A method for calculating the impedance of the installation foundation considering the coupling effect of the installation point

Abstract

The present application discloses a method for calculating the impedance of a mounting base taking into account the coupling effect of mounting points, and relates to the field of ship technology. The present application takes into account that when there are multiple mounting points for marine mechanical equipment, the mounting points will have coupling component influences on each other, and the coupling component has different influences on the single-point input impedance value in different frequency intervals. Therefore, by making corresponding corrections to the single-point input impedance values ​​in different frequency intervals to obtain the installation base impedance value when the coupling effect of the mounting point is taken into account, the calculation error introduced by directly using the single-point input impedance value in the general design method is overcome, and the installation status of the marine mechanical equipment can be reflected more accurately, providing useful engineering guidance for the integrated collaborative design of the installation method of the marine mechanical equipment and the hull installation foundation.

Description

Technical Field

[0001] The present application relates to the field of ship technology, and in particular to a method for calculating the impedance of an installation foundation taking into account the coupling effect of an installation point. Background Art

[0002] The impedance of the installation foundation of marine equipment is an important intermediate parameter in the design of ship vibration and noise reduction systems. It characterizes the control level of vibration energy input transmitted from the equipment itself to the hull foundation, and reflects the relationship between the vibration response and the excitation force caused by the characteristics of the equipment excitation source on the hull foundation. It directly affects the evaluation of the vibration isolation design effect of marine equipment and the analysis and calculation of equipment vibration transmission, and is further related to the installation and fixing method of marine equipment and the structural design scheme of the hull foundation.

[0003] Marine equipment generally adopts a multi-point installation method for machine feet. In traditional vibration isolation effect evaluation and vibration noise analysis, the single-point input impedance value of the installation foundation is generally used directly; in fact, the installation foundation impedance is not only a structural attribute of the hull foundation, but also related to the distribution of force on the equipment installation contact point. The single-point input impedance value does not take into account the coupling effect between the equipment installation points. Directly using the single-point input impedance value will introduce a large error into the calculation. Moreover, in actual engineering design, the installation foundation impedance considering the coupling effect of the installation point cannot be directly obtained, which brings great technical difficulties to the ship acoustic design. Summary of the invention

[0004] In view of the technical problem and technical requirement that the existing method for obtaining the installation foundation impedance is difficult to consider the coupling effect of the installation point of the marine equipment, the applicant proposes a method for calculating the installation foundation impedance considering the coupling effect of the installation point. The technical solution of this application is as follows:

[0005] For any nth mounting point of a marine mechanical device mounted on a mounting foundation:

[0006] Get the single-point input impedance value of the installation base at different frequencies at the nth installation point

[0007] Based on the consideration of the influence of the coupling components of other installation points of the marine machinery and equipment on the nth installation point, the single-point input impedance value in the frequency interval is corrected by using the correction parameters corresponding to the coupling component influence in each frequency interval based on the installation state parameters of the marine machinery and equipment. Get the installation foundation impedance value at different frequencies when considering the installation point coupling effect at the nth installation point

[0008] A further technical solution is to obtain the impedance value of the installation foundation at different frequencies when the installation point coupling effect is considered at the nth installation point. include:

[0009] Determine the expression for the installation foundation admittance value when considering the installation point coupling effect at the nth installation point Combined with the vibration modes of the installation foundation in different frequency ranges, the impedance values ​​of the installation foundation at different frequencies are obtained when the installation point coupling effect is considered at the nth installation point.

[0010] in, Enter the single point admittance value at the nth installation point, N m is the number of installation points of marine machinery and equipment, Y ni is the transfer admittance between the ith installation point and the nth installation point, F i is the excitation force at the ith installation point, F n is the excitation force at the nth mounting point.

[0011] A further technical solution is that the installation foundation impedance calculation method further includes:

[0012] Different frequency intervals are divided according to the mass M of the marine machinery and equipment.

[0013] A further technical solution is to divide different frequency intervals according to the mass M of the marine machinery and equipment, including:

[0014] Determine the first vibration frequency point f based on the mass M of the marine mechanical equipment l and the second vibration frequency point f u .

[0015] The divided frequency intervals include the first frequency interval f <f l , the second frequency interval f∈[f l , f u ], the third frequency interval f>f u The installation base exhibits low-frequency overall rigid body motion in the first frequency interval, the installation base exhibits medium-frequency mixed motion in the second frequency interval, and the installation base exhibits high-frequency local motion in the third frequency interval.

[0016] A further technical solution is to obtain the impedance value of the installation base in the first frequency interval when the installation point coupling effect is considered at the nth installation point.

[0017] A further technical solution is that obtaining the impedance value of the installation base in the first frequency interval when the installation point coupling effect is considered at the nth installation point includes:

[0018] Based on the characteristics of the installation base showing low-frequency overall rigid body motion in the first frequency interval, F is determined i =Fn , Substituting into the expression of the installation base admittance value, the correction parameter corresponding to the coupling component influence in the first frequency interval is obtained as follows: and get

[0019] A further technical solution is to obtain the impedance value of the installation base in the second frequency range when the installation point coupling effect is considered at the nth installation point.

[0020] A further technical solution is that obtaining the impedance value of the installation base in the second frequency range when the installation point coupling effect is considered at the nth installation point includes:

[0021] Based on the characteristics of the installation base in the second frequency interval showing medium-frequency mixed motion, the expression of the installation base admittance value is obtained by logarithmic interpolation method. The correction parameters corresponding to the coupling component influence in the second frequency interval are obtained as follows: and get

[0022] A further technical solution is that obtaining the installation base impedance value in the third frequency interval when the installation point coupling effect is considered at the nth installation point includes:

[0023] Based on the characteristics of the installation base showing high-frequency local motion in the third frequency interval, determine Y ni = 0, substituting into the expression of the installation base admittance value, the correction parameter corresponding to the coupling component influence in the third frequency interval is 1 and the

[0024] A further technical solution is to determine the first vibration frequency point f based on the mass M of the marine mechanical equipment. l and the second vibration frequency point f u include:

[0025] Determine the first vibration frequency point f l is the preset value, and the second vibration frequency point f u =10 -0.3(lgM-2)+4.3 ; Where lg is the logarithmic function with base 10.

[0026] The beneficial technical effects of this application are:

[0027] The installation foundation impedance calculation method considering the coupling effect of the installation point of the present application takes into account that when there are multiple installation points of marine mechanical equipment, the installation points will produce coupling components to influence each other, and the coupling components have different effects on the single-point input impedance value in different frequency ranges. Therefore, the single-point input impedance value in different frequency ranges is corrected accordingly to obtain the installation foundation impedance value when the coupling effect of the installation point is considered. This overcomes the calculation error introduced by directly using the single-point input impedance value in the general design method, can more accurately reflect the installation status of the marine mechanical equipment, and provides useful engineering guidance for the integrated collaborative design of the installation method of the marine mechanical equipment and the hull installation foundation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of a method for calculating the impedance of an installation base taking into account the coupling effect of an installation point in one embodiment of the present application.

[0029] Figure 2 It is a comparison chart of the single-point input impedance value obtained by finite element frequency response analysis in one embodiment of the present application and the installation base impedance value calculated by the present application. DETAILED DESCRIPTION

[0030] The specific implementation of the present application is further described below in conjunction with the accompanying drawings.

[0031] like Figure 1 As shown, the installation base impedance calculation method considering the installation point coupling effect of the present application includes for any nth installation point of the marine mechanical equipment installed on the installation base:

[0032] S110, obtain the single-point input impedance value of the installation base at the nth installation point at different frequencies

[0033] Optionally, get the single point input impedance value The method includes: performing a hammer vibration test on the installation foundation to obtain a single-point input impedance value, or obtaining the single-point input impedance value by numerical analysis and calculation of the frequency response under unit force single-point excitation.

[0034] (1) Performing a hammer vibration test on the installation foundation to obtain a single-point input impedance value includes: hammering the nth installation point of the installation foundation at different frequencies, obtaining the hammer acceleration V and hammer force F during the hammering, and determining the single-point input impedance value

[0035] (2) The single-point input impedance value is obtained by numerically analyzing the frequency response under unit force single-point excitation, including: constructing a finite element model of the installation foundation and the marine mechanical equipment, applying a unit force boundary condition to the nth installation point of the installation foundation in the finite element model at different frequencies, using frequency response analysis to obtain the simulated acceleration V' of the marine mechanical equipment, and determining the single-point input impedance value.

[0036] S120, based on the installation state parameters of the marine mechanical equipment, taking into account the influence of the coupling components of other installation points of the marine mechanical equipment on the nth installation point, and using the correction parameters corresponding to the influence of the coupling components in each frequency interval to correct the single-point input impedance value in the frequency interval. Get the installation foundation impedance value at different frequencies when considering the installation point coupling effect at the nth installation point

[0037] The present application takes into account that when there are multiple installation points for marine mechanical equipment, the installation points will have coupling component influences on each other, and the influence of the coupling components on the single-point input impedance value is different in different frequency ranges. Therefore, by making corresponding corrections to the single-point input impedance value in different frequency ranges, the calculation error introduced by directly using the single-point input impedance value in the general design method is overcome, and the installation status of the marine mechanical equipment can be more accurately reflected, providing useful engineering guidance for the integrated collaborative design of the installation method of the marine mechanical equipment and the hull installation foundation.

[0038] In order to more clearly illustrate the installation base impedance calculation method considering the installation point coupling effect of the present application, another embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0039] S210, obtain the single-point input impedance value of the installation base at the nth installation point at different frequencies

[0040] S220, based on the installation state parameters of the marine mechanical equipment, taking into account the influence of the coupling components of other installation points of the marine mechanical equipment on the nth installation point, and using the correction parameters corresponding to the influence of the coupling components in each frequency interval to correct the single-point input impedance value in the frequency interval. Get the installation foundation impedance value at different frequencies when considering the installation point coupling effect at the nth installation point

[0041] In this embodiment, the impedance values ​​of the installation base at different frequencies when the installation point coupling effect is considered at the nth installation point are obtained. include:

[0042] Considering that each installation point will generate velocity components for other installation points when marine machinery and equipment vibrates, determine the velocity of the installation base at the nth installation point. The expression is:

[0043]

[0044] in, Enter the single point admittance value at the nth installation point, F n is the excitation force at the nth mounting point, N m is the number of installation points of marine machinery and equipment, Y ni is the transfer admittance between the ith installation point and the nth installation point, F i is the excitation force at the i-th mounting point.

[0045] because Substituting into formula (1), the installation foundation admittance value considering the installation point coupling effect at the nth installation point is obtained: The expression is:

[0046]

[0047] in,

[0048] Combining formula (2) with the vibration modes of the installation foundation in different frequency ranges, the impedance values ​​of the installation foundation at different frequencies when the installation point coupling effect is considered at the nth installation point are obtained.

[0049] In this embodiment, different frequency intervals are divided according to the mass M of the marine mechanical equipment.

[0050] Optionally, different frequency intervals are divided according to the mass M of the marine machinery and equipment, including:

[0051] Determine the first vibration frequency point f based on the mass M of the marine mechanical equipment l and the second vibration frequency point f u .

[0052] The divided frequency intervals include the first frequency interval f <f l , the second frequency interval f∈[f l , f u ], the third frequency interval f>f u The installation base exhibits low-frequency overall rigid body motion in the first frequency interval, the installation base exhibits medium-frequency mixed motion in the second frequency interval, and the installation base exhibits high-frequency local motion in the third frequency interval.

[0053] In this embodiment, the first vibration frequency point f is determined based on the mass M of the marine mechanical equipment. land the second vibration frequency point f u include:

[0054] Determine the first vibration frequency point f l is the preset value, and the second vibration frequency point f u =10 -0.3(lgM-2)+4.3 ; Where lg is the logarithmic function with base 10.

[0055] Among them, f l The selection is estimated based on engineering experience, for example, to determine f l =5Hz.

[0056] The following discusses these three frequency ranges separately:

[0057] (1) Installation foundation impedance value in the first frequency range when considering the installation point coupling effect at the nth installation point

[0058] Specifically, based on the characteristics of the installation base in low-frequency overall rigid body motion in the first frequency interval, it can be known that in the first frequency interval, the excitation force amplitude and phase at each installation point are equal, and the transfer admittance Y between the i-th installation point and the n-th installation point is ni The single-point input admittance value at the nth installation point are equal, so we determine F i =F n , Substituting into formula (2), we get Determine the correction parameter corresponding to the coupling component influence in the first frequency interval as and get

[0059] (2) Installation foundation impedance value in the second frequency range when considering the installation point coupling effect at the nth installation point

[0060] Specifically, based on the feature of the installation base showing medium-frequency mixed motion in the second frequency interval, the expression of the installation base admittance value is obtained by logarithmic interpolation method based on the installation base The correction parameters corresponding to the coupling component influence in the second frequency interval are obtained as follows: and get

[0061] (3) Installation foundation impedance value in the third frequency range when considering the installation point coupling effect at the nth installation point

[0062] Specifically, based on the characteristics of the high-frequency local motion of the installation base in the third frequency interval, it can be known that in the third frequency interval, the excitation force amplitude and phase at each installation point are approximately equal, and the single-point input admittance value Y at the nth installation point is s n Much larger than the transfer admittance Y between the i-th installation point and the n-th installation point ni , so determine Y ni = 0 and substitute into formula (2), we get Determine that the correction parameter corresponding to the coupling component influence in the third frequency interval is 1 and obtain

[0063] In order to more clearly illustrate the installation base impedance calculation method considering the installation point coupling effect of the present application, it is described in detail below through an example.

[0064] In this example, the marine mechanical equipment is installed on the installation foundation at multiple points through the vibration isolation system. The mass of the marine mechanical equipment is M = 1000 kg, and the number of installation points of the marine mechanical equipment is N. m =4.

[0065] Determine the first vibration frequency point f l =5Hz, and substitute M=1000Kg into the expression of the second vibration frequency point f u =10 -0.3(lgM-2)+4.3 , calculate the second vibration frequency point f u =10000Hz.

[0066] The hammer vibration test was carried out on the nth installation point of the installation foundation at three vibration frequencies of f1 = 3Hz, f2 = 1000Hz, and f3 = 20000Hz, and the corresponding single-point input impedance values ​​were obtained respectively.

[0067] Since f1 <f l Located in the first frequency interval, the impedance value of the installation foundation when considering the installation point coupling effect at the nth installation point is determined when the vibration frequency f1 = 3Hz:

[0068]

[0069] Because f l ≤f2≤f u Located in the first frequency interval, the impedance value of the installation foundation when considering the installation point coupling effect at the nth installation point is determined when the vibration frequency f2 = 1000Hz:

[0070]

[0071] Since f3≥fu Located in the first frequency interval, the impedance value of the installation foundation when considering the installation point coupling effect at the nth installation point is determined when the vibration frequency f3 = 20000 Hz:

[0072]

[0073] like Figure 2 The figure shows a comparison of the single-point input impedance value obtained by finite element frequency response analysis and the installation base impedance value calculated by this application. Figure 2 It can be seen that the lower the vibration frequency, the greater the influence of the mounting point coupling effect on the mounting foundation impedance value, and the greater the error between the single-point input impedance value and the mounting foundation impedance value; and the higher the vibration frequency, the smaller the influence of the mounting point coupling effect on the mounting foundation impedance value, and the single-point input impedance value is closer to the mounting foundation impedance value.

[0074] The above is only a preferred embodiment of the present application, and the present application is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A method for calculating the impedance of an installation base taking into account the coupling effect of an installation point, characterized in that: The installation foundation impedance calculation method includes, for any nth installation point of the marine mechanical equipment installed on the installation foundation: Get the single-point input impedance value of the installation base at the nth installation point at different frequencies Based on the consideration of the effect of the coupling component of other installation points of the marine mechanical equipment on the nth installation point, the single-point input impedance value in the frequency interval is corrected by using the correction parameter corresponding to the effect of the coupling component in each frequency interval based on the installation state parameter of the marine mechanical equipment. Obtain the installation base impedance value at different frequencies when the installation point coupling effect is considered at the nth installation point Determine the expression for the installation base admittance value when the installation base takes into account the installation point coupling effect at the nth installation point In combination with the vibration modes of the installation base in different frequency intervals, the installation base impedance values ​​at different frequencies when the installation point coupling effect is considered at the nth installation point are obtained; in, Enter the single point admittance value at the nth installation point, N m is the number of installation points of the marine mechanical equipment, Y ni is the transfer admittance between the ith installation point and the nth installation point, F i is the excitation force at the ith installation point, F n is the excitation force at the nth mounting point.

2. The method for calculating the installation foundation impedance according to claim 1, characterized in that: The installation foundation impedance calculation method further includes: Different frequency intervals are divided according to the mass M of the marine mechanical equipment.

3. The method for calculating the installation foundation impedance according to claim 2, characterized in that: Different frequency intervals are divided according to the mass M of the marine machinery and equipment, including: Determine the first vibration frequency point f based on the mass M of the marine mechanical equipment l and the second vibration frequency point f u ; The divided frequency intervals include the first frequency interval f <f l , the second frequency interval f∈[f l , f u ], the third frequency interval f>f u The installation base exhibits low-frequency overall rigid body motion in the first frequency range, the installation base exhibits medium-frequency mixed motion in the second frequency range, and the installation base exhibits high-frequency local motion in the third frequency range.

4. The method for calculating the installation foundation impedance according to claim 3, characterized in that: Obtain the installation base impedance value in the first frequency range when the installation base is at the nth installation point and the installation point coupling effect is considered 5. The method for calculating the installation foundation impedance according to claim 4, characterized in that: Obtaining the installation base impedance value of the installation base in the first frequency interval when the installation point coupling effect is considered at the nth installation point includes: Based on the characteristic that the installation base exhibits low-frequency overall rigid body motion in the first frequency interval, F is determined. i =F n , Substituting the expression of the installation base admittance value into the equation, the correction parameter corresponding to the coupling component influence in the first frequency interval is obtained as follows: and get 6. The method for calculating the installation foundation impedance according to claim 3, characterized in that: Obtain the installation base impedance value in the second frequency range when the installation base is at the nth installation point and the installation point coupling effect is considered 7. The method for calculating the installation foundation impedance according to claim 6, characterized in that: Obtaining the installation base impedance value of the installation base in the second frequency range when the installation point coupling effect is considered at the nth installation point includes: Based on the feature that the installation base exhibits medium frequency mixed motion in the second frequency interval, the expression of the installation base admittance value at the installation base is obtained by logarithmic interpolation method. The correction parameters corresponding to the coupling component influence in the second frequency interval are obtained as follows: and get 8. The method for calculating the installation foundation impedance according to claim 3, characterized in that: Obtaining the installation base impedance value within the third frequency interval when the installation point coupling effect is considered at the nth installation point includes: Based on the characteristic that the installation base exhibits high-frequency local motion in the third frequency interval, determine Y ni = 0, substituting into the expression of the installation base admittance value, the correction parameter corresponding to the coupling component influence in the third frequency interval is 1 and the result is 9. The method for calculating the installation foundation impedance according to claim 3, characterized in that: Determine the first vibration frequency point f based on the mass M of the marine mechanical equipment l and the second vibration frequency point f u include: Determine the first vibration frequency point f l is the preset value, and the second vibration frequency point f u =10 -0.3(lgM-2)+4.3 ; Where lg is the logarithmic function with base 10.

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