A noise-reducing centrifugal fan volute and a sound-absorbing structure of its air inlet

Abstract

A sound absorption structure for a volute of a noise-reducing centrifugal fan and its air inlet, wherein a sound absorption plate is fixed on the volute side plate by a mounting plate, and a muffler chamber is formed between the sound absorption plate and the volute side plate; a plurality of web sound absorption plates are evenly arranged horizontally and vertically on the volute web plate; a plurality of obliquely arranged arc guide blocks are arranged on the arc-shaped side wall of the volute air inlet. Compared with the existing technology, the beneficial effects of the present invention are as follows: the present invention adopts a spatial sound absorption structure design, which greatly increases the sound absorption "effective area"; has a good noise reduction effect; has a safe and reliable structure, and does not require repeated maintenance and replacement during the service life; the sound absorption material has little effect on the fan performance, and the effect on the fan efficiency is less than 1%; and can be widely used in ventilation and air supply industries with high requirements for environmental comfort (low noise).

Description

Technical Field

[0001] The invention relates to the field of large centrifugal fans, and in particular to a noise-reducing centrifugal fan volute and a sound-absorbing structure of an air inlet thereof. Background Art

[0002] Centrifugal fans use high-speed rotating impellers (centrifugal force) to do work on gaseous media, and are power fluid machines that convert kinetic energy into potential energy (pressure energy) by changing the flow direction and flow velocity of the medium. Fans are widely used in construction engineering, boilers, chemicals, petroleum, and environmental protection industries, and have promising application prospects. However, its working noise has been constantly "criticized" by everyone, mainly because this noise seriously affects people's production and living comfort, and even endangers people's health. Therefore, fan noise has an impact that cannot be ignored. With the enhancement of people's environmental awareness, environmental protection departments have also begun to strictly control and refine the relevant indicators of such noise. Therefore, the sound-absorbing and noise-reducing fan structure will still be the focus and difficulty of fan product design in the future.

[0003] The main noise sources of centrifugal fans include: aerodynamic noise, electromagnetic noise and mechanical noise. With the continuous improvement of fan product processing technology, the influence of mechanical noise and electromagnetic noise is almost insignificant compared to aerodynamic noise. Then, as the main component of fan noise, the cause of aerodynamic noise must be closely related to the internal flow field of the fan. Centrifugal fans are driven fluid machinery. Based on their multi-curvature structural characteristics, when the Reynolds number is high, the flow field will show unsteady characteristics in time and space. Secondary flow, jet and wake flow are often generated due to uneven flow. In these complex flow phenomena, there are usually associated vortices, and aerodynamic noise is often caused by the stretching and rupture of these associated vortices. Due to the variety of types and movement modes of vortices in the flow field, the cause of aerodynamic noise of centrifugal fans becomes extremely complicated.

[0004] However, some researchers still focus on the radiation of aerodynamic noise in the free sound field, while neglecting the influence of mechanical structures such as volutes, air inlets and other main components on sound wave propagation.

[0005] At present, commonly used sound-absorbing materials are divided into porous absorption materials and resonant sound-absorbing structures. Porous materials include foams, particles, fibers, etc.; resonant sound-absorbing structures can be divided into thin plate resonant sound-absorbing structures and thin plate perforated resonant sound-absorbing structures. The perforated plate sound-absorbing structure is the Helmholtz resonator, and the principles of the two are roughly the same.

[0006] Porous absorption materials and resonant sound absorption structures or a combination of the two have appeared in the invention patents for noise reduction of centrifugal fan volutes and air inlets, but there are still many challenges in practical applications. First of all, porous absorption materials will have "survival" problems in flow fields with high flow rates. The porous materials will be washed away by the medium or even fall off and peel off, and the sound absorption effect will be "greatly reduced". Therefore, porous materials need to be replaced regularly. Furthermore, if the porous material contaminates the gas medium and causes the medium delivery pipeline to be blocked, it will undoubtedly cause the fan to fail to work properly; the resonant sound absorption structure is generally recognized to have the disadvantages of narrow sound absorption frequency band. The parameters such as perforation rate, cavity depth, aperture, and sheet thickness in the basic structural design need to be repeatedly calculated and verified for their sound absorption frequency band (frequency). The secondary vortex that appears inside the volute, especially near the volute tongue, is often very difficult to solve and calculate, and the expected noise reduction effect will become very limited if the volute with different pressures and flows adopts a fixed parameter structural design. Therefore, it is almost hopeless to achieve the noise reduction design index without precise calculation and testing of each model of volute and air inlet structure. Summary of the invention

[0007] The purpose of the present invention is to provide a noise-reducing centrifugal fan volute and its sound-absorbing structure for the air inlet, and to provide a design and arrangement method for the spatial sound-absorbing material structure of the centrifugal fan and its air inlet, which has a significant sound-absorbing effect, greatly increases the "effective area" of the fan volute for sound absorption, and has a good noise reduction effect. The sound-absorbing structure can not only reduce low-frequency noise, but also medium- and high-frequency noise, and has a wide noise reduction frequency band.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A sound absorbing structure for a volute of a noise-reducing centrifugal fan and its air inlet, wherein a sound absorbing plate is fixed on a volute side plate via a mounting plate, and a muffler chamber is formed between the sound absorbing plate and the volute side plate; a plurality of web sound absorbing plates are evenly arranged horizontally and vertically on the volute web; and a plurality of obliquely arranged arc guide blocks are arranged on the arc side wall of the volute air inlet.

[0010] The sound absorbing panels are of two types: sound absorbing panel I and sound absorbing panel II. The sound absorbing panels I and II are arranged horizontally and vertically with intervals. The sound absorbing panel I is rectangular as a whole, and the middle part of the outer surface of the sound absorbing panel I is convex. The sound absorbing panel II is rectangular as a whole.

[0011] A plurality of spherical holes are arranged on an inclined surface on one side of the outer surface of the sound absorbing plate I, and the side of the sound absorbing plate I with the spherical holes is installed toward the windward side of the volute.

[0012] The web sound absorbing plate is rectangular as a whole, and the side surfaces of the three sides of the web sound absorbing plate are arc-shaped, and the arc-shaped side surface in the middle position is installed toward the windward side of the volute.

[0013] The guide blocks are of two types: guide block I and guide block II. The guide block I is taller than the guide block II. Several guide blocks I are evenly distributed along the circumferential direction of the volute air inlet, and several guide blocks II are evenly distributed between two adjacent guide blocks I.

[0014] The spacing between the guide blocks is 45-55 mm.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] The present invention discloses a sound absorption structure of a volute of a noise-reducing centrifugal fan and its air inlet, which has excellent sound absorption and noise reduction performance without changing the volute of the fan and its air inlet body, and mainly includes:

[0017] 1) The present invention adopts a spatial sound absorption structure design and forms a silencer chamber in the volute structure, so that the fan volute has vibration reduction and sound insulation functions; the structural design and arrangement of the sound absorption material make the sound wave propagation produce a velocity gradient, the particle (fluid) vibration speed is different everywhere, and the viscosity and friction generated by the interaction between adjacent particles continuously hinder the movement of particles (fluid), continuously converting sound energy into heat energy, and the sound absorption effect is obvious. The sound absorption plate structure used in the volute belly plate and the sound absorption structure of the volute side plate produce diffraction and reflection effects in the spatial direction of sound wave transmission. Part of the sound waves will be diffracted or reflected through the gaps between the sound absorption structures to the back side of the structure for absorption, greatly increasing the sound absorption "effective area".

[0018] 2) The air inlet structure with the function of guiding air adopted in the present invention ensures that the medium air intake is smooth and uniform without backflow and secondary flow, and is combined with the volute sound absorption and noise reduction design to achieve good noise reduction effect.

[0019] 3) The present invention has a good noise reduction effect. The sound absorbing structure can not only reduce low-frequency noise, but also medium and high-frequency noise. The noise frequency band is relatively wide, and the sound absorption coefficients (Sabine absorption coefficient) of medium and high frequencies are all greater than 1.1.

[0020] 4) The sound absorbing material of the present invention can be made of, for example, ordinary carbon steel and welded, so the structure is safe and reliable and does not require repeated maintenance and replacement during the service life.

[0021] 5) The sound absorbing material has little effect on the fan performance, and the effect on the fan efficiency is less than 1%.

[0022] 6) The present invention can be widely used in ventilation and air supply industries that have high requirements for environmental comfort (low noise). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the sound-absorbing material of the fan volute.

[0024] Figure 2 It is a schematic diagram of the installation structure of the sound absorbing panels I and II on the side panels of the fan volute.

[0025] Figure 3 This is a plan view of the fan volute side panels with sound absorbing panels I and II installed.

[0026] Figure 4 It is a structural schematic diagram of a fan volute belly plate equipped with a belly plate sound absorbing panel.

[0027] Figure 5 It is a schematic diagram of the structure of sound absorbing panel I.

[0028] Figure 6 It is a schematic diagram of the structure of sound absorbing panel II.

[0029] Figure 7 It is a schematic diagram of the structure of the web sound absorbing panel.

[0030] Figure 8 It is a schematic diagram of the overall structure of the fan volute.

[0031] Fig. 9 It is a three-dimensional diagram of the sound absorption structure of the fan volute inlet.

[0032] Fig.10 This is the front view of the sound absorption structure of the fan volute inlet.

[0033] Fig.11 It is a schematic diagram of the three-dimensional structure of the guide block I.

[0034] Fig.12 It is a schematic diagram of the three-dimensional structure of guide block II.

[0035] In the figure: 1-volute belly plate, 2-belt sound absorbing plate, 2-1 arcuate side surface of belly sound absorbing plate, 3-sound absorbing plate II, 3-1 wedge-shaped surface on the side of sound absorbing plate II, 4-sound absorbing plate I, 4-1 protrusion, 4-2 spherical hole, 5-volute side plate, 6-mounting plate, 7-air inlet, 8-guide block II, 9-guide block I. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the embodiments, but the implementation scope of the present invention is not limited only to the following embodiments.

[0037] like Figure 1-Figure 12 As shown, a sound-absorbing structure of a volute of a noise-reducing centrifugal fan and its air inlet is provided, wherein a sound-absorbing plate is fixed on a volute side plate 5 by a mounting plate 6, and a muffler chamber is formed between the sound-absorbing plate and the volute side plate 5; a plurality of web sound-absorbing plates 2 are evenly arranged horizontally and vertically on a volute web 1; and a plurality of obliquely arranged arc-shaped guide blocks are provided on the arc-shaped side wall of the volute air inlet 7.

[0038] like Figure 1-Figure 3 As shown, the sound absorbing panels are two types: sound absorbing panels Ⅰ4 and sound absorbing panels Ⅱ3. The sound absorbing panels Ⅰ4 and sound absorbing panels Ⅱ3 are arranged horizontally and vertically and spaced apart. The sound absorbing panel Ⅰ4 is rectangular as a whole, and a protrusion having a flow-around effect is provided in the middle of the outer surface of the sound absorbing panel Ⅰ4 (see Figure 5 ); the sound absorbing plate II3 is rectangular as a whole, and the sides of the two opposite sides of the sound absorbing plate II3 are provided with wedge-shaped welding grooves (see Figure 6 ).

[0039] See Figure 5 A plurality of spherical holes 4-2 are provided on an inclined surface on one side of the outer surface of the sound absorbing plate Ⅰ4, and the side of the sound absorbing plate Ⅰ4 with the spherical holes 4-2 is installed toward the windward side of the volute.

[0040] The mounting plate 6 is welded to the volute side plate 5 as a whole, the sound absorbing plate I4 and the sound absorbing plate II3 are welded to the mounting plate 6, and a chamber is formed between the sound absorbing plate, the mounting plate 6 and the volute side plate 5.

[0041] like Figure 7 As shown, the web sound absorbing plate 2 is rectangular in shape as a whole, and the side surfaces of the three sides of the web sound absorbing plate 2 are arc-shaped, and the arc-shaped side surface in the middle position is installed toward the windward side of the volute. The web sound absorbing plate 2 is welded to the web 1 of the volute (see Figure 4 ).

[0042] like Figure 8-Figure 12 As shown, the guide blocks are of two types, namely, guide block I9 and guide block II8. The guide block I9 is ​​taller than the guide block II8. Several guide blocks I9 are evenly distributed along the circumferential direction of the volute air inlet 7, and several guide blocks II8 are evenly distributed between two adjacent guide blocks I9.

[0043] The spacing between the guide blocks is 45-55 mm.

[0044] The guide block I9 and the guide block II8 are welded to the air inlet 7 body.

[0045] The sound absorbing panels Ⅰ4 and Ⅱ3 are connected as a whole similar to a guard plate, and are installed on the inner wall of the volute side panel 5. On the one hand, a vibration-reducing and noise-reducing cavity is formed between the sound absorbing material and the volute side panel 5. The cavity is similar to the structure of an elastomer muffler chamber, which can simultaneously play a role in sound insulation and vibration reduction. The rectangular block-shaped sound absorbing panels Ⅰ4 and Ⅱ3 are jointly designed to absorb sound toward the source (sound source) side in the horizontal plane direction of sound source propagation, decelerate on the slope, and accelerate on the back side (sound source). In the spatial direction of sound source propagation, the arrangement of the sound absorbing material of the volute side panel 5 adopts an arrangement design with a gradient change in the sound wave velocity, so that the sound waves have diffraction and reflection effects.

[0046] The design of the sound absorption structure of the volute of the noise-reducing centrifugal fan and its air inlet adopted in the present invention has excellent sound absorption effect in medium and high frequency band tests.

[0047] The air inlet guide blocks Ⅰ9 and Ⅱ8 are innovatively designed and arranged according to the streamlines of the corresponding flow field simulation, which have the function of guiding the flow, ensuring the smooth and uniform air intake of the medium without backflow and secondary flow. Combined with the volute noise reduction design, the noise reduction effect is better.

[0048] There are two kinds of rib-shaped (ridge-shaped) guide blocks of different heights. The guide block I9 of large height guides the overall flow direction of the fluid, and the guide block II8 of small height guides the local flow direction. The two kinds of guide blocks are arranged at intervals.

Claims

1. A noise-reducing centrifugal fan volute and a sound-absorbing structure of its air inlet, characterized in that: A sound absorbing plate is fixed on the volute side plate through a mounting plate, and a muffler chamber is formed between the sound absorbing plate and the volute side plate; a plurality of web sound absorbing plates are evenly arranged horizontally and vertically on the volute web plate; a plurality of obliquely arranged arc guide blocks are arranged on the arc side wall of the volute air inlet; The sound absorbing panels are of two types: sound absorbing panel I and sound absorbing panel II. The sound absorbing panels I and II are arranged horizontally and vertically and spaced apart. The sound absorbing panel I is rectangular in shape as a whole, and the middle part of the outer surface of the sound absorbing panel I is convex. The sound absorbing panel II is rectangular in shape as a whole. A plurality of spherical holes are provided on an inclined surface on one side of the outer surface of the sound absorbing plate I, and the side of the sound absorbing plate I with the spherical holes is installed toward the windward side of the volute; The web sound absorbing plate is rectangular as a whole, and the side surfaces of the three sides of the web sound absorbing plate are arc-shaped, and the arc-shaped side surface in the middle position is installed toward the windward side of the volute; The guide blocks are of two types: guide block I and guide block II. The guide block I is taller than the guide block II. Several guide blocks I are evenly distributed along the circumferential direction of the volute air inlet, and several guide blocks II are evenly distributed between two adjacent guide blocks I.

2. The noise-reducing centrifugal fan volute and the sound-absorbing structure of its air inlet according to claim 1, characterized in that: The spacing between the guide blocks is 45-55 mm.

Images