A method for predicting ship piping noise

Abstract

The application discloses a ship pipeline noise prediction method, which comprises the following steps: S1, determining all elements in a target pipeline; S2, calculating the regenerated noise sound power level L wi of each element i in the target pipeline wi , wherein i is the number of the element; S3, determining the sound power level of a noise source in the target pipeline; sequentially calculating the sound power level L wi‑out of the noise after passing through each element i from the noise source, so as to obtain the sound power level after passing through the pipeline outlet; S4, obtaining the sound pressure level L p at a measuring point according to the positions of the measuring point and the pipeline outlet in a room. The method of the application can be carried out at the initial stage of ship design without detailed design parameters, avoids complex pipeline modeling, and has a simple and clear prediction process, high efficiency and low cost.

Description

Technical Field

[0001] This invention relates to the field of shipbuilding, and more particularly to a method for predicting ship pipeline noise. Background Technology

[0002] Ship systems contain numerous pipes, including the air intake and exhaust systems of major equipment, as well as air conditioning and ventilation systems. Noise generated in these pipes can adversely affect areas near the pipe outlets, such as chimneys and living quarters, and may even seriously impact the comfort and health of crew and passengers. The International Maritime Organization (IMO) has also set mandatory limits for noise levels in these areas. Therefore, predicting the noise levels of the ship's piping systems during the initial design phase is of significant practical importance for noise control.

[0003] Currently, some publicly available reports related to this invention include: Reference 1, Numerical Simulation and Optimization Design of Aerodynamic Noise in Ship Pipelines: Fluent is used to perform transient calculations on the internal flow field of the ventilation pipeline model, and LMS Virtual.LabAcoustics software is used for acoustic finite element calculations to obtain the aerodynamic noise characteristics of the pipeline and a more optimized ship pipeline form; Reference 2, Prediction and Acoustic Design of Air Conditioning Noise in Ship Cabins: Ansys is used to model the structure of typical ship cabins, and Virtual.Lab Acoustics software is used for calculation and analysis to study the prediction method and acoustic design method of ship cabin noise caused by air conditioning; Reference 3, Numerical Analysis and Control of Noise Characteristics of Ship Ventilation Pipelines: Nastran, Fluent, and Virtual.Lab software are mainly used to explore the noise spectrum characteristics of typical ship ventilation pipelines and the variation law under different flow velocities, and research on expansion pipe noise reduction technology is carried out; Reference 4, Low-Noise Design Research of Typical Ship Pipeline Systems: The influence law of flexible nozzles and bends on the pipeline system is obtained through Abaqus software simulation, and low-noise design experiments of the pipeline system are carried out.

[0004] A summary of the current research status at home and abroad reveals the following shortcomings in the prediction of pipeline noise on ships: 1. It is basically limited to the study of some simple pipeline components using numerical methods such as finite element method, boundary element method and computational fluid dynamics, resulting in low computational efficiency and high computational cost; 2. Prediction can only be carried out after detailed design parameters are available, which increases the construction cost caused by rework later; 3. There is a lack of a process and method for early and rapid prediction of such complex pipeline systems for the entire ship. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention provides a method for predicting the noise of ship pipelines. This method is designed for predicting the noise of complex pipeline systems on actual ships. It can quickly predict the noise level of any pipeline system in the early stages of design when detailed design parameters are lacking, thereby reducing repeated modifications caused by excessive pipeline noise in the later stages of design and reducing shipyard costs.

[0006] To achieve the above objectives, the present invention provides a method for predicting ship pipeline noise, comprising:

[0007] S1: Identify all components in the target pipeline;

[0008] S2: Calculate the regenerated noise power level L of each component i in the target pipeline. wi and noise attenuation , where i is the component number;

[0009] S3: Determine the sound power level of the noise source in the target pipeline; starting from the noise source, calculate the sound power level L of the noise after passing through each component i in sequence. wi-out The sound power level after passing through the pipe outlet is obtained;

[0010] S4: Based on the location of the measuring point and the pipe outlet in the room, obtain the sound pressure level L at the measuring point. p .

[0011] A further improvement of the present invention is that the components in the target pipeline include one or more combinations of straight pipes, elbows, branch pipes, reducers, pipe outlets, and silencers.

[0012] A further improvement of the present invention is that the regenerated noise power level L of the straight tube w This can be obtained through experimental testing or by the following formula:

[0013]

[0014]

[0015] Noise attenuation ΔL through straight pipe section r This can be obtained through experimental testing or by the following formula:

[0016]

[0017] In the formula, v represents the gas velocity in the pipeline, with units of m / s; S represents the cross-sectional area of ​​the pipeline, with units of m². 2 △Lw represents the correction value for each octave band, in dB; f m β represents the center frequency of the octave band, in Hz; β represents the attenuation coefficient of the straight pipe section; l represents the length of the straight pipe section, in meters.

[0018] A further improvement of the present invention is that the regenerated noise power level L of the elbow or branch pipe is... w This can be obtained through experimental testing or by the following formula:

[0019]

[0020]

[0021]

[0022] Noise attenuation ΔL through branch pipes r This can be obtained through experimental testing or by the following formula:

[0023]

[0024] In the formula, Δf represents the octave bandwidth, in Hz; d a This indicates the diameter of the elbow or branch pipe, in meters (m); v a This indicates the gas velocity in a branch pipe or bend, measured in m / s; v h St represents the gas velocity in the main branch pipe, in m / s; St represents the Strouhal number, St = f m *d a / v a ;f m The center frequency of the octave band is represented in Hz; r represents the fillet radius in meters; S i This represents the cross-sectional area of ​​the i-th branch pipe, in meters. 2 ;

[0025] Noise attenuation ΔL through the bend r Obtained through experimental testing or by looking up tables.

[0026] A further improvement of the present invention is that the regenerated noise power level L of the variable diameter pipe w Obtained through experimental testing or directly ignored; noise attenuation ΔL through the reducer. r This can be obtained through experimental testing or by the following formula:

[0027]

[0028] In the formula: r = S1 / S2 represents the ratio of the inlet to the outlet cross-section; S1 represents the inlet cross-sectional area, in m². 2 S2 represents the cross-sectional area of ​​the outlet, in meters. 2 .

[0029] A further improvement of the present invention is that the regenerated noise power level L at the pipeline outlet w This can be obtained through experimental testing or by the following formula:

[0030]

[0031] Pipeline outlet noise attenuation △L r This can be obtained through experimental testing or by the following formula:

[0032]

[0033] In the formula, v represents the gas velocity at the pipe outlet, in m / s; S is the cross-sectional area of ​​the pipe outlet, in m². 2 ρ represents the density of the gas in the pipeline, with units of kg / m³. 3 ;Δp t ΔL represents the pressure difference at the pipeline outlet, in Pa. w denoted by , f represents the correction value for each octave band, in dB; f represents the center frequency of the octave band, in Hz; c represents the speed of sound at the pipe outlet, in m / s; d represents the diameter of the pipe outlet, in m; k represents a coefficient related to the location of the pipe outlet, k=1 when the pipe outlet is in free space, and k=0.8 when the outlet is in a room.

[0034] A further improvement of the present invention is characterized in that the sound power level L after the noise passes through element i is calculated. wi-out The expression is:

[0035]

[0036] In the formula, It is the sound power level of the noise after passing through the preceding element i-1; ΔL ri It is the attenuation of component i; L wi It is the regenerated noise power level of component i.

[0037] A further improvement of the present invention is that, in step S4, the sound pressure level L at the measuring point is obtained based on the location of the measuring point and the pipe outlet in the room. p The expression is:

[0038]

[0039]

[0040] In the formula: Q represents the directivity factor; r represents the distance from the measuring point to the pipe outlet, in meters; R represents the room constant of the room where the pipe outlet is located, in meters. 2 S represents the surface area of ​​the room, in meters. 2 α represents the sound absorption coefficient of the cabin surface.

[0041] The method provided by this invention has the following technical effects:

[0042] (1) No detailed design parameters are required; the design can be carried out in the early stages of ship design.

[0043] (2) It avoids complex pipeline modeling, the forecasting process is simple and clear, and the forecasting method is efficient and low-cost;

[0044] (3) It is easy to operate and does not require much professional knowledge.

[0045] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the pipeline in an embodiment of the ship pipeline noise prediction method of the present invention;

[0047] Figure 2 It is a curve of the attenuation coefficient of the straight pipe section;

[0048] Figure 3 These are schematic diagrams of two types of branch pipelines;

[0049] Figure 4 This is a schematic diagram of a reducer;

[0050] Figure 5 These are the value curves of the correction values ​​for each octave band at the pipeline outlet;

[0051] Figure 6 This is a schematic diagram of an existing muffler.

[0052] Figure 7 This is a schematic diagram of the pipe outlet in the room. Detailed Implementation

[0053] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0054] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0055] Some exemplary embodiments of the invention have been described for illustrative purposes. It should be understood that the invention may be implemented in other ways not specifically shown in the accompanying drawings.

[0056] The present invention provides a method for predicting ship pipeline noise. The sound power level, sound pressure level, and attenuation used in this method are described below:

[0057]

[0058]

[0059] In the formula L w Sound power level is expressed in dB; W represents sound power, expressed in W. ref This represents the reference sound power, taken as 10. -12 W;L p The sound pressure level (P) is expressed in dB; p represents the sound pressure level (Pa). ref The reference sound pressure level is taken as 2 × 10⁻⁶. - 5 Pa;△L r This indicates the attenuation amount, measured in dB. Frequency band calculations typically use octaves, ranging from 31.5 to 8000 Hz.

[0060] The ship pipeline noise prediction method in this embodiment specifically includes the following steps:

[0061] S1: Identify all components in the target pipeline. In this step, the components in the target pipeline include one or more combinations of straight pipes, elbows, branch pipes, reducers, pipe outlets, and silencers. Based on the relevant drawings of the ship's piping system, identify all components in the pipeline to be predicted.

[0062] S2: Calculate the regenerated noise power level L of each component i in the target pipeline. wi and noise attenuation , where i is the component number. The process specifically includes:

[0063] Regenerated noise power level L of straight pipe w This can be obtained through experimental testing or by the following formula:

[0064]

[0065]

[0066] Noise attenuation ΔL through straight pipe section r This can be obtained through experimental testing or by the following formula:

[0067]

[0068] In the formula, v represents the gas velocity in the pipeline, with units of m / s; S represents the cross-sectional area of ​​the pipeline, with units of m². 2 △Lw represents the correction value for each octave band, in dB; f m The octave band center frequency is represented in Hz; β represents the straight pipe section attenuation coefficient, according to... Figure 2 The curve is used to take values. Figure 2 The horizontal axis represents the center frequency f of the octave band. m The vertical axis represents the attenuation coefficient β; l represents the length of the straight pipe section, in meters.

[0069] Regenerated noise power level L in elbows or branch pipes w It can be obtained through experimental testing or the following formula:

[0070]

[0071]

[0072]

[0073] Noise attenuation ΔL through branch pipes r It can be obtained through experimental testing or the following formula:

[0074]

[0075] In the formula, Δf represents the octave bandwidth, in Hz; d a This indicates the diameter of the elbow or branch pipe, in meters (m); v a This indicates the gas velocity in a branch pipe or bend, measured in m / s; v h St represents the gas velocity in the main branch pipe, in m / s; St represents the Strouhal number, St = f m *d a / v a ;f m The octave band center frequency is represented in Hz; r indicates... Figure 3 The fillets shown are in meters (m); S i This represents the cross-sectional area of ​​the i-th branch pipe, in meters. 2 The structure of the branch pipeline is as follows Figure 3 As shown.

[0076] Noise attenuation ΔL through the bend r The results can be obtained through experimental testing or by searching in Table 1.

[0077] Table 1 Noise Attenuation ΔL at Elbows r (dB)

[0078]

[0079] Regenerated noise power level L of reducer w The noise attenuation ΔL of the reducer can be obtained through experimental testing or can be ignored; r It can be obtained through experimental testing or the following formula:

[0080]

[0081] In the formula: r = S1 / S2 means that... Figure 4 The ratio of the inlet to the outlet cross-sections is shown; S1 represents the inlet cross-sectional area, in m². 2 S2 represents the cross-sectional area of ​​the outlet, in meters. 2 The structure of a reducing pipe is as follows Figure 4 As shown.

[0082] Regenerated noise power level L at pipeline outlet w It can be obtained through experimental testing or the following formula:

[0083]

[0084] Pipeline outlet noise attenuation △L r It can be obtained through experimental testing or the following formula:

[0085]

[0086] In the formula, v represents the gas velocity at the pipe outlet, in m / s; S is the cross-sectional area of ​​the pipe outlet, in m². 2 ρ represents the density of the gas in the pipeline, with units of kg / m³. 3 ;Δp t ΔL represents the pressure difference at the pipeline outlet, in Pa. w This represents the correction value for each octave band, in dB, ΔL. w according to Figure 5 The curve is used to take values. Figure 5 The horizontal axis represents the center frequency f of the octave band. m The vertical axis represents the octave band correction value ΔL. w f represents the center frequency of the octave band, in Hz; c represents the speed of sound at the pipe outlet, in m / s; d represents the diameter of the pipe outlet, in m; k represents a coefficient related to the location of the pipe outlet. When the pipe outlet is in free space, k=1; when the outlet is inside a room, k=0.8.

[0087] The regenerated noise power level L of the muffler wIt can usually be obtained from the equipment manufacturer. If the muffler has a simple structure as shown in Figure 7, it can also be obtained using the following formula:

[0088]

[0089]

[0090]

[0091] Muffler noise attenuation ΔL r (Silence reduction) is a key product performance parameter, generally obtained from the equipment manufacturer. In the formula, v represents the gas velocity in the silencer, in m / s; D represents the diameter of the silencer, in meters; Δp... t St represents the pressure difference of the gas after passing through the silencer, in Pa; St represents the Strouhal number, St=f m *D / v;f m This indicates the octave band center frequency, measured in Hz.

[0092] S3: Determine the sound power level of the noise source in the target pipeline; starting from the noise source, calculate the sound power level L of the noise after passing through each component i in sequence. wi-out The sound power level after passing through the pipe outlet is obtained. The sound power level L after the noise passes through component i is calculated. wi-out The expression is:

[0093]

[0094] In the formula, It is the sound power level of the noise after passing through the preceding element i-1; ΔL ri It is the attenuation of component i; L wi It is the regenerated noise power level of component i.

[0095] Specifically, such as Figure 1 As shown, the target pipeline in this embodiment (which is representative of ship piping systems) has a total of 7 components numbered from 1 to 7.

[0096] The sound power level L of noise source 0 is obtained from the equipment manufacturer. w0 ;

[0097] The regenerated noise power level L of silencer 1 can be obtained from the equipment manufacturer or the above formula. w1 and attenuation ΔL r1 The sound power level L after passing through silencer 1 was calculated. w1-out :

[0098]

[0099] The regenerated noise power level L of straight pipe section 2 can be obtained through experimental testing or the above formula. w2 and attenuation ΔL r2 The sound power level L after passing through straight pipe 2 was calculated. w2-out :

[0100]

[0101] The regenerated noise power level L of elbow 3 can be obtained through experimental testing or the above formula. w3 and attenuation ΔL r3 The sound power level L after passing through bend 3 was calculated. w3-out :

[0102]

[0103] The regenerated noise power level L of straight pipe section 4 can be obtained through experimental testing or the above formula. w4 and attenuation ΔL r4 The sound power level L after passing through straight pipe 4 was calculated. w4-out :

[0104]

[0105] The regenerated noise power level L in branch 5 can be obtained through experimental testing or the above formula. w5 and attenuation ΔL r5 The sound power level L after branch 5 was calculated. w5-out :

[0106]

[0107] The regenerated noise power level L of straight pipe section 6 was obtained through experimental testing or the above formula. w6 and attenuation ΔL r6 The sound power level L after passing through straight pipe 6 was calculated. w6-out :

[0108]

[0109] The regenerated noise power level L at outlet 7 can be obtained through experimental testing or the above formula. w7 and attenuation ΔL r7 The sound power level L after exiting outlet 7 was calculated. w7-out :

[0110]

[0111] S4: Based on the location of the measuring point and the pipe outlet in the room, obtain the sound pressure level L at the measuring point. p Its expression is:

[0112]

[0113]

[0114] In the formula: Q represents the directional factor, the value of which is related to the location of the pipe outlet, such as... Figure 7 As shown, Q=1 when the pipe outlet is in the center of the room; Q=2 when the pipe outlet is in the center of any surface in the room; Q=4 when the pipe outlet is in the center of any edge of the room; and Q=8 when the pipe outlet is in any corner of the room. r represents the distance from the measuring point to the pipe outlet, in meters (m); R represents the room constant of the room where the pipe outlet is located, in meters (m). 2 S represents the surface area of ​​the room, in meters. 2 α represents the sound absorption coefficient of the cabin surface.

[0115] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for predicting ship pipeline noise, characterized in that... include: S1: Identify all components in the target pipeline; S2: Calculate the regenerated noise power level L of each component i in the target pipeline. wi and noise attenuation , where i is the component number; S3: Determine the sound power level of the noise source in the target pipeline; starting from the noise source, calculate the sound power level L of the noise after passing through each component i in sequence. wi-out The sound power level after passing through the pipe outlet is obtained; S4: Based on the location of the measuring point and the pipe outlet in the room, obtain the sound pressure level L at the measuring point. p ; Calculate the sound power level L after the noise passes through element i. wi-out The expression is: ； In the formula, It is the sound power level of the noise after passing through the preceding element i-1; ΔL ri It is the attenuation of component i; L wi It is the regenerated noise power level of component i.

2. The method for predicting ship pipeline noise according to claim 1, characterized in that, The components in the target pipeline include one or more combinations of straight pipes, elbows, branch pipes, reducers, pipe outlets, and silencers.

3. The method for predicting ship pipeline noise according to claim 2, characterized in that, Regenerated noise power level L of straight pipe w This can be obtained through experimental testing or by the following formula: ； ； Noise attenuation ΔL through straight pipe section r This can be obtained through experimental testing or by the following formula: ； In the formula, v represents the gas velocity in the pipeline, with units of m / s; S represents the cross-sectional area of ​​the pipeline, with units of m². 2 ; △Lw represents the correction value for each octave band, in dB; f m β represents the center frequency of the octave band, in Hz; β represents the attenuation coefficient of the straight pipe section; l represents the length of the straight pipe section, in meters.

4. The method for predicting ship pipeline noise according to claim 2, characterized in that, Regenerated noise power level L in elbows or branch pipes w This can be obtained through experimental testing or by the following formula: ； ； ； Noise attenuation ΔL through branch pipes r This can be obtained through experimental testing or by the following formula: ； In the formula, Δf represents the octave bandwidth, in Hz; d a This indicates the diameter of the elbow or branch pipe, in meters (m); v a This indicates the gas velocity in a branch pipe or bend, measured in m / s; v h St represents the gas velocity in the main branch pipe, in m / s; St represents the Strouhal number, St = f m *d a / v a ;f m The center frequency of the octave band is represented in Hz; r represents the fillet radius in meters; S i This represents the cross-sectional area of ​​the i-th branch pipe, in meters. 2 ; Noise attenuation ΔL through the bend r Obtained through experimental testing or by looking up a table.

5. The method for predicting ship pipeline noise according to claim 2, characterized in that, Regenerated noise power level L of reducer w Obtained through experimental testing or directly ignored; noise attenuation ΔL through the reducer. r This can be obtained through experimental testing or by the following formula: ； In the formula: r = S1 / S2 represents the ratio of the inlet to the outlet cross-section; S1 represents the inlet cross-sectional area, in m². 2 ; S2 represents the exit cross-sectional area, in meters (m²). 2 .

6. The method for predicting ship pipeline noise according to claim 2, characterized in that, Regenerated noise power level L at pipeline outlet w This can be obtained through experimental testing or by the following formula: ； Pipeline outlet noise attenuation △L r This can be obtained through experimental testing or by the following formula: ； In the formula, v represents the gas velocity at the pipe outlet, in m / s; S is the cross-sectional area of ​​the pipe outlet, in m². 2 ρ represents the density of the gas in the pipeline, with units of kg / m³. 3 ;Δp t ΔL represents the pressure difference at the pipeline outlet, in Pa. w denoted by , f represents the correction value for each octave band in dB; f represents the center frequency of the octave band in Hz; c represents the speed of sound at the pipe outlet in m / s; d represents the diameter of the pipe outlet in m; k represents a coefficient related to the location of the pipe outlet, k=1 when the pipe outlet is in free space, and k=0.8 when the outlet is in a room.

7. The method for predicting ship pipeline noise according to claim 1, characterized in that, In step S4, the sound pressure level L at the measuring point is obtained based on the location of the measuring point and the pipe outlet in the room. p The expression is: ； ； In the formula: Q represents the directivity factor; r represents the distance from the measuring point to the pipe outlet, in meters; R represents the room constant of the room where the pipe outlet is located, in meters. 2 S represents the surface area of ​​the room, in meters. 2 α represents the sound absorption coefficient of the cabin surface.

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