A method for controlling the radiation noise of a through-hull pipe based on measured sound transmission characteristics

Abstract

The application discloses a kind of measured acoustic transmission characteristics of sea pipe orifice radiation noise control method, this method includes: the acoustic transmission characteristics of pump-pipeline-pipe orifice radiation in pipeline system is characterized;Measured and draw the sound pressure level difference-frequency curve of the flow noise of sea inlet or outlet pipeline to the radiation noise of sea orifice, analyze the frequency through characteristic of pipeline system acoustic transmission;Adjust sea system, obtain the acoustic matching relationship of pump sound source and pipeline system;After adjusting the sea system, evaluate the effect of noise control.The beneficial effects of the present application are: the present application provides a measured acoustic transmission characteristics of sea pipe orifice radiation noise control method from the perspective of pump sound source and pipeline system acoustic matching, for ship sea system radiation noise control, can significantly reduce the radiation noise of sea orifice.

Description

Technical Field

[0001] This invention relates to the field of marine machinery noise control, and specifically to a method for controlling radiated noise from a sea passage pipe based on measured sound transmission characteristics. Background Technology

[0002] The ship's sea passage system is directly connected to the seawater outside the hull. Pump noise radiates directly outwards along the fluid medium in the pipeline at the sea passage opening, making it a significant noise source for the ship. Currently, seawater silencer technology is a key technology for controlling flow noise in sea passage pipelines. After years of development, seawater silencer technology both domestically and internationally has matured. The developed airbag seawater silencer is widely used in the shipbuilding field, and overall, it has achieved good control results for the radiated noise of the sea passage system.

[0003] As independent noise reduction components, silencers typically do not consider the acoustic transmission characteristics of actual ship piping. With increasing demands for low-frequency line spectrum noise control in actual ships, the past three years have seen a focus on improving the control effect of low-frequency line spectrum noise in silencer technology both domestically and internationally. However, neglecting the influence of the acoustic transmission characteristics of the ship's sea passage system has led to the problem of pump blade frequency line spectrum noise amplification in practical applications of silencers. Although the acoustic transmission characteristics of the piping system have a significant impact on the radiated noise of the sea passage system, the shipbuilding industry has not yet paid sufficient attention to this, and related research is currently limited.

[0004] Therefore, it is necessary to propose a new system noise control method to address the impact of the acoustic transmission characteristics of actual ships on the radiated noise of the sea passage system. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for controlling radiated noise at a sea outlet based on measured sound transmission characteristics.

[0006] The technical solution adopted in this invention is: a method for controlling radiated noise at a sea passage pipe port based on measured acoustic transmission characteristics, the method comprising the following steps:

[0007] Step 1: Select the sound pressure level drop curve of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet as a function of frequency to characterize the acoustic transmission characteristics of the pump-pipeline-outlet radiation in the pipeline system.

[0008] Step 2: Measure the sound pressure level of the flow noise in the inlet or outlet pipeline of the sea-crossing pump and the sound pressure level of the radiated noise at the sea outlet;

[0009] Step 3: Plot the relationship curve between the sound pressure level drop and frequency of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet, and analyze the frequency transmission characteristics of the acoustic transmission of the pipeline system.

[0010] Step 4: Based on the frequency transmission characteristics of the pipeline system, adjust the Tonghai system to obtain the acoustic matching relationship between the pump sound source and the pipeline system.

[0011] Step 5: Conduct actual measurements on the adjusted sea passage system to evaluate the noise control effect.

[0012] According to the above scheme, the specific method of step two is as follows: a hydrophone is installed on the inlet pipe of the sea-crossing pump, and a water acoustic sensor is installed directly in front of the sea-crossing estuary. The sound pressure level P1 of the flow noise in the inlet pipe of the sea-crossing pump and the sound pressure level P2 of the radiated noise at the sea-crossing estuary are measured by the two hydrophones respectively.

[0013] According to the above scheme, in step three, the relationship curve between the sound pressure level difference from the inlet noise of the sea-crossing pump to the radiated noise at the sea-crossing estuary and the frequency satisfies the following formula:

[0014]

[0015] The noise level at the pump inlet is in dB. The noise level radiated at the estuary is expressed in dB; ΔL P In the formula,

[0016] P1 represents the sound pressure level difference between the flow noise at the pump inlet and the radiated noise at the estuary, in dB; P2 represents the sound pressure level of the flow noise at the pump inlet, in Pa; and P3 represents the sound pressure level of the radiated noise at the estuary, in Pa.

[0017] According to the above scheme, the frequency transmission characteristics of the acoustic transmission of the pipeline system are specifically manifested as follows: during the process of pump flow noise being transmitted along the pipeline fluid medium to generate radiated noise at the sea outlet, the sound pressure level difference from the pump inlet and outlet pipeline flow noise to the radiated noise at the sea outlet gradually decreases with increasing frequency, and the peak and valley values ​​of the sound pressure level difference appear alternately.

[0018] According to the above scheme, in step four, the adjustment methods for the Tonghai system include: adjusting the pump speed; adjusting the pipeline configuration, including the selection of the pump inlet or outlet pipeline.

[0019] According to the above scheme, the acoustic matching relationship between the pump sound source and the pipeline system is as follows: the frequency of the high-order characteristic line spectrum of the pump flow noise blade frequency corresponds to the peak region of the pipeline system transmission characteristic curve.

[0020] The beneficial effects of this invention are as follows: From the perspective of acoustic matching between the pump sound source and the pipeline system, this invention provides a method for controlling radiated noise at sea passage openings based on measured sound transmission characteristics. This method, applied to the control of radiated noise in ship sea passage systems, can significantly reduce radiated noise at sea passage openings, with particularly optimal control effect on high-order line spectrum noise. This invention can provide strong support for the acoustic optimization design of ship sea passage systems. Attached Figure Description

[0021] Figure 1 This is a diagram showing the arrangement of measuring points according to a specific embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the acoustic transmission characteristics curve of the sea passage system in this embodiment.

[0023] Figure 3 This is a schematic diagram illustrating the technical approach for acoustic matching between the pump sound source and the pipeline system in this embodiment.

[0024] Figure 4 This is a comparison diagram of the acoustic transmission characteristics of the pipeline system and the noise radiation resistance of the pump flow in this embodiment.

[0025] Figure 5 This is a schematic diagram illustrating the acoustic control effect of optimized piping configuration in this embodiment. Detailed Implementation

[0026] To better understand the present invention, it will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] like Figure 1 As shown, in this embodiment, the sea passage system includes a sea passage pump 1 and an inlet pipe 2. The sea passage pump 1 is installed on the ship's surface platform 5 via a base 4. The inlet of the sea passage pump 1 is connected to seawater via the inlet pipe 2. The horizontal section of the inlet pipe 2 extends to the side of the surface platform and connects with the vertical section of the inlet pipe 2. The port of the vertical section of the inlet pipe 2 is the sea passage outlet 3. The inlet pipe 2 constitutes the pipeline system.

[0028] A method for controlling radiated noise at a sea passage pipe with measured acoustic transmission characteristics, the method comprising the following steps:

[0029] Step 1: Select the sound pressure level drop curve of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet as a function of frequency to characterize the acoustic transmission characteristics of the pump-pipeline-outlet radiation in the pipeline system.

[0030] Analysis of extensive ship noise test data revealed that the sound pressure level of the flow noise in the inlet and outlet pipelines of the actual pipeline system is much higher than the sound pressure level of the radiated noise at the sea outlet. Therefore, this invention proposes to use the sound pressure level difference-frequency curve between the flow noise in the pump inlet and outlet pipelines and the radiated noise at the sea outlet to characterize the acoustic transmission characteristics of the pump-pipeline-pipe outlet radiation in the pipeline system. The sound pressure level difference is the total acoustic transmission loss of the pipeline system.

[0031] Step 2: Install a hydrophone S1 at the pump inlet and a hydroacoustic sensor S2 in front of the estuary to measure the sound pressure level of the flow noise in the inlet or outlet pipeline of the estuary pump and the sound pressure level of the radiated noise at the estuary.

[0032] In this embodiment, the method for measuring the sound pressure level of the flow noise in the inlet or outlet pipeline of the sea-crossing pump and the sound pressure level of the radiated noise at the sea outlet is as follows: a hydrophone S1 is placed in the inlet pipeline (i.e., the pump set pipe) of the sea-crossing pump, and a hydroacoustic sensor S2 is placed 1m directly in front of the sea outlet. The sound pressure level of the flow noise in the inlet pipeline of the sea-crossing pump P1 and the sound pressure level of the radiated noise at the sea outlet P2 are measured by the two hydrophones respectively.

[0033] Step 3: Plot the relationship curve between the sound pressure level drop and frequency of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet, and analyze the frequency transmission characteristics of the acoustic transmission of the pipeline system.

[0034] In this invention, the relationship between the sound pressure level difference from the inlet noise of the sea-crossing pump to the radiated noise at the sea outlet and the frequency satisfies the following formula:

[0035]

[0036] The noise level at the pump inlet is in dB. The noise level radiated at the estuary is expressed in dB; ΔL P In the formula,

[0037] P1 represents the sound pressure level difference between the flow noise at the pump inlet and the radiated noise at the estuary, in dB; P2 represents the sound pressure level of the flow noise at the pump inlet, in Pa; and P3 represents the sound pressure level of the radiated noise at the estuary, in Pa. In this embodiment, the relationship curve between the sound pressure level difference between the flow noise at the pump inlet and the radiated noise at the estuary and the frequency is shown below. Figure 2 As shown in the figure. By analyzing the above curves, it can be seen that the frequency transmission characteristics of the acoustic transmission of the pipeline system are specifically manifested as follows: during the process of pump flow noise being transmitted along the pipeline fluid medium to generate radiated noise at the sea outlet, the sound pressure level difference from the pump inlet and outlet pipeline flow noise to the radiated noise at the sea outlet gradually decreases with increasing frequency, and the peak and valley values ​​of the sound pressure level difference appear alternately.

[0038] Step 4: Based on the frequency transmission characteristics of the pipeline system, adjust the Tonghai system and use finite element simulation analysis or equivalent sound velocity theory analysis and calculation to obtain the acoustic matching relationship between the pump sound source and the pipeline system. That is, the frequency of the high-order characteristic line spectrum of the pump flow noise blade frequency corresponds to the peak region of the pipeline system transmission characteristic curve.

[0039] The adjustment methods for the Tonghai system include adjusting the pump speed and adjusting the pipeline configuration, including the selection of the pump inlet or outlet pipeline.

[0040] The power of the noise radiated from the sea-going pump flow along the pipeline fluid medium to the outside is usually proportional to the radiation resistance. The radiation power is proportional to the square of the sound pressure level P2 of the radiated noise at the pipe outlet. Therefore, the radiation resistance R of the sea-going pump flow noise and the sound pressure level P2 satisfy the following relationship:

[0041]

[0042] In the formula, 2π represents the surface area of ​​a hemisphere with a radius of 1m, and 6.28m 2 ρ0 represents the density of water, with a density of 1.0 being 3 kg / m³; c0 represents the speed of sound in water, 1500 m / s.

[0043] Considering the pump inlet pipe diameter d (in meters), the radiation resistance is normalized according to the pump flow noise sound pressure level (normalization is a common technique in this field), and the radiation resistance R per unit sound pressure of the pump flow noise can be obtained. I See the following formula:

[0044]

[0045] Radiation resistance per unit sound pressure of pump flow noise in logarithmic coordinates The expression is:

[0046]

[0047] By comparing the acoustic transmission characteristic curves of the pump-pipe-nozzle radiation in the pipeline system with the radiation resistance-frequency curve of the pump noise per unit sound pressure, it can be found that the peak region of the total transmission loss of the pipeline system corresponds to the valley region of the pump noise radiation resistance. (See...) Figure 4 As shown. Therefore, assuming the acoustic transmission characteristics of the pump sound source and the piping system are matched, see... Figure 3 As shown, the pipeline system experiences the greatest transmission loss for high-order line spectrum noise, such as pump flow noise at the blade frequency. Simultaneously, the corresponding pump flow noise radiated power is the lowest, and the corresponding pump flow noise line spectrum sound pressure level reaches its minimum value. Therefore, by acoustically matching the pump sound source with the pipeline system, the sound pressure level of the sound source can be reduced while simultaneously increasing the acoustic transmission loss of the pipeline system, thereby achieving the goal of controlling radiated noise at the estuary.

[0048] The frequencies of the high-order characteristic spectrum of pump noise, such as the blade frequency, generally change with the pump speed. The acoustic transmission characteristics of the pump-pipeline-nozzle radiation in a sea-crossing system are inherent characteristics of the pipeline system, and the transmission characteristic curve generally changes with the pipeline configuration. Therefore, the frequencies of the blade frequency and other characteristic spectra can be altered by changing the pump speed, or the acoustic transmission characteristic curve of the pipeline system can be changed by adjusting the configuration of the sea-crossing pipeline. This allows the frequencies of the high-order characteristic spectrum of pump noise, such as the blade frequency, to correspond to the peak region of the pipeline system's transmission characteristic curve (the peak region refers to the frequency range covering 70% of the peak frequency band centered on the peak frequency). In other words, the frequencies of the high-order characteristic spectrum of pump noise, such as the blade frequency, are located within the peak region of the pipeline system's transmission characteristic curve, achieving acoustic matching between the pump sound source and the pipeline system. See [link to relevant documentation]. Figure 3As shown, the closer the blade frequency is to the peak frequency of the transmission characteristic curve, the better the acoustic matching. Figure 3 (a) When the acoustic transmission characteristics of the pump sound source and the pipeline system are mismatched, the acoustic transmission characteristic curve A1 of the pipeline system and the sound pressure level curve B1 of the pump flow noise are shown. The blade frequency of the sound pressure level curve B1 is not in the first peak region of the curve A1 (that is, not in the corresponding frequency range), and the octave frequency of the sound pressure level curve B1 does not fall in the second peak region of the curve A1. At this time, the peak region of the transmission characteristic curve A1 of the pipeline system is offset from the frequency of the sound pressure level curve B1 of the pump flow noise. Figure 3 (b) After adjusting the pump speed, the acoustic transmission curve A1 of the pipeline system and the sound pressure level curve B2 of the pump flow noise are matched with the acoustic transmission characteristics of the pump sound source and the pipeline system. The sound pressure level curve B2 of the pump flow noise is shifted to the left relative to the curve B1. At this time, the blade frequency of the sound pressure level curve B2 of the pump flow noise is located in the first peak area of ​​the acoustic transmission curve A1 of the pipeline system (specifically within the corresponding frequency range), and the double blade frequency of the sound pressure level curve B2 of the pump flow noise is located in the second peak area of ​​the acoustic transmission curve A1 of the pipeline system. Figure 3 (c) After adjusting the pipeline configuration, under the condition that the acoustic transmission characteristics of the pump sound source and the pipeline system are matched, the peak region of the pipeline system acoustic transmission curve A2 and the pump flow noise sound pressure level curve B1 shifts to the right compared with curve A1. At this time, the blade frequency of the pump flow noise sound pressure level curve B1 is located in the first peak region of curve A2, and the octave frequency of the pump flow noise sound pressure level curve B1 is located in the second peak region of curve A2.

[0049] In this embodiment, to address the issue of blade frequency radiated noise control for the 300t / h pump unit, a DN250 pipeline is preferred, replacing the original DN175 pipeline (inlet pipeline). By adjusting the acoustic transmission characteristic curve of the pipeline system, a better acoustic match between the pump sound source and the pipeline system can be achieved. Figure 5 As shown.

[0050] Step 5: Conduct actual measurements on the adjusted sea passage system to evaluate the noise control effect.

[0051] In this embodiment, with the pump operating parameters such as flow rate, speed, and head being exactly the same, after adjusting the pipeline configuration (that is, replacing the original DN175 pipeline with a DN250 pipeline), the test results show that adjusting the "local valley matching" of the pump blade frequency characteristic line spectrum and the pipeline acoustic transmission characteristic curve to "local peak matching" increases the transmission loss of the pipeline system to the pump blade frequency line spectrum noise by 2.3dB, reduces the pump flow noise sound pressure level by 5.4dB, and ultimately reduces the pump blade frequency line spectrum radiated noise by 7.7dB.

[0052] This invention addresses the noise control problem in sea passage systems by proposing a method for characterizing the acoustic transmission characteristics of pipeline systems, providing a system noise control method for acoustic matching between pump sets and pipeline systems, and revealing the physical mechanism of acoustic matching control of radiated noise at sea passages.

[0053] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0054] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. However, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling radiated noise at a sea outlet based on measured acoustic transmission characteristics, characterized in that, The method includes the following steps: Step 1: Select the sound pressure level drop curve of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet as a function of frequency to characterize the acoustic transmission characteristics of the pump-pipeline-outlet radiation in the pipeline system. Step 2: Measure the sound pressure level of the flow noise in the inlet or outlet pipeline of the sea-crossing pump and the sound pressure level of the radiated noise at the sea outlet; Step 3: Plot the relationship curve between the sound pressure level drop and frequency of the flow noise from the inlet or outlet pipeline of the sea-crossing pump to the radiated noise at the sea outlet, and analyze the frequency transmission characteristics of the acoustic transmission of the pipeline system. Step 4: Based on the frequency transmission characteristics of the pipeline system, adjust the Tonghai system to obtain the acoustic matching relationship between the pump sound source and the pipeline system. Step 5: Conduct on-site measurements of the adjusted sea passage system to evaluate the noise control effect; The specific method for step two is as follows: a hydrophone is installed on the inlet pipe of the sea-crossing pump, and a hydroacoustic sensor is installed directly in front of the sea outlet. The sound pressure level of the flow noise in the inlet pipe of the sea-crossing pump, P1, and the sound pressure level of the radiated noise in the sea outlet, P2, are measured by the two hydrophones respectively. The frequency transmission characteristics of the acoustic transmission in the pipeline system are specifically manifested as follows: during the process of pump flow noise being transmitted along the pipeline fluid medium to generate radiated noise at the sea outlet, the sound pressure level difference from the pump inlet and outlet pipeline flow noise to the radiated noise at the sea outlet gradually decreases with increasing frequency, and the peak and valley values ​​of the sound pressure level difference appear alternately. The acoustic matching relationship between the pump sound source and the pipeline system is as follows: the frequency of the high-order characteristic line spectrum of the pump flow noise corresponds to the peak region of the pipeline system's transmission characteristic curve, and the frequency of the high-order characteristic line spectrum of the pump flow noise blade frequency is located within the peak region of the pipeline system's transmission characteristic curve. This achieves acoustic matching between the pump sound source and the pipeline system. The closer the blade frequency is to the peak frequency of the transmission characteristic curve, the better the acoustic matching. The peak region refers to the frequency range centered on the peak frequency, covering 70% of the peak frequency band.

2. The method for controlling radiated noise at a sea outlet based on measured acoustic transmission characteristics as described in claim 1, characterized in that, In step three, the relationship between the sound pressure level difference from the inlet noise of the estuary pump to the radiated noise at the estuary and the frequency satisfies the following formula: （1）； In the formula, The noise level at the pump inlet is in dB. The noise level radiated at the estuary is expressed in dB. P1 represents the sound pressure level difference between the flow noise at the pump inlet and the radiated noise at the estuary, in dB; P2 represents the sound pressure level of the flow noise at the pump inlet, in Pa; and P3 represents the sound pressure level of the radiated noise at the estuary, in Pa.

3. The method for controlling radiated noise at a sea outlet based on measured acoustic transmission characteristics as described in claim 1, characterized in that, In step four, the adjustment methods for the Tonghai system include: adjusting the pump speed; and adjusting the pipeline configuration, including the selection of the pump inlet or outlet pipeline.

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