A test bench and method for testing sea pump flow noise by simulating real ship sound boundary

Abstract

The present invention discloses a test bench for testing the flow noise of a sea pump that simulates the sound boundary of a real ship, comprising a sea pump and an inlet pipeline. The sea pump is set up on the lake embankment through a base; the inlet pipeline comprises a connected horizontal section and a vertical section, the horizontal section of the inlet pipeline is a test section, the outlet of the horizontal section is connected to the inlet of the sea pump, and the inlet of the vertical section of the inlet pipeline extends below the water surface of the lake; a pipeline hydrophone is arranged in the test section. The present invention also discloses a design and installation method for testing the flow noise of a sea pump that simulates the sound boundary of a real ship. The beneficial effects of the present invention are: determining the key influencing parameters of the acoustic transmission impedance conditions of the sea pipeline system and the boundary conditions of the infinite radiation sound field of the pipe mouth of the real ship sea system, and based on this, designing a test bench that can simulate the acoustic impedance conditions of the pump-excited pipeline sound transmission of the real ship sea system to the greatest extent.

Description

Technical Field

[0001] The invention relates to the field of ship machinery noise control, and in particular to a sea pump flow noise test bench and a method thereof for simulating a real ship sound boundary. Background Art

[0002] The radiated noise of the sea-going system is the main acoustic energy component that affects the underwater noise of ships. There are many sound sources inside the sea-going system, including pumps and pipeline accessories such as valves, elbows, and filters. Among them, the pump is the main noise source of pipeline flow noise.

[0003] For any Tonghai system, the flow rate and head parameters of the pump determine the size of the fluid load on the blades, and thus determine the intensity of the pump flow noise source. The dipole sound source intensity of the pump flow noise is an inherent characteristic of the Tonghai pump itself, and depends on the functional parameters of the pump such as flow rate and head. The pump acts as a sound source to excite pipeline flow noise, and the noise energy level is determined by the impedance conditions of the pipeline system sound transmission.

[0004] The piping configuration of the actual ship's sea-going system is relatively complex, including many piping accessories such as heat exchangers, filters, valves, elbows, and flexible pipes, but the most important feature is the limited length of the pipeline and the infinite sound field boundary of the sea vent. Each configuration of the actual ship's pipeline will affect the acoustic impedance of the sea-going system, but the impact of each configuration varies greatly. Through the analysis of the previous bench test data, it was found that the impact of filters, valves, and flexible pipes on the acoustic impedance of the sea-going system is generally less than 3dB, the impact of the heat exchanger of the outlet pipeline is generally less than 5dB, and the impact of the pipeline diameter exceeds 7.7dB, and the impact of the pipeline length exceeds 10dB. It can be seen that the length of the pipeline is a key factor affecting the acoustic impedance of the sea-going system.

[0005] At present, in the shipbuilding industry, for the test of pump flow noise characteristics, a closed test bench of pump-inlet and outlet pipelines (metal)-extra-long inlet and outlet rubber hoses-pressure water tanks is usually used, and the length of the inlet and outlet pipelines (metal) is completely determined by the test site conditions and has nothing to do with the configuration parameters of the actual ship pipeline. It can be seen that the current pump flow noise characteristic test method only evaluates the acoustic characteristics of the pump itself, and does not consider important influencing factors such as the length of the actual ship pipeline and the radiation boundary conditions of the pipe orifice. Therefore, when the test data is used for the estimation of the radiation noise of the actual ship pipeline system, it will cause a large deviation, and the engineering applicability of the data is poor. Summary of the invention

[0006] The object of the present invention is to provide a test bench and method for testing sea pump flow noise which can simulate the sound boundary of a real ship and have accurate and reliable test results, in view of the deficiencies in the prior art.

[0007] The technical solution adopted by the present invention is: a test bench for testing the flow noise of a sea pump simulating the sound boundary of a real ship, comprising a sea pump and an inlet pipeline, wherein the sea pump is erected on the lake embankment through a base; the inlet pipeline comprises a connected horizontal section and a vertical section, the horizontal section of the inlet pipeline is a test section, the outlet of the horizontal section is connected to the inlet of the sea pump, and the inlet of the vertical section of the inlet pipeline extends below the water surface of the lake; a pipeline hydrophone is arranged in the test section.

[0008] According to the above plan, the depth of the lake is not less than 10m, the width is not less than 100m, and the length is not less than 1000m.

[0009] According to the above solution, the immersed length of the vertical section of the water inlet pipe is not less than 1.5m.

[0010] According to the above scheme, the length of the test section is ≥2m.

[0011] The present invention also provides a method for designing and setting up a test bench for testing the noise of a sea pump flow, the method comprising the following steps:

[0012] Step 1: Determine the key influencing parameters of the acoustic transfer impedance conditions of the seagoing pipeline system, including the length and diameter of the pipeline configuration;

[0013] Step 2: Determine the boundary conditions of the infinite radiation sound field of the pipe opening of the actual ship sea-going system;

[0014] Step 3: Based on the key influencing parameters, use an inlet pipeline that is consistent with the length and diameter of the actual ship pipeline; based on the boundary conditions, select an open lake as the test bench construction site;

[0015] Step 4: Set up the test bench for the sea pump flow noise test as described above: install the sea pump through the base beside the lake embankment, connect the sea pump and the inlet pipeline, and the vertical section port of the inlet pipeline extends below the water surface of the lake;

[0016] Step 5: Install the pipeline hydrophone in the test section of the inlet pipeline.

[0017] The beneficial effects of the present invention are as follows: the present invention determines the key influencing parameters of the acoustic transfer impedance conditions of the seagoing pipeline system and the boundary conditions of the infinite radiation sound field of the pipe mouth of the actual ship seagoing system, and based on this, designs a test bench that simulates the acoustic transfer impedance of the pipeline of the actual ship seagoing system, which can simulate the acoustic impedance conditions of the acoustic transmission of the pump-excited pipeline of the actual ship seagoing system to the greatest extent, and the test results are accurate and reliable, which solves the problem of large deviations in the test results of the pump group flow noise of the traditional closed bench in the actual ship noise assessment, and provides technical support for the accurate testing of the noise source characteristics of the seagoing pump flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a structural schematic diagram of the Tonghai pump flow noise test bench in the present invention.

[0019] Figure 2 It is the relationship between the valley value of the acoustic transfer characteristic curve of the sea-going pipeline and the pipeline length in the present invention. DETAILED DESCRIPTION

[0020] In order to better understand the present invention, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0021] like Figure 1 The test bench for testing the flow noise of a sea pump simulating the sound boundary of a real ship shown in the figure comprises a sea pump 1 and an inlet pipeline 2. The sea pump 1 is erected on the lake embankment 4 of a lake through a base 3; the inlet pipeline 2 comprises a connected horizontal section and a vertical section, the horizontal section of the inlet pipeline is a test section 2.1, and its horizontal section outlet is connected to the inlet of the sea pump 1, the vertical section inlet of the inlet pipeline 2 extends below the water surface of the lake, and the inlet end of the vertical section is a sea outlet 2.2; a pipeline hydrophone is arranged in the test section; the outlet of the sea pump 1 is connected to the drainage pipeline 5.

[0022] In the present invention, an inlet pipeline 1 with the same pressure resistance grade as the sea-going system of an actual ship is adopted, and the length and diameter of the pipeline are consistent with those of the actual ship, so as to ensure accurate simulation of the frequency passing characteristics of acoustic transmission of the actual ship pipeline.

[0023] Preferably, the lake has a depth of not less than 10 m (specifically, the water depth from the water surface to the bottom is not less than 10 m), a width of not less than 100 m, and a length of not less than 1000 m.

[0024] In the present invention, the lake is required to be of sufficient size to avoid low-frequency reverberation as much as possible, so that the frequency characteristics of the low-frequency radiation impedance of the nozzle are close to the nozzle radiation impedance of the infinite radiation sound field of the actual ship, ensuring that the sound radiation boundary conditions are consistent with those of the actual ship.

[0025] Preferably, the submerged length of the vertical section of the water inlet pipe is not less than 1.5 m.

[0026] Preferably, the length of the test section is ≥ 2 m.

[0027] In the present invention, the pipeline is deeply immersed in water. Under the condition of ensuring the length of the pipeline flow noise test section, the length of the pipeline immersed section is increased as much as possible to reduce the adverse effect of water surface sound reflection on the radiation boundary condition of the pipe mouth.

[0028] In this embodiment, a test bench with a 300t / h flow rate sea pump and a 4.6m long DN250 inlet pipeline is established. Figure 1 shown.

[0029] A design and erection method of a test bench for testing the noise of a sea pump flow as described above, the method comprising the following steps:

[0030] Step 1: Determine the key influencing parameters of the acoustic transfer impedance conditions of the sea pipeline system, including the length and diameter of the pipeline configuration, that is, the length and diameter of the inlet pipeline.

[0031] For the seagoing pipeline system, the fluid medium inside the pipeline is affected by the elastic pipe wall, and its sound propagation speed is different from that of the single water medium. The equivalent sound speed method is used in acoustics to evaluate the acoustic propagation characteristics of the pipeline system (represented by the symbol C). The specific formula is as follows:

[0032]

[0033] In the above formula, 1500 is the speed of sound in water in infinite water area, m / s; 2.3×10 9 is the bulk modulus of water, N / m 2 ; d is the inner diameter of the pipeline, m; h is the pipe wall thickness, m; E is the elastic modulus of the pipeline material, MPa.

[0034] In actual engineering, seagoing pipelines are generally metal pipelines, and their elastic moduli are basically at the same level; on the other hand, the specifications of pipelines are generally based on relevant standards. Under the same pressure conditions, the diameter of the pipeline generally determines the thickness of the pipeline. Therefore, in the equivalent sound velocity formula, the main influencing parameter is the diameter of the pipeline.

[0035] Generally speaking, the acoustic transfer resistance and reactance of the piping system are related. The piping configuration affects both the acoustic resistance and the acoustic reactance. From the perspective of noise control of the sea-connected system, the acoustic resistance part is directly related to the radiated noise, while the acoustic reactance part is not related to the radiated noise. Therefore, only the influence of the piping configuration on the acoustic resistance is analyzed.

[0036] Previous studies have shown that the acoustic transmission of the Tonghai pipeline system itself exhibits certain frequency passing characteristics. The relationship curve between the sound pressure level drop and frequency of the radiated noise from the Tonghai pump inlet to the Tonghaikou was selected (the sound pressure level of the Tonghai pump inlet pipeline flow noise and the Tonghaikou radiated noise sound pressure level were measured using two hydrophones respectively, and the relationship curve between the sound pressure level difference and frequency was drawn) to characterize the acoustic transmission characteristics of the pipeline system. The valley value of the pipeline system acoustic transmission characteristic curve corresponds to the peak value of the pipeline acoustic resistance. The relationship curve between the sound pressure level drop and frequency of the Tonghai pump inlet flow noise to the Tonghaikou radiated noise satisfies the following formula:

[0037]

[0038] is the flow noise at the pump group outlet, in dB; is the radiated noise of Tonghaikou, in dB; ΔL P In the formula,

[0039] is the sound pressure level difference between the flow noise at the pipe outlet of the pump group and the radiation noise at the Tonghaikou, in dB; P1 is the flow noise sound pressure at the pipe outlet of the pump group, in Pa, and P2 is the radiation noise sound pressure at the Tonghaikou, in Pa.

[0040] Further analysis can directly infer that the valley frequency of the acoustic transfer characteristic curve is closely related to the equivalent sound velocity of pipeline sound propagation and the pipeline length, see Appendix Figure 2 As shown in the figure, the equivalent sound wavelength corresponding to the first valley frequency (140Hz) is twice the length of the pipeline; the equivalent sound wavelength corresponding to the second valley frequency (280Hz) is four times the length of the pipeline, and so on. See the attached Figure 2 shown.

[0041] Therefore, in summary, the length and diameter of the pipeline configuration are the key influencing factors affecting the acoustic transfer impedance conditions of the sea pipeline system.

[0042] Step 2: Determine the boundary conditions of the infinite radiation sound field of the pipe outlet of the real ship to sea system: open lake. The boundary conditions of the infinite radiation sound field of the pipe outlet of the real ship to sea system are the core boundary conditions that determine the acoustic transfer impedance of the pipeline system.

[0043] Step 3. Based on the key influencing parameters, use an inlet pipeline that is consistent with the length and diameter of the actual ship pipeline to ensure accurate simulation of the frequency passing characteristics of acoustic transmission of the actual ship pipeline; based on the boundary conditions, select an open lake as the site for the test bench construction.

[0044] In the present invention, an open lake is a lake of sufficient size, with a depth of not less than 10m, a width of not less than 100m, and a length of not less than 1000m. Low-frequency reverberation is avoided as much as possible, and the frequency characteristics of the low-frequency radiation impedance of the pipe mouth are made as close as possible to the pipe mouth radiation impedance of the infinite sound field of the real ship, so as to ensure that the sound radiation boundary conditions are consistent with the real ship. If the water depth near the lake embankment is not enough, the lake embankment is extended to ensure that the water depth meets the sound field conditions of sound radiation.

[0045] Step 4: Set up the test bench for the sea pump flow noise test as described above: install the sea pump through the base beside the lake embankment, connect the sea pump and the inlet pipeline, the vertical section of the inlet pipeline extends below the water surface of the lake, and the length of the vertical section immersed in water is not less than 1.5m.

[0046] In the present invention, the test section length of the inlet pipeline is ≥2m. Under the condition of ensuring the length of the pipeline flow noise test section, the length of the pipeline immersed section is increased as much as possible to reduce the adverse effects of water surface sound reflection on the radiation boundary conditions of the pipe mouth.

[0047] Step 5: Install the pipeline hydrophone in the test section of the inlet pipeline.

[0048] In this embodiment, a test bench for a 300t / h seagoing pump and a 4.6m long DN250 inlet pipeline is established. In the test pipe section of the built test bench pipeline, the flow noise of the pump group inlet pipeline is tested using a pipeline hydrophone, so that the flow noise source characteristics of the 300t / h pump under the actual ship pipeline configuration conditions can be obtained.

[0049] The present invention establishes accurate acoustic impedance boundary conditions in the pump group flow noise test, determines the key influencing factors of the sea-going system pipeline configuration that affect the system acoustic impedance and the boundary conditions of the infinite radiation sound field of the pipe outlet of the actual ship sea-going system, and thus proposes an experimental simulation technology for the acoustic transfer impedance conditions of the actual ship sea-going system.

[0050] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0051] Finally, it should be noted that the above are only 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, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to replace some of the technical features therein with equivalents. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A design and erection method of a test bench for testing sea-going pump flow noise simulating the sound boundary of a real ship, wherein the test bench for testing sea-going pump flow noise simulating the sound boundary of a real ship comprises a sea-going pump and an inlet pipeline, wherein the sea-going pump is erected on the lake embankment through a base; the inlet pipeline comprises a connected horizontal section and a vertical section, wherein the horizontal section of the inlet pipeline is a test section, wherein the outlet of the horizontal section is connected to the inlet of the sea-going pump, and the inlet of the vertical section of the inlet pipeline extends below the water surface of the lake; a pipeline hydrophone is arranged in the test section; and the characteristics are as follows: The method comprises the following steps: Step 1: Determine the key influencing parameters of the acoustic transfer impedance conditions of the sea pipeline system; Step 2: Determine the boundary conditions of the infinite radiation sound field of the pipe opening of the actual ship sea-going system; Step 3: Based on the key influencing parameters, use an inlet pipeline that is consistent with the length and diameter of the actual ship pipeline; based on the boundary conditions, select an open lake as the test bench construction site; Step 4: Set up the test bench for the sea pump flow noise test as described above: install the sea pump through the base beside the lake embankment, connect the sea pump and the inlet pipeline, and the vertical section port of the inlet pipeline extends below the water surface of the lake; Step 5: Install the pipeline hydrophone in the test section of the inlet pipeline.

2. The design and erection method of the sea pump flow noise test bench simulating the real ship sound boundary as claimed in claim 1 is characterized in that: In step one, key influencing parameters include the length and diameter of the pipe configuration.

3. The design and erection method of the sea pump flow noise test bench simulating the real ship sound boundary as claimed in claim 1 is characterized in that: The lake shall have a depth of not less than 10m, a width of not less than 100m and a length of not less than 1000m.

4. The design and erection method of the sea pump flow noise test bench simulating the real ship sound boundary as claimed in claim 1 is characterized in that: The submerged length of the vertical section of the inlet pipeline is not less than 1.5m.

5. The design and erection method of the sea pump flow noise test bench simulating the real ship sound boundary as claimed in claim 1 is characterized in that: The length of the test section is ≥2m.

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