A method for determining the parameters of a single-layer wallboard noise index of a propeller aircraft

Abstract

The application relates to a propeller airplane single-layer wallboard noise index parameter decomposition determination method, which comprises the following steps: step one, calculating the critical frequency of the single-layer wallboard; step two, calculating the sound transmission loss based on the critical frequency of the single-layer wallboard; step three, calculating the single-layer wallboard surface turbulent boundary layer noise; step four, calculating the near-field noise of the propeller distributed along the single-layer wallboard; step five, calculating the propeller airplane cabin noise by using the sound transmission loss of the single-layer wallboard, the single-layer wallboard surface turbulent boundary layer noise and the near-field noise of the propeller distributed along the single-layer wallboard; and step six, if the propeller airplane cabin noise cannot meet the cabin noise index requirement, adjusting the single-layer wallboard structure and material parameters, optimizing the single-layer wallboard structure and material parameters, and then performing steps one to five again until the propeller airplane cabin noise meets the cabin noise index requirement, so as to obtain the sound transmission loss of the single-layer wallboard and the structure and material parameters.

Description

Technical Field

[0001] The present application belongs to the technical field of single-layer wall panel design for propeller aircraft, and specifically relates to a method for decomposing and determining noise index parameters of a single-layer wall panel for a propeller aircraft. Background Art

[0002] During the development of propeller aircraft, it is necessary to control the cabin noise.

[0003] The near-field noise of propeller aircraft mainly comes from the propeller. There are a large number of single-layer wall panels on propeller aircraft. In order to ensure that the cabin noise meets the index requirements, it is necessary to decompose the cabin noise index into single-layer wall panels and determine the structure and material parameters of the single-layer wall panels. However, at present, there is a lack of efficient and feasible methods for this. In view of this, this application is proposed. Summary of the Invention

[0004] The purpose of this application is to provide a method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, so as to guide the design of the single-layer wall panel during the aircraft development process.

[0005] The technical solution of this application is:

[0006] A method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft comprises:

[0007] Step 1: Calculate the critical frequency of the single-layer wall panel;

[0008] Step 2: Calculate the sound transmission loss based on the critical frequency of the single-layer wall panel;

[0009] Step 3: Calculate the turbulent boundary layer noise on the surface of the single-layer wall panel;

[0010] Step 4: Calculate the near-field noise of the propeller distributed along the single-layer wall panel;

[0011] Step 5: Calculate the cabin noise of the propeller aircraft based on the sound transmission loss of the single-layer wall panel, the turbulent boundary layer noise on the surface of the single-layer wall panel, and the near-field noise distributed along the single-layer wall panel.

[0012] Step 6: If the cabin noise of the propeller aircraft cannot meet the cabin noise index requirements, adjust the structure and material parameters of the single-layer wall panel, optimize the structure and material parameters of the single-layer wall panel, and repeat steps 1 to 5 until the cabin noise of the propeller aircraft meets the cabin noise index requirements, and obtain the sound transmission loss of the single-layer wall panel and its structure and material parameters.

[0013] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, the structural parameters of the single-layer wall panel mainly include the cross-sectional thickness t of the single-layer wall panel.

[0014] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, the material parameters of the single-layer wall panel mainly include the elastic modulus E and Poisson's ratio B of the single-layer wall panel material.

[0015] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step 1 is specifically as follows:

[0016]

[0017] in

[0018] f c is the critical frequency of the single-layer wall panel;

[0019] m is the mass per unit area of ​​a single-layer wall panel;

[0020] D is the bending stiffness per unit width of a single-layer wall panel;

[0021] c s is the speed of sound in air on both sides of a single-layer wall panel;

[0022] φ is the incident angle of the incident sound wave, which is taken as 90°.

[0023] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step 1 includes:

[0024]

[0025] in,

[0026] E is the elastic modulus of the single-layer siding material;

[0027] t is the thickness of a single wall panel;

[0028] B is the Poisson's ratio of the single-layer siding material.

[0029] Optionally, in the above-mentioned method for determining the noise index parameters of a single-layer wall panel of a propeller aircraft, in step 2, the noise cutoff frequency f is less than the critical frequency f of the single-layer wall panel. c When , the sound transmission loss TL of a single-layer wall panel is calculated as:

[0030]

[0031] in,

[0032] ω is the angular velocity of the incident wave;

[0033] ρ0 is the air density.

[0034] Optionally, in the above-mentioned method for determining the noise index parameters of a single-layer wall panel of a propeller aircraft, in step 2, the noise cutoff frequency f is equal to the critical frequency f of the single-layer wall panel.c When , the sound transmission loss TL of a single-layer wall panel is calculated as:

[0035]

[0036] in,

[0037] η is the loss factor of the single-layer wall panel structure.

[0038] Optionally, in the above-mentioned method for determining the noise index parameters of a single-layer wall panel of a propeller aircraft, in step 2, the noise cutoff frequency f is greater than the critical frequency f of the single-layer wall panel. c When , the sound transmission loss TL of a single-layer wall panel is calculated as:

[0039]

[0040] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step three is specifically as follows:

[0041]

[0042] in,

[0043] TBL is the turbulent boundary layer noise on the surface of a single-layer panel;

[0044] τ w is the shear stress of the single-layer wall panel;

[0045] δ * is the displacement thickness of the turbulent boundary layer on the surface of the single-layer panel;

[0046] U0 is the flight speed.

[0047] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step three includes:

[0048]

[0049]

[0050] in,

[0051] ρ is the air density;

[0052] Re δ Calculate intermediate parameters for single-layer panel wall shear stress;

[0053] υ is the kinematic viscosity of air.

[0054] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step three includes:

[0055]

[0056] in,

[0057] x0 is the distance between the single-layer wall panel and the front end of the machine head.

[0058] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step 4 is specifically as follows:

[0059] Based on the flight status of a propeller aircraft, a propeller near-field noise source model is constructed. The propeller diameter, power, thrust, number of blades, rotational speed, speed of sound, flight speed, ambient temperature, number of propellers, blade width at a radius of 0.8, distance between the wingtip and the single-layer wall panel, and air density are used as key parameters. The near-field noise ROR of the propeller distributed along the single-layer wall panel within the noise cutoff frequency range is obtained.

[0060] Optionally, in the above-mentioned method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, step five is specifically as follows:

[0061]

[0062] in,

[0063] SPL is the cabin noise of propeller aircraft.

[0064] This application has at least the following beneficial technical effects:

[0065] A method for decomposing and determining noise index parameters of single-layer panels of propeller aircraft is provided. Based on theoretical analysis of the sound transmission loss of single-layer panels of propeller aircraft and the cabin noise under excitation of an external sound source, the cabin noise index is decomposed into single-layer panels. The sound transmission loss of the single-layer panels and their structural and material parameters are iteratively calculated to ultimately obtain the sound transmission loss of the single-layer panels and their structural and material parameters that meet the cabin noise index requirements. This method is convenient and efficient and can guide the design of single-layer panels during aircraft development. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 Schematic diagram of a method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft provided in an embodiment of the present application.

[0067] In order to better illustrate this embodiment, certain contents of the drawings are only used for illustrative purposes and should not be understood as limiting the present application. DETAILED DESCRIPTION

[0068] To make the technical solution and its advantages of this application more clear, the technical solution of this application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described here are only some of the embodiments of this application and are only used to explain this application, not to limit this application. It should be noted that for ease of description, only the parts relevant to this application are shown in the accompanying drawings, and other relevant parts can refer to the general design.

[0069] In addition, unless otherwise defined, the technical terms or scientific terms used in the description of this application should have the usual meanings understood by those skilled in the art in the field to which this application belongs. The words indicating orientation used in the description of this application are only used to indicate relative directions or positional relationships. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. The word "include" used in the description of this application means that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0070] In addition, it should be noted that, unless otherwise clearly stipulated and limited, the words "installation", "connection" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. Technical personnel in the field can understand its specific meaning in this application according to the specific circumstances.

[0071] The embodiment of the present application provides a method for decomposing and determining noise index parameters of a propeller aircraft single-layer wall panel based on the theoretical analysis of the sound transmission loss of the propeller aircraft single-layer wall panel and the cabin noise under the excitation of an external sound source. Figure 1 shown.

[0072] Step 1: Calculate the critical frequency of the single-layer wall panel.

[0073] The structural parameters of the single-layer wall panel mainly include the single-layer wall panel section thickness t, etc.

[0074] The material parameters of the single-layer wall panel mainly include the elastic modulus E, Poisson's ratio B, etc. of the single-layer wall panel material.

[0075]

[0076] in

[0077] f c is the critical frequency of the single-layer wall panel;

[0078] m is the mass per unit area of ​​a single-layer wall panel;

[0079] D is the bending stiffness per unit width of a single-layer wall panel;

[0080] c s is the speed of sound in air on both sides of a single-layer wall panel;

[0081] φ is the incident angle of the incident sound wave. When φ = 90°, the minimum coupling frequency value is obtained, which is the critical frequency f c .

[0082]

[0083] in,

[0084] E is the elastic modulus of the single-layer siding material;

[0085] t is the thickness of a single wall panel;

[0086] B is the Poisson's ratio of the single-layer siding material.

[0087] Step 2: Calculate the sound transmission loss based on the critical frequency of the single-layer wall panel.

[0088] The ratio of the sound pressure at the outlet to the sound pressure at the inlet of a single-layer wall panel is:

[0089]

[0090] in,

[0091] ρ0 is the air density;

[0092] ω is the angular velocity of the incident wave;

[0093] k is the incident wave number, which is the correlation function of frequency;

[0094] k b is the free bending wave number of the incident wave, and

[0095] η is the loss factor of the single-layer wall panel structure.

[0096] Considering the random incident angle of the sound wave, the sound pressure ratio τ d for:

[0097]

[0098] Based on the ratio τ of the sound pressure at the outlet to the sound pressure at the inlet of a single-layer wall panel, the expression of the sound transmission loss TL is:

[0099]

[0100] Further deduction, the sound transmission loss TL of a single-layer wall panel can be calculated by frequency band:

[0101] The noise cutoff frequency f is less than the critical frequency f of the single-layer wall panel cWhen , the sound transmission loss TL of a single-layer wall panel is calculated as follows:

[0102]

[0103] The noise cutoff frequency f is equal to the critical frequency f of the single-layer wall panel c When , the sound transmission loss TL of a single-layer wall panel is calculated as follows:

[0104]

[0105] The noise cutoff frequency f is greater than the critical frequency f of the single-layer wall panel c When , the sound transmission loss TL of a single-layer wall panel is calculated as follows:

[0106]

[0107] Step 3: Calculate the turbulent boundary layer noise on the surface of a single-layer wall panel.

[0108]

[0109] in,

[0110] TBL is the turbulent boundary layer noise on the surface of a single-layer panel;

[0111] τ w is the shear stress of the single-layer wall panel;

[0112] δ * is the displacement thickness of the turbulent boundary layer on the surface of the single-layer panel;

[0113] U0 is the flight speed.

[0114]

[0115]

[0116] in,

[0117] ρ is the air density;

[0118] Re δ Calculate intermediate parameters for single-layer panel wall shear stress;

[0119] υ is the kinematic viscosity of air.

[0120]

[0121] in,

[0122] x0 is the distance between the single-layer wall panel and the front end of the machine head.

[0123] Step 4: Calculate the near-field noise of the propeller distributed along the single-layer wall panel.

[0124] Based on the flight status of a propeller aircraft, a propeller near-field noise source model is constructed. The propeller diameter, power, thrust, number of blades, rotational speed, speed of sound, flight speed, ambient temperature, number of propellers, blade width at a radius of 0.8, distance between the wingtip and the single-layer wall panel, and air density are used as key parameters. The near-field noise ROR of the propeller distributed along the single-layer wall panel within the noise cutoff frequency range is obtained.

[0125] Step 5: Calculate the cabin noise of the propeller aircraft based on the sound transmission loss of the single-layer wall panel, the turbulent boundary layer noise on the surface of the single-layer wall panel, and the near-field noise distributed along the single-layer wall panel.

[0126]

[0127]

[0128] in,

[0129] SPL is the cabin noise of propeller aircraft.

[0130] Step 6. If the cabin noise of the propeller aircraft cannot meet the cabin noise index requirements, adjust the structure and material parameters of the single-layer wall panel, optimize the structure and material parameters of the single-layer wall panel, and repeat steps 1 to 5 until the cabin noise of the propeller aircraft meets the cabin noise index requirements. The sound transmission loss of the single-layer wall panel and its structure and material parameters are obtained as design indicators for the single-layer wall panel.

[0131] In a specific example,

[0132] The single-layer wall panel material is aluminum alloy with thickness t=3mm, density ρ=2700kg / m3, unit area mass 8.1kg / m2, elastic modulus E=70000MPa, Poisson's ratio B=0.3, unit width bending stiffness D=173, and structural loss factor η=0.3.

[0133] The propeller plane is cruising at an altitude of 5 km. The speed of sound in the air on both sides of a single-layer wall is C. s =320m / s, corresponding to air density ρ0=0.413kg / m3, angular velocity ω=2πf, the full-band sound transmission loss TL of the single-layer wall panel can be calculated.

[0134] The propeller aircraft flight speed U0 = 0.7 Ma, the distance between the single-layer wall panel and the front end of the nose x0 = 5 m, and the air viscosity υ = 2.8×10-5 were selected to calculate the turbulent boundary layer noise TBL on the surface of the ribbed single-layer wall panel.

[0135] With propeller diameter, power, thrust, number of blades, rotation speed, speed of sound, flight speed, ambient temperature, number of propellers, blade width at 0.8 radius, distance between wingtip and single-layer wall panel, and air density as key parameters, a propeller near-field noise source model is constructed, and the near-field noise ROR of the propeller distributed along the single-layer wall panel is obtained.

[0136] The propeller aircraft cabin noise SPL is calculated based on the sound transmission loss of a single-layer panel, the turbulent boundary layer noise on the surface of the single-layer panel, and the near-field noise distributed by the propeller along the single-layer panel. If the cabin noise index is not met, the structure and material parameters of the single-layer panel are adjusted and optimized. The above process is repeated until the propeller aircraft cabin noise SPL meets the cabin noise index requirements. The sound transmission loss TL of the single-layer panel and its structure and material parameters are obtained.

[0137] The above-mentioned disclosed method for decomposing and determining the noise index parameters of a single-layer wall panel of a propeller aircraft is based on an open-theory analysis of the sound transmission loss of a single-layer wall panel of a propeller aircraft and the cabin noise under excitation of an external sound source. The cabin noise index is decomposed into a single-layer wall panel. Through iterative calculation of the sound transmission loss and structural and material parameters of the single-layer wall panel, the sound transmission loss and structural and material parameters of the single-layer wall panel that meet the cabin noise index requirements are finally obtained. This method is convenient and efficient and can guide the design of single-layer wall panels during the aircraft development process.

[0138] So far, the technical solution of the present application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of the present application is obviously not limited to these specific embodiments. Without departing from the principles of the present application, those skilled in the art can make equivalent changes or replacements to the relevant technical features, and the technical solutions after these changes or replacements will fall within the scope of protection of the present application.

Claims

1. A method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft, characterized in that: include: Step 1: Calculate the critical frequency of the single-layer wall panel; Step 2: Calculate the sound transmission loss based on the critical frequency of the single-layer wall panel; Step 3: Calculate the turbulent boundary layer noise on the surface of the single-layer wall panel; Step 4: Calculate the near-field noise of the propeller distributed along the single-layer wall panel; Step 5: Calculate the cabin noise of the propeller aircraft based on the sound transmission loss of the single-layer wall panel, the turbulent boundary layer noise on the surface of the single-layer wall panel, and the near-field noise distributed along the single-layer wall panel. Step 6: If the cabin noise of the propeller aircraft cannot meet the cabin noise index requirements, adjust the structure and material parameters of the single-layer wall panel, optimize the structure and material parameters of the single-layer wall panel, and repeat steps 1 to 5 until the cabin noise of the propeller aircraft meets the cabin noise index requirements, and obtain the sound transmission loss of the single-layer wall panel and its structure and material parameters.

2. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 1, characterized in that: The structural parameters of the single-layer wall panel include the section thickness t of the single-layer wall panel.

3. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 2, characterized in that: The material parameters of the single-layer wall panel include the elastic modulus E and Poisson's ratio B of the single-layer wall panel material.

4. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 3, characterized in that: Step 1 is as follows: in f c is the critical frequency of the single-layer wall panel; m is the mass per unit area of ​​a single-layer wall panel; D is the bending stiffness per unit width of a single-layer wall panel; c s is the speed of sound in air on both sides of a single-layer wall panel; φ is the incident angle of the incident sound wave, which is taken as 90°.

5. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 4, characterized in that: In step one: in, E is the elastic modulus of the single-layer siding material; t is the thickness of a single wall panel; B is the Poisson's ratio of the single-layer siding material.

6. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 5, characterized in that: In step 2, the noise cutoff frequency f is less than the critical frequency f of the single-layer wall panel c When , the sound transmission loss TL of a single-layer wall panel is calculated as: in, ω is the angular velocity of the incident wave; ρ0 is the air density.

7. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 6, characterized in that: In step 2, the noise cutoff frequency f is equal to the critical frequency f of the single-layer wall panel c When , the sound transmission loss TL of a single-layer wall panel is calculated as: in, η is the loss factor of the single-layer wall panel structure.

8. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 7, characterized in that: In step 2, the noise cutoff frequency f is greater than the critical frequency f of the single-layer wall panel c When , the sound transmission loss TL of a single-layer wall panel is calculated as:

9. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 8, characterized in that: Step three is as follows: in, TBL is the turbulent boundary layer noise on the surface of a single-layer panel; τ w is the shear stress of the single-layer wall panel; δ * is the displacement thickness of the turbulent boundary layer on the surface of the single-layer panel; U0 is the flight speed.

10. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 9, characterized in that: In step three: in, ρ is the air density; Re δ Calculate intermediate parameters for single-layer panel wall shear stress; υ is the kinematic viscosity of air.

11. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 10, characterized in that: In step three: in, x0 is the distance between the single-layer wall panel and the front end of the machine head.

12. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 11, characterized in that: Step 4 is as follows: Based on the flight status of a propeller aircraft, a propeller near-field noise source model is constructed. The propeller diameter, power, thrust, number of blades, rotational speed, speed of sound, flight speed, ambient temperature, number of propellers, blade width at a radius of 0.8, distance between the wingtip and the single-layer wall panel, and air density are used as key parameters. The near-field noise ROR of the propeller distributed along the single-layer wall panel within the noise cutoff frequency range is obtained.

13. The method for decomposing and determining noise index parameters of a single-layer wall panel of a propeller aircraft according to claim 12, characterized in that: Step 5 is as follows: in, SPL is the cabin noise of propeller aircraft.

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