CN111611651B - Design method of turbofan engine nacelle sound absorption structure - Google Patents

Design method of turbofan engine nacelle sound absorption structure Download PDF

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CN111611651B
CN111611651B CN202010439547.7A CN202010439547A CN111611651B CN 111611651 B CN111611651 B CN 111611651B CN 202010439547 A CN202010439547 A CN 202010439547A CN 111611651 B CN111611651 B CN 111611651B
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sound absorption
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CN111611651A (en
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高飞
王美燕
顾金桃
肖乾
胡陈映
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AVIC First Aircraft Institute
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Abstract

The application belongs to the field of airplane noise control, and particularly relates to a design method of a sound absorption structure of a nacelle of a turbofan engine, which comprises the following steps: step one, judging a perforated plate or a micro-perforated plate; step two, calculating the acoustic impedance ratio; step three, calculating resonance frequency; step four, correcting the resonance frequency; judging the difference relation between the noise frequency and the resonant frequency of the engine; step six, calculating the maximum sound absorption coefficient; step seven, correcting the maximum sound absorption coefficient and judging whether the maximum sound absorption coefficient meets the requirement; step eight, parameter variation calculation is carried out; ninthly, constructing optimization function optimization analysis; and step ten, obtaining the optimal sound absorption structure parameters for sound absorption structure design. The design method of the sound absorption structure of the turbofan engine nacelle is simple in analysis steps, convenient for computer automation iterative computation and capable of greatly improving working efficiency, and the designed sound absorption structure of the turbofan engine nacelle is simple in form, easy to machine and capable of greatly reducing engine noise.

Description

Turbofan engine nacelle sound absorption structure design method
Technical Field
The application belongs to the field of airplane noise control, and particularly relates to a design method of a sound absorption structure of a nacelle of a turbofan engine.
Background
Most of the current advanced transport aircraft use turbofan engines (referred to as turbofan engines), and turbofan engine noise is one of the main noise sources of the aircraft. Turbofan engine noise mainly includes: fan noise, compressor noise, turbine combustion chamber noise, jet noise, and the like, wherein the fan noise and the compressor noise are mainly propagated forward through a nacelle air inlet and are important factors affecting the environment during the takeoff phase of the aircraft. Aiming at the problem, the CCAR-36 part of China civil aviation airworthiness standard specially limits the takeoff noise. Therefore, by analyzing the noise transmission path of the engine, the sound absorption structure is added on the inner wall of the air inlet channel of the nacelle, so that the forward transmission noise of the engine can be reduced.
Perforated plate and microperforated plate sound absorbing structures are currently used in a wide variety of applications including construction, plumbing, industrial, traffic, and the like. However, most of the above applications are those in which the flow rate of the gas stream is low, and the flow rate is generally not more than 0.3 Ma. However, in high-speed flow conditions, particularly for high-speed flying aircraft, in order to ensure aircraft safety, environmental protection and economy, the design of noise elimination of the air inlet based on the perforated sound absorption structure is limited by the following conditions: flow field distortion and overlarge flow resistance are not generated, and the air inlet efficiency of the engine is ensured; does not generate large secondary noise; more importantly, the composite sound-absorbing material has enough sound-absorbing performance and wide sound-absorbing frequency band under the complex flowing environment.
Disclosure of Invention
In order to solve at least one of the technical problems, the application provides a design method of a sound absorption structure of a perforated plate of a nacelle of a turbofan engine.
The application discloses a turbofan engine nacelle sound absorption structure design method, which comprises the following steps:
step one, judging whether the sound absorption structure is a perforated plate or a micro-perforated plate according to the following conditions:
when k is 1 d>When 10, it is a perforated plate sound absorption structure;
when 1 is>k 1 d>When 10, it is a micro-perforated plate sound absorption structure;
wherein the content of the first and second substances,
Figure BDA0002503608650000011
f is the frequency, v is the motion viscosity coefficient;
step two, calculating the acoustic impedance of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure;
step three, calculating the resonance frequency of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure;
step four, correcting the resonance frequency of the corresponding sound absorption structure to obtain the corrected resonance frequency of the corresponding sound absorption structure;
calculating the noise frequency of the engine, and judging whether the difference value between the noise frequency of the engine and the resonance frequency corrected by the corresponding sound absorption structure meets a first set condition; if yes, performing the sixth step, otherwise, returning to the first step, and adjusting preset structure parameters of the corresponding sound absorption structure;
sixthly, calculating the maximum sound absorption coefficient of the corresponding sound absorption structure according to the resonance frequency of the corresponding sound absorption structure;
step seven, correcting the maximum sound absorption coefficient of the corresponding sound absorption structure to obtain the corrected maximum sound absorption coefficient of the corresponding sound absorption structure, and judging whether the corrected maximum sound absorption coefficient of the corresponding sound absorption structure meets a second set condition; if yes, performing the step eight, otherwise, returning to the step one, and adjusting preset structure parameters of the corresponding sound absorption structure;
step eight, reserving preset structure parameters of the corresponding sound absorption structure, returning to the step one, and performing variable parameter calculation to analyze the performance of the corresponding sound absorption structure;
constructing an optimization function, wherein the aim is to maximize the sound absorption coefficient of the corresponding sound absorption structure;
and step ten, obtaining the optimal structure parameters of the corresponding sound absorption structure according to the optimization calculation result, and using the optimal structure parameters for designing the sound absorption structure of the turbofan engine nacelle.
According to at least one embodiment of the present application, when k is 1 d>10, when the sound absorption structure is a perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
z＝r+jχ；
where r is the relative acoustic resistivity:
Figure BDA0002503608650000021
χ is the relative acoustic reactance:
Figure BDA0002503608650000022
j represents an imaginary part; omegaIs the angular frequency, ω ═ 2 π f; f is the frequency; c is the speed of sound; d is the pore diameter; t is the perforated plate thickness; d is the cavity depth of the perforated plate sound absorption structure; p is the perforation rate; v is the gas viscosity coefficient; δ is the hole end correction factor; v 0 Is the flow rate in the bore; c d Is the flow coefficient of the orifice; k is a constant.
According to at least one embodiment of the present application, in the third step, the resonant frequency f r Obtained by the following relation:
Figure BDA0002503608650000031
according to at least one embodiment of the present application, 1>k 1 d>10, when the sound absorption structure is a micro-perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
Figure BDA0002503608650000032
where r is the relative acoustic resistivity:
Figure BDA0002503608650000033
m is the relative acoustic mass:
Figure BDA0002503608650000034
ω is angular frequency, ω ═ 2 π f; f is the frequency; d is the cavity depth of the sound absorption structure of the micro-perforated plate; c is the speed of sound; j represents an imaginary part; d is the pore diameter; t is the microperforated panel thickness; p is the perforation rate; k r Is the acoustic resistance constant:
Figure BDA0002503608650000035
K m is the acoustic reactance constant:
Figure BDA0002503608650000036
in the third step, the resonance frequency f according to at least one embodiment of the present application r Obtained by the following relation:
Figure BDA0002503608650000037
according to at least one embodiment of the present application, in the fourth step, the sound absorption coefficient after modification f 0 ：f 0 ＝κf r And κ is a correction coefficient, wherein the first setting condition in the step five is
Figure BDA0002503608650000038
According to at least one embodiment of the present application, in the seventh step, the maximum sound absorption coefficient α is obtained max Correcting to obtain the corrected sound absorption coefficient alpha 0 ：α 0 ＝μα max μ is a correction coefficient;
wherein the second setting condition is alpha 0 ≥0.7。
According to at least one embodiment of the present application, the optimization function in the ninth step is:
α 0 ＝F(d,t,D)
Max:α 0
Figure BDA0002503608650000039
according to at least one embodiment of the present application, the preset structural parameters of the sound absorbing structure include: the hole diameter D, the perforated plate thickness t, the sound absorbing structure cavity depth D and the plate perforation rate p.
The application has at least the following beneficial technical effects:
the design method of the sound absorption structure of the turbofan engine nacelle is simple in analysis steps, convenient for computer automation iterative computation and capable of greatly improving working efficiency, and the designed sound absorption structure of the turbofan engine nacelle is simple in form, easy to machine and capable of greatly reducing engine noise.
Drawings
FIG. 1 is a flow chart of a turbofan engine nacelle sound absorbing structure design method of the present application.
Detailed Description
In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are a subset of the embodiments in the present application and not all embodiments in the present application. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.
The method for designing the sound absorption structure of the nacelle of a turbofan engine according to the present invention will be described in further detail with reference to fig. 1.
The application discloses a turbofan engine nacelle sound absorption structure design method, which comprises the following steps:
step one, judging whether the sound absorption structure is a perforated plate or a micro-perforated plate according to the aperture and the perforation rate, specifically judging whether the sound absorption structure is a perforated plate or a micro-perforated plate according to the following conditions:
when k is 1 d>When 10, it is a perforated plate sound absorption structure;
when 1 is>k 1 d>When 10, it is a micro-perforated plate sound absorption structure;
wherein, the first and the second end of the pipe are connected with each other,
Figure BDA0002503608650000041
f is the frequency and ν is the motion viscosity coefficient.
And step two, calculating the acoustic impedance of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure.
The preset structural parameters are the main structural parameters and can be carried out according to the form of the corresponding sound absorption structureIt is determined that, in this embodiment, the method preferably includes: aperture D, perforated plate thickness t, sound absorbing structure cavity depth D and the perforation rate p of the plate: p is A hole /A plate 。
In the first case, when k 1 d>10, when the sound absorption structure is a perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
z＝r+jχ；
where r is the relative acoustic resistivity:
Figure BDA0002503608650000051
χ is the relative acoustic reactance:
Figure BDA0002503608650000052
j represents an imaginary part; ω is angular frequency, ω ═ 2 π f; f is the frequency; c is the speed of sound; d is the pore diameter; t is the perforated plate thickness; d is the cavity depth of the perforated plate sound absorption structure; p is the perforation rate; v is the gas viscosity coefficient; δ is the hole end correction factor; v 0 Is the flow rate in the bore; c d Is the flow coefficient of the orifice; k is a constant. The value of the constant K may be appropriately selected as needed, and in this embodiment, the theoretical value of the constant K is preferably 0.43, and in addition,
Figure BDA0002503608650000053
in the second case, when k 1 d>10, when the sound absorption structure is a micro-perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
Figure BDA0002503608650000054
where r is the relative acoustic resistivity:
Figure BDA0002503608650000055
m is the relative acoustic mass:
Figure BDA0002503608650000056
ω is angular frequency, ω ═ 2 π f; f is the frequency; d is the cavity depth of the sound absorption structure of the micro-perforated plate; c is the speed of sound; j represents an imaginary part; d is the pore diameter; t is the microperforated panel thickness; p is the perforation rate; k r Is the acoustic resistance constant:
Figure BDA0002503608650000057
K m is the acoustic reactance constant:
Figure BDA0002503608650000058
and step three, calculating the resonance frequency of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure.
This step can be divided into two cases as well, when k is 1 d>10, when the sound absorption structure is a perforated plate, in the third step, the resonant frequency f r Obtained by the following relation:
Figure BDA0002503608650000059
and when 1>k 1 d>When the sound absorption structure is a micro-perforated plate sound absorption structure in 10 hours, the resonant frequency f in the third step r Obtained by the following relation:
Figure BDA00025036086500000510
and step four, correcting the resonance frequency of the corresponding sound absorption structure to obtain the corrected resonance frequency of the corresponding sound absorption structure.
In this step, the corrected sound absorption coefficient f is obtained regardless of the sound absorption structure of the perforated plate or the sound absorption structure of the microperforated plate 0 ：f 0 ＝κf r And κ is a correction coefficient.
Step five, calculating the noise frequency f of the engine e Judging whether the difference value of the engine noise frequency and the resonance frequency corrected by the corresponding sound absorption structure meets a first set condition or not according to an empirical formula or an engine noise test; if yes, proceeding the stepSixthly, if not, returning to the step one, and adjusting preset structure parameters of the corresponding sound absorption structure; in the present embodiment, the first setting condition is preferably
Figure BDA0002503608650000061
And step six, calculating the maximum sound absorption coefficient of the corresponding sound absorption structure according to the resonance frequency of the corresponding sound absorption structure.
Wherein, for perforated plate sound absorbing structure, its sound absorption coefficient alpha obtains through following relational expression:
Figure BDA0002503608650000062
for a sound absorption structure of a micro-perforated plate, the sound absorption coefficient alpha is obtained by the following relational expression:
Figure BDA0002503608650000063
then, the sound absorption coefficient of the corresponding sound absorption structure can be calculated according to the acoustic impedance, a sound absorption coefficient curve is constructed according to the sound absorption coefficient, and finally the maximum sound absorption coefficient alpha is obtained according to the sound absorption coefficient curve max (ii) a The larger the value is and the closer to 1, the better the sound absorption effect is.
Step seven, correcting the maximum sound absorption coefficient of the corresponding sound absorption structure to obtain the corrected maximum sound absorption coefficient of the corresponding sound absorption structure, and judging whether the corrected maximum sound absorption coefficient of the corresponding sound absorption structure meets a second set condition; and step eight is carried out if the preset structure parameters meet the preset structure parameters, otherwise, the step one is returned to, and the preset structure parameters of the corresponding sound absorption structure are adjusted.
Wherein, for the maximum sound absorption coefficient alpha max Correcting to obtain the corrected sound absorption coefficient alpha 0 ：α 0 ＝μα max μ is a correction coefficient; in the present embodiment, it is preferable that the second setting condition is α 0 ≥0.7。
Step eight, reserving the preset structure parameters of the corresponding sound absorption structure, returning to the step one, and performing variable parameter calculation to analyze the performance of the corresponding sound absorption structure.
Step nine, because the result meeting the requirements is not unique within the set sound absorption structure parameter range, an optimization function needs to be constructed, and an optimal solution meeting all constraint conditions is calculated by utilizing an optimization algorithm; wherein the optimization objective is to maximize the sound absorption coefficient of the corresponding sound absorbing structure.
Further, in this embodiment, the optimization function is preferably:
α 0 ＝F(d,t,D)
Max:α 0
Figure BDA0002503608650000071
and step ten, obtaining the optimal structure parameters of the corresponding sound absorption structure according to the optimization calculation result, and using the optimal structure parameters for designing the sound absorption structure of the nacelle of the turbofan engine.
In summary, the design method of the turbofan engine nacelle sound absorption structure has the advantages that analysis steps are simple, computer automatic iterative calculation is facilitated, work efficiency can be greatly improved, the designed turbofan engine nacelle sound absorption structure is simple in form and easy to process, engine noise can be greatly reduced, tests show that main frequency noise of the engine is reduced by more than 6dB, and total sound pressure level is reduced by more than 3 dB.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (9)

1. A method for designing a sound absorption structure of a turbofan engine nacelle is characterized by comprising the following steps:
step one, judging whether the sound absorption structure is a perforated plate or a micro-perforated plate according to the following conditions:
when k is 1 d>When 10, it is a perforated plate sound absorption structure;
when 1 is>k 1 d>When 10, it is a micro-perforated plate sound absorption structure;
wherein, the first and the second end of the pipe are connected with each other,
Figure FDA0002503608640000011
f is the frequency, v is the motion viscosity coefficient;
step two, calculating the acoustic impedance of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure;
step three, calculating the resonance frequency of the corresponding sound absorption structure according to the preset structure parameters of the corresponding sound absorption structure;
correcting the resonance frequency of the corresponding sound absorption structure to obtain the corrected resonance frequency of the corresponding sound absorption structure;
calculating the noise frequency of the engine, and judging whether the difference value of the noise frequency of the engine and the resonance frequency corrected by the corresponding sound absorption structure meets a first set condition; if yes, carrying out the sixth step, otherwise, returning to the first step, and adjusting preset structure parameters of the corresponding sound absorption structure;
sixthly, calculating the maximum sound absorption coefficient of the corresponding sound absorption structure according to the resonance frequency of the corresponding sound absorption structure;
step seven, correcting the maximum sound absorption coefficient of the corresponding sound absorption structure to obtain the corrected maximum sound absorption coefficient of the corresponding sound absorption structure, and judging whether the corrected maximum sound absorption coefficient of the corresponding sound absorption structure meets a second set condition; if yes, carrying out the step eight, otherwise, returning to the step one, and adjusting preset structure parameters of the corresponding sound absorption structure;
step eight, reserving preset structure parameters of the corresponding sound absorption structure at this time, returning to the step one, and performing variable parameter calculation to analyze the performance of the corresponding sound absorption structure;
constructing an optimization function with the aim of maximizing the sound absorption coefficient of the corresponding sound absorption structure;
and step ten, obtaining the optimal structure parameters of the corresponding sound absorption structure according to the optimization calculation result, and using the optimal structure parameters for designing the sound absorption structure of the nacelle of the turbofan engine.
2. The method of designing a turbofan engine nacelle sound absorbing structure of claim 1 wherein k is k 1 d>10, when the sound absorption structure is a perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
z＝r+jχ；
where r is the relative acoustic resistivity:
Figure FDA0002503608640000021
χ is the relative acoustic reactance:
Figure FDA0002503608640000022
j represents an imaginary part; ω is angular frequency, ω ═ 2 π f; f is the frequency; c is the speed of sound; d is the pore diameter; t is the perforated plate thickness; d is the cavity depth of the perforated plate sound absorption structure; p is the puncture rate; v is the gas viscosity coefficient; δ is the hole end correction factor; v 0 Is the flow rate in the bore; c d Is the flow coefficient of the orifice; k is a constant.
3. The method of designing a turbofan engine nacelle sound absorbing structure according to claim 2 wherein in step three, the resonance frequency f r Obtained by the following relation:
Figure FDA0002503608640000023
4. the method of designing a turbofan engine nacelle sound absorbing structure of claim 1 wherein 1 is>k 1 d>10, when the sound absorption structure is a micro-perforated plate sound absorption structure, in the second step, the specific acoustic impedance Z is obtained through the following relational expression:
Figure FDA0002503608640000024
where r is the relative acoustic resistivity:
Figure FDA0002503608640000025
m is the relative acoustic mass:
Figure FDA0002503608640000026
ω is angular frequency, ω ═ 2 π f; f is the frequency; d is the cavity depth of the sound absorption structure of the micro-perforated plate; c is the speed of sound; j represents an imaginary part; d is the pore diameter; t is the microperforated panel thickness; p is the perforation rate; k is r Is the acoustic resistance constant:
Figure FDA0002503608640000027
K m is the acoustic reactance constant:
Figure FDA0002503608640000028
5. the method of designing a turbofan engine nacelle sound absorbing structure according to claim 4 wherein in step three, the resonance frequency f r Obtained by the following relation:
Figure FDA0002503608640000029
6. the method for designing a sound absorbing structure of a turbofan engine nacelle according to claim 3 or 5 wherein in the fourth step, the sound absorbing coefficient f after modification is 0 ：f 0 ＝κf r And κ is a correction coefficient, wherein the first setting condition in the fifth step is
Figure FDA0002503608640000031
7. The method of designing a turbofan engine nacelle sound absorbing structure of claim 6 wherein the method is characterized byStep seven, the maximum sound absorption coefficient alpha is adjusted max Correcting to obtain the corrected sound absorption coefficient alpha 0 ：α 0 ＝μα max μ is a correction coefficient;
wherein the second setting condition is alpha 0 ≥0.7。
8. The method of designing a turbofan engine nacelle sound absorbing structure according to claim 7 wherein the optimization function in the ninth step is:
α 0 ＝F(d,t,D)
Max:α 0
Figure FDA0002503608640000032
9. the method of designing a turbofan engine nacelle sound absorbing structure according to claim 1 wherein the preset structural parameters of the sound absorbing structure include: the aperture D, the perforated or microperforated plate thickness t, the sound-absorbing structure cavity depth D, and the perforation rate p of the plate.
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Publication number Priority date Publication date Assignee Title
CN102063896A (en) * 2010-10-15 2011-05-18 南京航空航天大学 Parameter design method of resonance sound absorption structure of engineering-oriented microperforated panel
CN106057190A (en) * 2016-05-28 2016-10-26 中国船舶重工集团公司第七〇九研究所 Method for calculating parameters of silencing microperforated plate

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应用微穿孔板吸声结构的飞机座舱内部噪声控制实验研究;孙亚飞等;《声学学报(中文版)》;20030710(第04期);全文 *
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