JPH07209067A - Method and device for analyzing operation sound of jet engine - Google Patents

Abstract

PURPOSE:To provide a method and device for analyzing operation sound of a jet engine, which can specify the cause for generating the specified sound on the basis of the operation sound of the jet engine. CONSTITUTION:The device is provided with a reference microphone 12 fitted to a part near an opening part 1a of a jet engine 1, a cylindrical duct 14, of which one end is adhered to the opening part 1a of the jet engine 1 and of which the other end is opened and which is arranged concentrically with the jet engine 1, and a measuring microphone 16 fitted to the duct 14. The duct 14 is rotated around an axis Z thereof, and while pressure 7 of the operation sound of the jet engine 1 is measured by the reference microphone 12 and the measuring microphone 16, and a phase difference of the operation sound is computed on the basis of the pressure measured.by the reference microphone 12 and the measuring microphone 16, and a mode of the operation sound is computed on the basis of this phase difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of analyzing a driving sound generated by a jet engine and an analyzer using this method.

[0002]

2. Description of the Related Art A jet engine 1 has, as shown in FIG. 4, a fan 2 rotating at a high speed, a stator 3 fixed to the rear of the fan, a strut 4 located further behind, and the like. Generates various driving sounds.
In the conventional analysis means, as illustrated in FIG. 5, a large number of microphones 5 are arranged so as to surround the jet engine 1 and the sound insulation plate 6 is provided.
Therefore, the front or rear sound of the jet engine is shielded, and the driving sound propagating to the front or rear of the jet engine is measured. The driving sound measured by such means is shown in FIG.
It is displayed in the relationship between the frequency and the pressure (sound pressure) of the operating noise as illustrated in, for example, from this figure, in 75% NLD (NLD is the rated rotation speed of the fan), there is a peak portion of the pressure indicated by the arrow, It can be confirmed that an offensive high-frequency sound (a squealing sound) is generated at this frequency.

[0003]

However, the operating noise of the jet engine is, for example, a noise generated by a fan, an interference noise between a fan and a stator, an interference noise between a fan and a strut, or a moving blade of the internal turbine, a static noise. It is a sound generated by a wing or the like and an interference sound. Since the above-mentioned conventional analysis means measure these sounds in a mixed state, it is not possible to specify the cause of generation of a specific sound (for example, the above-mentioned annoying high-frequency sound). There was a problem.

The present invention was created to solve such problems. That is, it is an object of the present invention to provide a jet engine driving sound analysis method and device capable of identifying a cause of generation of a specific sound (for example, the above-mentioned offensive high-frequency sound) from the driving sound of the jet engine. .

[0005]

According to the present invention, a reference microphone mounted in the vicinity of an opening of a jet engine and an inner surface flush with the opening, one end of which closely contacts the opening of the jet engine. A cylindrical duct having the other end open and arranged concentrically with the jet engine, and a measurement microphone attached to the duct are provided, and the reference microphone and the measurement are performed while rotating the duct about its axis. A microphone measures the pressure of the driving sound of the jet engine, the phase difference of the driving sound is calculated from the pressure measured by the reference microphone and the measurement microphone, and the number of modes of the driving sound is calculated from the phase difference. A jet engine driving sound analysis method is provided.

Further, according to the present invention, in the vicinity of the opening portion of the jet engine, a reference microphone having an inner end flush with the inner surface of the jet engine and an inner surface flush with the opening portion are provided. Is in close contact with the opening of the jet engine, the other end is open, and is arranged concentrically with the jet engine and is rotated about its axis, and the inner end is flush with the inner surface of the duct. A plurality of measurement microphones that are attached and arranged at intervals in the axial direction, a phase analyzer that calculates the phase difference of the driving sound from the pressure measured by the reference microphone and the measuring microphone, and a driving sound from the phase difference And a calculator for calculating the number of modes of the jet engine, by which the pressure of the operation sound of the jet engine is measured by the reference microphone and the measurement microphone while rotating the duct about its axis, and the phase of the operation sound from the pressure is measured. And calculates the number of modes of operation noise from the phase difference, the operation sound analysis unit for a jet engine is provided, characterized in that.

[0007]

According to the above-mentioned structure of the present invention, the jet engine is rotated while the duct is rotated about the axis by the reference microphone mounted near the opening of the jet engine and the measurement microphone mounted on the cylindrical duct. By measuring the pressure of the driving sound, the pressure distribution of the driving sound propagating in the circumferential direction of the duct can be measured, and the frequency of the driving sound (in other words, the number of modes) can be calculated. That is, by calculating the phase difference of the driving sound propagated to the duct and calculating the number of modes of the driving sound from the phase difference, a specific driving sound is generated from this number of modes, that is, the sound generated by the fan, the fan and the stator. Whether the sound is an interference sound or an interference sound between a fan and a strut can be specified from the number of modes (frequency).

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. In the drawings, common parts are designated by the same reference numerals and used. FIG. 1 is an overall configuration diagram of a jet engine driving sound analysis apparatus according to the present invention.
In this figure, an analysis device 10 of the present invention shows a reference microphone 12 mounted near the opening 1 a of a jet engine 1.
And a cylindrical duct 14 arranged concentrically with the jet engine 1, and a measurement microphone 16 attached to the duct 14.

The reference microphone 12 has its inner end flush with the inner surface of the jet engine 1. The cylindrical duct 14 has an inner surface that is flush with the opening 1a of the jet engine 1, one end of which is in close contact with the opening of the jet engine 1 and the other end of which is open. Also, this cylindrical duct 14
The rotation drive motor 15 rotates about the axis. In addition, the measurement microphones 16 are mounted such that their inner ends are flush with the inner surface of the duct 14, and a plurality of measurement microphones 16 are arranged at intervals in the axial direction of the duct 14.

Further, the analyzing apparatus 10 of the present invention comprises an amplifier 17 for amplifying the pressure measured by the reference microphone 12 and the measuring microphone 16, and a phase analyzer 18 for calculating the phase difference of the driving sound from the pressure. And a calculator 20 for calculating the number of modes of the driving sound from the phase difference. The reference microphone 12, the measurement microphone 16, and the amplifier 17 are connected with a measurement cable, and the measurement cable has sufficient slack so that the cylindrical duct 14 can be rotated within a range necessary for measurement. It has become. In addition, using a slip ring, etc.
The cylindrical duct 14 may be endlessly rotatable. The calculation result of the calculator 20 is output to an appropriate output device (not shown) such as a printer, a CRT, or another calculation device.

FIG. 2 is a diagram schematically showing the analysis method according to the present invention. In this figure, the pressure 7 of the operating noise of the jet engine is propagated in the duct 14 in the axial direction of the duct 14 while swirling around the axis Z, for example.
According to the method of the present invention, the reference microphone 12 and the measurement microphone 16 are rotated while rotating the duct 14 about its axis Z.
The pressure 7 of the driving sound of the jet engine is measured with, the phase difference of the pressure 7 is calculated from the pressures measured by the reference microphone 12 and the measurement microphone 16, and the mode number of the driving sound is calculated from this phase difference (in this figure, Calculate number = 5). The frequency may be calculated from the phase difference.

In addition, a plurality of measuring microphones 16 and reference microphones 12 arranged in the axial direction of the duct 14 are connected to the duct 14.
It is also possible to measure the pressure 7 of the operating noise of the jet engine propagating in the axial direction of, and calculate the same mode number (or frequency).

FIG. 3 shows the relationship between the number of modes of the operating noise of the jet engine and the amplitude of the pressure wave obtained by the method and apparatus of the present invention. The horizontal axis indicates the number of operating noise modes. The vertical axis represents the dimensionless pressure wave amplitude.
From this figure, the number of modes (frequency) included in the operating noise of the jet engine can be specified. From this number of modes, the specific operating noise is generated by the fan, the interference noise between the fan and the stator, or the fan noise. Whether the sound is an interference sound with a strut can be specified from the number of modes (frequency).

As described above, according to the method and apparatus of the present invention, the duct is centered on the axial center by the reference microphone mounted near the opening of the jet engine and the measurement microphone mounted in the cylindrical duct. By measuring the pressure of the operating noise of the jet engine while rotating the jet engine, the pressure distribution of the operating noise propagating in the circumferential direction of the duct can be measured and the frequency (number of modes) of the operating noise can be calculated. That is, by calculating the phase difference of the driving sound propagated to the duct and calculating the number of modes of the driving sound from the phase difference, a specific driving sound is generated from this number of modes, that is, the sound generated by the fan, the fan and the stator. Whether the sound is an interference sound or an interference sound between a fan and a strut can be specified from the number of modes (frequency).

The present invention is not limited to the above embodiment,
Of course, various modifications can be made without departing from the spirit of the present invention.

[0016]

As described above, the method and apparatus of the present invention have an excellent effect of being able to identify the cause of generation of a specific sound (for example, the above-mentioned annoying high frequency sound) from the running sound of the jet engine. .

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a jet engine driving sound analysis apparatus according to the present invention.

FIG. 2 is a diagram schematically showing an analysis method according to the present invention.

FIG. 3 is a graph showing the relationship between the number of modes of operation noise of a jet engine and the amplitude of a pressure wave obtained by the method and device of the present invention.

FIG. 4 is a diagram showing a configuration of a jet engine.

FIG. 5 is a diagram showing a conventional analysis means.

FIG. 6 is an example of a measurement result by a conventional analysis means.

[Explanation of symbols]

 1 Jet Engine 1a Opening 2 Fan 3 Stator 4 Strut 5 Microphone 6 Sound Insulation Plate 7 Driving Sound 10 Analysis Device 12 Reference Microphone 14 Duct 15 Rotation Drive Motor 16 Measurement Microphone 17 Amplifier 18 Phase Analyzer 20 Computer Z Axis Center

Claims (2)

[Claims] 1. A reference microphone mounted in the vicinity of an opening of a jet engine, and an inner surface flush with the opening, one end being in close contact with the opening of the jet engine and the other end being open.
It also has a cylindrical duct arranged concentrically with the jet engine, and a measurement microphone attached to the duct. While rotating the duct around its axis, the reference microphone and the measurement microphone drive the jet engine The jet engine driving sound is characterized in that the pressure difference between the driving sound is calculated from the pressures measured by the reference microphone and the measurement microphone, and the mode difference of the driving sound is calculated from the phase difference. analysis method. 2. A reference microphone, the inner end of which is mounted flush with the inner surface of the jet engine, in the vicinity of the opening of the jet engine; and an inner surface flush with the opening, one end of which has the opening of the jet engine. A cylindrical duct that is in close contact with the jet engine and is open at the other end and that is concentric with the jet engine and that rotates about its axis; and that the inner end is flush with the inner surface of the duct and is attached to the duct, and the axial direction A plurality of measurement microphones arranged at intervals, a phase analyzer that calculates the phase difference of the driving sound from the pressure measured by the reference microphone and the measurement microphone, and the number of modes of the driving sound from the phase difference With a computer, by which, while rotating the duct about its axis, the pressure of the operating noise of the jet engine is measured by the reference microphone and the measurement microphone, the phase difference of the operating noise is calculated from the pressure, and the phase is calculated. To calculate the number of modes of operation noise from the operating noise analyzer a jet engine, characterized in that.