Design method of array type silencer adaptive to main ventilation air path between stator core of hydraulic generator and air cooler and array type silencer

Abstract

The invention discloses a design method of an array type silencer adaptive to a main ventilation air path between a stator iron core of a hydraulic generator and an air cooler and the array type silencer, and relates to the technical field of suppression or reduction of noise of the hydraulic generator. The method comprises the steps of S1, obtaining aerodynamic noise data and airflow parameters of a main ventilation air path, S2, determining a silencing thought and a micro-perforated plate array core structure according to broadband vortex, discrete rotation, vortex falling and surge noise, S3, determining the boundary dimension and preliminarily calculating the airflow parameters, S4, designing plate parameters in combination with a micro-perforated resonance formula, and S5, calculating the noise of the micro-perforated plate array. S5, performing simulation optimization and S6, accurately accounting airflow parameters, and locking a scheme meeting requirements; the silencer comprises a shell and a plurality of micro-perforated plates, and the multiple layers of micro-perforated plates are arranged in series. The invention has the advantages of no sound absorption material, low wind resistance (the air volume attenuation is less than or equal to 5%, and the pressure loss is less than or equal to 200Pa), the noise of the main wind path is reduced by 5-7dB (A), the service life is long, the operation and maintenance cost is low, and the requirements of the main wind path are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of inhibiting or reducing the noise of a hydroelectric generator, and more particularly to a design method of an array silencer adapted to the main ventilation air passage between the stator core and the air cooler of a hydroelectric generator and the array silencer. BACKGROUND

[0002] In the field of energy equipment, the operating noise of a hydroelectric generator 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. Currently, the electromagnetic design and structural design of large design companies 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 air passage) accounts for a significant proportion in high-speed and large-capacity units, becoming the core direction to be conquered in noise reduction technology.

[0003] Currently, the noise reduction technology of a hydroelectric generator mainly focuses on the three paths of "sound insulation, sound absorption, and sound elimination", forming a relatively mature application system: 1. Sound insulation technology uses sound energy shielding principle to block the noise radiation to the outside by setting special structures such as airtight soundproof enclosure and sound barrier, or using high sound insulation performance materials to coat the generator body. This technology can directly reduce the noise transmission of the whole machine to the outside, but it cannot reduce the noise from the source, and may affect the heat dissipation efficiency and maintenance convenience of the unit; 2. The sound absorption technology is to lay sound absorption materials (such as glass wool, polyester fiber cotton, rock wool, etc.) on the inner wall of the generator pit, the inside of the soundproof enclosure, or the surface of the unit body structure, to achieve noise reduction by absorbing and dissipating sound energy through the pores of the materials. However, the core of this technology depends on the acoustic performance of the sound absorption materials, and such materials generally have defects such as easy aging, moisture absorption and deterioration, dust accumulation and pollution, which leads to a significant decrease in sound elimination effect over time. Therefore, regular replacement is required, increasing the operation and maintenance cost and downtime; 3. The sound elimination technology is to arrange a silencer on the noise propagation path to achieve sound energy attenuation by changing the airflow passage structure, which is a key means to specifically address aerodynamic noise. Currently, the mainstream silencers are mainly used in the ventilation path of the soundproof enclosure of a hydroelectric generator, as noise control components of the auxiliary ventilation system.

[0004] However, the existing sound elimination technology and products have two major defects, which seriously limit their application and noise reduction effect in the main ventilation air passage of a hydroelectric generator: First, the muffler body design has inherent shortcomings. Existing mufflers generally rely on sound-absorbing materials to achieve noise reduction. The fiber structure or porous structure of such materials significantly increases airflow resistance, resulting in increased pressure loss of the ventilation system. To compensate for the loss of air volume, the power of the ventilation fan needs to be increased, which in turn increases the noise of the fan itself, forming a vicious cycle of "noise reduction-noise increase", ultimately affecting the noise control effect of the entire machine; at the same time, the aging and deterioration of sound-absorbing materials cannot be completely solved, which not only shortens the service life of the muffler (usually 3-5 years need to be replaced once), but also may cause safety hazards due to material falling and polluting internal components (such as stator coils and air coolers) of the unit.

[0005] Second, the installation position design is away from the core noise area. Existing mufflers are arranged in the auxiliary ventilation path of the soundproof cover, and the air volume of this path is only about 0.3% of the total ventilation volume of the generator, with low wind speed and weak airflow disturbance, which is not the main area of aerodynamic noise. The main ventilation path of the hydroelectric generator (the airflow channel between the stator core and the air cooler) is the core area with the most concentrated air volume (total air volume of the machine), the highest wind speed, and the strongest aerodynamic noise. If the existing high wind resistance muffler is installed in this area, the air volume of the main ventilation system will be attenuated by more than 10%, seriously affecting the heat dissipation effect of key components such as the stator and rotor, and may cause problems such as overheating of the unit and aging of the insulation. Therefore, the existing muffler cannot meet the installation requirements of the main ventilation path.

[0006] In summary, due to the dual limitations of "relying on sound-absorbing materials leading to high wind resistance and short service life" and "installation position away from the core noise area", the existing hydroelectric generator muffling technology cannot effectively and long-term control the aerodynamic noise of the main ventilation path. It is necessary to develop a new type of muffler without sound-absorbing materials, low wind resistance, and suitable for the installation requirements of the main ventilation path, to fill the gap in existing technology. SUMMARY

[0007] In order to overcome the defects and deficiencies existing in the prior art, the application provides an array type muffler design method and an array type muffler which are suitable for adapting the main ventilation air path between the stator core and the air cooler of a hydroelectric generator. The application aims to provide an array type muffler and a design method without sound absorbing material and with low air resistance, so that the array type muffler can be installed in the main ventilation air path of the hydroelectric generator, long-term and accurate aerodynamic noise can be controlled, and the problems of short service life, large air resistance and inability to adapt to the main air path of the existing muffler can be avoided. The design method of the array type muffler provided by the application is based on the ventilation parameters (flow rate, flow) and noise spectrum data of the hydroelectric generator, estimates the hole diameter, micro-perforated plate thickness, hole spacing and cavity thickness in the micro-perforated plate in the array muffler by combining the transmission loss formula, completes the preliminary design in combination with the structure size of the stator frame, adjusts the hole diameter, micro-perforated plate thickness, hole spacing and cavity thickness in the micro-perforated plate through flow field analysis and noise reduction simulation verification, and optimizes the scheme to meet the dual requirements of ventilation and noise reduction, and the array combination structure of the metal micro-perforated plate without sound absorbing material is adopted. The effect achieved by the method is that the muffler has small air resistance, can adapt to the main ventilation air path and has little influence on the air volume, does not affect the heat dissipation of the unit, the metal structure has no aging problem, has a long service life and can reduce operation and maintenance costs, can accurately target the strong noise area of the main air path, effectively reduce the aerodynamic noise and improve the sound quality of the unit.

[0008] In order to solve the problems existing in the prior art, the application is realized through the following technical scheme.

[0009] The first aspect of the application provides a design method of an array type resistive-reactive composite muffler suitable for adapting the main ventilation air path between the stator core and the air cooler of a hydroelectric generator, which comprises the following steps: S1, pre-parameter acquisition step, through ventilation simulation of the main ventilation air path between the stator core and the air cooler of the hydroelectric generator, theoretical calculation of the ventilation system or actual measurement of unit noise data and airflow data under different working conditions; specifically including the following contents: (1) analyzing the noise frequency distribution and noise spectrum characteristics, locking the dominant frequency band of the aerodynamic noise in the main ventilation air path, recording the peak sound pressure level corresponding to each frequency band, studying the internal relationship between the working condition and the noise, clearly defining the noise change rule under different working conditions, combining the unit noise limit of the hydroelectric generator, inversely calculating the minimum noise reduction amount to be achieved, and forming a quantitative noise reduction target; (2) focusing on the aerodynamic noise generation mechanism in the main ventilation air path, quantifying the contribution proportion of the turbulence mechanism, vortex shedding mechanism, boundary layer mechanism and polar mechanism in the total aerodynamic noise; at the same time, positioning the specific position of each noise generation mechanism in the stator frame, and clearly defining the noise propagation path; obtaining the basic airflow data of the main ventilation air path, including the total flow, average airflow velocity, unit allowable pressure loss threshold and air volume attenuation limit; S2, determine the noise reduction idea and core structure scheme step, based on the S1 step clear main ventilation air path aerodynamic noise generation mechanism, noise characteristics and frequency spectrum distribution, determine the noise reduction idea, and lock the core structure of the array silencer; S3, determine the array silencer size and preliminary air flow calculation step, according to the size of the hydro-generator stator frame and the measured data, combining the air flow circulation demand of the main ventilation air path, determine the shape constraint and preliminary design feasibility scheme of the silencer, secondly, combining the determined size and the main ventilation air path basic air flow data obtained in S1 step, preliminarily calculate the ventilation resistance and air volume attenuation, avoid the influence of silencer design on ventilation safety demand, if not satisfied, return to adjust the silencer design; S4, initial scheme design step, based on the advantage frequency band, noise mechanism and contribution ratio of S1 step, the core structure of the array silencer determined in S2 step, the size constraint and preliminary air flow parameter of S3 step, combining the micro-perforated sound absorption theory, develop the initial scheme design of the array silencer; including the array silencer micro-perforated plate aperture, micro-perforated plate thickness, hole spacing and cavity thickness; S5, simulation analysis and optimization step, according to the initial scheme of the array silencer determined in S4 step, establish the three-dimensional model of the array silencer, use ANSYS to establish the noise reduction scheme model, set the boundary conditions; first, use fiuent module to simulate the air flow field of the main ventilation air path through the array silencer, get the pressure data as the initial parameter; then import the Mechanical model, simulate the fluid noise and noise reduction effect, analyze the noise reduction amount of different frequency bands; adjust the aperture, hole spacing, plate thickness and space thickness of the micro-perforated plate comprehensively, optimize the ventilation performance, reduce the pressure loss and air volume attenuation under the premise of ensuring the noise reduction effect, get the better parameter combination and noise reduction effect; S6, fluid parameter accurate calculation and scheme locking step, according to the better parameter combination obtained in S5 step, carry out the calculation of the core air flow parameter of the main ventilation air path; if the air volume and pressure loss exceed the air volume attenuation limit value and pressure loss threshold value of step S2, adjust the aperture, hole spacing, plate thickness and / or space thickness of the micro-perforated plate, carry out S5-S6 step again, until the optimal parameter combination and noise reduction effect are obtained, finally lock the design scheme meeting the dual requirements of ventilation and noise reduction.

[0010] Further preferably, in S2 step, based on the S1 step clear main ventilation air path aerodynamic noise generation mechanism, noise characteristics and frequency spectrum distribution, determine the noise reduction idea, specifically: For broadband vortex noise, resistive sound absorption technology path is adopted, the frictional viscous effect of micro-perforated plate is used to convert sound energy into heat energy, realizing broadband noise reduction; For discrete rotating noise, the resonance noise elimination technology path is adopted, the micro-perforated plate parameters are matched, the resonance frequency of the muffler is aligned with the noise peak frequency, and the sound wave interference is used to eliminate the energy; For vortex shedding and surge noise, a technical path of flow field optimization and noise elimination cooperation is adopted, and the flow separation is reduced through structural design, and the noise is weakened by cooperating with the noise elimination structure.

[0011] Further preferably, in the S2 step, the core structure of the array-type muffler is locked, specifically, the micro-perforated plate array is determined as the core carrier, a wide frequency band is covered through the series combination of multiple plates, the micro-perforated plates with different parameters are arranged in the series direction along the airflow path, the micro-perforated plates are matched with different frequency bands of medium and high frequencies respectively, and a multi-dimensional noise elimination array is formed.

[0012] Further preferably, for flow field optimization, a bending part is arranged on the micro-perforated plate at the air inlet and air outlet of the muffler, and the bending part is configured to guide the airflow to transition smoothly and control the ventilation resistance.

[0013] Further preferably, the micro-perforated plate is bent at the air inlet and air outlet of the shell, and the bending angle is 45°.

[0014] Further preferably, in the S4 step, the initial scheme design of the array-type muffler is carried out, specifically, according to the dominant noise frequency band determined in the S1 step, the hole diameter, hole spacing, plate thickness and cavity thickness of the micro-perforated plate are back calculated by combining the resonance frequency calculation formula of the micro-perforated plate.

[0015] Further preferably, the resonance frequency calculation formula of the micro-perforated plate is:

[0016] In the formula, The sound speed is represented by v, the unit is m / s, and the value at normal temperature is about 340 m / s; The perforation rate is represented by f, that is, the total area of the holes accounts for the proportion of the area of the micro-perforated plate; t is the thickness of the micro-perforated plate, the unit is m; L is the depth of the cavity behind the micro-perforated plate, the unit is m; The hole diameter end correction is represented by d0, and d0 is equal to 0.8d; d is the hole diameter.

[0017] Further preferably, in the S4 step, the hole diameter of the micro-perforated plate needs to satisfy the condition that the hole diameter < target noise elimination frequency corresponding wavelength / 10.

[0018] Further preferably, the hole diameters of the micro-holes on the plate body of a single micro-perforated plate are consistent.

[0019] Further preferably, in the S4 step, the micro-holes on each micro-perforated plate are uniformly distributed, the hole spacing on the micro-perforated plate is determined according to the perforation rate, and the perforation rate refers to the total area of all micro-holes on a single micro-perforated plate accounts for the percentage of the area of the micro-perforated plate.

[0020] Further preferably, the S3 step determines the size of the muffler, specifically, measuring the internal space size of the stator frame of the main ventilation air passage between the stator core and the air cooler, to ensure that the muffler does not interfere with the stator core and the air cooler after installation; based on the above internal space size, in combination with the micro-perforated plate array structure determined in the S2 step, the size of the muffler shell is designed, the size of the shell matches the flow cross section of the main ventilation air passage, and the length adapts to the structure requirement of multiple plate series connection.

[0021] The second aspect of the present application provides an array type muffler adapted to the main ventilation air passage between the stator core and the air cooler of a hydroelectric generator, which is designed based on the design method of the array type muffler adapted to the main ventilation air passage between the stator core and the air cooler of a hydroelectric generator according to the first aspect described above, and comprises a shell and a plurality of micro-perforated plates arranged in the shell; the plurality of micro-perforated plates are arranged in series with a spacing, the spacing between adjacent micro-perforated plates is a cavity thickness, the hole diameters of a single micro-perforated plate are consistent, and the micro-holes are uniformly distributed, and different micro-perforated plates adopt different hole diameters according to the dominant noise frequency.

[0022] Further preferably, the array type muffler is a resistance-reactance composite muffler, which obtains high transmission loss in a wider frequency band.

[0023] Further preferably, the array type muffler is free of sound-absorbing cotton.

[0024] Further preferably, the array type muffler is made of metal.

[0025] Further preferably, the micro-perforated plate is bent at the air inlet and air outlet of the shell, and the bending angle is 45°.

[0026] Compared with the prior art, the present application has the following beneficial technical effects: 1、The present application quantifies the contribution ratio of four types of aerodynamic noise mechanisms (such as 50%~60% of vortex shedding noise and 30%~40% of turbulent noise) in the main ventilation air passage through the S1 step, and locates the noise generation position (such as the vortex shedding noise source at the outlet of the stator core ventilation groove), avoiding the blindness of traditional mufflers "non-discriminatory noise reduction"; then through the S2 step, the dedicated noise reduction technology path is matched for three types of core aerodynamic noise (wide frequency vortex, discrete rotation, vortex shedding and surge), and the precise calculation of the micro-perforated plate parameters (the deviation between the resonance frequency and the noise peak frequency is ≤5%) is combined with the S4 step, so that the sound energy dissipation efficiency is improved to 0.8~0.9, and finally the main ventilation air passage noise is reduced by 5~7dB(A), compared with the existing auxiliary ventilation air passage muffler, the noise reduction effect is improved by 4~5 times, and the aerodynamic noise problem of high-speed and large-capacity units is completely solved.

[0027] 2、The application realizes the balance of wind resistance and ventilation through multi-stage air flow accounting and structure optimization: S3 step preliminary accounting ensures that the cross-sectional area of the silencer shell is not less than 95% of the cross-sectional area of the air duct, and preliminarily controls the wind volume attenuation ≤8%, the pressure loss ≤250Pa; S5 step accurately optimizes the air flow path through ANSYS Fluent flow field simulation, and cooperates with the "45° bending micro-hole plate" designed in S2 step to guide the smooth transition of air flow (local wind speed ≤10m / s); finally, S6 step locks the parameter combination of wind volume attenuation ≤5%, pressure loss ≤200Pa, completely avoids the problem that the existing silencer installed in the main air duct leads to wind volume attenuation exceeding 30%, ensures the heat dissipation demand of key components such as stator and rotor, strictly controls the temperature rise of stator coil within the design limit, and eliminates the risk of overheating and insulation aging of the unit.

[0028] 3、The application discards the sound-absorbing materials such as glass wool and polyester fiber relied on by traditional silencers, and adopts metal micro-perforated plate array structure, which fundamentally solves the defects of material aging, moisture absorption, metamorphic, dust accumulation and blockage: on the one hand, the metal structure has no aging failure problem, and does not need to be replaced regularly, so that the service life of the silencer is extended to more than 40 years, the downtime maintenance time is reduced by 85%, and the annual average operation and maintenance cost is reduced by 85%; on the other hand, the safety hazards of material falling off polluting the stator coil and air cooler are eliminated, and the insulation failure rate of the unit caused by silencer design is 0, which significantly improves the long-term operation reliability of the unit.

[0029] 4、The application breaks through the design mode of traditional silencer trial and error experience, and establishes a standardized process of parameter acquisition-scheme design-simulation optimization: the noise spectrum and air flow data obtained in S1 step provide quantitative basis for design; S4 step inversely deduces key parameters based on the resonance frequency formula of micro-perforated plate, avoiding blind selection of parameters; S5 step verifies the flow field and noise reduction effect simultaneously through ANSYS Fluent+Mechanical coupled simulation, the parameter optimization efficiency is improved by 60%, without repeatedly producing physical prototype, the research and development cycle is shortened by 50%, and the research and development cost is reduced by more than 40%; at the same time, each step in the design process forms clear constraints (such as S3 shape size constraint S4 parameter design), ensuring that the final scheme has both technical feasibility and engineering landing nature.

[0030] 5、The S3 step of the application designs the silencer shape based on the actual measured space size of the stator frame, ensuring that there is no interference with the stator core and air cooler interface, and the structure adaptability reaches 100%; the shell and micro-hole plate are fixed by bolts, and the installation interface and the reserved bolt hole of the stator frame are accurately matched (deviation ≤1mm), so that the core components of the modified unit do not need to be disassembled, and the installation efficiency is improved by 80%; in addition, the array structure of micro-perforated plate in series supports flexible expansion - if the noise frequency shifts due to subsequent unit working condition changes, only the micro-hole plate of the corresponding frequency band needs to be replaced, without replacing the whole silencer, which adapts to the noise reduction demand of different capacity and speed units, and the universality is significantly better than that of traditional fixed structure silencer.

[0031] 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

[0032] Figure 1 This is a schematic diagram of the three-dimensional structure of the array-type muffler of the present invention; Figure 2 This is a schematic diagram of the micro-perforated plate arrangement structure in the array-type muffler of the present invention; Figure 3 This is a schematic diagram of different micro-perforated plate combinations in the array-type muffler of the present invention; Figure 4 This is a schematic diagram of the arrangement of micro-perforated plates in the array-type muffler of the present invention; 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; Reference numerals: 1. Array-type silencer, 2. Housing, 3. Micro-perforated plate, 4. Stator core, 5. Stator frame, 6. Air cooler. Detailed Implementation

[0033] 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.

[0034] Example 1 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 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 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. 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 scheme of the array-type silencer 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 flow field of the main ventilation path flowing through the array-type silencer is simulated using the fiuent 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.

[0035] Example 2 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: 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.

[0036] 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.

[0037] 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°.

[0038] In this embodiment, the noise reduction strategy is determined based on the noise generation mechanism, noise characteristics, and noise spectrum distribution at different locations: Among them, the noise generation mechanism should be clearly defined: whether it is electromagnetic force noise, aerodynamic noise, or mechanical force noise; 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). 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... 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: 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. —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; 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.

[0039] 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): 1) Source control (core): Through optimized fan design and air duct optimization; 2) Airflow path treatment (key measure for air outlets): Install silencers; 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. 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). Composite silencer: Combining reactive and resistive structures, it achieves full-frequency noise reduction and is the most commonly used form for motor air outlets; Design considerations: The design of a muffler must balance noise reduction, aerodynamic performance (low pressure loss), and size.

[0040] 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.

[0041] 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.

[0042] Example 3 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.

[0043] As an example, the formula for calculating the resonant frequency of a micro-perforated plate is:

[0044] 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.

[0045] 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.

[0046] In a preferred embodiment of this invention, step S4 involves defining and determining the parameters in the initial design of the array-type muffler: 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. 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. 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:

[0047] 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.

[0048] 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.

[0049] c. Determine the specific plate thickness, hole diameter, perforation rate, and cavity thickness. 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.

[0050] Plate thickness: Related to aperture, generally too thin and the mechanical strength is insufficient, too thick and the acoustic impedance is too high.

[0051] 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.

[0052] 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... .

[0053] 2) The relationship between the number of microplates and the space (basic logic): 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Example 4 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.

[0058] 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.

[0059] 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.

[0060] Example 5 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.

[0061] 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°.

[0062] 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 the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0063] 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 of an array silencer adapted to a main ventilation air passage between a stator core of a hydroelectric generator and an air cooler, characterized by, The design method comprises the following steps: S1, a pre-parameter acquisition step, through ventilation simulation of a main ventilation air passage between a stator core of a hydro-generator and an air cooler, theoretical calculation of a ventilation system, or measurement of unit noise data and airflow data under different working conditions; specifically comprising the following contents: (1) analyzing noise frequency distribution and noise spectrum characteristics, locking the dominant frequency band of aerodynamic noise of the main ventilation air passage, recording the peak sound pressure level corresponding to each frequency band; studying the internal relationship between working conditions and such noise, clarifying the noise variation law under different working conditions, combining the hydro-generator whole machine noise limit, backstepping the minimum noise reduction amount to be achieved, and forming a quantitative noise reduction target; (2) focusing on the aerodynamic noise generation mechanism in the main ventilation air passage, quantifying the contribution proportion of the turbulence mechanism, vortex shedding mechanism, boundary layer mechanism and polar mechanism in the total aerodynamic noise; at the same time, positioning the specific position of each noise generation mechanism inside the stator frame, and clarifying the noise propagation path; obtaining the basic airflow data of the main ventilation air passage, including the total flow, the average airflow velocity, the pressure loss threshold allowed by the unit, and the air volume attenuation limit; S2, a step of determining the noise elimination and reduction idea and the core structure scheme, based on the noise generation mechanism, noise characteristics and spectrum distribution of the main ventilation air passage in S1, the noise elimination and reduction idea is determined, and the core structure of the array type silencer is locked; S3, a step of determining the array type silencer size and preliminary airflow calculation, according to the size of the stator frame of the hydro-generator and the measured data, combining the airflow flow demand of the main ventilation air passage, the shape constraint and the preliminary design feasibility scheme of the silencer are determined, secondly, combining the determined size and the basic airflow data of the main ventilation air passage obtained in S1, the ventilation resistance and air volume attenuation are preliminarily calculated to avoid affecting the ventilation safety demand caused by the design of the silencer, if not satisfied, return to adjust the design of the silencer; S4, an initial scheme design step, based on the dominant frequency band, noise mechanism and contribution proportion, quantitative noise reduction target in S1, the core structure of the array type silencer determined in S2, the size constraint and preliminary airflow parameters in S3, combining the micro-perforated silencing theory, the initial scheme design of the array type silencer is carried out; including the aperture, plate thickness, hole spacing and cavity thickness of the micro-perforated plate of the array type silencer; S5, a simulation analysis and optimization step, according to the initial scheme of the array type silencer determined in S4, a three-dimensional model of the array type silencer is established, ANSYS is used to establish the noise reduction scheme model, and the boundary conditions are set; first, the fiuent module is used to simulate the airflow field of the main ventilation air passage flowing through the array type silencer, the pressure data is obtained as the initial parameter; then the Mechanical model is imported, the fluid noise and noise reduction effect are simulated, and the noise reduction amount of different frequency bands is analyzed; comprehensively adjusting the aperture, hole spacing, plate thickness and space thickness of the micro-perforated plate, under the premise of ensuring the silencing effect, the ventilation performance, pressure loss and air volume attenuation are optimized, and the better parameter combination and noise reduction effect are obtained; S6, precise calculation of fluid parameters and scheme locking step, according to the preferred parameter combination obtained in step S5, the core air flow parameter of the main ventilation air path is calculated; if the air volume and pressure loss exceed the air volume attenuation limit and pressure loss threshold in step S2, adjust the hole diameter, hole spacing, plate thickness and / or space thickness of the micro-perforated plate, and perform steps S5-S6 again until the optimal parameter combination and noise reduction effect are obtained, and finally lock the design scheme that meets the dual requirements of ventilation and noise reduction.

2. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and an air cooler according to claim 1, characterized in that: In step S2, based on the aerodynamic noise generation mechanism, noise characteristics and frequency spectrum distribution of the main ventilation air path determined in step S1, the noise reduction idea is determined, which is specifically: For broadband vortex noise, the resistive sound absorption technology path is adopted, the frictional viscous effect of the micro-perforated plate is used to convert sound energy into heat energy, and broadband noise reduction is achieved; For discrete rotating noise, the resonant noise elimination technology path is adopted, the micro-perforated plate parameters are matched, the resonant frequency of the muffler is aligned with the noise peak frequency, and the sound wave interference is used to offset the energy; For vortex shedding and surge noise, the flow field optimization and noise elimination collaborative technology path is adopted, the airflow separation is reduced through structural design, and the noise is weakened by cooperating with the noise elimination structure.

3. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and the air cooler according to claim 2, characterized in that: In step S2, the core structure of the array type muffler is locked, which is specifically to determine the micro-perforated plate array as the core carrier, realize wide frequency band coverage through multi-plate series combination, arrange micro-perforated plates with different parameters in series direction along the airflow path, match different frequency bands of medium and high frequencies respectively, and form a multi-dimensional noise elimination array.

4. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and an air cooler according to claim 3, characterized in that: For flow field optimization, a bending part is arranged on the micro-perforated plate at the air inlet and air outlet of the muffler, and the bending part is configured to guide the airflow to transition smoothly and control the ventilation resistance.

5. The method of designing an array silencer for adapting the main ventilation air path between the stator core of a hydroelectric generator and the air cooler according to claim 4, characterized in that: The micro-perforated plate is bent at the air inlet and air outlet of the shell, and the bending angle is 45°.

6. The method of designing an array silencer for adapting the main ventilation air path between the stator core of a hydroelectric generator and the air cooler according to any one of claims 1 to 5, characterized in that: In step S4, the initial scheme design of the array type muffler is carried out, which is specifically to determine the hole diameter, hole spacing, plate thickness and cavity thickness of the micro-perforated plate according to the dominant noise frequency band determined in step S1 and the resonant frequency calculation formula of the micro-perforated plate.

7. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and the air cooler according to claim 6, characterized in that: The resonant frequency calculation formula of the micro-perforated plate is: wherein denotes the sound velocity, in m / s, which is about 340 m / s at normal temperature; denotes the perforation ratio, i.e. the ratio of the total area of the holes to the area of the micro-perforated panel; t is the thickness of the micro-perforated panel, in m; L is the depth of the cavity behind the micro-perforated panel, in m; denotes the hole diameter end correction, taken as d is the hole diameter.

8. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and an air cooler according to claim 7, characterized in that: In step S4, the determination of the hole diameter of the micro-perforated plate needs to meet the condition that the hole diameter < target noise elimination frequency corresponding wavelength / 10.

9. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and an air cooler according to claim 7, characterized in that: The hole diameters of the micro-holes on the single micro-perforated plate body are consistent.

10. The method of designing an array silencer for adapting the main ventilation air passage between the stator core of a hydroelectric generator and an air cooler according to claim 7, characterized in that: In step S4, the micro-holes on each micro-perforated plate are uniformly distributed, and the hole spacing on the micro-perforated plate is determined according to the perforation rate, which is the percentage of the total area of all micro-holes on a single micro-perforated plate to the area of the micro-perforated plate.

11. The method of designing an array silencer for adapting the main ventilation air path between the stator core of a hydroelectric generator and the air cooler according to any one of claims 1 to 5, characterized in that: In step S3, the size of the muffler is determined, which is specifically to measure the internal space size of the main ventilation air path between the stator core and the air cooler, to ensure that the muffler does not interfere with the stator core and the air cooler after installation; based on the above internal space size, the size of the muffler shell is designed according to the micro-perforated plate array structure determined in step S2, the size of the shell matches the flow cross section of the main ventilation air path, and the length adapts to the structure requirement of multi-plate series connection.

12. An array silencer adapted to the main ventilation air passage between the stator core of a hydro-generator and an air cooler, characterized in that: The array silencer is designed based on the design method of the array silencer for adapting the main ventilation air passage between the stator core of the water turbine generator and the air cooler according to any one of claims 1-11, comprising a shell and a plurality of micro-perforated panels arranged in the shell; the plurality of micro-perforated panels are arranged in series at intervals, the interval between adjacent micro-perforated panels is the thickness of the cavity, the aperture of each micro-perforated panel is consistent, and the micro-holes are uniformly distributed, and different micro-perforated panels adopt different apertures according to the dominant noise frequency.

13. The arrayed silencer for adapting the main ventilation air passage between the stator core of a hydro-generator and an air cooler according to claim 12, characterized in that: The array silencer is made of metal without sound-absorbing cotton.

14. The arrayed silencer for adapting the main ventilation air passage between the stator core of a hydro-generator and an air cooler according to claim 12, characterized in that: The micro-perforated panel is bent at the air inlet and outlet of the shell, and the bending angle is 45°.

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