Ship noise forecasting method based on mother type ship database

Abstract

The invention relates to a mother-type ship database-based ship noise forecasting method, which comprises the following steps of: collecting mother-type ship noise actual measurement data, performing arrangement by taking each place as a dimension, and establishing a mother-type ship database; carrying out statistical processing on the data, and calculating statistical indexes of noise measured values of all rooms of all mother type ships; the measured values of the same place of each mother ship are regarded as different results repeatedly measured for the same experiment, and a normal distribution model is established; adding the average value of the noise measured values at all positions and the standard deviation of a certain multiple of the normal distribution model as the noise basic value of the new ship; comparing the difference between a noise source and a propagation path between the predicted ship and the mother ship, establishing a function relationship between a single difference and a noise level by using an empirical formula or an actual measurement result similar to new ship equipment arrangement, and superposing all change influence results to obtain a total influence result of the noise at the place; and obtaining a predicted value of the noise of the new ship based on a superposition result of the noise basic value and the total influence result.

Description

Technical Field

[0001] The present invention relates to the technical field of ship noise prediction, and in particular to a ship noise prediction method based on a parent ship database. Background Art

[0002] On ships, strong noise can harm the physical and mental health of crew members, affect their work, and lead to work errors that endanger the safe operation of the ship and cause safety accidents. Therefore, the level of cabin noise in the ship's living area plays a vital role in the rest and recovery of the crew. When designing a new ship, in order to avoid or reduce the impact of necessary noise reduction remedial measures on the ship's cabin layout, empty ship weight and shipbuilding costs after the ship is built, it is urgent to conduct noise forecasts as early as possible in the ship design stage, consider noise control, and take appropriate vibration and noise reduction measures to build low-noise ships at low cost and high efficiency.

[0003] The existing technology generally adopts the empirical formula prediction method or the numerical calculation method, among which the empirical formula prediction method is suitable for ship noise prediction in the basic design stage. The empirical formula method calculates the cabin noise caused by each main noise source one by one, and then adds all the noise components to obtain the total air noise level of the cabin. In the numerical calculation method, the low-frequency cabin noise prediction is generally carried out using the finite element method, which discretizes the ship structure and sound field into several units, establishes and solves the dynamic equation matrix of the entire ship system, obtains the vibration response calculation results of the nodes, and then obtains the sound pressure calculation results. The medium and high frequency cabin noise prediction is generally carried out using the statistical energy method, which divides the ship into several subsystems, and obtains the cabin noise of the entire ship system by establishing and solving the energy balance equation of each subsystem.

[0004] Neither the empirical formula method nor the numerical prediction method can utilize the noise results measured on the actual ship. A completely new design must be started from scratch. According to the ship structure drawings, the air noise and structural noise characteristics of all noise sources, the material properties of the ship structure and the medium properties of the sound field, including the elastic modulus, Poisson's ratio, loss factor, sound absorption coefficient, etc. of various materials, must be collected. A large number of assumptions must be made and multiple parameter factors must be introduced. Specialized computing software must be used to perform complex and tedious modeling and calculations of the entire ship, which is costly and results in large errors. Summary of the invention

[0005] To solve the above problems, the present invention adopts a new ship noise prediction method, which analyzes the measured data of the mother ship and calculates based on the results, avoiding the complicated calculation and modeling process, and predicting the ship cabin noise at low cost and high efficiency. It is helpful to effectively predict and control the noise level of the living cabin in the early stage, avoid rework and save costs.

[0006] The technical means adopted by the present invention are as follows:

[0007] A ship noise prediction method based on a parent ship database comprises the following steps:

[0008] Step 1: Collect the measured noise data of the mother ship, organize it by location, and establish a mother ship database;

[0009] Step 2, statistically process the data and calculate the statistical index of the noise measured value of each room of each mother ship;

[0010] Step 3: The measured values ​​of the same location of each mother ship are regarded as different results of repeated measurements of the same experiment. The measured value results obey the normal distribution, and a normal distribution model is established;

[0011] Step 4: The average value of the noise measured in each location plus a certain multiple of the standard deviation of the normal distribution model is taken as the basic value of the noise of the new ship;

[0012] Step 5: Compare the differences in noise sources and propagation paths between the predicted ship and the parent ship, use empirical formulas or actual measurement results similar to the equipment layout of the new ship to establish a functional relationship between individual differences and noise levels, and superimpose the impact results of each change to obtain the total impact result of the location noise;

[0013] Step 6: Based on the noise base value of step 4 and the total impact result of step 5, the predicted value of the new ship noise is obtained.

[0014] Furthermore, in step 4, a 90% confidence interval is used, which means that 90% of the noise measurement values ​​of the ships are within the range of ±1.65 times the standard deviation of the mean value, only 5% of the ships are less than the mean value minus 1.65 times the standard deviation due to some special circumstances, and 5% of the ships are greater than the mean value plus 1.65 times the standard deviation due to some special circumstances, and 95% of the ships have noise values ​​no greater than the mean value + 1.65 times the standard deviation; the average value of the actual noise measurement values ​​at each location plus 1.65 times the standard deviation is taken as the basic noise value of the new ship.

[0015] Furthermore, the differences in noise sources and propagation paths between the predicted ship and the parent ship include differences in the models and powers of the main engines, generators, and fans, as well as differences in deck thickness, layout changes, etc. in the propagation paths.

[0016] Compared with the prior art, the present invention has the following advantages: the present invention can predict the ship cabin noise at low cost and high efficiency when there is a large amount of measured data of the mother ship. By analyzing the measured data of the mother ship and calculating based on the results, the complex calculation and modeling process is avoided, which helps to effectively predict and control the noise level of the living cabin in the early stage, avoid rework and save costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 It is a flow chart of the present invention.

[0019] Figure 2 This is a normal distribution model diagram. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, the numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0024] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention: the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0025] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below their position devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0026] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0027] like Figure 1As shown, the embodiment of the present invention discloses a ship noise prediction method based on a parent ship database, comprising the following steps:

[0028] Step 1: Collect the measured noise data of the mother ship, organize it by location, and establish a mother ship database;

[0029] Step 2, statistically process the data and calculate the statistical index of the noise measured value of each room of each mother ship;

[0030] Step 3: The measured values ​​of the same location of each mother ship are regarded as different results of repeated measurements of the same experiment. The measured value results obey the normal distribution and establish the following Figure 2 Normal distribution model shown;

[0031] Step 4: The average value of the noise measured in each location plus a certain multiple of the standard deviation of the normal distribution model is taken as the basic value of the noise of the new ship;

[0032] Step 5: Compare the differences in noise sources and propagation paths between the predicted ship and the parent ship, use empirical formulas or actual measurement results similar to the equipment layout of the new ship to establish a functional relationship between individual differences and noise levels, and superimpose the impact results of each change to obtain the total impact result of the location noise;

[0033] Step 6: Based on the noise base value of step 4 and the total impact result of step 5, the predicted value of the new ship noise is obtained.

[0034] In step 4, in order to pay special attention to the limit of the predicted ship noise, a 90% confidence interval is used, which means that 90% of the noise measurement values ​​of the ships are within the range of ±1.65 times the standard deviation of the mean value, only 5% of the ships are less than the mean value minus 1.65 times the standard deviation due to some special circumstances, and 5% of the ships are greater than the mean value plus 1.65 times the standard deviation due to some special circumstances. The noise values ​​of 95% of the ships are not greater than the mean value + 1.65 times the standard deviation; the average value of the actual noise values ​​of each location plus 1.65 times the standard deviation is taken as the basic noise value of the new ship.

[0035] The differences in noise sources and propagation paths between the predicted ship and the parent ship include differences in the models and powers of the main engines, generators, and fans, as well as differences in deck thickness, layout changes, etc. in the propagation paths.

[0036] Example 1

[0037] In this embodiment, the ship noise prediction method of the present invention is explained by taking the change of noise source in a residential area of ​​a ship as an example.

[0038] The main noise sources in the living area of ​​a certain ship are the main engine and generator in the engine room, and the engine room fan and kitchen exhaust fan on the B deck. The equipment parameters are compared with those of the original ship as follows.

[0039] Table 1 Comparison of main noise sources

[0040]

[0041] The main engine is located at the double bottom of the engine room. The air noise and structure-borne noise generated during operation will affect the noise level of the cabin in the living area. In the example, a ship project meets the requirements of IMO EEDI phase 3 by reducing the MCO point power. The original ship type B main engine cannot meet the requirements, and the example ship uses type A main engine instead. The noise and vibration levels of these two types of main engines under NCR are provided by the manufacturer, and the comparison is shown in the following table:

[0042] Table 2 Original ship type B main engine

[0043]

[0044] Table 3 Example A type main engine of a certain ship

[0045]

[0046] It can be seen that the noise and vibration levels provided by the manufacturers of the two types of main engines are almost the same. It can be considered that the change of the main engine itself has no change in the noise impact on the living cabin.

[0047] However, according to the specification, "Measurements shall be taken at normal service speed and no less than 80% of the maximum continuous rating". The original ship's main engine Normal output is 6870kW (71% MCO), and the noise measurement experiment needs to be carried out at 80% MCO. However, the ship's main engine Normal output in the embodiment is 6550kW (85% MCO), and the noise measurement experiment needs to be carried out at 85% MCO. As shown in the following table

[0048] Table 4 Comparison of main engine operating conditions during the experiment

[0049] <![CDATA[Host Norma l output]]> Experimental conditions Host operating conditions during the experiment original ship 6870kW (71% MCO, 79rpm) 80% MCO 7736kW (80% MCO, 83rpm). Example Ship 6550kW (85% MCO, 81rpm) 85% MCO 6550kW (85% MCO, 81rpm)

[0050] It can be seen that the main engine power and speed during the noise test of a certain ship in the embodiment are smaller than the main engine power and speed during the original ship test, and the influence of the experimental conditions on the cabin noise is compared from two aspects.

[0051] 1) Air noise.

[0052] According to the following formula, it can be estimated that the host air noise will theoretically be reduced by about 0.7dB.

[0053] Lw =101g P e +57+C w

[0054] Where: P e ——Rated power of diesel engine,

[0055] C w ——octave band correction value of diesel engine air noise,

[0056] Octave band correction value of diesel engine air noise

[0057] Octave center frequency (Hz) 63 125 250 500 1000 2000 4000 8000 Correction value above 600r / min (dB) 21 27 28 26 24 20 13 4 Correction value below 600r / min (dB) 18 24 25 23 21 17 10 1

[0058] 2)Structural noise.

[0059] The living area of ​​the embodiment ship is very similar to that of the original ship, and the vibration of the original ship can be referred to. As shown in the following table, it can be inferred that the excitation frequency N1 of the embodiment ship during the experiment is lower than the excitation frequency N2 of the original ship during the experiment. The excitation frequency during the experiment is lower, and the difference with the natural frequency of the living area will be greater, which will improve the vibration and structural noise of the living area.

[0060] Table 5 Comparison of vibration frequencies during the experiment

[0061]

[0062] According to the following formula, it can be estimated that the host structure noise will theoretically be reduced by about 0.9dB.

[0063]

[0064] Where: m——the mass of the diesel engine,

[0065] P e ——Rated power of diesel engine,

[0066] n e ——Rated speed of diesel engine,

[0067] n——operating speed of diesel engine,

[0068] C a ——octave band correction value of diesel engine vibration, dB;

[0069] Octave band correction value of diesel engine vibration

[0070] Octave center frequency (Hz) 63 125 250 500 1000 2000 4000 8000 Correction value (dB) 5 11 16 21 27 29 27 22

[0071] Refer to the following empirical formula

[0072] The noise level in the source cabin is calculated as follows:

[0073]

[0074] Where: ——noise level in the source cabin, dB;

[0075] L w ——sound power level of the sound source, dB;

[0076] Q——directivity factor of the sound source,

[0077] r——the distance from the center of the cabin to the sound source, m;

[0078] α (1) ——sound absorption coefficient of the source cabin;

[0079] S——Total indoor wall area of ​​the source compartment, m 2 .

[0080] The noise level transmitted into the cabin is calculated as follows:

[0081]

[0082] Where: ——Noise level at the center of the source compartment wall, dB;

[0083] R——sound insulation of bulkhead, dB;

[0084] F——area of ​​bulkhead, m 2 .

[0085] A——Total sound absorption in the room, m 2 ;

[0086] ΔR - Correction to take into account the acoustic covering on the bulkhead.

[0087] It can be seen that when other conditions (such as cabin absorption coefficient, area, etc.) remain unchanged, the noise change of the noise source will directly affect the noise level of the cabin. Therefore, the noise reduction caused by the change of the main engine and the operating conditions during the main engine test will directly reduce the UPPER deck cabin noise by 1.1dB.

[0088] Example 2

[0089] Based on Example 1, two engine room fans are located in the fan rooms on the left and right sides of the B deck, close to the stern cabin of the living area. The air volume of the engine room fan of the example ship is increased from 1100m 3 / h, reduced to 1000m 3 / h, the fan selection was changed accordingly. According to the actual test results of the fan manufacturer, the noise at 1.2m from the fan outlet was reduced by 0.7dB.

[0090] Similarly, referring to the above empirical formula, the cabin noise at the stern of decks A, B, and C will decrease as the fan noise decreases. For the impact on each cabin, the forecast value is estimated by reducing the basic value by 0.3dB.

[0091] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ship noise prediction method based on a parent ship database, characterized in that: The steps include: Step 1: Collect the measured noise data of the mother ship, organize it by location, and establish a mother ship database; Step 2, statistically process the data and calculate the statistical index of the noise measured value of each room of each mother ship; Step 3: The measured values ​​of the same location of each mother ship are regarded as different results of repeated measurements of the same experiment. The measured value results obey the normal distribution, and a normal distribution model is established; Step 4: The average value of the noise measured in each location plus a certain multiple of the standard deviation of the normal distribution model is taken as the basic value of the noise of the new ship; Step 5: Compare the differences in noise sources and propagation paths between the predicted ship and the parent ship, use empirical formulas or actual measurement results similar to the equipment layout of the new ship to establish a functional relationship between individual differences and noise levels, and superimpose the impact results of each change to obtain the total impact result of the location noise; Step 6: Based on the noise base value of step 4 and the total impact result of step 5, the predicted value of the new ship noise is obtained.

2. The ship noise prediction method based on the parent ship database according to claim 1 is characterized in that: In step 4, a 90% confidence interval is used, which means that 90% of the noise measurement values ​​of the ships are within the range of ±1.65 times the standard deviation of the mean value, only 5% of the ships are less than the mean value minus 1.65 times the standard deviation due to some special circumstances, and 5% of the ships are greater than the mean value plus 1.65 times the standard deviation due to some special circumstances. The noise values ​​of 95% of the ships are not greater than the mean value + 1.65 times the standard deviation; the average value of the actual noise measurement values ​​of each location plus 1.65 times the standard deviation is taken as the basic noise value of the new ship.

3. The ship noise prediction method based on the parent ship database according to claim 1 is characterized in that: The differences in noise sources and propagation paths between the predicted ship and the parent ship include differences in the models and powers of the main engines, generators, and fans, as well as differences in deck thickness, layout changes, etc. in the propagation paths.

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