A design method for the sound-generating structure of a mechanical low-frequency noise generating device

Abstract

The present invention discloses a method for designing a sound-generating structure of a mechanical low-frequency noise generating device, comprising: (1) designing a sound-generating structure, including a motor, an impeller, and an incoming flow disruptor; (2) extracting an initial unsteady axial exciting force of the impeller; (3) extracting a frequency spectrum distribution within a target low-frequency band, and picking up a frequency point with the highest amplitude; (4) calculating a corresponding energy proportion #imgabs0# according to a target frequency f0; if #imgabs1# is greater than a target value #imgabs2#, the sound-generating structure design is completed; if #imgabs3# is less than a target value #imgabs4#, the impeller diameter D is optimized; and (5) gradually adjusting D to an upper limit D max If #imgabs5# is greater than the target value #imgabs6#, the sound structure design is complete; if #imgabs7# is less than #imgabs8# after adjustment, the initial chord length l is optimized; (6) the impeller chord length l is adjusted. If #imgabs9# is greater than the target value #imgabs10#, the sound structure design is complete; if #imgabs11# is less than #imgabs12#, the chord length optimization continues. The present invention uses the unsteady data of the axial excitation force as the sound performance criterion to provide an efficient generation method for the sound structure.

Description

Technical Field

[0001] The present invention belongs to the field of ships, and in particular relates to a design method for a sound-generating structure of a mechanical low-frequency noise generating device. Background Art

[0002] The application demand for underwater low-frequency sound sources is very extensive and urgent, especially for accurate target simulation. However, the generation and control of low-frequency characteristic sound sources is a technical bottleneck and a common problem that has attracted great attention in related fields both domestically and internationally.

[0003] With the development of modern sonar technology and the continuous expansion of sonar application fields, the low-end operating frequency of sonar has extended to several hundred hertz, and in some new fields, even tens of hertz operating frequencies have been adopted. Therefore, it is necessary to develop low-frequency noise generating devices.

[0004] Existing noise simulations often rely on underwater acoustic transducer systems: The noise spectrum is generated through pre-recording or numerical calculations, processed by digital circuits, and then transmitted by an underwater acoustic transducer. This method offers good frequency controllability and continuity in noise simulation, and can simulate noise spectrum characteristics under various operating conditions, from startup and speed changes to steady-state navigation. Underwater acoustic transducers can be categorized by their vibration modes, including longitudinal, cylindrical, flexural, flexural-extensional, spherical, and shear vibration transducers.

[0005] Japan has developed a rare earth low-frequency, high-power circular transducer for ocean tomography. Its resonant frequency is 30 Hz, its maximum dimension is 2 meters, and its weight in air is 5 tons. Another multiport transducer, with a resonant frequency of 200 Hz, is 2.46 meters long and has a maximum diameter of 0.73 meters.

[0006] Moving-coil transducers are also excellent sound sources for achieving low-frequency radiation. Their structure primarily consists of a magnetic circuit and a rigid piston connected to a vibrating coil. Compressed gas is typically used as a pressure release mechanism to address hydrostatic pressure resistance. They are low-frequency, broadband, and low-power transducers. Their low power is due to the mutual constraints between the magnetic induction coefficient and the product of the wire length and the load current. However, another drawback of moving-coil transducers is that their performance is significantly affected by operating depth.

[0007] Existing noise simulation systems are suitable for simulating mid- and high-frequency noise, but due to the structure of the underwater acoustic transducer system, they face technical bottlenecks in simulating low-frequency noise. The volume and mass of the transducer are closely related to the frequency range of the transmitted noise. The lower the transmission frequency, the larger the transducer volume and mass, and the less feasible the sound source simulation. In addition, some transducers (such as dynamic coil transducers) have limited operating depths due to the transducer principle and cannot operate stably at large working depths.

[0008] Therefore, it is necessary to use mechanical methods to generate and simulate low-frequency noise based on the principle of low-frequency noise, forming a new technical approach for low-frequency noise simulation to supplement the low-frequency noise simulation capability of the transducer. Summary of the Invention

[0009] The present invention provides a design method for the sound-generating structure of a mechanical low-frequency noise generating device. Based on the unsteady data of the axial exciting force as the sound-generating performance criterion, an efficient generation method is provided for the sound-generating structure of the mechanical low-frequency noise generating device.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] A method for designing a sound-generating structure of a mechanical low-frequency noise generating device comprises the following steps:

[0012] (1) Design a sound-generating structure, which includes a motor, an impeller mounted at the end of the motor shaft, and an incoming flow disruptor mounted on the motor housing near the impeller. The initial diameter of the impeller is D, and the impeller is provided with m identical blades uniformly distributed along the circumference, and the initial chord length of the blades is l. The target frequency of the design is f0, and the target energy proportion of the target frequency is

[0013] (2) The impeller speed n is calculated based on the target frequency f0; the unsteady calculation of the impeller is performed using numerical simulation software to extract the initial unsteady axial excitation force of the impeller;

[0014] (3) Based on the fast Fourier transform method, the spectrum distribution in the low-frequency band of a certain target is obtained, and the frequency point with the highest amplitude is picked up as the intensity amplitude corresponding to f0

[0015] (4) Calculate the corresponding energy ratio according to the target frequency f0 like Greater than target value The sound structure design is completed; if Less than target value Then proceed to the next step to adjust the initial diameter D of the impeller;

[0016] (5) Gradually adjust the initial diameter D of the impeller to the upper limit Dmax , repeat steps (2)-(4) after each adjustment, if Greater than target value The sound structure design is completed; if each adjustment Both are less than the target value Then proceed to the next step to optimize the initial chord length l of the impeller;

[0017] (6) Adjust the impeller chord length l and repeat steps (2)-(4). If Greater than target value The sound structure design is completed; if Less than target value Continue optimizing the chord length until Greater than target value Finally, the sound structure design is completed.

[0018] The design concept of the present invention is based on the noise mechanism of rotating machinery such as propellers. It innovatively uses the unsteady data of axial exciting force as the criterion for sound performance, and obtains a design method for the sound structure of a mechanical low-frequency noise generating device.

[0019] In the present invention, the motor is used to provide power, and an incoming flow disruptor is used to disturb the inlet flow field of the impeller, thereby generating low-frequency noise by rotating the blades on the impeller.

[0020] Furthermore, in step (1), the gap δ between the incoming flow disruptor and the impeller is not greater than 0.1D.

[0021] Preferably, the impeller is provided with three identical blades evenly distributed along the circumference.

[0022] Optionally, the inflow disruptor adopts one or more static cylindrical structures, or other structures with active movement.

[0023] Furthermore, the installation angle of the blades on the impeller is less than 45°.

[0024] In step (2), the formula for calculating the impeller speed n based on the target frequency f0 is:

[0025]

[0026] Where m represents the number of blades in the impeller.

[0027] In step (4), the corresponding energy ratio is calculated according to the target frequency f0 The formula is:

[0028]

[0029] in, is the intensity amplitude corresponding to f0, is the mean value of the axial unsteady exciting force.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The design method of the present invention is based on the unsteady data of the axial exciting force as the sound performance criterion, and provides an efficient generation method for the sound structure of the mechanical low-frequency noise generating device. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the sound-generating structure of a mechanical low-frequency noise generating device according to the present invention;

[0033] Figure 2 A flow chart of the design method of the present invention;

[0034] Figure 3 : This is a time domain diagram of the axial unsteady exciting force extracted in an embodiment of the present invention;

[0035] Figure 4 The spectrum distribution in the frequency band of 0 to 20 Hz is obtained based on the fast Fourier transform method in the embodiment of the present invention;

[0036] Figure 5a This is a time domain diagram of the axial unsteady exciting force after the impeller diameter is optimized in an embodiment of the present invention;

[0037] Figure 5b This is a frequency domain diagram of the axial unsteady exciting force after the impeller diameter is optimized in an embodiment of the present invention;

[0038] Figure 6a This is a time domain diagram of the axial unsteady exciting force after optimizing the chord length in an embodiment of the present invention.

[0039] Figure 6b This is a frequency domain diagram of the axial unsteady exciting force after the chord length is optimized in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended to facilitate understanding of the present invention and do not have any limiting effect on the present invention.

[0041] The present invention proposes a design method for the sound-generating structure of a mechanical low-frequency noise generating device based on the noise mechanism of rotating machinery such as propellers.

[0042] like Figure 1As shown in the figure, the sound-generating structure of the mechanical low-frequency noise generating device includes a motor, an impeller 2 mounted on the end of the motor shaft, and an inflow disruptor 1 mounted on the motor housing near the impeller 2. The motor is used to provide power, and the inflow disruptor 1 is used to disturb the inflow field of the impeller 2, generating low-frequency noise by rotating the blades on the impeller 2.

[0043] The initial diameter of the impeller 2 is D, and the impeller 2 is provided with m identical blades evenly distributed along the circumference, with an initial chord length of l and an installation angle less than 45°. Due to the volume limitation of the sound generating device, the upper limit of D is D max , l upper limit is l max , the gap δ between the inflow disruptor 1 and the impeller 2 is not greater than 0.1D. The target frequency of the design is f0, and the target energy ratio of the target frequency is

[0044] like Figure 2 As shown, the design method of the present invention is as follows:

[0045] 1) Calculate the impeller speed n from f0 The unsteady calculation of the impeller is performed using numerical simulation software to extract the initial unsteady axial excitation force of the impeller.

[0046] 2) Based on the fast Fourier transform method, the spectrum distribution within a certain target low-frequency band is obtained, and the frequency point with the highest amplitude is picked;

[0047] 3) According to the following formula, the energy ratio corresponding to f0 is obtained: in, is the intensity amplitude corresponding to f0, is the mean value of the axial unsteady exciting force:

[0048]

[0049] like Greater than target value The design of the acoustic simulator is completed;

[0050] like Less than target value Then proceed to the next step to adjust the impeller diameter;

[0051] 4) Gradually adjust the initial diameter D of the impeller to the upper limit D max Repeat steps 1)-3) after each adjustment:

[0052] like Greater than target value The sound structure design is completed;

[0053] If each adjustment Both are less than the target value Then proceed to the next step to optimize the initial chord length l of the impeller;

[0054] 5) Adjust the impeller chord length l and repeat 1)-3):

[0055] like Greater than target value The design of the acoustic simulator is completed;

[0056] like Less than target value Continue to optimize the chord length.

[0057] The following is an example of a sound structure with 3 blades, an initial impeller diameter D = 400mm, an initial chord length l = 99mm, and a gap δ = 1mm between the flow disruptor and the impeller. Figure 2 Specifically describe the design process of the present invention, the target frequency f0 is 19.5Hz, the target energy ratio of the target frequency 5%, D max =550mm. The following steps are included:

[0058] 1) The impeller speed n = 6.5 rps is calculated from f0, and the time domain diagram of the axial unsteady exciting force is extracted as follows Figure 3 shown.

[0059] 2) Based on the fast Fourier transform method, the spectrum distribution in the frequency band of 0 to 20 Hz is obtained, and the frequency point with the highest amplitude is picked up, such as Figure 4 shown.

[0060] 3) According to the formula, the energy ratio corresponding to f0 is obtained in, Mean value of axial unsteady exciting force but

[0061] 4) Optimize the impeller diameter D until D = 550 mm, and obtain the time domain and frequency domain diagrams of the axial unsteady exciting force, as shown in Figure 5a and Figure 5b shown.

[0062] Calculate the energy ratio corresponding to f0 in, Mean value of axial unsteady exciting force but If the condition is not met but D has reached the upper limit, the chord length is optimized.

[0063] 5) Reduce the chord length and take l = 82.5 mm to obtain the time domain and frequency domain diagrams of the axial unsteady exciting force, as shown in Figure 6a and Figure 6b shown.

[0064] Calculate the energy ratio corresponding to f0 in, Mean value of axial unsteady exciting force but If the conditions are met, the sound structure is obtained.

[0065] The design method of the present invention is based on the unsteady data of the axial exciting force as the sound performance criterion, and provides an efficient generation method for the sound structure of the mechanical low-frequency noise generating device.

[0066] In the embodiment of the present invention, the incoming flow disruptor is a single, static cylindrical structure, but a number of incoming flow disruptors with active motion and other structural forms are also within the scope of the present invention.

[0067] In the embodiment of the present invention, the three-bladed propeller with specially designed blades and equidistant distribution can be replaced with other specially designed rotating machinery. In addition, the number of blades and the non-equidistant distribution of blades are also within the design parameters that can be covered by the design method of the present invention.

[0068] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a sound-generating structure of a mechanical low-frequency noise generating device, characterized in that: The steps include: (1) Design a sound-generating structure, which includes a motor, an impeller mounted at the end of the motor shaft, and an incoming flow disruptor mounted on the motor housing near the impeller. The initial diameter of the impeller is D, and the impeller is provided with m identical blades uniformly distributed along the circumference, and the initial chord length of the blades is l. The target frequency of the design is f0, and the target energy proportion of the target frequency is (2) The impeller speed n is calculated based on the target frequency f0; the unsteady calculation of the impeller is performed using numerical simulation software to extract the initial unsteady axial excitation force of the impeller; (3) Based on the fast Fourier transform method, the spectrum distribution in the low-frequency band of a certain target is obtained, and the frequency point with the highest amplitude is picked up as the intensity amplitude corresponding to f0 (4) Calculate the corresponding energy ratio according to the target frequency f0 like Greater than target value The sound structure design is completed; if Less than target value Then proceed to the next step to adjust the initial diameter D of the impeller; (5) Gradually adjust the initial diameter D of the impeller to the upper limit D max , repeat steps (2)-(4) after each adjustment, if Greater than target value The sound structure design is completed; If each adjustment Both are less than the target value Then proceed to the next step to optimize the initial chord length l of the impeller; (6) Adjust the impeller chord length l and repeat steps (2)-(4). If Greater than target value The sound structure design is completed; if Less than target value Continue optimizing the chord length until Greater than target value Finally, the sound structure design is completed.

2. The method for designing the sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: In step (1), the gap δ between the incoming flow disruptor and the impeller is not greater than 0.1D.

3. The method for designing the sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: The impeller is provided with three identical blades evenly distributed along the circumference.

4. The method for designing a sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: The inflow disruptor adopts one or more static cylindrical structures, or other structural forms with active movement.

5. The method for designing a sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: The motor is used to provide power, and uses an incoming flow disruptor to disturb the inflow field of the impeller, thereby generating low-frequency noise by rotating blades on the impeller.

6. The method for designing a sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: The installation angle of the blades on the impeller is less than 45°.

7. The method for designing a sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: In step (2), the formula for calculating the impeller speed n based on the target frequency f0 is: Where m represents the number of blades in the impeller.

8. The method for designing a sound-generating structure of a mechanical low-frequency noise generating device according to claim 1, characterized in that: In step (4), the corresponding energy ratio is calculated according to the target frequency f0 The formula is: in, is the intensity amplitude corresponding to f0, is the mean value of the axial unsteady exciting force.

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