CN-114818114-B - Device and method for simulating sound source of air inlet channel of aircraft APU (auxiliary Power Unit)

CN114818114BCN 114818114 BCN114818114 BCN 114818114BCN-114818114-B

Abstract

The invention discloses an aircraft APU air inlet channel sound source simulation device and a simulation method, and belongs to the technical field of aircraft noise testing. The aircraft APU air inlet sound source simulation device comprises a loudspeaker, a waveguide tube, a fixed connection assembly, a measuring microphone and an electric and signal control assembly, wherein the measuring microphone and the waveguide tube are fixed on the fixed connection assembly, the loudspeaker is fixed on the waveguide tube, one end of the electric and signal control assembly is connected with the measuring microphone, the other end of the electric and signal control assembly is connected with the loudspeaker, and the aircraft APU air inlet sound source simulation method comprises a method for simulating an acoustic mode sound source and a method for simulating broadband noise/single-frequency noise. The invention aims at the acoustic mode generating device in the rectangular pipeline of the APU air inlet channel, and the control method part has great innovation in an equation set formed by response functions.

Inventors

ZHANG TAO
ZHANG YINGZHE
LIN DAKAI
ZHANG WEIGUANG

Assignees

中国商用飞机有限责任公司北京民用飞机技术研究中心
中国商用飞机有限责任公司

Dates

Publication Date: 20260512
Application Date: 20220318

Claims (7)

1. A sound source simulation device in a rectangular pipeline of an aircraft APU air inlet is characterized by comprising a loudspeaker, a waveguide tube, a fixed connection assembly, a measuring microphone and an electric and signal control assembly, Wherein the measurement microphone and the waveguide are fixed on the fixed connection assembly; wherein the speaker is fixed on the waveguide; Wherein one end of the electric and signal control component is connected with the measuring microphone, and the other end is connected with the loudspeaker; The fixed connection assembly comprises a first silencing terminal, a transition section pipeline, an acoustic mode generator main pipeline, a first microphone array installation pipeline, an APU air inlet channel test pipeline or an acoustic liner, a second microphone array installation pipeline and a second silencing terminal which are connected in sequence, wherein the first silencing terminal comprises a first silencing terminal pipeline, a second silencing terminal pipeline and a first sound absorption sponge and a second sound absorption sponge which are respectively positioned on the first silencing terminal pipeline and the second silencing terminal pipeline; The upper end of the waveguide tube is a cylindrical section, the diameter of the waveguide tube is matched with the diameter of a sound head of the loudspeaker, the loudspeaker is connected and fixed with the upper end of the waveguide tube, meanwhile, sealing measures are taken to avoid the occurrence of sound leakage, the middle of the waveguide tube is a cylindrical throat, the diameter of the throat is smaller than that of the upper end, high-order sound modes are cut off, only plane waves pass through the throat, the lower end of the waveguide tube is a gradually expanding conical surface, in order to reduce interference with the size of an adjacent waveguide tube, the two ends of the waveguide tube are cut flat, and the end face of an outlet is approximately rectangular.
2. The device for simulating sound sources in a rectangular duct of an aircraft APU inlet according to claim 1, wherein the waveguide is fixed in a main duct of an acoustic mode generator, and the measurement microphone is inserted into a mounting hole of the first/second microphone array mounting duct to be directly pluggable.
3. A method for simulating an acoustic source of an APU air intake duct of an aircraft, the simulation method operating based on an acoustic source simulation device in a rectangular duct of an APU air intake duct of an aircraft according to claim 1 or 2, the simulation method comprising method 1 for acoustic modal acoustic source simulation and method 2 for broadband noise/single frequency noise simulation; The method 1 for simulating the acoustic modal sound source comprises the following steps: step 11, calculating the voltage signal amplitude and phase required by each loudspeaker by using a loudspeaker input voltage signal calculation method according to the target acoustic modal amplitude, modal order and frequency; step 12, inputting a measurement and control program and starting according to the amplitude and the phase of the voltage signal, generating a voltage signal through a signal generating card, amplifying the voltage signal through a power amplifier, driving a loudspeaker to sound, and generating an acoustic mode under the set frequency under the combined action of an array formed by the loudspeaker; Step 13, collecting noise signals of an array formed by microphones by using a measurement and control program and a data acquisition card, calculating acoustic modes in a pipeline by using an acoustic mode decomposition program, and determining whether the required acoustic modes are generated or not; step 14, repeating the steps 11-13 for the next group of test targets; the method 2 for broadband noise/single-frequency noise simulation comprises the following steps: step 21, generating white noise signals with specified amplitude and frequency range or sine wave signals under single frequency by using a signal generating card, and driving a loudspeaker array to generate a sound source through a power amplifier; Step 22, collecting noise signals of an array formed by microphones by using a measurement and control program and a data acquisition card, measuring sound pressure levels at different positions in a pipeline, further calculating sound power levels in the pipeline, and determining insertion loss and transmission loss of a tested noise elimination component as evaluation indexes of noise reduction quantity; step 23, repeating the steps 21-22 for the next group of test targets.
4. The method for simulating the sound source of the air intake duct of the APU of the aircraft according to claim 3, wherein in the step 11, the method for calculating the input voltage of the speaker is as follows: Step 111, according to the propagation theory of the vibration sound source in the pipeline, establishing a response function relation between the vibration speed of sound particles on the end surface of the waveguide tube outlet and the sound pressure of any point in the pipeline; step 112, determining the acoustic mode distribution function and the transmissible acoustic mode order in the pipeline; Step 113, establishing an acoustic mode generation control equation set ax=b, wherein A is an equation set coefficient matrix, and b is a column vector formed by a target control acoustic mode; Step 114, calculating a matrix A of acoustic mode generation control equation set, wherein the number M of matrix lines is the total number of acoustic modes transmitted at a set frequency, the number N of columns is the number of loudspeakers, and M is less than or equal to N according to the existing equation set with a solution condition; Step 115, constructing a target acoustic mode column vector according to the target acoustic mode, wherein the number of lines is M; step 116, solving a linear equation set ax=b to obtain a velocity column vector x of sound particles at the end face of the waveguide tube, wherein the number of the rows corresponds to the number N of the loudspeakers; Step 117, determining the response relationship between the input voltage of each loudspeaker and the sound particle velocity of the end face of the waveguide outlet under different frequencies by using a calibration test method; step 118, calculating the input voltage value of each loudspeaker, including amplitude and phase, by using the response relation determined in step 117.
5. The method for simulating the sound source of an APU air intake duct of an aircraft according to claim 4, wherein in step 111, a response function relationship between the vibration velocity of sound particles on the outlet end face of the waveguide and the sound pressure at any point in the pipeline is as follows: wherein: -air density; -the frequency of the circle, ; -Test frequency; -main conduit cross-sectional area; -acoustic modal order, long side and short side respectively; -sound particle vibration volume velocity; -the area of the waveguide outlet end face; -a modal shape function; -acoustic mode normalization coefficients; -acoustic mode wave number; -any point position coordinates in the main pipe; the acoustic source coefficients of the waveguide outlet cross section are respectively corresponding to the acoustic mode orders Waveguide cross-sectional dimension in z-coordinate direction Correlation; -the imaginary number unit of the whole number, ; -The z-direction coordinate of the geometrical center position of the waveguide outlet end face; for an array formed by a plurality of loudspeakers, the sound pressure of any point in a pipeline is as follows: wherein: -total number of loudspeakers; -the i-th waveguide outlet end face sound particle vibration volume velocity; the area of the outlet end face of the ith waveguide tube, -The sound source coefficients of the i-th waveguide outlet end face, respectively.
6. The method for simulating an aircraft APU inlet sound source according to claim 4, wherein in step 112, the in-pipeline acoustic mode distribution function is: Wherein, the -Incident wave mode amplitude; -reflected wave mode amplitude; Is a natural index; For a transmissible mode of a certain order, its cut-off frequency The method comprises the following steps: Wherein, the -The long side dimension of the main pipe of the acoustic mode generator; -the short side dimension of the main pipe of the acoustic mode generator; -sound speed; Starting from 0, respectively, the cut-off frequency is smaller than the test frequency All acoustic modes of (a) can be transmitted in the pipeline, and the maximum mode order of the acoustic modes which can be transmitted in the long side direction of the rectangular pipeline is recorded as The transmissible maximum mode order of the short side direction of the rectangular pipeline is recorded as 。
7. The method for simulating an aircraft APU intake channel sound source of claim 4, wherein in step 113, the set of coefficients a is: The coefficient matrix is: the matrix of the variables to be solved is x, which represents the average sound particle vibration speed of the end face of the waveguide tube outlet: matrix composed of target control acoustic mode matrix: 。

Description

Device and method for simulating sound source of air inlet channel of aircraft APU (auxiliary Power Unit) Technical Field The invention belongs to the technical field of airplane noise testing, relates to a sound source device required in a laboratory testing stage in an airplane APU air inlet channel acoustic liner research and development test, and particularly relates to an airplane APU air inlet channel sound source simulation device and a simulation method. Background The APU (auxiliary power unit) of an aircraft starts working when passengers get on and off the airport, and is a main apron noise source. Similar to an aircraft engine, acoustic liners may be installed in its intake tract to achieve noise reduction. The APU intake channel noise propagates outwardly in the form of a pipe acoustic mode. In the development test of the acoustic liner of the air inlet channel of the APU, a set of acoustic source devices is required to generate acoustic modes of the APU. Unlike aircraft nacelle inlet channels, APU inlet channel cross-sectional shapes are rectangular. In the scheme of the prior art 1, aiming at the acoustic mode generating device of the annular pipeline, as shown in fig. 1, a plurality of annular speaker arrays are arranged along the axial direction of the mode excitation pipeline, each annular speaker array comprises a plurality of speakers arranged along the circumferential direction of the mode excitation pipeline, in the control method, the contribution of each speaker to the acoustic mode is determined according to the installation position of the speaker, an equation set of a sound source and a mode coefficient is constructed, the sound source information is obtained through solving, and the speakers are controlled to sound to form a specific acoustic mode. Prior art 2 describes NASA Curved Duct Test Rig (CDTR) devices (FIG. 2) that generate acoustic modes in rectangular ducts with a cross section of 0.152m by 0.381m using 16 loudspeakers with a maximum controllable frequency of 2500Hz and a controllable acoustic mode order of long side 5 and short side 2. The method adopts a filtered-X LMS algorithm aiming at the control method part of the acoustic mode. Firstly, the response relation of 31 microphones of a single loudspeaker on the wall surface of a pipeline to form an array is measured to form a transfer function matrix. And calculating the sound pressure of the target sound mode at the microphone position, and correcting the input value of the loudspeaker end by using the transfer function matrix according to the sound pressure obtained by actual measurement until the expected target sound mode is obtained. In the prior art 1, aiming at a circular/annular pipeline, sound source simulation in a rectangular pipeline such as an APU air inlet channel cannot be realized. And NASA CDTR device employs a measurement-feedback control algorithm. The sound pressure of the microphone array in the pipeline is measured in advance and compared with the expected sound pressure, and the feedback is carried out through a computer program until the control of the target sound mode is realized. The main disadvantage is that this feedback mechanism requires a certain time, in particular an array of loudspeakers, which requires a very high efficiency of the feedback algorithm and does not guarantee a certain convergence. In testing of a large number of conditions, a long test time is required to complete the test. Disclosure of Invention In order to solve the problems, the invention provides an aircraft APU air inlet channel sound source simulation device and a simulation method. Compared with the prior art, the invention aims at the acoustic mode generating device in the rectangular pipeline of the APU air inlet channel, controls the method part, and has great innovation in an equation set formed by response functions. Meanwhile, the transfer function relation between the input voltage of the loudspeaker and the acoustic mode is directly established by a method combining theoretical deduction and measurement, the input voltage of the loudspeaker is directly calculated according to the amplitude of the target acoustic mode, and then the corresponding value is directly input into measurement and control software, so that the expected acoustic mode can be obtained. The process of obtaining the target acoustic mode is quicker than using a measurement-feedback control algorithm. According to a first aspect of the invention, there is provided an aircraft APU inlet sound source simulation device comprising a loudspeaker, a waveguide, a fixed connection assembly, a measurement microphone and an electrical and signal control assembly, Wherein the measurement microphone and the waveguide are fixed on the fixed connection assembly; wherein the speaker is fixed on the waveguide; And one end of the electric and signal control component is connected with the measuring microphone, and the other end of the electric and s