Design method of array muffler for main ventilation air passage between stator core of water turbine generator and air cooler and array muffler

Abstract

The application discloses a design method of an array silencer for adapting to a main ventilation air passage between a stator core of a hydro-generator and an air cooler and the array silencer, and relates to the technical field of suppressing or reducing the noise of a hydro-generator. The method comprises the following steps: S1, acquiring the aerodynamic noise data and airflow parameters of the main ventilation air passage; S2, determining the silencing idea and the core structure of the micro-perforated plate array according to the broadband vortex noise, discrete rotation, vortex shedding and surge noise; S3, determining the outer size and preliminarily calculating the airflow parameters; S4, designing the plate parameters in combination with the micro-perforated resonance formula; S5, simulating and optimizing; S6, accurately calculating the airflow parameters, and locking the scheme meeting the requirements; and the silencer comprises a shell and a plurality of micro-perforated plates, and the plurality of micro-perforated plates are arranged in series. The application does not use sound-absorbing materials, has low wind resistance (the wind volume attenuation is less than or equal to 5%, and the pressure loss is less than or equal to 200 Pa), reduces the main air passage noise by 5-7 dB(A), has long service life and low operation and maintenance cost, and is suitable for the requirements of the main air passage.

Description

Technical Field

[0001] This invention relates to the technical field of suppressing or reducing noise from hydro-generators, and more specifically to a design method and an array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator. Background Technology

[0002] In the field of energy equipment, the operating noise of hydro generators is a key indicator affecting the overall performance of the unit and the user experience. The main sources of noise include electromagnetic noise, mechanical vibration noise and aerodynamic noise. At present, the electromagnetic design and structural design of large design manufacturers are relatively mature, and the electromagnetic noise and mechanical noise are relatively small. However, aerodynamic noise still exists, and aerodynamic noise (especially the airflow disturbance noise of the main ventilation path) accounts for a significant proportion in high-speed and large-capacity units, which has become the core direction for noise reduction technology.

[0003] Currently, noise reduction technology for hydro-generators mainly revolves around three major approaches: sound insulation, sound absorption, and noise reduction, forming a relatively mature application system.

[0004] 1. Sound insulation technology uses special structures such as sealed soundproof covers and sound barriers, or uses high sound insulation materials to cover the generator body, and uses the principle of sound energy shielding to block noise from radiating outward. This technology can directly reduce the external noise transmission of the whole machine, but it cannot reduce noise from the source and may affect the heat dissipation efficiency and maintenance convenience of the unit.

[0005] 2. Sound absorption technology involves laying sound-absorbing materials (such as glass wool, polyester fiber wool, rock wool, etc.) on the inner wall of the generator pit, inside the sound insulation enclosure, or on the surface of the unit structure. Noise reduction is achieved by absorbing and dissipating sound energy through the pores of the material. However, its core depends on the acoustic performance of the sound-absorbing material. Such materials generally have defects such as easy aging, moisture absorption and deterioration, dust accumulation and blockage, and pollution, which cause the sound absorption effect to decrease significantly over time. They usually need to be replaced regularly, which increases the operation and maintenance costs and downtime.

[0006] 3. Silencing technology involves placing silencers along the noise propagation path and attenuating sound energy by changing the airflow channel structure. It is a key means of targeted control of aerodynamic noise. Currently, most mainstream silencers are used in the ventilation path of the soundproof enclosure of hydro generators as noise control components of auxiliary ventilation systems.

[0007] However, existing noise reduction technologies and products have two major flaws that severely limit their application and noise reduction effect in the main ventilation path of hydro generators:

[0008] Firstly, the design of the silencer itself has inherent shortcomings. Existing silencers generally rely on sound-absorbing materials for noise reduction. The fibrous or porous structure of these materials significantly increases airflow resistance, leading to increased pressure loss in the ventilation system. To compensate for the airflow loss, the power of the ventilation fan needs to be increased. However, the increase in fan power will also lead to an increase in the fan's own noise, forming a vicious cycle of "noise reduction-noise increase," ultimately affecting the overall noise control effect of the unit. At the same time, the aging and deterioration of the sound-absorbing materials cannot be completely eliminated. This not only shortens the service life of the silencer (usually requiring replacement every 3-5 years), but may also cause material to fall off and contaminate internal components of the unit (such as stator coils and air coolers), posing a safety hazard.

[0009] Secondly, the installation location is designed to be away from the core noise area. Existing silencers are all placed in the auxiliary ventilation path of the soundproof enclosure. The air volume in this path is only about 0.3% of the total ventilation volume of the generator. The wind speed is low and the airflow disturbance is weak. It is not the main area for generating aerodynamic noise. However, the main ventilation path of the hydro generator (the airflow channel between the stator core and the air cooler) is the core area with the most concentrated air volume (total motor air volume), the highest wind speed, and the strongest aerodynamic noise. If the existing high-resistance silencers are installed in this area, the air volume of the main ventilation system will be reduced by more than 10%, which will seriously affect the heat dissipation of key components such as the stator and rotor. It may cause problems such as overheating of the unit and insulation aging. Therefore, the existing silencers cannot meet the installation requirements of the main ventilation path.

[0010] In summary, existing hydro-generator noise reduction technologies suffer from the dual limitations of "relying on sound-absorbing materials, resulting in high wind resistance and short lifespan" and "installation location deviating from the core noise area," making it difficult to achieve efficient and long-term control of aerodynamic noise in the main ventilation path. There is an urgent need to develop a new type of silencer and design method that is free of sound-absorbing materials, has low wind resistance, and is adapted to the needs of the main ventilation path, in order to fill the existing technological gap. Summary of the Invention

[0011] To overcome the defects and shortcomings of the existing technology, this invention provides a design method and a design method for an array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator. The purpose of this invention is to provide a low-resistance array-type silencer without sound-absorbing materials, enabling its installation in the main ventilation path of a hydro-generator for long-term and precise aerodynamic noise control, while avoiding the problems of short lifespan, high wind resistance, and incompatibility with the main ventilation path of existing silencers. The design method of the array-type silencer provided by this invention is based on the ventilation parameters (flow velocity, flow rate) and noise spectrum data of the hydro-generator. It estimates the aperture, thickness, spacing, and cavity thickness of the micro-perforated plates in the array silencer using the transmission loss formula, and completes the preliminary design by relating it to the stator frame structural dimensions. Then, through flow field analysis and noise reduction simulation verification, the aperture, thickness, spacing, and cavity thickness of the micro-perforated plates are adjusted to optimize the design and meet both ventilation and noise reduction requirements. Furthermore, it employs a metal micro-perforated plate array combination structure without sound-absorbing materials. The method achieves the following effects: the silencer has low wind resistance, can be adapted to the main ventilation airflow path and has little impact on airflow, and does not affect the unit's heat dissipation; the metal structure has no aging problems, has a long service life, and can reduce operation and maintenance costs; it can also accurately target the strong noise area of ​​the main airflow path, effectively reduce aerodynamic noise, and improve the unit's sound quality.

[0012] To address the problems existing in the prior art, the present invention is implemented through the following technical solution.

[0013] The first aspect of this invention provides a design method for an array-type reactive-resistive composite silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator. This design method includes the following steps:

[0014] S1. Preliminary parameter acquisition steps: This involves ventilation simulation of the main ventilation path between the turbine generator stator core and the air cooler, theoretical calculations of the ventilation system, or actual measurements of unit noise and airflow data under different operating conditions. Specifically, this includes the following:

[0015] (1) Analyze the noise frequency distribution and noise spectrum characteristics, identify the dominant frequency range of aerodynamic noise in the main ventilation path, and record the peak sound pressure level corresponding to each frequency range; study the intrinsic relationship between the working conditions and this type of noise, clarify the noise change law under different working conditions, and combine the overall noise limit of the hydro-generator to back-calculate the minimum noise reduction amount to be achieved, and form a quantitative noise reduction target.

[0016] (2) Focus on the aerodynamic noise generation mechanism in the main ventilation duct, quantify the contribution ratio of turbulence mechanism, vortex shedding mechanism, boundary layer mechanism and pole mechanism in the total aerodynamic noise; at the same time, locate the specific location of each noise generation mechanism inside the stator frame, and clarify the noise propagation path; obtain basic airflow data of the main ventilation duct, including total flow rate, average airflow velocity and allowable pressure loss threshold and airflow attenuation limit of the unit;

[0017] S2. Determine the noise reduction strategy and core structure scheme steps. Based on the aerodynamic noise generation mechanism, noise characteristics and spectrum distribution of the main ventilation air path as defined in step S1, determine the noise reduction strategy and lock in the core structure of the array silencer.

[0018] S3. Determine the external dimensions and preliminary airflow calculation steps of the array-type silencer. Based on the dimensions of the stator frame of the hydro-generator and the measured data, combined with the airflow requirements of the main ventilation duct, determine the external constraints and preliminary design feasibility of the silencer. Secondly, combined with the determined external dimensions and the basic airflow data of the main ventilation duct obtained in step S1, perform preliminary calculations of ventilation resistance and airflow attenuation to avoid the silencer design affecting ventilation safety requirements. If the requirements are not met, return to adjust the silencer design.

[0019] S4. Initial Scheme Design Steps: Based on the advantageous frequency band, noise mechanism and contribution ratio, and quantified noise reduction target determined in step S1, the core structure of the array-type muffler determined in step S2, and the external dimensional constraints and preliminary airflow parameters in step S3, combined with the micro-perforated silencing theory, the initial scheme design of the array-type muffler is carried out; including the aperture, thickness, hole spacing, and cavity thickness of the micro-perforated plate of the array-type muffler.

[0020] S5. Simulation Analysis and Optimization Steps: Based on the initial array-type silencer scheme determined in step S4, a three-dimensional model of the array-type silencer is established. ANSYS is used to build a noise reduction scheme model and set boundary conditions. First, the airflow field through the array-type silencer in the main ventilation path is simulated using the Fluent module to obtain pressure data as initial parameters. Then, the Mechanical model is imported to simulate fluid noise and noise reduction effect, and the noise reduction amount in different frequency bands is analyzed. By comprehensively adjusting the aperture, spacing, thickness, and spatial thickness of the micro-perforated plate, ventilation performance is optimized, pressure loss and airflow attenuation are reduced while ensuring the silencing effect, resulting in a better parameter combination and noise reduction effect.

[0021] S6. Accurate calculation of fluid parameters and solution locking: Based on the optimal parameter combination obtained in step S5, calculate the core airflow parameters of the main ventilation path. If the air volume and pressure loss exceed the air volume attenuation limit and pressure loss threshold in step S2, adjust the micro-perforated plate aperture, hole spacing, plate thickness and / or space thickness, and repeat steps S5-S6 until the optimal parameter combination and noise reduction effect are obtained, and finally lock in the design solution that meets the dual requirements of ventilation and noise reduction.

[0022] In a further preferred embodiment, in step S2, based on the aerodynamic noise generation mechanism, noise characteristics, and spectral distribution of the main ventilation path as defined in step S1, a noise reduction strategy is determined, specifically referring to:

[0023] To address broadband eddy current noise, a resistive sound absorption technology is employed, which converts sound energy into heat energy through the frictional viscosity effect of micro-perforated plates, thereby achieving broadband noise reduction.

[0024] To address discrete rotational noise, a resonant silencing technology approach is adopted. By matching the parameters of the micro-perforated plate, the resonant frequency of the silencer is aligned with the peak frequency of the noise, and the energy is canceled out by sound wave interference.

[0025] To address eddy shedding and surge noise, a technical approach combining flow field optimization and noise reduction is adopted. This involves reducing airflow separation through structural design and simultaneously weakening noise through noise reduction structures.

[0026] In a further preferred embodiment, in step S2, locking the core structure of the array-type silencer specifically means determining that a micro-perforated plate array is used as the core carrier, and achieving wide-band coverage through multi-plate series combination. Micro-perforated plates with different parameters are arranged along the airflow path in the series direction to match different mid-to-high frequency bands, forming a multi-dimensional silencer array.

[0027] In a further preferred embodiment, for flow field optimization, bends are provided on the micro-perforated plates at the air inlet and outlet of the silencer. These bends are configured to guide the airflow through a smooth transition and control ventilation resistance.

[0028] In a further preferred embodiment, the microperforated plate is bent at the air inlet and air outlet of the outer casing at a bending angle of 45°.

[0029] In a further preferred embodiment, step S4, which involves designing the initial scheme for the array-type silencer, specifically refers to back-calculating the aperture, spacing, thickness, and cavity thickness of the micro-perforated plate based on the dominant noise frequency band determined in step S1 and the resonant frequency calculation formula of the micro-perforated plate.

[0030] A further preferred formula for calculating the resonant frequency of the micro-perforated plate is:

[0031]

[0032] In the formula, This indicates the speed of sound, measured in m / s, which is approximately 340 m / s at room temperature. The perforation rate is the ratio of the total area of ​​the holes to the area of ​​the micro-perforated plate; t is the thickness of the micro-perforated plate in meters; and L is the depth of the cavity behind the micro-perforated plate in meters. This represents the end-diameter correction amount, taken as... d is the aperture.

[0033] More preferably, in step S4, the determination of the aperture of the micro-perforated plate must satisfy the condition that the aperture is less than the wavelength corresponding to the target noise reduction frequency / 10.

[0034] Even more preferably, the pore diameters of the micropores on a single microperforated plate are consistent.

[0035] More preferably, in step S4, the micropores on each microperforated plate are evenly distributed, and the spacing between the micropores on the microperforated plate is determined according to the perforation rate, which refers to the percentage of the total area of ​​all micropores on a single microperforated plate to the total area of ​​the microperforated plate.

[0036] In a further preferred embodiment, step S3, determining the external dimensions of the muffler, specifically involves measuring the internal space dimensions of the stator frame in the main ventilation path between the stator core and the air cooler to ensure that the muffler does not interfere with the stator core and air cooler after installation. Based on the aforementioned internal space dimensions, and in conjunction with the micro-perforated plate array structure determined in step S2, the dimensions of the muffler housing are designed. The dimensions of the housing match the flow cross-section of the main ventilation path, and the length is adapted to the structural requirements of multiple plates connected in series.

[0037] The second aspect of the present invention provides an array-type silencer adapted to the main ventilation path between the stator core and the air cooler of a hydro-generator. The array-type silencer is designed based on the design method of the array-type silencer adapted to the main ventilation path between the stator core and the air cooler of the hydro-generator described in the first aspect above. It includes a housing and several micro-perforated plates placed inside the housing. The several micro-perforated plates are arranged in series at intervals, with the distance between adjacent micro-perforated plates being the cavity thickness. The aperture of each micro-perforated plate is consistent, and the micro-holes are evenly distributed. Different micro-perforated plates adopt different apertures according to the dominant noise frequency.

[0038] More preferably, the array-type muffler is a reactive-resistive composite muffler, which achieves high transmission loss over a wider frequency band.

[0039] More preferably, the array-type silencer has no sound-absorbing cotton.

[0040] More preferably, the array-type muffler is made of metal.

[0041] In a further preferred embodiment, the microperforated plate is bent at the air inlet and air outlet of the outer casing at a bending angle of 45°.

[0042] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0043] 1. This invention quantifies the contribution ratio of four aerodynamic noise mechanisms—turbulence, vortex shedding, boundary layer, and poles—within the main ventilation path through step S1 (e.g., vortex shedding noise accounts for 50%~60%, and turbulence noise accounts for 30%~40%), and locates the noise generation location (e.g., vortex shedding noise originates from the stator core ventilation groove outlet), avoiding the blind "indiscriminate noise reduction" of traditional silencers. Then, through step S2, it matches exclusive silencing technology paths for three core aerodynamic noises (wideband vortex, discrete rotation, vortex shedding, and surge), combined with the precise calculation of micro-perforated plate parameters in step S4 (resonance frequency and noise peak frequency deviation ≤5%), thereby improving the sound energy dissipation efficiency to 0.8~0.9, ultimately achieving a 5~7 dB(A) reduction in main ventilation path noise. Compared with existing auxiliary ventilation path silencers, the noise reduction effect is improved by 4~5 times, completely solving the aerodynamic noise problem of high-speed, large-capacity units.

[0044] 2. This invention achieves a balance between wind resistance and ventilation through multi-stage airflow calculation and structural optimization: Step S3 initially calculates to ensure that the cross-sectional area of ​​the silencer shell is not less than 95% of the cross-sectional area of ​​the air duct, and initially controls the airflow attenuation to ≤8% and the pressure loss to ≤250Pa; Step S5 uses ANSYS Fluent flow field simulation to accurately optimize the airflow path, and in conjunction with the “45° bent micro-perforated plate” designed in Step S2, guides the airflow to a smooth transition (local wind speed ≤10m / s); Finally, Step S6 locks in the parameter combination of airflow attenuation ≤5% and pressure loss ≤200Pa, completely avoiding the problem of airflow attenuation exceeding 30% caused by the existing silencer being installed in the main air duct, ensuring the heat dissipation requirements of key components such as the stator and rotor, and strictly controlling the temperature rise of the stator coil within the design limit, eliminating the risk of unit overheating and insulation aging.

[0045] 3. This invention abandons the sound-absorbing materials such as glass wool and polyester fiber that traditional silencers rely on, and adopts a metal micro-perforated plate array structure to fundamentally solve the defects of material aging, moisture absorption and deterioration, and dust accumulation and blockage: On the one hand, the metal structure has no aging failure problem, and there is no need to replace materials regularly, which extends the service life of the silencer to more than 40 years, reduces downtime maintenance time by 85%, and reduces the average annual operation and maintenance cost by 85%; on the other hand, it eliminates the safety hazards of material falling off and contaminating the stator coil and air cooler, and the unit insulation failure rate caused by the silencer design is 0, which significantly improves the long-term operational reliability of the unit.

[0046] 4. This invention breaks through the traditional experience-based trial-and-error design mode of silencers and establishes a standardized process of parameter acquisition, scheme design, and simulation optimization: The noise spectrum and airflow data acquired in step S1 provide a quantitative basis for the design; Step S4 uses the resonant frequency formula of the micro-perforated plate to back-derive key parameters, avoiding blind parameter selection; Step S5 uses ANSYS Fluent + Mechanical coupled simulation to simultaneously verify the flow field and noise reduction effect, improving parameter optimization efficiency by 60%, eliminating the need for repeated physical prototype production, shortening the R&D cycle by 50%, and reducing R&D costs by more than 40%; At the same time, each step in the design process forms clear constraints (such as the external dimension constraints in S3 and parameter design in S4), ensuring that the final scheme has both technical feasibility and engineering feasibility.

[0047] 5. Step S3 of this invention designs the muffler shape based on the measured spatial dimensions of the stator frame, ensuring no interference with the stator core and air cooler interfaces, achieving 100% structural compatibility. The outer shell and micro-perforated plate are fixed with bolts, and the installation interface precisely matches the reserved bolt holes in the stator frame (deviation ≤1mm). The modified unit does not require disassembly of core components, improving installation efficiency by 80%. In addition, the array structure of micro-perforated plates in series supports flexible expansion—if subsequent changes in unit operating conditions cause noise frequency shifts, only the micro-perforated plate corresponding to the frequency band can be replaced, without replacing the entire muffler, adapting to the noise reduction needs of units with different capacities and speeds, and its versatility is significantly better than that of traditional fixed structure mufflers.

[0048] 6. The low wind resistance design eliminates the need for capacity expansion of the main ventilation fan, reducing fan power loss by 15%~20%. Based on a 10MW unit, this translates to an average annual power saving of 5000~10000kWh, aligning with the energy-saving trend in energy equipment. The cost of metal is lower than that of specialized sound-absorbing materials, and the mature laser drilling technology (hole diameter tolerance ±0.05mm) reduces manufacturing costs by 20%~30% compared to traditional silencers after large-scale production. Simultaneously, the overall noise level is reduced to below 65dB(A), meeting the Class I environmental limits of the "Emission Standard for Industrial Enterprises Noise at Boundary" (GB12348-2022). This significantly improves the comfort of the power plant's operating environment, reduces occupational health risks for maintenance personnel, and achieves a triple unity of technical, economic, and environmental benefits. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the three-dimensional structure of the array-type muffler of the present invention;

[0050] Figure 2 This is a schematic diagram of the micro-perforated plate arrangement structure in the array-type muffler of the present invention;

[0051] Figure 3 This is a schematic diagram of different micro-perforated plate combinations in the array-type muffler of the present invention;

[0052] Figure 4This is a schematic diagram of the arrangement of micro-perforated plates in the array-type muffler of the present invention;

[0053] Figure 5 This is a schematic diagram of the assembly structure of the stator core, stator frame, array-type silencer, and air cooler in the hydro-generator of the present invention.

[0054] Reference numerals: 1. Array-type silencer, 2. Housing, 3. Micro-perforated plate, 4. Stator core, 5. Stator frame, 6. Air cooler. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0056] Example 1

[0057] As a preferred embodiment of the present invention, the present invention discloses a design method for an array-type silencer adapted to the main ventilation path between the stator core and the air cooler of a hydro-generator, the design method comprising the following steps:

[0058] S1. Preliminary parameter acquisition steps: This involves ventilation simulation of the main ventilation path between the turbine generator stator core and the air cooler, theoretical calculations of the ventilation system, or actual measurements of unit noise and airflow data under different operating conditions. Specifically, this includes the following:

[0059] (1) Analyze the noise frequency distribution and noise spectrum characteristics, identify the dominant frequency range of aerodynamic noise in the main ventilation path, and record the peak sound pressure level corresponding to each frequency range; study the intrinsic relationship between the working conditions and this type of noise, clarify the noise change law under different working conditions, and combine the overall noise limit of the hydro-generator to back-calculate the minimum noise reduction amount to be achieved, and form a quantitative noise reduction target.

[0060] (2) Focus on the aerodynamic noise generation mechanism in the main ventilation duct, quantify the contribution ratio of turbulence mechanism, vortex shedding mechanism, boundary layer mechanism and pole mechanism in the total aerodynamic noise; at the same time, locate the specific location of each noise generation mechanism inside the stator frame, and clarify the noise propagation path; obtain basic airflow data of the main ventilation duct, including total flow rate, average airflow velocity and allowable pressure loss threshold and airflow attenuation limit of the unit;

[0061] S2. Determine the noise reduction strategy and core structure scheme steps. Based on the aerodynamic noise generation mechanism, noise characteristics and spectrum distribution of the main ventilation air path as defined in step S1, determine the noise reduction strategy and lock in the core structure of the array silencer.

[0062] S3. Determine the external dimensions and preliminary airflow calculation steps of the array-type silencer. Based on the design of the stator frame of the hydro-generator and the airflow requirements of the main ventilation path, determine the external dimension constraints and preliminary feasibility of the silencer. Then, based on the determined external dimensions and the basic airflow data of the main ventilation path obtained in step S1, perform preliminary calculations of ventilation resistance and airflow attenuation to avoid the external design affecting ventilation safety. If the requirements are not met, return to adjust the external dimensions.

[0063] S4. Initial Scheme Design Steps: Based on the advantageous frequency band, noise mechanism and contribution ratio, and quantified noise reduction target determined in step S1, the core structure of the array-type muffler determined in step S2, and the external dimensional constraints and preliminary airflow parameters in step S3, combined with the micro-perforated silencing theory, the initial scheme design of the array-type muffler is carried out; including the aperture, thickness, hole spacing, and cavity thickness of the micro-perforated plate of the array-type muffler.

[0064] S5. Simulation Analysis and Optimization Steps: Based on the initial array-type silencer scheme determined in step S4, a three-dimensional model of the array-type silencer is established. ANSYS is used to build a noise reduction scheme model and set boundary conditions. First, the airflow field through the array-type silencer in the main ventilation path is simulated using the Fluent module to obtain pressure data as initial parameters. Then, the Mechanical model is imported to simulate fluid noise and noise reduction effect, and the noise reduction amount in different frequency bands is analyzed. By comprehensively adjusting the aperture, spacing, thickness, and spatial thickness of the micro-perforated plate, ventilation performance is optimized, pressure loss and airflow attenuation are reduced while ensuring the silencing effect, resulting in a better parameter combination and noise reduction effect.

[0065] S6. Accurate calculation of fluid parameters and solution locking: Based on the optimal parameter combination obtained in step S5, calculate the core airflow parameters of the main ventilation path. If the air volume and pressure loss exceed the air volume attenuation limit and pressure loss threshold in step S2, adjust the micro-perforated plate aperture, hole spacing, plate thickness and / or space thickness, and repeat steps S5-S6 until the optimal parameter combination and noise reduction effect are obtained, and finally lock in the design solution that meets the dual requirements of ventilation and noise reduction.

[0066] Example 2

[0067] As another preferred embodiment of the present invention, this embodiment further supplements and elaborates on the technical solution of the present invention based on the above embodiment 1. In this embodiment, in step S2, based on the aerodynamic noise generation mechanism, noise characteristics and spectral distribution of the main ventilation path as defined in step S1, a noise reduction strategy is determined, specifically referring to:

[0068] To address broadband eddy current noise, a resistive sound absorption technology is employed, which converts sound energy into heat energy through the frictional viscosity effect of micro-perforated plates, thereby achieving broadband noise reduction.

[0069] To address discrete rotational noise, a resonant silencing technology approach is adopted. By matching the parameters of the micro-perforated plate, the resonant frequency of the silencer is aligned with the peak frequency of the noise, and the energy is canceled out by sound wave interference.

[0070] To address eddy shedding and surge noise, a technical approach combining flow field optimization and noise reduction is adopted. This involves reducing airflow separation through structural design and simultaneously weakening noise through noise reduction structures.

[0071] In step S2, locking the core structure of the array-type muffler specifically means determining that the micro-perforated plate array is the core carrier, and achieving wide-band coverage through multi-plate series connection. The series connection direction is arranged along the airflow path with micro-perforated plates of different parameters to match different mid-to-high frequency bands respectively; ultimately forming a reactive-resistive composite muffler.

[0072] For flow field optimization, bends are incorporated into the micro-perforated plates at the muffler's inlet and outlet. These bends are configured to guide a smooth airflow transition and control ventilation resistance. As an example, the micro-perforated plates are bent at the inlet and outlet of the housing at a bend angle of 45°.

[0073] In this embodiment, the noise reduction strategy is determined based on the noise generation mechanism, noise characteristics, and noise spectrum distribution at different locations:

[0074] Among them, the noise generation mechanism should be clearly defined: whether it is electromagnetic force noise, aerodynamic noise, or mechanical force noise;

[0075] Noise characteristics and spectral distribution mainly refer to the noise spectrum. Based on the generation mechanism, it is used to determine whether the noise is high-frequency or low-frequency, discrete pure tone or broadband random noise, thereby determining its propagation path (propagation medium).

[0076] The approach to noise reduction varies depending on the noise generation mechanism. This application primarily addresses the aerodynamic noise in the main ventilation path between the turbine generator stator core and the air cooler; specifically...

[0077] Aerodynamic noise mainly originates from the cooling fan and rotor rotation, and is directly related to the air outlet. Due to differences in its generation mechanism and characteristics, it can be further subdivided into three types:

[0078] One of them is eddy noise (wideband noise): When the fan blades rotate, they create eddies in the air around them. These eddies are constantly forming and breaking up, causing air pressure pulsations and generating noise. Its characteristics and spectrum: wideband noise, with a very wide spectrum distribution, from tens of Hz to tens of thousands of Hz.

[0079] —Secondly, there is rotational noise (discrete noise): this is caused by the periodic beating of air by the blades, resulting in air pressure pulsations. When the passing frequency of the blades coincides with a certain structural characteristic frequency, a strong "whistling" sound (steam whistle effect) is produced. Its characteristics and spectrum are discrete single tones, with the fundamental frequency being the number of blades multiplied by the rotational speed, accompanied by higher harmonics. There are obvious peaks in the spectrum;

[0080] Thirdly, there is the issue of eddy current shedding and surge noise: When airflow passes through the narrow and complex air ducts inside the motor (especially near the air outlet), separation and eddy currents will occur, causing pressure pulsations and noise. When the airflow path is obstructed, surge will occur, producing a low-frequency roar.

[0081] The array-type reactive-resistive composite silencer in this invention primarily reduces noise in the main ventilation path. Aerodynamic noise reduction strategies (based on mechanism and spectrum):

[0082] 1) Source control (core): Through optimized fan design and air duct optimization;

[0083] 2) Airflow path treatment (key measure for air outlets): Install silencers;

[0084] Reactive silencers: These primarily reduce noise through the reflection and interference of sound waves, and are particularly effective against low-to-mid-frequency noise (such as the fundamental frequency of rotating noise). Internal structures include expansion chambers and resonant cavities.

[0085] Resistive silencers: lined with sound-absorbing materials (such as glass wool, mineral wool, rock wool, etc.), they convert sound energy into heat energy through friction, and are most effective against mid-to-high frequency noise (such as broadband eddy current noise).

[0086] Composite silencer: Combining reactive and resistive structures, it achieves full-frequency noise reduction and is the most commonly used form for motor air outlets;

[0087] Design considerations: The design of a muffler must balance noise reduction, aerodynamic performance (low pressure loss), and size.

[0088] Mechanical noise (mainly originating from bearings and rotors): The generation mechanisms include bearing friction, frame vibration, improper assembly, etc.; or rotor dynamic imbalance, where the rotor's center of mass does not coincide with its center of rotation, generating periodic centrifugal force, leading to vibration and noise. Its noise characteristics and spectrum distribution: Bearing noise is a high-frequency "hissing" or "rumbling" sound with a wide spectrum, but usually includes characteristic frequencies determined by the bearing's geometry; rotor imbalance noise is a low-frequency "rumbling" sound (the frequency is consistent with the rotor's rotational frequency). Noise reduction strategies: Select high-precision, low-noise bearings, ensure good lubrication, and improve the machining and assembly accuracy of bearing components; add weight to the rotor and perform dynamic and static balancing corrections.

[0089] Electromagnetic noise (mainly originating from the interaction between the stator and rotor magnetic fields): Electromagnetic noise is radiated noise generated by the vibration of the stator and rotor structure caused by the alternating electromagnetic force in the air gap. Tooth frequency vibration noise is the most significant, mainly manifested as discrete noise caused by the 5th, 7th, 11th, and 13th order electromagnetic harmonics, fractional harmonic noise, 100Hz vibration noise caused by rotor eccentricity and stator non-roundness, and rotational frequency noise caused by rotor non-roundness. Specific control methods include selecting a reasonable pole-slot ratio, controlling manufacturing and installation quality, and conducting dynamic balancing tests on the rotor. Currently, electromagnetic design is relatively mature, and manufacturing and installation quality are generally well controlled, resulting in relatively low electromagnetic noise, which accounts for a very small proportion of the overall unit noise.

[0090] Example 3

[0091] As another preferred embodiment of the present invention, this embodiment is a further detailed supplement and explanation of the technical solution of the present invention based on the above embodiment 1 or embodiment 2. In this embodiment, step S4, carrying out the initial design of the array-type silencer specifically refers to, based on the dominant noise frequency band determined in step S1, and combined with the formula for calculating the resonant frequency of the micro-perforated plate, back-calculating the aperture, spacing, thickness, and cavity thickness of the micro-perforated plate.

[0092] As an example, the formula for calculating the resonant frequency of a micro-perforated plate is:

[0093]

[0094] In the formula, This indicates the speed of sound, measured in m / s, which is approximately 340 m / s at room temperature. The perforation rate is the ratio of the total area of ​​the holes to the area of ​​the micro-perforated plate; t is the thickness of the micro-perforated plate in meters; and L is the depth of the cavity behind the micro-perforated plate in meters. This represents the end-diameter correction amount, taken as... d is the aperture.

[0095] In step S4, the aperture of the micro-perforated plate must be determined to satisfy the condition that the aperture is less than the wavelength corresponding to the target noise reduction frequency / 10. The apertures of the micro-holes on a single micro-perforated plate are uniform. In step S4, the micro-holes on each micro-perforated plate are evenly distributed, and the spacing between the holes on the micro-perforated plate is determined based on the perforation rate, which refers to the percentage of the total area of ​​all micro-holes on a single micro-perforated plate to the total area of ​​the micro-perforated plate.

[0096] In a preferred embodiment of this invention, step S4 involves defining and determining the parameters in the initial design of the array-type muffler:

[0097] Design logic: First, determine the resonant frequency of the structure based on the peak frequency of the target noise to be controlled, and then calculate or optimize a set of feasible parameters using formulas.

[0098] Step 1: Determine the target frequency: Based on the previous noise spectrum analysis, identify the main noise components that need to be suppressed, such as the peak frequency of the air outlet noise; design the resonant frequency of the micro-perforated plate structure to be near this peak.

[0099] Step 2: Calculation and Selection of Key Parameters: The resonant frequency of the micro-perforated plate is mainly determined by the acoustic mass (determined by the micropores) and acoustic compliance (determined by the cavity). The approximate calculation formula is as follows:

[0100] a. Resonance frequency formula (determines frequency tuning) Where: The resonant frequency (Hz) represents the frequency with the highest sound absorption coefficient, and δ is the end correction factor, typically taken as 0.8~1.0. The cavity thickness adjusts the resonant frequency. The most sensitive parameter. The greater the thickness, The lower the value, the higher the perforation rate. It will also increase. However, it primarily affects the sound absorption coefficient and bandwidth. Plate thickness and aperture: (t+δ·d) can be considered as the "effective plate thickness," and the larger its value, the greater the effect. The lower.

[0101] b. Calculation of perforation rate: The perforation rate is the ratio of the total area of ​​the holes to the total area of ​​the plate. For a square array of holes: the hole diameter and the hole spacing together determine the perforation rate.

[0102] c. Determine the specific plate thickness, hole diameter, perforation rate, and cavity thickness.

[0103] This is a multi-objective optimization process without a single unique solution. Selection and balancing within a reasonable range are necessary, while also considering the manufacturing process. Aperture: The core requirement is to meet the "micro-perforation" condition, meaning the aperture is much smaller than the wavelength to ensure sufficient acoustic resistance. The smaller the aperture, the greater the acoustic resistance, the narrower the sound absorption bandwidth, and the more difficult the manufacturing process.

[0104] Plate thickness: Related to aperture, generally too thin and the mechanical strength is insufficient, too thick and the acoustic impedance is too high.

[0105] Perforation rate: Generally between 0.5% and 3%. If the perforation rate is too small, the acoustic impedance is too large, resulting in poor sound absorption; if the perforation rate is too large, the acoustic impedance is too small, and the structure is close to being completely transparent, resulting in poor sound absorption.

[0106] Cavity thickness: calculated by reversing the resonant frequency formula. For example, the target... With a frequency of 800Hz, assuming a perforation rate of 1%, a plate thickness of 1mm, and a hole diameter of 0.8mm, the cavity thickness can be calculated to be approximately 20mm to 50mm. This thickness must be matched to the existing space of the mounting base. If the calculated cavity thickness is too large, other parameters need to be adjusted (such as increasing the perforation rate) or a different... .

[0107] 2) The relationship between the number of microplates and the space (basic logic):

[0108] a. Single-cavity structure: a single layer of micro-perforated plate + a rear cavity. This is a Helmholtz resonator array, which is highly efficient at absorbing sound in only a narrow frequency band.

[0109] b. Multi-cavity series structure: In order to broaden the sound absorption frequency band, multiple micro-perforated plate sound-absorbing units with different resonant frequencies are arranged in series in the airflow direction to form a "resistive-resistant" composite structure, which achieves high transmission loss over a wider frequency band.

[0110] Therefore, the number of microperforated plates directly determines the bandwidth that can be covered and the overall noise reduction. A larger number of microperforated plates increases the difficulty of design and manufacturing, and may also increase the airflow pressure drop. A trade-off needs to be struck based on the complexity of the noise spectrum and the noise reduction objectives.

[0111] Estimation of transmission loss: The core mechanism of micro-perforated panel silencing is resonant sound absorption, converting sound energy into heat energy for dissipation rather than reflection. A micro-perforated panel structure with a cavity at the back can be considered a mass-acoustic compliance-acoustic impedance (MAR) system. Its acoustic characteristics can be described by acoustic impedance. Substituting the acoustic impedance of the micro-perforated panel into the more general acoustic transmission matrix method allows for accurate calculation of its transmission loss. For micro-perforated panel structures, a more commonly used performance evaluation index is the "absorption coefficient," which describes how much incident sound energy is absorbed rather than reflected. After designing specific micro-perforated panel parameters, the curve of its absorption coefficient versus frequency can be obtained through theoretical calculation or software simulation. Then, by placing this sound-absorbing structure in a channel or silencer and combining it with boundary conditions, the transmission loss of the entire device can be calculated.

[0112] Example 4

[0113] As another preferred embodiment of the present invention, this embodiment further supplements and elaborates on the technical solution of the present invention based on the above embodiment 1 or embodiment 2. In this embodiment, step S3 clarifies the physical size constraints of the muffler, specifically by measuring the internal space dimensions of the stator frame of the main ventilation path between the stator core and the air cooler to ensure that the muffler does not interfere with the stator core and air cooler after installation; based on the above internal space dimensions, combined with the micro-perforated plate array structure determined in step S2, the dimensions of the muffler shell are designed, the dimensions of the shell are matched with the flow cross section of the main ventilation path, and the length is adapted to the structural requirements of multi-plate series connection.

[0114] The choice of micro-perforated panels is due to their significant advantages over traditional resistive sound-absorbing materials: 1) High temperature and airflow erosion resistance; the high temperature and fast flow rate of the cooling airflow of generator motors can easily cause traditional sound-absorbing materials such as glass wool to be blown away and pulverized, leading to failure and pollution; 2) Micro-perforated panels are made of metal materials, making them sturdy and durable; 3) Environmentally friendly, with no fiber pollution; 4) Excellent mid-to-high frequency sound absorption performance: through careful design, it can effectively cover the main frequency bands of motor aerodynamic and electromagnetic noise; 5) Compact structure: it can be integrated with the base structure; 6) High operability: it is easy to implement using common materials and conventional processing methods.

[0115] Core sound absorption mechanism: The micro-perforated plate sound absorption structure is a resonant sound absorber. When sound waves are incident, they force air to move back and forth in the micropores. Due to the small size of the pores, the friction and viscosity effects between the air and the pore walls are very significant, efficiently converting sound energy (mechanical energy) into heat energy.

[0116] Example 5

[0117] As another preferred embodiment of the present invention, this embodiment discloses an array-type silencer adapted to the main ventilation path between the stator core and the air cooler of a hydro-generator. The array-type silencer is fixed on the stator frame of the main ventilation path between the stator core and the air cooler. (Refer to the appendix of the specification.) Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 and attached Figure 5 As shown, the array-type silencer is designed based on the design method of the array-type silencer adapted to the main ventilation air path between the stator core and the air cooler of the hydro-generator described in Embodiments 1, 2, 3 or 4 above. It includes a shell and several micro-perforated plates placed inside the shell. The several micro-perforated plates are arranged in series at intervals, and the distance between adjacent micro-perforated plates is the cavity thickness. The aperture of a single micro-perforated plate is consistent and the micro-holes are evenly distributed. Different micro-perforated plates adopt different apertures according to the dominant noise frequency.

[0118] As an example of this embodiment, the array-type silencer is made of metal. The microperforated plate is bent at the air inlet and outlet of the outer casing at a bending angle of 45°.

[0119] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0120] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A design method for an array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator, characterized in that, This design method includes the following steps: S1. Preliminary parameter acquisition steps: This involves ventilation simulation of the main ventilation path between the turbine generator stator core and the air cooler, theoretical calculations of the ventilation system, or actual measurements of unit noise and airflow data under different operating conditions. Specifically, this includes the following: (1) Analyze the noise frequency distribution and noise spectrum characteristics, identify the dominant frequency range of aerodynamic noise in the main ventilation path, and record the peak sound pressure level corresponding to each frequency range; study the intrinsic relationship between the working conditions and this type of noise, clarify the noise change law under different working conditions, and combine the overall noise limit of the hydro-generator to back-calculate the minimum noise reduction amount to be achieved, and form a quantitative noise reduction target. (2) Focus on the aerodynamic noise generation mechanism in the main ventilation duct, quantify the contribution ratio of turbulence mechanism, vortex shedding mechanism, boundary layer mechanism and pole mechanism in the total aerodynamic noise; at the same time, locate the specific location of each noise generation mechanism inside the stator frame, and clarify the noise propagation path; obtain basic airflow data of the main ventilation duct, including total flow rate, average airflow velocity and allowable pressure loss threshold and airflow attenuation limit of the unit; S2. Determine the noise reduction strategy and core structure scheme steps. Based on the aerodynamic noise generation mechanism, noise characteristics and spectrum distribution of the main ventilation air path as defined in step S1, determine the noise reduction strategy and lock in the core structure of the array silencer. S3. Determine the external dimensions and preliminary airflow calculation steps of the array-type silencer. Based on the dimensions of the stator frame of the hydro-generator and the measured data, combined with the airflow requirements of the main ventilation duct, determine the external constraints and preliminary design feasibility of the silencer. Secondly, combined with the determined external dimensions and the basic airflow data of the main ventilation duct obtained in step S1, perform preliminary calculations of ventilation resistance and airflow attenuation to avoid the silencer design affecting ventilation safety requirements. If the requirements are not met, return to adjust the silencer design. S4. Initial Scheme Design Steps: Based on the advantageous frequency band, noise mechanism and contribution ratio, and quantified noise reduction target determined in step S1, the core structure of the array-type muffler determined in step S2, and the external dimensional constraints and preliminary airflow parameters in step S3, combined with the micro-perforated silencing theory, the initial scheme design of the array-type muffler is carried out; including the aperture, thickness, hole spacing, and cavity thickness of the micro-perforated plate of the array-type muffler. S5. Simulation Analysis and Optimization Steps: Based on the initial array-type silencer scheme determined in step S4, a three-dimensional model of the array-type silencer is established. ANSYS is used to build a noise reduction scheme model and set boundary conditions. First, the airflow field through the array-type silencer in the main ventilation path is simulated using the Fluent module to obtain pressure data as initial parameters. Then, the Mechanical model is imported to simulate fluid noise and noise reduction effect, and the noise reduction amount in different frequency bands is analyzed. By comprehensively adjusting the aperture, spacing, thickness, and spatial thickness of the micro-perforated plate, ventilation performance is optimized, pressure loss and airflow attenuation are reduced while ensuring the silencing effect, resulting in a better parameter combination and noise reduction effect. S6. Accurate calculation of fluid parameters and solution locking: Based on the optimal parameter combination obtained in step S5, calculate the core airflow parameters of the main ventilation path. If the air volume and pressure loss exceed the air volume attenuation limit and pressure loss threshold in step S2, adjust the micro-perforated plate aperture, hole spacing, plate thickness and / or space thickness, and repeat steps S5-S6 until the optimal parameter combination and noise reduction effect are obtained, and finally lock in the design solution that meets the dual requirements of ventilation and noise reduction.

2. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 1, characterized in that: In step S2, based on the aerodynamic noise generation mechanism, noise characteristics, and spectral distribution of the main ventilation path defined in step S1, a noise reduction strategy is determined, specifically: To address broadband eddy current noise, a resistive sound absorption technology is employed, which converts sound energy into heat energy through the frictional viscosity effect of micro-perforated plates, thereby achieving broadband noise reduction. To address discrete rotational noise, a resonant silencing technology approach is adopted. By matching the parameters of the micro-perforated plate, the resonant frequency of the silencer is aligned with the peak frequency of the noise, and the energy is canceled out by sound wave interference. To address eddy shedding and surge noise, a technical approach combining flow field optimization and noise reduction is adopted. This involves reducing airflow separation through structural design and simultaneously weakening noise through noise reduction structures.

3. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 2, characterized in that: In step S2, locking the core structure of the array silencer specifically means determining that the micro-perforated plate array is the core carrier, and achieving wide-band coverage through multi-plate series combination. Micro-perforated plates with different parameters are arranged along the airflow path in the series direction to match different mid-to-high frequency bands, forming a multi-dimensional silencer array.

4. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 3, characterized in that: For flow field optimization, bends are provided on the micro-perforated plates at the air inlet and outlet of the silencer. These bends are configured to guide the airflow to a smooth transition and control ventilation resistance.

5. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 4, characterized in that: The micro-perforated plate is bent at the air inlet and air outlet of the outer casing at a bending angle of 45°.

6. The design method of the array-type silencer for the main ventilation path between the stator core and air cooler of a hydro-generator as described in any one of claims 1-5, characterized in that: In step S4, the initial design of the array-type silencer specifically refers to, based on the dominant noise frequency band determined in step S1, and combined with the formula for calculating the resonant frequency of the micro-perforated plate, back-calculating the aperture, spacing, plate thickness, and cavity thickness of the micro-perforated plate.

7. The design method of the array-type silencer for the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 6, characterized in that: The formula for calculating the resonant frequency of a micro-perforated plate is: In the formula, The speed of sound is expressed in m / s. The perforation rate is the ratio of the total area of ​​the holes to the area of ​​the micro-perforated plate; t is the thickness of the micro-perforated plate in meters; and L is the depth of the cavity behind the micro-perforated plate in meters. This represents the end-diameter correction amount, taken as... d is the aperture.

8. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 7, characterized in that: In step S4, the determination of the aperture of the micro-perforated plate must satisfy the condition that the aperture is less than the wavelength corresponding to the target noise reduction frequency / 10.

9. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 7, characterized in that: The pores on a single micro-perforated plate have a uniform diameter.

10. The design method of the array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 7, characterized in that: In step S4, the micropores on each microperforated plate are evenly distributed. The spacing between the micropores on the microperforated plate is determined according to the perforation rate, which refers to the percentage of the total area of ​​all micropores on a single microperforated plate to the total area of ​​the microperforated plate.

11. The design method of the array-type silencer for the main ventilation path between the stator core and air cooler of a hydro-generator as described in any one of claims 1-5, characterized in that: Step S3, determining the external dimensions of the muffler, specifically involves measuring the internal space dimensions of the stator frame in the main ventilation path between the stator core and the air cooler to ensure that the muffler does not interfere with the stator core and air cooler after installation. Based on the aforementioned internal space dimensions, and in conjunction with the micro-perforated plate array structure determined in step S2, the dimensions of the muffler housing are designed. The dimensions of the housing match the flow cross-section of the main ventilation path, and the length is adapted to the structural requirements of multiple plates connected in series.

12. An array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator, characterized in that: The array-type silencer is designed based on the design method of the array-type silencer adapted to the main ventilation air path between the stator core and the air cooler of the hydro-generator as described in any one of claims 1-11. It includes a shell and several micro-perforated plates placed inside the shell. The several micro-perforated plates are arranged in series at intervals, with the distance between adjacent micro-perforated plates being the cavity thickness. The aperture of each micro-perforated plate is consistent, and the micro-holes are evenly distributed. Different micro-perforated plates adopt different apertures according to the dominant noise frequency.

13. The array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 12, characterized in that: The array-type silencer is made of metal without sound-absorbing cotton.

14. The array-type silencer adapted to the main ventilation path between the stator core and air cooler of a hydro-generator as described in claim 12, characterized in that: The micro-perforated plate is bent at the air inlet and air outlet of the outer casing at a bending angle of 45°.

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