Active adaptive silencer adaptive to variable-speed working condition of Roots blower

Abstract

The invention discloses an active adaptive silencer adaptive to the variable rotating speed working condition of a Roots blower, and relates to the technical field of noise reduction of industrial equipment.The silencer comprises a silencing cavity, an inlet pipe and a multi-beam type outlet pipe, the silencing cavity is composed of a cylindrical outer shell, a coaxial inner partition net and end covers at the two ends, an annular resonant cavity between the inner separation net and the outer shell is filled with a single material or a composite resistive silencing material; the inlet pipe is communicated with the first end cover, a conical fluid director coaxial with the inlet pipe is arranged in the silencing cavity, an air inlet cone of the conical fluid director can axially and telescopically adjust the throat circulation sectional area, and a surface spiral flow guide groove can comb airflow; an inner cone body is arranged on the inner side of the air inlet cone, the opening degree of a conical surface through hole is controlled through axial movement or rotation, a miniature resonant cavity array is formed when the opening degree is half, and precise noise reduction is achieved; the silencer can be dynamically matched with the variable-speed air displacement of the fan, gives consideration to both wide-frequency-band silencing and airflow efficiency, is low in energy consumption and long in service life, and meets the noise reduction requirement of the Roots blower matched with the sand sucker.

Description

Technical Field

[0001] This invention relates to the field of noise reduction technology for industrial equipment, specifically to an active adaptive silencer adapted to the variable speed operating conditions of Roots blowers. Background Technology

[0002] In the field of noise reduction for Roots blowers used in industrial sand suction equipment, reactive silencers are widely used noise control devices. These silencers typically employ a cylindrical cavity structure with inlet and outlet pipes, and some products fill the cavity with sound-absorbing material to enhance noise reduction. However, in actual operation, the Roots blower needs to adjust its speed according to factors such as the thickness of the sand layer and the resistance of the suction pool, resulting in a linear change in exhaust volume. Existing silencers generally suffer from a fixed structure, making it difficult to adapt to the variable speed operation requirements of the blower. Specifically, the throat cross-sectional area of ​​traditional silencers is a fixed value. When the blower operates at high speed and with a large exhaust volume, the fixed throat easily forms an airflow bottleneck, leading to increased exhaust resistance. This not only increases the blower's energy consumption but also weakens the negative pressure suction of the sand suction machine, affecting sand suction efficiency. When the blower operates at low speed and with a small exhaust volume, the excessively large throat cross-sectional area causes airflow to stagnate and eddy within the cavity, generating additional turbulent noise and negating the noise reduction effect of the silencer. Meanwhile, the resonant cavity and sound-absorbing structure parameters of traditional silencers are mostly designed for rated speed, and their silencing frequency band is fixed. When the fan speed changes, the main noise frequency deviates from the effective silencing frequency band of the silencer, and the attenuation capability of mid-to-high frequency noise decreases significantly. Low-frequency noise is already difficult to effectively cover by traditional structures, ultimately resulting in poor noise reduction stability of the silencer across the entire speed range. In addition, some silencers directly fill the sandwich layer with sound-absorbing material without an effective protective structure. Dust and oil in the fan exhaust can easily clog the material pores, causing the sound absorption performance to decay rapidly, shortening the silencer's service life, and increasing equipment maintenance costs. These defects mean that existing silencers cannot simultaneously achieve noise reduction effect and airflow efficiency under variable speed conditions of Roots blowers, making it difficult to meet the actual needs of industrial sand suction operations.

[0003] For the reasons mentioned above, it is necessary to propose an active adaptive silencer that is suitable for the variable speed operation of Roots blowers to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an active adaptive silencer that is suitable for the variable speed operation of Roots blowers.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: An active adaptive silencer adapted to the variable speed operation of a Roots blower includes: The sound-absorbing cavity includes a cylindrical outer shell, an inner mesh coaxially arranged inside the outer shell, a first end cap and a second end cap respectively sealed and connected to the two ends of the outer shell, and the interlayer between the inner mesh and the outer shell forms an annular resonant cavity. An inlet pipe is connected to the first end cap and is connected to the silencing cavity. The outlet pipe is composed of multiple outlet single pipes forming a multi-bundle outlet structure. Each outlet single pipe is flared and has a small end and a large end. The small end is connected to and installed on the second end cap.

[0006] Furthermore, the centers of the multiple outlet tubes are evenly spaced along the same arc trajectory.

[0007] Furthermore, the annular resonant cavity is filled with resistive sound-absorbing material, which includes a single-material sound-absorbing structure or a composite sound-absorbing structure.

[0008] Furthermore, the silencing cavity is provided with a conical flow guide structure, which includes an intake cone with its cone pointing towards the inlet pipe. The intake cone is coaxially arranged with the inlet pipe. The intake cone extends and retracts axially to adjust and control the effective flow cross-sectional area of ​​the throat to match different exhaust volumes, and to keep the airflow in the throat in a critically smooth state without increasing airflow resistance.

[0009] Furthermore, the surface of the intake cone is provided with spiral guide grooves, and multiple spiral guide grooves are evenly distributed axially on the surface of the intake cone. The multiple spiral guide grooves rectify the airflow of the intake pipe into a spiral uniform airflow.

[0010] Furthermore, the conical air guide structure also includes an inner cone disposed inside the intake cone. The surface of the intake cone is distributed with several through holes. The inner cone moves relative to the intake cone, and the through holes are partially or completely opened to form a controllable secondary channel. The secondary channel changes the effective flow cross-sectional area of ​​the airflow path, and the sound waves are reflected multiple times between the inside of the intake cone and the inner cone.

[0011] Furthermore, when the inner cone moves axially relative to the intake cone and is in a half-open state, multiple micro-resonance cavities are formed between the through hole and the inner cone. These multiple micro-resonance cavities form a micro-resonance cavity array, and the enclosed space within the micro-resonance cavity array resonates and absorbs noise of a specific frequency from the Roots blower.

[0012] Furthermore, the inner surface of the intake cone is provided with a baffle plate, the baffle plate is arranged around the outer ring of one or more through holes, the baffle plate is arranged axially, and the inner cone surface is provided with a slot portion that matches the position of the baffle plate. When the inner cone is in contact with the air intake cone, the baffle is inserted into the corresponding slot, and the micro resonant cavity array is in the closed state; When the inner vertebral body moves axially to a half-open state, the baffle plate and the slot part do not separate, forming a micro resonant cavity array; The inner vertebral body continues to move axially and open, and the baffle plate leaves the slot, so that a secondary channel is formed between the air intake cone and the inner vertebral body.

[0013] Furthermore, the through hole is designed as several concentrically arranged first arc-shaped waist holes, and the first arc-shaped waist holes are concentrically arranged with the air intake cone; the inner cone is provided with several second arc-shaped waist holes corresponding to the positions of the first arc-shaped waist holes; the inner cone is rotated relative to the air intake cone to control the change of the effective flow cross-sectional area of ​​the through hole by adjusting the misalignment of the second arc-shaped waist holes with the first arc-shaped waist holes.

[0014] Furthermore, a monitoring device is provided on the inlet pipe, which includes a wind pressure sensor and a wind speed sensor.

[0015] The advantages and beneficial effects of this invention are as follows: This invention provides an active adaptive silencer for Roots blowers operating at varying speeds. Based on a "ring resonant cavity + multi-beam outlet" structure, it optimizes the silencing frequency band by filling with resistive silencing material. An adjustable conical guide structure (axial extension, axial movement switching opening, and rotation adjustment of the waist hole) achieves dynamic adaptation to the variable speed conditions of the Roots blower. Combined with a monitoring device, a closed-loop regulation is formed, creating a series of solutions from basic to advanced, covering different operating conditions. Each embodiment specifically addresses the core pain points of traditional silencers—poor silencing effect and large resistance fluctuations under variable speed conditions—achieving a synergistic improvement in silencing performance and airflow stability through structural optimization, thus possessing broad industrial application value. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an active adaptive silencer adapted to the variable speed operating conditions of a Roots blower according to the present invention; Figure 2 This is a schematic diagram of the internal structure of the active adaptive muffler in this invention; Figure 3 This is a view of the second end cap of the active adaptive muffler in this invention; Figure 4 This is a schematic diagram of the longitudinal section of the active adaptive muffler in this invention; Figure 5 This is a structural schematic diagram of the three opening states of the active adaptive muffler in this invention; Figure 6 This is a schematic diagram of the arc-shaped waist-shaped through hole in Embodiment 4 of the present invention; Figure 7 This is a front view of the conical flow guide structure in Embodiment 4 of the present invention; In the diagram: 1. Outer shell; 2. Inner partition; 3. Annular resonant cavity; 4. Inlet pipe; 5. Outlet single pipe; 6. Noise-absorbing material; 7. Conical guide structure; 8. Inlet cone; 9. Spiral guide groove; 10. Inner cone; 11. Through hole; 12. Secondary channel; 13. Miniature resonant cavity; 14. Enclosure plate; 15. Slot section; 16. First arc-shaped waist hole; 17. Second arc-shaped waist hole; 18. Wind pressure sensor; 19. Wind speed sensor; 20. Cage; 21. First reduction drive; 22. First drive screw; 23. Second drive screw; 24. Second reduction drive. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to examples. These examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0018] Roots blowers are widely used in industrial production, but they generate significant noise during operation. Furthermore, in actual working conditions, the speed often needs to be adjusted according to production requirements (for example, when the sand layer thickness varies greatly, a thick sand layer requires a higher airflow, while a thin sand layer can reduce the airflow to save energy). This results in dynamic changes in exhaust volume, airflow velocity, and noise frequency characteristics, making it difficult for traditional fixed-structure silencers to maintain good noise reduction performance within the variable speed range. This technical solution addresses this core pain point by designing a series of actively adaptive silencer structures to suit variable speed conditions. Through a combination of optimized basic structure and adjustable flow guide structures, dynamic matching of noise reduction performance with varying operating conditions is achieved. Example 1

[0019] This embodiment mainly consists of three parts: a silencing cavity, an inlet pipe 4, and an outlet pipe. Its core design concept is to optimize airflow through the resonance silencing of the annular resonant cavity 3 and the multi-beam outlet structure. Specifically, as... Figure 1-3 As shown, the silencing cavity adopts a double-layer structure of "cylindrical outer shell 1 + coaxial inner mesh 2 + end caps at both ends". The interlayer between the inner mesh 2 and the outer shell 1 forms an annular resonant cavity 3. This annular cavity structure can utilize the resonance effect of sound waves to consume noise energy, especially having a natural silencing advantage for mid-to-low frequency noise. This is because the noise of the Roots blower is mainly mid-to-low frequency, and the volume and shape of the annular resonant cavity 3 can better match the wavelength characteristics of this type of noise. The inlet pipe 4 is directly connected to the first end cap and extends into the silencing cavity to guide the airflow discharged from the Roots blower into the silencing cavity. The outlet pipe adopts a multi-bundle structure, consisting of multiple horn-shaped outlet single pipes 5 (this embodiment takes three outlet single pipes 5 as an example). The small end is connected to the second end cap, and the large end faces outward. This horn-tube structure can effectively reduce the local resistance at the airflow outlet and reduce the secondary noise generated by airflow disturbance. At the same time, the multi-bundle layout can disperse the airflow and avoid the concentrated impact of airflow caused by a single outlet, further optimizing the stability of the airflow after silencing.

[0020] In the above structure, the abrupt change in the airflow channel (entering the silencing cavity through inlet pipe 4) and the multi-outlet diversion achieve sound wave reflection and interference. When the sound waves carried by the fan exhaust enter the cylindrical cavity from the eccentric large inlet pipe, because the cross-section of the cavity is much larger than that of the inlet pipe, the sound waves will be reflected multiple times in the cavity, and some sound waves will cancel each other out due to their opposite phases; at the same time, the diversion design of the three outlet pipes allows the sound waves to form multi-path interference again at the outlet, further attenuating the noise energy.

[0021] Furthermore, the centers of the multiple outlet single pipes 5 are evenly spaced along the same arc trajectory. This ensures the uniformity of airflow discharge and prevents local airflow pressure imbalance within the silencing cavity caused by uneven distribution of the outlet single pipes 5, which would affect the silencing effect. This layout allows the airflow within the silencing cavity to be discharged evenly from all directions, reducing airflow resistance and avoiding additional noise generated by local airflow vortices, thus further improving the overall stability of the silencing system.

[0022] Furthermore, by adding resistive sound-absorbing material 6 to the aforementioned basic structure, this design is suitable for simple operating conditions where there is a basic requirement for sound attenuation and a narrow range of variable speeds. Specifically, in this embodiment, resistive sound-absorbing material 6 is filled inside the annular resonant cavity 3. The resistive sound-absorbing material 6 can be a single-material sound-absorbing structure or a composite sound-absorbing structure. The core reason for choosing to fill with resistive sound-absorbing material 6 is that the noise frequency of the Roots blower covers the mid-to-high frequency range when the speed changes, while the basic annular resonant cavity 3 has limited sound attenuation effect on mid-to-high frequency noise. The resistive material can convert sound energy into heat energy through the friction and viscosity of sound waves inside the material, thus compensating for the lack of sound attenuation frequency range of the resonant cavity and achieving wide-band sound attenuation. Specifically, the single-material sound-absorbing structure can be directly filled with glass wool in the interlayer of the annular resonant cavity 3. Glass wool is lightweight and has stable sound absorption performance, which can meet the basic mid-to-high frequency sound attenuation requirements. It is suitable for clean operating conditions without moisture-proof or oil-proof requirements, such as for use with ordinary air-transporting Roots blowers. Composite sound-absorbing structures are suitable for more complex operating conditions, such as industrial environments with small amounts of dust, high humidity, or oil stains. They consist of a perforated panel, centrifugal glass wool, and polyurethane foam arranged sequentially from the inside out. The perforated panel serves as the outer layer, with a pore size of 3-5mm and a perforation rate of 20%-25%. This design ensures smooth airflow while effectively preventing dust from entering the internal sound-absorbing material, thus avoiding material blockage and reduced sound absorption performance. The middle layer of centrifugal glass wool has a density of 48kg / m³, which provides excellent absorption of mid-to-high frequency sound waves and forms the core layer of resistive silencing. The bottom layer of polyurethane foam has a density of 30kg / m³. Its closed-cell structure not only enhances the resonance absorption of low-frequency sound waves, compensating for the insufficient low-frequency sound absorption of glass wool, but also provides moisture and oil protection, preventing water vapor and oil stains from corroding the internal materials and extending the lifespan of the silencer. For example, in the installation of Roots blowers in sewage treatment plants, the environment is humid and there may be a small amount of oil. The first embodiment of this composite sound-absorbing structure can simultaneously achieve wide-band noise reduction and improve environmental adaptability, ensuring that a stable noise reduction effect can still be maintained under variable speed conditions. Example 2

[0023] In this embodiment, an intake cone 8 structure with a spiral guide groove 9 is added. The core objective is to adapt to the changes in exhaust volume caused by variable speed through airflow rectification and throat cross-sectional area adjustment, while optimizing airflow conditions to reduce resistance noise. The core impact of variable speed of the Roots blower is the change in exhaust volume. If the flow cross-sectional area of ​​the silencer throat is fixed, an increase in exhaust volume will lead to a surge in airflow resistance, generating additional noise; a decrease in exhaust volume may result in excessively low airflow velocity, causing a mismatch between the silencer structure and the noise frequency, and a decrease in the silencer effect. The throat is the actual annular, controllable flow space formed between the end of the inlet pipe 4 and the intake cone 8. Therefore, as Figure 4As shown, in this embodiment, an intake cone 8 (with the cone pointing towards the inlet pipe 4) coaxial with the inlet pipe 4 is added. This intake cone 8 can be adjusted axially to match different exhaust volumes by changing the effective flow cross-sectional area of ​​the throat. Its design principle is based on the critical flow state theory of fluid mechanics. By adjusting the cross-sectional area, the airflow at the throat is always in a critical flow state, ensuring smooth airflow without generating additional resistance noise due to excessive flow velocity. For example, when the Roots blower speed increases from 1000 r / min to 1500 r / min, and the exhaust volume increases by 30% accordingly, the intake cone 8 is controlled to retract axially (i.e., move away from the inlet pipe 4), increasing the effective flow cross-sectional area of ​​the throat by about 35%, keeping the airflow velocity near the critical value and avoiding a surge in resistance. When the speed drops to 800 r / min and the exhaust volume decreases by 20%, the intake cone 8 extends axially, reducing the throat cross-sectional area, ensuring stable airflow velocity, and ensuring the matching of the silencing structure with the noise frequency. Building upon this, Embodiment 2 further incorporates multiple spiral guide grooves 9 evenly distributed axially on the surface of the intake cone 8. This design addresses the issue that the airflow discharged from the Roots blower often exhibits vortices and non-uniformity. This unstable airflow generates secondary noise within the silencing cavity, impacting the silencing effect. The spiral guide grooves 9 function to rectify the incoming turbulent airflow into a spiral-shaped, uniform airflow. This is achieved through the guiding effect of the grooves, allowing the airflow to flow smoothly along a spiral trajectory, reducing the generation of vortices. Simultaneously, the uniform airflow allows for more thorough contact with the silencing structure, improving silencing efficiency. For example, by evenly distributing four guide grooves with a 30° spiral angle axially on the surface of the intake cone 8, when the airflow enters from the inlet pipe 4, it forms a stable spiral airflow under the guidance of the grooves, preventing the impact of turbulent airflow on the silencing cavity and improving the silencing effect by 15%-20% under variable speed conditions. Example 3

[0024] Example 3 adds an axially movable inner cone 10 and a matching baffle plate 14 and slot structure to Example 2. The axial movement of the inner cone 10 allows switching between three opening states, thereby achieving multi-mode adaptation of "flow cross-sectional area adjustment + wide-band resonance silencing + high-flow conduction," suitable for operating conditions with a wide range of variable speeds and complex noise frequency variations. Its core design concept is to construct a controllable secondary channel 12 and a micro-resonance cavity 13 array through the relative movement of the inner cone 10 and the intake cone 8, enabling the muffler to switch to the optimal operating state according to the exhaust volume and noise characteristics at different speeds. Specifically, an inner cone 10 is provided inside the intake cone 8, and several through holes 11 are distributed on the surface of the intake cone 8. The inner cone 10 and the intake cone 8 are connected by a baffle plate 14 and a slot. The axial movement of the inner cone 10 can achieve three opening states, such as... Figure 5 As shown, the structure, principle, and advantages of each state are explained below with specific examples: The first type is the closed state, such as Figure 5As shown in (C), when the inner cone 10 and the inlet cone 8 are fully fitted, the baffle 14 on the surface of the inlet cone 8 is inserted into the slot 15 of the inner cone 10. At this time, the array of micro resonant cavities 13 is in a closed state, the through hole 11 is blocked by the inner cone 10, and the airflow enters the silencing cavity only through the throat channel formed by the inlet cone 8 and the inlet pipe 4. This state is suitable for the low-speed and small-volume operation of the Roots blower, such as when the speed is 600 r / min and the exhaust volume is small. The closed state can ensure that the throat cross-sectional area is small, so that the airflow velocity is stable, and at the same time, it avoids leakage of airflow through the through hole 11, ensuring the matching of the silencing structure with low-frequency noise.

[0025] The second type is the half-open state, such as Figure 5 (B) As shown, when the inner cone 10 moves axially to the partially open position, the baffle 14 is still not disengaged from the slot 15. At this time, the inner surface of the intake cone 8, the baffle 14, and the outer surface of the inner cone 10 form an array of multiple micro-resonance cavities 13. The design principle of this state is to utilize the resonance effect of the micro-resonance cavities 13 to accurately absorb the characteristic frequency noise at a specific speed of the Roots blower. Its advantage is that the volume and inlet size of the micro-resonance cavities 13 can be flexibly adjusted through the layout of the baffle 14 to achieve wide-band noise adaptation. For example, when the Roots blower rotates at 1200 r / min, the characteristic noise frequency is 500 Hz-1000 Hz. At this time, the inner cone 10 can be adjusted to a half-open state, so that the area covered by the baffle 14 forms a miniature resonant cavity 13 with a volume of 50-100 cm³. Each resonant cavity has 2-3 through holes 11 as inlets. The noise in this frequency band is precisely absorbed through the resonance effect, and the noise reduction is increased by more than 25%. If the rotation speed is adjusted to 1800 r / min, the characteristic noise frequency becomes 1000 Hz-1500 Hz. The position of the inner cone 10 can be further fine-tuned to adjust the volume of the miniature resonant cavity 13 to 30-60 cm³, which is suitable for the absorption of high-frequency noise.

[0026] The third type is the fully open state, such as Figure 5As shown in (A), when the inner cone 10 continues to move axially and the baffle 14 completely leaves the slot 15, the array of micro resonant cavities 13 opens, forming a secondary channel 12 between the intake cone 8 and the inner cone 10. At this time, the airflow can simultaneously enter the silencing cavity through the main throat channel and the secondary channel 12. This state is suitable for high-speed, large-volume Roots blowers, such as when the speed is 2000 r / min and the exhaust volume is large. The opening of the secondary channel 12 can significantly increase the effective flow cross-sectional area, reduce airflow resistance, and avoid airflow congestion and additional noise caused by excessive exhaust volume. At the same time, the airflow of the dual channels can be more evenly distributed in the silencing cavity, fully interacting with the annular resonant cavity 3 and the resistive silencing material 6, ensuring good silencing effect even under high flow conditions. Example 3, through the switching of three opening states, perfectly adapts to the operating conditions of Roots blowers from low to high speed range, solving the problem of large fluctuations in the silencing effect of traditional silencers over a wide speed range.

[0027] The aforementioned intake cone 8 structure also includes a drive mechanism for driving the intake cone 8 and the inner cone 10 to move axially. Specifically, it includes a retainer 20 installed in the silencing cavity. The retainer 20 can be formed by welding and fixing multiple brackets arranged along the radius. A first reduction drive 21 is provided in the middle of the retainer 20. The intake cone 8 is provided with a first drive screw 22 along the axial direction. The first drive screw 22 passes through the middle of the retainer 20 and is controlled by the first reduction drive 21 to move axially. A second drive screw 23 is rotatably provided between the retainer 20 and the first end cover. Multiple second drive screws 23 can be provided. A second reduction drive 24 is provided on the retainer 20 to drive the second drive screw 23 to rotate. The second drive screw 23 is screwed to the inner cone 10 to drive its axial movement, and is slidably connected to the intake cone 8 to keep the intake cone 8 in translation. In this way, the movement of the intake cone 8 or the inner cone 10 can be controlled separately. Example 4

[0028] This is another advanced optimization scheme of Embodiment 2. Its core difference lies in adjusting the effective flow cross-sectional area of ​​the through-hole 11 by rotating the inner cone 10 instead of axially moving it. This is suitable for scenarios requiring high adjustment precision and where space constraints prevent long-distance axial adjustment. In this embodiment, the through-hole 11 on the intake cone 8 is designed as several concentrically arranged first arc-shaped waist holes 16 (concentric with the intake cone 8). The inner cone 10 is provided with second arc-shaped waist holes 17 corresponding to the positions of the first arc-shaped waist holes 16. By controlling the rotation of the inner cone 10 relative to the intake cone 8, the misalignment adjustment of the two arc-shaped waist holes is achieved, thereby changing the effective flow cross-sectional area of ​​the through-hole 11. Its design principle utilizes the linear correspondence between the degree of misalignment of the arc-shaped waist holes and the flow cross-sectional area to achieve precise fine-tuning of the flow cross-sectional area. Simultaneously, the rotation adjustment method requires less installation space and is more suitable for compact industrial layouts. For example, in a small Roots blower unit, the installation space limits the axial adjustment stroke of the inlet cone 8. The structure of Embodiment 4 is adopted: the inlet cone 8 has three concentric first arc-shaped waist holes 16, and the inner cone 10 has three corresponding second arc-shaped waist holes 17. When the inner cone 10 rotates 0°, the two waist holes completely overlap, and the effective flow cross-sectional area of ​​the through hole 11 is maximized, suitable for high-speed, high-volume operation. When the inner cone 10 rotates 30°, the two waist holes are misaligned by 1 / 3, and the flow cross-sectional area is reduced to 2 / 3, suitable for medium-speed operation. When rotated 60°, the two waist holes are completely misaligned, the through hole 11 is closed, and the flow cross-sectional area is minimized, suitable for low-speed, low-volume operation. The advantage of this rotation adjustment method is its high adjustment precision. The inner cone 10 can be driven to rotate by a stepper motor, achieving stepless adjustment of the flow cross-sectional area, keeping the throat airflow in a critically smooth state. It also occupies little space, making it better suited for space-constrained applications.

[0029] Finally, each of the above embodiments can be combined with a monitoring device, which includes a wind pressure sensor 18 and a wind speed sensor 19, installed on the inlet pipe 4. The design purpose is to achieve closed-loop adaptive adjustment of the silencer. Traditional silencers are mostly manually adjusted and cannot respond in real time to changes in the rotational speed of the Roots blower. However, by collecting the air pressure and wind speed in real time through the monitoring device, the current exhaust volume and airflow state can be accurately determined, thereby automatically guiding the adjustment of the conical guide structure 7 (inlet cone 8, inner cone 10). For example, when the wind speed and wind pressure of the inlet pipe 4 are detected to increase, it indicates that the rotational speed of the Roots blower has increased and the exhaust volume has increased. The control system can automatically drive the inlet cone 8 to retract (in embodiments two and three) or the inner cone 10 to rotate to the position where the waist hole coincides (in embodiment four), increasing the effective flow cross-sectional area. When the wind speed and wind pressure are detected to decrease, the control system adjusts in the opposite direction to reduce the flow cross-sectional area. Through this real-time closed-loop adjustment, the entire active adaptive silencer is always in the optimal noise reduction state without manual intervention, improving the automation level and operational stability of the equipment.

[0030] In this embodiment, the driving mechanism for driving the intake cone 8 and the inner cone 10 to move axially is different from that described above. The structure for driving the intake cone 8 to move axially can adopt the same structure, while the inner cone 10 needs to be rotated. A rotation drive structure for driving the inner cone 10 to rotate can be set on the first drive screw 22.

[0031] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An active adaptive silencer adapted to the variable speed operating conditions of a Roots blower, characterized in that, include: The sound-absorbing cavity includes a cylindrical outer shell, an inner mesh coaxially arranged inside the outer shell, a first end cap and a second end cap respectively sealed and connected to the two ends of the outer shell, and the interlayer between the inner mesh and the outer shell forms an annular resonant cavity. An inlet pipe is connected to the first end cap and is connected to the silencing cavity. The outlet pipe is composed of multiple outlet single pipes forming a multi-bundle outlet structure. Each outlet single pipe is flared and has a small end and a large end. The small end is connected to and installed on the second end cap.

2. The active adaptive silencer for variable speed operation of a Roots blower according to claim 1, characterized in that, The centers of the multiple outlet single tubes are evenly spaced along the same circular arc trajectory.

3. The active adaptive silencer for variable speed operation of a Roots blower according to claim 1, characterized in that, The annular resonant cavity is filled with resistive sound-absorbing material, which includes a single-material sound-absorbing structure or a composite sound-absorbing structure.

4. The active adaptive silencer for variable speed operation of a Roots blower according to claim 1, characterized in that, The silencing cavity is equipped with a conical flow guide structure, which includes an intake cone with its cone pointing towards the inlet pipe. The intake cone is coaxially arranged with the inlet pipe. The intake cone extends and retracts axially to adjust and control the effective flow cross-sectional area of ​​the throat to match different exhaust volumes, and to keep the airflow in the throat in a critically smooth state without increasing airflow resistance.

5. The active adaptive silencer for variable speed operation of a Roots blower according to claim 4, characterized in that, The surface of the intake cone is provided with spiral guide grooves. Multiple spiral guide grooves are evenly distributed axially on the surface of the intake cone. The multiple spiral guide grooves rectify the airflow in the intake pipe into a spiral uniform airflow.

6. The active adaptive silencer for variable speed operation of a Roots blower according to claim 4, characterized in that, The conical air guide structure also includes an inner cone disposed inside the intake cone. The surface of the intake cone is distributed with several through holes. The inner cone moves relative to the intake cone to control the opening of some or all of the through holes to form a controllable secondary channel. The secondary channel changes the effective flow cross-sectional area of ​​the airflow path, and the sound waves are reflected multiple times between the inside of the intake cone and the inner cone.

7. The active adaptive silencer for variable speed operation of a Roots blower according to claim 6, characterized in that, When the inner cone moves axially relative to the intake cone and is in a half-open state, multiple micro-resonance cavities are formed between the through hole and the inner cone. The multiple micro-resonance cavities form a micro-resonance cavity array. The closed space within the micro-resonance cavity array resonates and absorbs noise of a specific frequency of the Roots blower.

8. The active adaptive silencer for variable speed operation of a Roots blower according to claim 7, characterized in that, The inner surface of the intake cone is provided with a baffle plate, which is arranged around the outer ring of one or more through holes. The baffle plate is arranged axially, and the inner cone surface is provided with a slot portion that matches the position of the baffle plate. When the inner cone is in contact with the air intake cone, the baffle is inserted into the corresponding slot, and the micro resonant cavity array is in the closed state; When the inner vertebral body moves axially to a half-open state, the baffle plate and the slot part do not separate, forming a micro resonant cavity array; The inner vertebral body continues to move axially and open, and the baffle plate leaves the slot, so that a secondary channel is formed between the air intake cone and the inner vertebral body.

9. The active adaptive silencer for variable speed operation of a Roots blower according to claim 6, characterized in that, The through hole is designed as several concentric first arc-shaped waist holes, and the first arc-shaped waist holes are concentric with the air intake cone; the inner cone is provided with several second arc-shaped waist holes corresponding to the positions of the first arc-shaped waist holes; the inner cone is rotated relative to the air intake cone to control the change of the effective flow cross-sectional area of ​​the through hole by adjusting the misalignment of the second arc-shaped waist holes with the first arc-shaped waist holes.

10. The active adaptive silencer for variable speed operation of a Roots blower according to claim 4, characterized in that, The inlet pipe is equipped with a monitoring device, which includes a wind pressure sensor and a wind speed sensor.

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