Low noise steam eductor with serrated nozzle and annular groove and noise reduction method

Abstract

The present application belongs to the field of ejector, the existing steam ejector contains Laval nozzle structure, the supersonic steam formed by the structure produces huge noise pollution, the factory noise is seriously overproof, the present application discloses a kind of low-noise steam ejector with sawtooth nozzle and annular groove and noise reduction method, low-noise steam ejector includes Laval nozzle, straight pipe section, suction chamber, mixing chamber and diffuser chamber.Laval nozzle nozzle end surface uses sawtooth structure, mixing chamber inner wall surface uses annular groove structure.Main stream steam forms supersonic flow after passing through Laval nozzle, and after mixing uniformly with secondary flow steam in suction chamber and mixing chamber, it is discharged from outlet after passing through diffuser chamber.Supersonic flow in ejector produces huge aerodynamic noise, and the sawtooth structure of nozzle end surface and the annular groove structure of mixing chamber inner wall surface can intensify fluid disturbance, make large-scale vortex break into multiple small-scale vortex, and then play obvious noise reduction effect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ejector, and particularly relates to a low-noise steam ejector with a sawtooth nozzle and an annular groove and a noise reduction method. BACKGROUND

[0002] In recent years, with the rapid development of society and the increasing improvement of people's living standards, the demand for urban central heating is increasing, but there is still a lot of room for improvement in energy utilization. In order to further improve energy efficiency and accelerate energy saving and emission reduction, urban central heating can fully utilize low-grade waste heat energy, reduce carbon emissions through large-scale recycling of waste heat energy, and achieve industrial low carbonization. Steam ejector can recycle a large amount of low-grade heat energy through high-grade heat energy, improve energy utilization, and has obvious effect in energy saving and emission reduction. However, due to the presence of Laval nozzle structure in the steam ejector, the supersonic steam formed by the structure will produce huge noise pollution, and the noise level is comparable to that of an airplane engine. The factory noise is seriously over-standard, and the surrounding environment is deteriorating. Therefore, it is of great significance to reduce the huge noise generated by the steam ejector during operation for the popularization and use of the ejector. SUMMARY

[0003] Based on the above background, the present application provides a low-noise steam ejector with a sawtooth nozzle and an annular groove, i.e. a noise reduction method. The present application sets a sawtooth structure at the jet end of the Laval nozzle and sets an annular groove structure on the inner wall of the mixing chamber to change the scale of the vortex in the flow field, thereby achieving the effect of noise reduction.

[0004] To achieve the above-mentioned purpose, the specific technical scheme adopted by the present application is as follows:

[0005] A low-noise steam ejector with a sawtooth nozzle and an annular groove mixing chamber, the low-noise steam ejector comprising a Laval nozzle and an ejector structure, the Laval nozzle being provided with a sawtooth structure at the jet end face of the nozzle, the ejector structure comprising a straight pipe section, a suction chamber, a mixing chamber and a diffuser chamber which are fixedly connected in sequence along the flow direction, and the inner wall surface of the mixing chamber being provided with a plurality of annular grooves; the Laval nozzle is located inside the straight pipe section and the suction chamber.

[0006] Further, the straight pipe section, the suction chamber, the mixing chamber and the diffuser chamber are in coaxial position.

[0007] Further, the flow passage cross-sectional area of the suction chamber gradually decreases along the flow direction, the mixing chamber is an equal cross-section flow passage, and the flow passage cross-sectional area of the diffuser chamber gradually increases along the flow direction.

[0008] Further, the part of the flow passage cross-sectional area of the Laval nozzle located in the straight pipe section is an equal cross-section flow passage, and the part of the flow passage cross-sectional area of the Laval nozzle located in the suction chamber first decreases and then increases along the flow direction.

[0009] Further, the sawtooth structures are uniformly distributed in a circumferential array on the end face of the Laval nozzle, the sawtooth structure tooth length L is 0.05-1.0 times of the inner diameter of the Laval nozzle outlet end, and the sawtooth number is 4-30.

[0010] Further, the mixing chamber is provided with a plurality of annular grooves on the inner wall surface and uniformly spaced along the axial direction, and the annular grooves are arranged along the circumferential direction of the inner wall surface of the mixing chamber.

[0011] Further, the groove depth of the annular groove is 0.01-0.3 times of the inner diameter of the mixing chamber, the groove width of the annular groove is 0.5-10 times of the groove depth h of the annular groove, and the groove spacing is 1-20 times of the groove depth.

[0012] A method for reducing steam noise by using a sawtooth nozzle and an annular groove mixing chamber, using the above low-noise steam ejector, high-pressure steam as working fluid enters the low-noise steam ejector through the Laval nozzle, when passing through the Laval nozzle, the sawtooth structure at the end of the nozzle forms turbulent disturbance to the high-pressure steam, breaks the large-scale vortex into a plurality of small-scale vortexes, so that a radial high-vortex area appears near the central axis of the steam ejector, and then the aerodynamic noise is weakened, and the high-pressure steam forms supersonic steam after passing through the Laval nozzle; after the supersonic steam is ejected from the Laval nozzle, it passes through the annular groove structure of the mixing chamber, due to the inertia of the steam, there is still a flow in the direction of the annular groove after entering the annular groove, and after colliding with the wall surface of the annular groove, a severe turbulent flow is formed, so that the high-vortex area range at the junction of the annular groove and the inner wall surface is increased, and then the noise is weakened, and the supersonic steam and the secondary flow steam are mixed uniformly in the suction chamber and the mixing chamber and then enter the diffuser chamber, and the mixed steam is discharged from the outlet of the diffuser chamber.

[0013] Compared with the prior art, the low-noise steam ejector has the advantages and effects as follows:

[0014] The low-noise steam ejector of the present application has the advantages of simple structure and easy processing, by setting the sawtooth structure at the outlet end of the Laval nozzle and the annular grooves with equal spacing on the inner wall of the mixing chamber, the flow field of the nozzle outlet and the near-wall surface of the mixing chamber is affected, the fluid disturbance in the steam ejector is intensified, the large-scale vortex is broken into a plurality of small-scale vortexes, thereby improving the aerodynamic noise generated by the steam ejector during operation, and achieving obvious noise reduction effect. The sound pressure level of the low-noise steam ejector (nozzle with sawtooth and mixing chamber with annular groove) of the present application is reduced from 138dB to 123.9dB compared with the ordinary steam ejector (nozzle without sawtooth and mixing chamber without groove), which is reduced by 10.2%, and the noise of the steam ejector, especially the low-frequency noise of the main part, is significantly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a schematic diagram of the outer contour structure of the present application.

[0016] Figure 2is a schematic diagram of the three-dimensional structure of the present application.

[0017] Figure 3 is a sectional view of the present application.

[0018] Figure 4 is a schematic diagram of the trailing edge structure of the sawtooth nozzle Figure 3 in the A-A view).

[0019] Figure 5 is Figure 1 a partial enlarged view of the sawtooth structure of the Laval nozzle.

[0020] Figure 6 is a sectional view of the annular groove mixing chamber Figure 3 in the B-B view).

[0021] Figure 7 is a noise frequency doubling diagram of a common steam ejector and the present application.

[0022] Wherein: 1 is a Laval nozzle, 2 is a straight pipe section, 3 is an absorption chamber, 4 is a mixing chamber, 5 is a diffuser, 6 is a sawtooth structure, 7 is an annular groove, 8 is a sawtooth tip, 9 is a sawtooth bottom, 10 is the outer wall surface of the mixing chamber, 11 is the annular groove wall surface, 12 is the inner wall surface of the mixing chamber, L is the sawtooth length, P is the sawtooth pitch, and h is the groove depth of the annular groove. DETAILED DESCRIPTION

[0023] The present application will be further described in detail below in conjunction with the accompanying drawings and examples. The following examples are merely preferred embodiments of the present application and are not intended to limit the present application. Any modification or equivalent replacement within the spirit of the present application is within the scope of protection of the present application.

[0024] As Figures 1 to 6 shown, the present application discloses a low-noise steam ejector with a sawtooth nozzle and an annular groove mixing chamber, mainly including a Laval nozzle 1 and an ejecting structure. The Laval nozzle 1 is provided with a sawtooth structure 6 at the jet end surface of the nozzle, and the ejecting structure includes a straight pipe section 2, an absorption chamber 3, a mixing chamber 4, a diffuser 5, and a plurality of annular grooves 7 provided on the inner wall surface of the mixing chamber 4, which are sequentially fixed and connected along the flow direction.

[0025] The straight pipe section 2, the absorption chamber 3, the mixing chamber 4, and the diffuser 5 are coaxially arranged in sequence along the flow direction, and can be connected by flanges or other fixed connection methods. The flow passage cross-sectional area of the absorption chamber 3 gradually decreases along the flow direction, the mixing chamber 4 has an equal cross-section flow passage, and the flow passage cross-sectional area of the diffuser 5 gradually increases along the flow direction. The Laval nozzle 1 is located inside the straight pipe section 2 and the absorption chamber 3, and the flow passage cross-sectional area of the Laval nozzle 1 is an equal cross-section flow passage in the straight pipe section 2 and gradually increases after decreasing along the flow direction in the absorption chamber 3.

[0026] The Laval nozzle 1 is provided with a plurality of sawtooth structures 6 on the nozzle end face in a circumferential array, the sawtooth length L of the sawtooth structure 6 is 0.05-1.0 times the diameter of the outlet end of the Laval nozzle 1, and the number of sawteeth is 4-30.

[0027] The mixing chamber 4 is provided with a plurality of annular grooves 7 on the wall surface in an axial uniform interval, the annular grooves 7 are arranged along the circumferential direction of the inner wall surface of the mixing chamber 4, the groove depth h of the annular groove 7 is 0.01-0.3 times the inner diameter of the mixing chamber 4, the groove width of the annular groove 7 is 0.5-10 times the groove depth h, and the groove spacing is 1-20 times the groove depth h.

[0028] The sawteeth on the end face of the Laval nozzle 1 can be obtained by milling processing, and the annular grooves on the inner wall surface of the mixing chamber 4 can be obtained by boring processing.

[0029] The application further discloses a method for reducing steam noise by using the sawtooth nozzle and the annular groove mixing chamber, high-pressure steam is used as the working fluid to enter the low-noise steam ejector through the Laval nozzle 1, when passing through the Laval nozzle 1, the sawtooth structure 6 at the nozzle end part forms turbulent disturbance to the high-pressure steam, breaks large-scale vortices into a plurality of small-scale vortices, makes a radial high-vortex area appear near the central axis of the steam ejector, and further weakens the aerodynamic noise, and the high-pressure steam forms supersonic steam after passing through the Laval nozzle; after the supersonic steam is sprayed out from the Laval nozzle 1, when passing through the annular groove 7 structure of the mixing chamber 4, the steam has a flow in the direction due to inertia after entering the annular groove 7, collides to the wall surface of the annular groove 7, forms severe turbulent flow, makes the high-vortex area range of the junction of the annular groove 7 and the inner wall surface increase, and further weakens the noise, and the supersonic steam and the secondary flow steam are mixed uniformly in the suction chamber 3 and the mixing chamber 4, and then enter the diffuser chamber 5, and the mixed steam is discharged from the outlet of the diffuser chamber 5.

[0030] In the embodiment, the main steam parameters are: pressure 20.0 MPa, temperature 566℃, and mass flow 69.4 kg / s; the induced steam parameters are: pressure 3.9 MPa, temperature 340℃, and mass flow 69.4 kg / s. The inlet diameter of the steam ejector Laval nozzle 1 is 207.63 mm, the outlet diameter of the Laval nozzle 1 is 81.46 mm, the diameter of the mixing chamber 4 is 169.00 mm, the outlet diameter of the diffuser chamber 5 is 372.52 mm, the length of the gradual expansion section of the Laval nozzle 1 is 97.24 mm, the length of the mixing chamber 4 is 1183.00 mm, the length of the diffuser chamber 5 is 1322.89 mm, the length of the sawtooth 6 on the end face of the Laval nozzle 1 is 8 mm, and the number of sawteeth is 14; the depth of the annular groove 7 of the mixing chamber 4 is 25 mm, the width of the annular groove 7 is 25 mm, and the spacing of the annular groove 7 is 50 mm.

[0031] The sound pressure level at 2 meters outside the center line outlet of the steam ejector is monitored by numerical simulation, Figure 7 The noise frequency doubling comparison chart of the common steam ejector and the low-noise steam ejector is shown. Figure 7 It can be seen that, compared with the common steam ejector (the nozzle is not sawtooth and the mixing chamber is not grooved), the sound pressure level of the low-noise steam ejector (the nozzle is sawtooth and the mixing chamber is annular grooved) of the present application is reduced from 138 dB to 123.9 dB, which is reduced by 10.2%. This is because when the supersonic steam passes through the sawtooth structure 6 of the Laval nozzle 1, the steam flows through the wedge-shaped space area between adjacent teeth, which is easy to form turbulent disturbance, leading to large-scale vortex being broken into multiple small-scale vortexes, so that the radial high-vortex area appears near the central axis of the steam ejector, and then the aerodynamic noise is weakened. When the supersonic steam passes through the annular groove 7 structure of the mixing chamber 4, under the action of inertia, there is still a flow in the direction after entering the annular groove 7, but it soon collides with the wall surface of the annular groove 7, forming a severe turbulent flow, so that the high-vortex area range of the annular groove 7 and the inner wall surface is increased, and then the noise is weakened.

[0032] The low-noise steam ejector of the present application reduces the noise generated by the steam ejector during operation by changing the structure of the Laval nozzle 1 and the mixing chamber 4, which is simple in structure and low in cost, and reduces noise pollution while recycling waste heat energy.

[0033] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

Claims

1. A low noise steam eductor with a serrated nozzle and an annular channel mixing chamber, characterized by: The low-noise steam ejector comprises a Laval nozzle (1) and an ejecting structure, the Laval nozzle (1) is provided with a sawtooth structure (6) at the jet end face of the nozzle, the ejecting structure comprises a straight pipe section (2), a suction chamber (3), a mixing chamber (4) and a diffuser chamber (5) which are fixedly connected in sequence along the flow direction, and the inner wall surface of the mixing chamber (4) is provided with a plurality of annular grooves (7); the Laval nozzle (1) is located inside the straight pipe section (2) and the suction chamber (3). The mixing chamber (4) is uniformly spaced in the axial direction and is provided with a plurality of annular grooves (7) on the inner wall surface.

2. A low noise steam eductor with serrated nozzle and annular channel mixing chamber according to claim 1, characterized in that: The straight pipe section (2), the suction chamber (3), the mixing chamber (4) and the diffuser chamber (5) are coaxial.

3. The low noise vapor eductor of claim 1, wherein: The flow passage cross-sectional area of the suction chamber (3) gradually decreases along the flow direction, the mixing chamber (4) is an equal cross-section flow passage, and the flow passage cross-sectional area of the diffuser chamber (5) gradually increases along the flow direction.

4. The low noise vapor eductor of claim 1, wherein: The flow passage cross-sectional area of the Laval nozzle (1) is an equal cross-section flow passage at the part of the straight pipe section (2), and the flow passage cross-sectional area of the Laval nozzle (1) gradually increases after decreasing along the flow direction at the part of the suction chamber (3).

5. The low noise vapor ejector of claim 1, wherein: The sawtooth structure (6) is uniformly distributed in a circumferential array at the end face of the Laval nozzle (1), the tooth length L of the sawtooth structure (6) is 0.05-1.0 times the inner diameter of the outlet end of the Laval nozzle (1), and the number of sawteeth is 4-30.

6. The low noise vapor eductor of claim 1, wherein: The groove depth of the annular groove (7) is 0.01-0.3 times the inner diameter of the mixing chamber (4), the groove width of the annular groove (7) is 0.5-10 times the groove depth of the annular groove (7), and the groove spacing is 1-20 times the groove depth. h the groove depth of the annular groove (7) is 0.01-0.3 times the inner diameter of the mixing chamber (4), the groove width of the annular groove (7) is 0.5-10 times the groove depth of the annular groove (7), and the groove spacing is 1-20 times the groove depth.

7. A method of reducing steam noise by using a sawtooth nozzle and an annular channel mixing chamber, using the low noise steam eductor according to any one of claims 1 to 6, characterized in that: High-pressure steam enters the low-noise steam ejector through the Laval nozzle (1), and when passing through the Laval nozzle (1), the sawtooth structure (6) at the end of the nozzle forms turbulent disturbance to the high-pressure steam, breaks large-scale vortices into multiple small-scale vortices, causes a radial high-vortex area to appear near the central axis of the steam ejector, and thus weakens the aerodynamic noise, and the high-pressure steam forms supersonic steam after passing through the Laval nozzle; after the supersonic steam is ejected from the Laval nozzle (1), when passing through the annular groove (7) structure of the mixing chamber (4), the steam still has a flow in the flow direction after entering the annular groove (7) due to its inertia, collides with the wall surface of the annular groove (7), forms intense turbulent flow, increases the range of the high-vortex area at the junction of the annular groove (7) and the inner wall surface, and thus weakens the noise, and the supersonic steam and secondary flow steam are mixed uniformly in the suction chamber (3) and the mixing chamber (4) and then enter the diffuser chamber (5), and the mixed steam is discharged from the outlet of the diffuser chamber (5).

Images