the minimum diameter end of the contraction section is connected to the throttling section, and the minimum diameter end of the diffuser section is connected to the throttling section;

[0005] The small hole diffusion silencer pipe comprises an inner pipe and an outer pipe which are nested inside and outside; the two ends of the outer pipe are closed, and an air outlet is provided on the pipe wall of the outer pipe; the inner pipe is coaxially inserted in the outer pipe, and one end of the inner pipe extends from one end of the outer pipe to form an air inlet, and a plurality of small holes are evenly opened on the pipe wall of the inner pipe.

[0006] Optionally, the Venturi silencer pipe is bent at the diffusion section to form an L-shaped elbow.

[0007] Optionally, there is a smooth transition between the inlet section and the contraction section, between the contraction section and the throttling section, and between the throttling section and the diffusion section.

[0008] Optionally, the Venturi silencer pipe is integrally cast from cast iron or is formed by sectionally machining and then welding stainless steel.

[0009] Optionally, the air inlet end of the Venturi silencer is chamfered.

[0010] Optionally, the diameter of the air outlet end of the Venturi silencer is greater than or equal to the diameter of the air inlet end thereof.

[0011] Optionally, the diameter of the inlet section is 2 to 4 times the diameter of the throttling section.

[0012] Optionally, the cone angle of the contraction section is less than or equal to 20°.

[0013] Optionally, the diameter of the outer tube is greater than or equal to 2 times the diameter of the inner tube.

[0014] Optionally, the diameter of the small holes is less than 3 mm, and the total flow area of ​​all the small holes is greater than 1.5 times the flow area of ​​the inner tube.

[0015] Optionally, the spacing between adjacent small holes is greater than or equal to 6 times the diameter of the small holes.

[0016] Optionally, stainless steel wire is filled between the inner tube and the outer tube.

[0017] Optionally, removable cover plates are respectively installed at both ends of the outer tube, and one end of the inner tube extends out from one of the cover plates.

[0018] The embodiments of the present invention have the following beneficial effects:

[0019] 1. Set up a Venturi silencer and / or a small hole diffusion silencer. The Venturi silencer has an obvious silencing effect on medium and low frequency noise below 1000Hz, and the small hole diffusion silencer has an obvious silencing effect on high frequency noise above 1000Hz. The Venturi silencer and the small hole diffusion silencer can be used separately or in combination according to the actual operation of the compressor; when the two silencers are used in combination, a better silencing function can be achieved in a very wide frequency band.

[0020] 2. The Venturi silencer is designed as an L-shaped elbow so that it can also serve as part of the air pipeline to simplify the air pipeline system of the compressor.

[0021] 3. It has a simple structure and low cost, and is particularly suitable for high-temperature and pollution-free applications. At the same time, it does not pollute the gas, has no wearing parts, does not require regular maintenance, has a long service life, and is not within the scope of inspection of pressure vessels. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0024] Figure 2 A cross-sectional view of a venturi muffler tube in an embodiment of the present invention;

[0025] Figure 3 Schematic diagram of the chamfer of the air inlet end of the venturi muffler in the embodiment of the present invention;

[0026] Figure 4 A cross-sectional view of one structure of a small hole diffusion silencer pipe in an embodiment of the present invention;

[0027] Figure 5 A cross-sectional view of another structure of a small hole diffusion silencer pipe in an embodiment of the present invention;

[0028] The numbers in the figure represent:

[0029] 1. Venturi silencer;

[0030] 1.1, inlet section; 1.2, contraction section; 1.3, throttling section; 1.4, diffusion section;

[0031] 2. Small hole diffusion silencer;

[0032] 2.1, inner tube; 2.2, outer tube; 2.3, air outlet; 2.4, air inlet; 2.5, small hole; 2.6, cover plate. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0034] For the exhaust silencer of oil-free screw compressor, it usually needs to have the following characteristics:

[0035] 1. High temperature resistance

[0036] Since the exhaust temperature of the oil-free screw compressor is relatively high, the material of the silencer needs to be able to withstand a high temperature of 250°C for a long time.

[0037] 2. Mainly used to eliminate high-frequency noise

[0038] Due to the structural characteristics of the oil-free screw compressor, the noise at the exhaust end is mainly high-frequency noise from 1000Hz to 5000Hz.

[0039] 3. Low pressure loss

[0040] Lower pressure loss means less energy loss and a more energy-efficient compressor.

[0041] 4. No pollution

[0042] Compressed air must not be contaminated during the compression process and the fewer dust particles the better.

[0043] 5. Simple structure and small size

[0044] Due to the compact structure of the compressor, the silencer needs to be designed according to the direction of the pipeline.

[0045] According to the above requirements, in combination with the arrangement of the compressor, an embodiment of the present invention provides an exhaust silencer for an oil-free screw compressor, including a venturi silencer pipe 1 and / or a small hole diffusion silencer pipe 2, that is, the venturi silencer pipe 1 and the small hole diffusion silencer pipe 2 can be used alone or as Figure 1 The venturi silencer 1 is used in combination as shown. It draws on the structural features of some venturi tubes and is designed based on the principle that changes in cross section cause changes in acoustic impedance. It has a significant silencing effect on medium and low frequency noises below 1000Hz. The small hole diffusion silencer 2 utilizes the design principle of small hole diffusion and has a significant silencing effect on high frequency noises above 1000Hz. The combination of the above two silencers can achieve better silencing function within a very wide frequency band; of course, you can also choose to use either the venturi silencer 1 or the small hole diffusion silencer 2 alone according to the actual operation of the compressor.

[0046] Specifically, Figure 2 As shown, the venturi silencer 1 includes a cylindrical inlet section 1.1, a conical contraction section 1.2, a cylindrical throttling section 1.3 and a conical diffusion section 1.4 from its air inlet end to the air outlet end. One end of the inlet section 1.1 is connected to the exhaust end of the compressor as the air inlet end of the venturi silencer 1, and the other end is connected to the maximum diameter end of the contraction section 1.2. One end of the throttling section 1.3 is connected to the minimum diameter end of the contraction section 1.2, and the other end is connected to the minimum diameter end of the diffusion section 1.4. The maximum diameter end of the diffusion section 1.4 is connected to the rear-end pipeline or the small-hole diffusion silencer 2 as the air outlet end of the venturi silencer 1. In order to reduce the flow pressure loss of the gas, the inner surface of the venturi silencer 1 should be as smooth as possible, the surface roughness should be as small as possible, and there should be smooth transitions between the inlet section 1.1 and the contraction section 1.2, between the contraction section 1.2 and the throttling section 1.3, and between the throttling section 1.3 and the diffusion section 1.4.

[0047] Furthermore, the Venturi silencer pipe 1 can be bent at the diffuser section 1.4 to form an L-shaped elbow according to the direction of the compressor exhaust pipe, so that it can also serve as part of the air pipe, thereby simplifying the air pipe system of the compressor.

[0048] The venturi muffler 1 can be made of cast iron as a whole, or can be made of stainless steel after segmented machining and welding. Since metal castings have good sound insulation performance, the venturi muffler 1 made of a whole has a better muffler function.

[0049] The diameter φA of the inlet section 1.1 can be calculated based on the exhaust volume of the compressor, and its length D can be as long as possible if the structural dimensions allow.

[0050] The cone angle G of the contraction section 1.2 is generally less than or equal to 20° and can be adjusted in a small range according to the overall structural dimensions. The length E of the contraction section 1.2 is determined by the diameter φA at the maximum diameter end, the diameter φB at the minimum diameter end and the cone angle G.

[0051] The diameter φA of the inlet section 1.1 can be 2 to 4 times the diameter φB of the throttling section 1.3, that is, φA / φB=2 to 4. The greater the difference between the two diameters, the better the silencing effect, but the greater the flow pressure loss of the gas. When the Mach number Ma of the gas at the throttling section 1.3 is 0.3, the gas becomes a compressible flow field, and the flow pressure loss of the gas increases sharply. Therefore, in general, φA / φB=2 is more appropriate. The length F of the throttling section 1.3 can be the same as its diameter B.

[0052] The bending radius R of the diffuser section 1.4 is as large as possible when the structural dimensions allow, and the cone angle H of the diffuser section 1.4 is as small as possible when the structural dimensions allow, so that the cone can gradually become larger, thereby minimizing the disturbance pressure loss during gas flow.

[0053] The diameter φC of the air outlet end of the Venturi silencer 1 is preferably greater than or equal to the diameter φA of the air inlet end thereof, that is, φC ≥ φA.

[0054] In addition, the air inlet end of the venturi muffler 1 can be chamfered (such as Figure 3 As shown, chamfered right angles or rounded corners) can increase the size of the air inlet end and form a gradually smaller transition with the contraction section 1.2 at the other end of the inlet section 1.1 to reduce the flow pressure loss of the gas.

[0055] The venturi silencer 1 has a good silencing effect on medium and low frequency noises below 1000Hz, so it is more suitable for the first-stage exhaust pipeline of the compressor.

[0056] like Figure 4As shown, the small hole diffusion silencer tube 2 includes an inner tube 2.1 and an outer tube 2.2 which are nested inside and outside; the outer tube 2.2 is closed at both ends, and an air outlet 2.3 is provided on the tube wall of the outer tube 2.2; the inner tube 2.1 is coaxially inserted in the outer tube 2.2, and one end of the inner tube 2.1 extends from one end of the outer tube 2.2 to form an air inlet 2.4, and a plurality of small holes 2.5 are evenly provided on the tube wall of the inner tube 2.1. The gas flows into the inner tube 2.1 from the air inlet 2.4 at one end of the inner tube 2.1, then flows out from the small holes 2.5 on the inner tube 2.1 and converges in the outer tube 2.2, and finally flows out from the air outlet 2.3 on the outer tube 2.2. When the gas flows out from the small holes 2.5, a series of small jets are formed, which can transfer the audible sound energy to the ultrasonic frequency band with higher frequency and less impact on the human body, and the ultrasound can be quickly attenuated in a short distance, thereby achieving the purpose of silencing.

[0057] Both the inner tube 2.1 and the outer tube 2.2 can be directly welded and processed by steel pipes, which is convenient to manufacture and has low cost. Moreover, due to the small inner diameter, it avoids the inspection scope of the pressure vessel.

[0058] The diameter φa of the inner tube 2.1 can be the same as the diameter φC of the outlet end of the venturi silencer 1. The diameter φb of the outer tube 2.2 is greater than or equal to twice the diameter φa of the inner tube 2.1, that is, φb≥2×φa, so that there is enough flow area in the outer tube 2.2 to effectively reduce the flow pressure loss of the gas.

[0059] The diameter φc of the small hole 2.5 is less than 3mm, so that a certain silencing effect can be achieved. In combination with the actual processing conditions, the diameter φc of the small hole 2.5 is more suitable to be 1mm or 1.5mm, which is easy to process and has a good silencing effect. The number of small holes 2.5 should be such that the total flow area S1 of all small holes 2.5>1.5×the flow area S of the inner tube 2.1.

[0060] The spacing d between adjacent small holes 2.5 is preferably greater than or equal to 6 times the diameter φc of the small holes 2.5, that is, d≥6c. The overall length L of the small hole diffusion silencer 2 is determined by the number of small holes 2.5. If the spacing d between adjacent small holes 2.5 is less than 6c due to the limitation of the overall length L, the airflow ejected from each small hole 2.5 will quickly converge, forming interference noise, greatly reducing the silencing effect. At this time, stainless steel wire can be filled between the inner tube 2.1 and the outer tube 2.2 to prevent the airflow from converging. The filling rate is generally about 30%. Of course, if stainless steel wire is filled, preventive measures such as a screen need to be designed at the air outlet 2.3 to prevent the stainless steel wire from being blown out by the airflow.

[0061] Further, such as Figure 5As shown, the outer tube 2.2 can also be in the form of a casting, and detachable cover plates 2.6 are respectively installed at both ends of the outer tube 2.2. One end of the inner tube 2.1 extends out from one of the cover plates 2.6. During assembly, the inner tube 2.1 can be welded and fixed to the cover plate 2.6 first, and then the cover plate 2.6 is installed on the outer tube 2.2 by bolts. After the stainless steel wire is filled between the inner tube 2.1 and the outer tube 2.2, the other end of the outer tube 2.2 is sealed with another cover plate 2.6. This detachable structure not only ensures the silencing effect of the small hole diffusion silencer 2, but also facilitates the filling of the stainless steel wire.

[0062] In addition, for the convenience of connection, connecting flanges can be provided at the air inlet and air outlet ends of the Venturi silencer 1, and the air inlet 2.4 and air outlet 2.3 of the small hole diffusion silencer 2. The shape and size of the connecting flanges can be specifically designed according to actual requirements.

[0063] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present invention. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An exhaust muffler for an oil-free screw compressor, characterized in that: It includes a venturi silencer and / or a small hole diffusion silencer; the venturi silencer includes a cylindrical inlet section, a conical contraction section, a cylindrical throttling section and a conical diffusion section from its air inlet end to its air outlet end, the maximum diameter end of the contraction section is connected to the inlet section, the minimum diameter end of the contraction section is connected to the throttling section, and the minimum diameter end of the diffusion section is connected to the throttling section; The small hole diffusion silencer pipe comprises an inner pipe and an outer pipe which are nested inside and outside; the two ends of the outer pipe are closed, and an air outlet is provided on the pipe wall of the outer pipe; the inner pipe is coaxially inserted in the outer pipe, and one end of the inner pipe extends from one end of the outer pipe to form an air inlet, and a plurality of small holes are evenly opened on the pipe wall of the inner pipe.

2. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The Venturi silencer pipe is bent at the diffusion section to form an L-shaped elbow.

3. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: There is a smooth transition between the inlet section and the contraction section, between the contraction section and the throttling section, and between the throttling section and the diffusion section.

4. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The venturi silencer is integrally cast from cast iron or is welded after being machined in sections from stainless steel.

5. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The air inlet end of the Venturi silencer is chamfered.

6. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The diameter of the air outlet end of the Venturi silencer pipe is greater than or equal to the diameter of the air inlet end thereof.

7. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The diameter of the inlet section is 2 to 4 times the diameter of the throttling section.

8. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The cone angle of the contraction section is less than or equal to 20°.

9. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The diameter of the outer tube is greater than or equal to 2 times the diameter of the inner tube.

10. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The diameter of the small holes is less than 3 mm, and the total flow area of ​​all the small holes is greater than 1.5 times the flow area of ​​the inner tube.

11. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: The spacing between adjacent small holes is greater than or equal to 6 times the diameter of the small holes.

12. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: Stainless steel wires are filled between the inner tube and the outer tube.

13. The exhaust muffler of an oil-free screw compressor according to claim 1, characterized in that: Both ends of the outer tube are respectively installed with detachable cover plates, and one end of the inner tube extends out from one of the cover plates.

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