Novel cooling tower fan silencer based on Laval nozzle and application method thereof

Abstract

The invention provides a novel cooling tower fan silencer based on a Laval nozzle, which is suitable for silencing a pressure type fan and comprises a shell, an acoustic board and a fusiform core, a circular air duct is arranged in the shell, and an acoustic board is laid on the inner wall of the air duct and used for restraining noise transmitted out of the interior of the pressure type draught fan. A spindle-shaped core is arranged in the center of the air channel, and sound absorption plates are laid on the periphery of the spindle-shaped core and used for improving the airflow circulation efficiency. The air duct can be matched with the pressure type fan after being designed into the shape of the Laval nozzle, airflow exhausted by the fan is accelerated, and therefore the airflow circulation efficiency is improved, and the heat dissipation effect of the fan is not affected while the reactive muffler is used. In addition, a traditional silencer is only provided with the inner wall for mounting the sound absorption unit, and the core surface can be used for mounting the sound absorption unit after the fusiform core is placed, so that the total sound absorption area is greatly increased, and a better silencing effect can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of mufflers, and in particular to a novel cooling tower fan muffler based on a Laval nozzle and an application method thereof. Background Art

[0002] Most of the existing cooling tower fan mufflers are resistive mufflers, which achieve the purpose of noise reduction by setting resistive materials on the inner wall of the air duct. However, the noise reduction effect of resistive materials on low-frequency noise is limited, and low-frequency noise is the main component of fan noise, which leads to limited overall effect of the muffler. In practice, in order to achieve a given noise reduction effect, it is often necessary to increase the length of the muffler, resulting in the size and weight of the muffler being too large. The lengthening of the muffler with resistive materials will affect the efficiency of airflow, thereby affecting the normal operation of the fan. In addition, resistive materials are not environmentally friendly, and their effects will vary greatly in different environments, and their noise reduction effect will decrease with the increase of usage time.

[0003] The reactive muffler based on the resonant cavity structure does not have many disadvantages of the resistive muffler. The cavity size of the reactive muffler can be flexibly designed and adjusted according to the frequency of the noise, and a good sound absorption effect can be achieved for low-frequency noise; the material selection of the reactive muffler is flexible, as long as the acoustic impedance is much greater than that of air, and a large number of environmentally friendly materials can meet this requirement; the reactive muffler has good environmental adaptability, and environmental factors such as temperature and humidity will not affect its sound absorption effect; the reactive muffler is also stable, and the sound absorption effect will not decrease over time. However, the disadvantage of the reactive muffler is that its cavity structure will also disturb the airflow movement, thereby affecting the efficiency of the fan airflow. Summary of the invention

[0004] The purpose of the present invention is to provide a new cooling tower fan muffler based on a Laval nozzle, which has a large sound absorbing material area, good sound absorbing effect, can accelerate the airflow on the basis of a resistant sound absorbing structure, and does not affect the working efficiency of the fan, and an application method thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A new cooling tower fan silencer based on Laval nozzle is suitable for silencing pressure-type fans, and includes a shell, a sound-absorbing panel and a spindle-shaped core; a circular air duct is arranged in the shell, and a sound-absorbing panel is laid on the inner wall of the air duct to suppress the noise transmitted from the pressure-type fan; a spindle-shaped core is suspended at the center of the air duct by means of a tether, and the spindle-shaped core adopts an olive-shaped structure, and a Laval nozzle structure is formed between the two sides of the spindle-shaped core and the air duct; a sound-absorbing panel is laid around the outer wall of the spindle-shaped core to improve the efficiency of airflow.

[0007] Preferably, a petal-shaped sawtooth structure is evenly provided on the top of the air duct to achieve a rectifying effect on the airflow and optimize the noise reduction effect in the far field.

[0008] Preferably, the spindle-shaped core is made of a hard material, and the hard material is made of sound-absorbing cotton.

[0009] Preferably, the sound absorbing panel comprises a plurality of Helmholtz resonators, which are arranged in parallel and divided into an upper Helmholtz resonator group and a lower Helmholtz resonator group; the size parameters of the resonator cavity formed by each Helmholtz resonator are flexibly set according to the frequency of the noise to achieve a sound-absorbing effect.

[0010] Preferably, a resistive sound-absorbing material is provided on the inner wall of each of the Helmholtz resonators to achieve a sound-absorbing effect on high-frequency noise.

[0011] Preferably, each of the Helmholtz resonators is provided with a drainage system to prevent rainwater from penetrating into the interior of the Helmholtz resonator during use, thereby affecting the sound-absorbing effect.

[0012] Preferably, the drainage system includes a small hole at the bottom of each of the Helmholtz resonators, and the Helmholtz resonator group forms a small hole group corresponding to the small holes;

[0013] The small hole groups between the adjacent Helmholtz resonator groups are connected, and the bottom of the air duct is provided with a drainage port connected with the small hole group on the Helmholtz resonator group at the bottom layer;

[0014] Rainwater drips from the small hole group between the adjacent Helmholtz resonator groups by gravity, and is discharged to the outside through the drainage port at the bottom of the air duct connected to the small hole group on the Helmholtz resonator group at the bottom layer, without affecting the daily use of the muffler.

[0015] The present invention also provides an application method of a novel cooling tower fan muffler based on a Laval nozzle, comprising the following steps:

[0016] Step S1: placing a muffler on the exhaust port of the pressure type blower and on the fan side of the pressure type blower;

[0017] Step S2: When the pressure-type fan is started, the operating noise of the pressure-type fan itself and the noise of the fan pass through the inner wall of the air duct and the plurality of sound-absorbing panels on the spindle-shaped core. The spindle-shaped core and the sound-absorbing panels both use a plurality of Helmholtz resonators arranged in parallel and divided into upper and lower layers to suppress the noise transmitted from the pressure-type fan. The resistive sound-absorbing material installed on the inner wall of the Helmholtz resonator can take into account the sound-absorbing effect of high-frequency noise.

[0018] The noise inside the pressure-type fan passes through the spindle-shaped core in the muffler air duct. The spindle-shaped core adopts an olive-shaped structure, which transitions from a bulge in the middle to two sharp ends, so that a Laval nozzle structure is naturally formed between the two sides of the spindle-shaped core and the air duct.

[0019] During the application process, the pressure-type fan discharges airflow. When the airflow passes through the Laval nozzle structure formed between the air duct and the spindle-shaped core, according to the principle of the Laval nozzle, the airflow is accelerated to improve the efficiency of the airflow circulation, so as to achieve the use of the resistive silencer without affecting the heat dissipation effect of the fan;

[0020] When it rains, rainwater flows into the air duct, and drips from top to bottom through the small hole group between the adjacent Helmholtz resonator groups by gravity, and is discharged to the outside through the drainage port at the bottom of the air duct that communicates with the small hole group on the Helmholtz resonator group at the bottom layer, without affecting the daily use of the muffler.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The muffler of the present invention has a large sound absorbing material area and a good sound absorbing effect. In addition, the present invention can accelerate the airflow based on the use of a resistant sound absorbing structure without affecting the working efficiency of the fan.

[0023] (2) The present invention can customize the corresponding unit structure size according to different noise frequencies and has wide adaptability.

[0024] (3) The present invention can optimize the design of noise reduction effect for specific far-field locations.

[0025] (4) The present invention adopts a resistant sound absorption structure. The raw materials of the silencer can be selected from a wide range. The material for constructing the resonance chamber can be an acoustically rigid material without special requirements. It can be flexibly selected based on cost, environmental protection requirements and actual usage.

[0026] (5) The present invention is provided with a drainage system to prevent the influence of bad weather on its noise reduction effect.

[0027] (6) The present invention does not require subsequent maintenance, and the noise reduction effect will not decrease over time after one installation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic structural diagram of a novel cooling tower fan muffler based on a Laval nozzle provided in an embodiment of the present invention;

[0029] Figure 2 A schematic cross-sectional view of a novel cooling tower fan muffler based on a Laval nozzle provided in an embodiment of the present invention;

[0030] Figure 3 A schematic structural diagram of an upper Helmholtz resonator group and a lower Helmholtz resonator group in a novel cooling tower fan muffler based on a Laval nozzle provided in an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of the installation and application structure of a novel cooling tower fan muffler based on a Laval nozzle provided in an embodiment of the present invention;

[0032] Figure 5 A schematic structural diagram of a Laval nozzle known in the prior art provided for an embodiment of the present invention.

[0033] The serial numbers in the figure are as follows:

[0034] 1. Shell; 2. Sawtooth structure; 3. Sound-absorbing panel; 4. Spindle-shaped core; 5. Upper Helmholtz resonator group; 6. Lower Helmholtz resonator group; 7. Upper small channel; 8. Lower small channel; 9. Rainwater. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0036] like Figure 1 and Figure 2 As shown, the novel cooling tower fan muffler based on the Laval nozzle provided in this embodiment is suitable for the muffler of the pressure type fan, and includes a shell 1, a sound absorbing plate 3 and a spindle-shaped core 4.

[0037] A circular air duct is provided in the shell 1, which is a resonance cavity. A sound absorbing plate 3 is laid on the inner wall of the air duct. The sound absorbing plate 3 uses a number of Helmholtz resonators arranged in parallel. The size parameters of the resonator cavity formed by each Helmholtz resonator are flexibly set according to the frequency of the noise to achieve the sound elimination effect. The shape of the resonator cavity can also be flexibly designed according to the actual use situation, as long as the resonance condition is met. In addition, a resistive sound-absorbing material is provided on the inner wall of each Helmholtz resonator to take into account the sound elimination effect of high-frequency noise.

[0038] In this embodiment, the parallel Helmholtz resonators are divided into upper and lower layers of Helmholtz resonator groups, including upper two layers of Helmholtz resonator groups 5 and lower two layers of Helmholtz resonator groups 6. (For the convenience of the following description, the upper and lower two layers of Helmholtz resonator groups are only one solution of this embodiment. In actual applications, multiple layers of stacking can be set according to different sizes or needs. The size of the Helmholtz resonator is determined by the main frequency of the noise, and the size of the muffler is determined by the actual application scenario. After the two sizes are determined, the Helmholtz resonators are spread all over the inner wall of the muffler's air duct and around the spindle-shaped core 4 as needed.)

[0039] A spindle-shaped core 4 is suspended in the center of the air duct by means of a tether. The spindle-shaped core 4 adopts an olive-shaped structure, and the olive-shaped structure transitions from a bulge in the middle to two pointed ends, so that a Laval nozzle structure is naturally formed between the two sides of the spindle-shaped core 4 and the air duct; a sound-absorbing panel 3 is laid around the spindle-shaped core 4 to suppress the noise transmitted from the inside of the pressure-type fan.

[0040] It is known that the front half of the Laval nozzle shrinks from large to small and shrinks to a narrow throat in the middle, and then expands from small to large and expands outward to the outlet after the narrow throat. The inflowing gas enters the front half of the nozzle under pressure, passes through the narrow throat and escapes from the back half. This structure can change the speed of the airflow due to the change of the nozzle cross-sectional area, and can even make the airflow change from subsonic to sonic, and even accelerate to supersonic. Therefore, people call this trumpet-shaped nozzle a transonic nozzle. Because it was invented by the Swede Laval, it is also called a "Laval nozzle".

[0041] The principle of Laval nozzle is as follows Figure 5 As shown in the figure, under the action of pressure, the incident airflow moves backward through the nozzle and enters the convergent tube of the nozzle. At this stage, the airflow movement follows the principle that "when the fluid moves in the tube, the flow velocity is large where the cross-section is small, and the flow velocity is small where the cross-section is large", so the airflow continues to accelerate. When reaching the narrow throat, the airflow velocity has greatly exceeded the initial velocity at the entrance. However, high-speed fluids, especially transonic fluids, no longer follow the principle of "the flow velocity is large where the cross-section is small, and the flow velocity is small where the cross-section is large" when moving, but on the contrary, the larger the cross-section, the faster the flow velocity, so the speed of the airflow will be further accelerated after entering the expansion tube. The Laval nozzle actually plays the role of a "flow velocity amplifier", and this feature makes it widely used in rockets, missiles, jet aircraft and other fields.

[0042] Furthermore, the spindle-shaped core 4 is made of hard material, and the specific material can be flexibly selected according to the requirements of environmental protection and other aspects, and only needs to meet the acoustic hard boundary conditions. In this embodiment, the hard material of the spindle-shaped core 4 is a sound-absorbing cotton material, and a Laval nozzle structure is formed between the two sides of the spindle-shaped core 4 and the air duct to improve the efficiency of airflow.

[0043] Furthermore, in this embodiment, a petal-shaped sawtooth structure 2 is evenly provided at the top of the air duct to achieve the effect of rectifying the airflow and optimizing the noise reduction effect in the far field. The basic principle is that there is a phase difference between the noise diffracted from the bottom and top of a single petal-shaped sawtooth, which will produce an interference effect in the far field to form peaks and valleys for noise propagation. In practical applications, the noise of the cooling tower fan often only affects a specific location. When designing the muffler, the corresponding sawtooth size can be pre-calculated based on the distance from the location to the fan, thereby placing this location in the valley of noise propagation, and using the interference effect to further enhance the noise reduction effect of the muffler.

[0044] Furthermore, in this embodiment, each Helmholtz resonator is provided with a drainage system to prevent rainwater from penetrating into the interior of the Helmholtz resonator during use, thereby affecting the muffler effect. The drainage system includes a small channel at the bottom of each of the Helmholtz resonators; the upper small channel 7 of the adjacent upper Helmholtz resonator group 5 is connected to the lower small channel 8 of the lower Helmholtz resonator group 6, so that the rainwater 6 in the upper Helmholtz resonator group 5 flows into the lower Helmholtz resonator group 6 from top to bottom by gravity, thereby draining the rainwater 6 to the outside without affecting the daily use of the muffler.

[0045] Furthermore, the size of the drainage channel opening can be optimized by calculation during design, which will not affect the resonant sound absorption effect produced by the resonator unit of the Helmholtz resonator.

[0046] like Figure 3 As shown, the application method of the novel cooling tower fan muffler based on the Laval nozzle provided by the present invention comprises the following steps:

[0047] Step S1: placing the muffler 100 on the exhaust port of the pressure type blower and on the fan side of the pressure type blower;

[0048] Step S2: When the pressure-type fan is started, the operating noise of the pressure-type fan itself and the noise of the fan pass through the inner wall of the air duct and the plurality of sound-absorbing panels 3 on the spindle-shaped core 4. The spindle-shaped core 4 and the sound-absorbing panels 3 both use a plurality of Helmholtz resonators arranged in parallel and divided into two layers, which are used to suppress the noise transmitted from the pressure-type fan. The resistive sound-absorbing material installed on the inner wall of the Helmholtz resonator can take into account the sound-absorbing effect of high-frequency noise.

[0049] The noise inside the pressure-type fan passes through the spindle-shaped core 4 in the air duct of the muffler 100. The spindle-shaped core 4 adopts an olive-shaped structure, and the olive-shaped structure transitions from a bulge in the middle to two sharp ends, so that a Laval nozzle structure is naturally formed between the two sides of the spindle-shaped core 4 and the air duct;

[0050] During application, the pressure-type fan discharges airflow, and when the airflow passes through the Laval nozzle structure formed between the air duct and the spindle-shaped core 4, according to the above-mentioned principle of the Laval nozzle, the airflow is accelerated to improve the efficiency of the airflow circulation, thereby achieving the use of a resistive silencer without affecting the heat dissipation effect of the fan.

[0051] When it rains, rainwater 9 flows into the air duct, and drips from top to bottom through the small hole group between the adjacent Helmholtz resonator groups by gravity, and is discharged to the outside through the drainage port at the bottom of the air duct that communicates with the small hole group on the Helmholtz resonator group at the bottom layer, without affecting the daily use of the muffler.

[0052] The sound absorbing material area of ​​the silencer of this embodiment is large, and the sound absorbing effect is good. In addition, the present invention can accelerate the airflow based on the use of a resistant sound absorbing structure without affecting the working efficiency of the fan. This embodiment can customize the corresponding unit structure size according to different noise frequencies, and has a wide range of adaptability. This embodiment can optimize the design of the noise reduction effect for specific far-field locations. This embodiment adopts a resistant sound absorbing structure, and the raw materials of this silencer can be selected from a wide range of options. The material for constructing the resonance chamber can be an acoustically rigid material without special requirements. It can be flexibly selected based on cost, environmental protection requirements, and actual usage. This embodiment is equipped with a drainage system to prevent bad weather from affecting its noise reduction effect. This embodiment does not require subsequent maintenance, and the noise reduction effect will not decrease over time after one installation.

[0053] After the muffler of this embodiment designs the air duct into the shape of a Laval nozzle, it can cooperate with a pressure-type fan to accelerate the exhaust airflow of the fan, thereby improving the efficiency of airflow circulation, and achieving the heat dissipation effect of the fan while using a resistant muffler. In addition, the traditional muffler only has the inner wall for installing the sound absorption unit, and after the spindle-shaped core is placed, the core surface can also be used to install the sound absorption unit. This design greatly increases the total sound absorption area, which is conducive to achieving a better sound elimination effect.

[0054] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0055] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0056] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. The new cooling tower fan muffler based on Laval nozzle is suitable for the silencer of pressure type fans, and is characterized by: It comprises a shell (1), a sound absorbing plate (3) and a spindle-shaped core (4); A circular air duct is provided in the housing (1), and a sound absorbing plate (3) is laid on the inner wall of the air duct to suppress the noise emitted from the inside of the pressure-type fan; A spindle-shaped core (4) is suspended at the center of the air duct by means of a tether, the spindle-shaped core (4) adopts an olive-shaped structure, and a Laval nozzle structure is formed between the two sides of the spindle-shaped core (4) and the air duct; a sound-absorbing panel (3) is laid around the outer wall of the spindle-shaped core (4) to improve the efficiency of airflow.

2. The novel cooling tower fan muffler based on Laval nozzle according to claim 1 is characterized in that: The top of the air duct is evenly provided with a petal-shaped sawtooth structure (2) for achieving an airflow rectification effect and optimizing a far-field noise reduction effect.

3. The novel cooling tower fan muffler based on Laval nozzle according to claim 1 is characterized in that: The spindle-shaped core (4) is made of a hard material, and the hard material is made of sound-absorbing cotton.

4. The novel cooling tower fan muffler based on Laval nozzle according to claim 1 is characterized in that: The sound absorbing plate (3) comprises a plurality of Helmholtz resonators, which are arranged in parallel and divided into at least two layers of Helmholtz resonator groups. The size parameters of the resonator cavity formed by each Helmholtz resonator are flexibly set according to the frequency of the noise, so as to achieve a sound elimination effect.

5. The novel cooling tower fan muffler based on Laval nozzle according to claim 4 is characterized in that: The inner wall of each Helmholtz resonator is provided with a resistive sound-absorbing material, so as to achieve the sound-absorbing effect of high-frequency noise.

6. The novel cooling tower fan muffler based on Laval nozzle according to claim 4 is characterized in that: Each of the Helmholtz resonators is provided with a drainage system to prevent rainwater from seeping into the interior of the Helmholtz resonator during use, thereby affecting the sound-absorbing effect.

7. The novel cooling tower fan muffler based on Laval nozzle according to claim 6 is characterized in that: The drainage system includes a small hole at the bottom of each of the Helmholtz resonators, and a small hole group is formed on the Helmholtz resonator group corresponding to the small hole; The small hole groups between the adjacent Helmholtz resonator groups are connected, and the bottom of the air duct is provided with a drainage port connected with the small hole group on the Helmholtz resonator group at the bottom layer; Rainwater (9) drips downward from the small hole groups between the adjacent Helmholtz resonator groups by gravity, and is discharged to the outside through the drainage port at the bottom of the air duct that communicates with the small hole groups on the Helmholtz resonator groups at the bottom layer, without affecting the daily use of the muffler.

8. The application method of the novel cooling tower fan muffler based on Laval nozzle according to any one of claims 1 to 7, characterized in that: The steps include: Step S1: placing the muffler (100) on the exhaust port of the pressure type blower and on the fan side of the pressure type blower; Step S2: When the pressure-type fan is started, the operating noise of the pressure-type fan itself and the fan noise are transmitted through the inner wall of the air duct and the plurality of sound-absorbing panels (3) arranged on the spindle-shaped core (4). The spindle-shaped core (4) and the sound-absorbing panels (3) both use a plurality of Helmholtz resonators arranged in parallel and divided into two layers, which are used to suppress the noise transmitted from the pressure-type fan. The resistive sound-absorbing material installed on the inner wall of the Helmholtz resonator can also achieve the sound-absorbing effect of high-frequency noise. The noise inside the pressure-type fan passes through the spindle-shaped core (4) in the air duct of the muffler (100). The spindle-shaped core (4) adopts an olive-shaped structure, and the olive-shaped structure transitions from a bulge in the middle to sharp points at both ends, so that a Laval nozzle structure is naturally formed between the two sides of the spindle-shaped core (4) and the air duct; During the application process, the pressure-type fan discharges airflow, and when the airflow passes through the Laval nozzle structure formed between the air duct and the spindle-shaped core (4), according to the principle of the Laval nozzle, the airflow is accelerated to improve the efficiency of the airflow circulation, so as to achieve the heat dissipation effect of the fan without affecting the use of the resistive silencer; When it rains, rainwater (9) flows into the air duct, and drips from the small hole group between the adjacent Helmholtz resonator groups by gravity, and is discharged to the outside through the drainage port at the bottom of the air duct that communicates with the small hole group on the Helmholtz resonator group at the bottom layer, without affecting the daily use of the muffler.

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