CN110779616A - A flight test sonic boom signal measurement method - Google Patents

Abstract

The invention discloses a method for measuring a sonic boom signal in a flight test. Capacitive low-frequency microphones, preamplifiers, data collectors and portable computers. At each measurement point, multiple capacitive low-frequency microphones are used and preamplifiers are respectively configured to form a microphone array. The electrical signals of the microphone array are connected to the data collector. Data acquisition The electrical signal is connected to the portable computer, and the data is collected before the aircraft reaches the sky above the measurement area. After the sonic boom signal is successfully measured, the data collection is stopped, and the measured sonic boom signal is analyzed and processed from the time period of data collection. The invention can realize the accurate measurement of the ground sound explosion signal of the supersonic aircraft.

Description

A method for measuring sonic boom signal in flight test

technical field

The invention belongs to the technical field of aero-aerodynamic flight tests, in particular to a method for measuring sonic boom signals in a flight test.

Background technique

The new generation of environmentally friendly supersonic civil aircraft has become a hot research field for aviation powers in the world. The sonic boom problem caused by aircraft flying at supersonic speed has always been a key technical problem that plagues the development of supersonic civil aircraft. High-precision and high-reliability sonic boom prediction technology is the basis for the aerodynamic layout design of low-sonic boom supersonic civil aircraft. There are three main methods to study the sonic boom problem, namely numerical simulation, wind tunnel test and flight test. The flight test that can study the sonic boom characteristics under real atmospheric conditions is a direct verification method for the sonic boom prediction technology. Aerodynamic theory, establishment of high-precision sonic boom prediction technology, and exploration of sonic boom suppression methods are all of great significance.

The measurement study of the sonic boom problem in flight tests usually includes two aspects: first, before the sonic boom signal propagates to the ground, in the near-field, mid-field or far-field of the supersonic vehicle, the detection aircraft or the tethered balloon is used as a platform to carry out Measurement; the second is to use acoustic measurement equipment near the ground to measure after the sonic boom signal propagates to the ground. Since the ground sonic boom signal is directly related to people's intuitive perception of sonic boom noise and the damage to ground buildings, it is urgent to invent a method for measuring the ground sonic boom signal of supersonic aircraft.

SUMMARY OF THE INVENTION

Based on the above shortcomings, the present invention proposes a method for measuring the sonic boom signal of a flight test, which can realize the accurate measurement of the ground sonic boom signal of a supersonic aircraft.

The technology adopted in the present invention is as follows: a method for measuring the sonic boom signal of a flight test, as follows: the measurement position of the ground sonic boom signal is obtained by calculating the parameters of the flight Mach number, the flight height and the attitude angle, and the position of the measurement point and the measurement point are reasonably selected. Quantity, the measurement equipment includes capacitive low-frequency microphones, preamplifiers, data collectors and portable computers. At each measurement point, multiple capacitive low-frequency microphones are used and preamplifiers are respectively configured to form a microphone array, and the electrical signals of the microphone arrays are connected to data. The collector, the data collector is connected to the portable computer for electrical signals, starts to collect data before the aircraft reaches the sky above the measurement area, stops collecting data after the sonic boom signal is successfully measured, and analyzes and processes the measured sonic boom from the time period of data collection. Signal.

The specific calculation method of the measurement position of the ground sonic boom signal is as follows: According to the flight Mach number M, M>1, calculate and obtain the Mach angle a, and the calculation formula is as follows:

According to the basic theory of geometric acoustics, the sound ray and the Mach cone are perpendicular to each other. From the flight height h and the Mach angle a, calculate the horizontal distance x that the sonic boom signal generated by the supersonic vehicle at a certain position at a certain time propagates to the ground. The calculation formula as follows:

Therefore, the measurement position of the ground sonic boom signal corresponding to the sonic boom signal generated by the supersonic aircraft at this position at this moment is obtained, that is, the ground sonic boom signal measurement position is increased by x distance along the flight direction on the basis of the ground coordinates of the aircraft at this moment. .

The advantages and beneficial effects of the invention are: according to the flight parameters, the propagation direction of the supersonic aircraft sonic boom signal and the specific position on the ground can be calculated at any time, and the accurate measurement of the supersonic aircraft ground sonic boom signal can be realized.

Description of drawings

Fig. 1 is a schematic diagram of the calculation of the measurement position of the ground sonic boom signal of a supersonic aircraft;

Figure 2 is a schematic diagram of a supersonic vehicle ground sonic boom signal measurement system;

Figure 3 is a composition diagram of a sensor for measuring the ground sonic boom signal of a supersonic vehicle;

1. Supersonic vehicle, 2. Flight direction, 3. Sound rays, 4. Ground, 5. Mach cone, 6. Measurement position, 7. Microphone array, 8. Data collector, 9. Portable computer, 10. Windshield, 11, low frequency microphone, 12, adapter, 13, preamplifier.

Detailed ways

The present invention will be described in further detail below with reference to the accompanying drawings.

Example 1

As shown in Figure 1-3, a flight test sonic boom signal measurement method is as follows: First, the measurement position of the ground sonic boom signal is calculated according to the flight parameters of the supersonic aircraft. According to the basic theory of geometric acoustics, the sound ray and the wavefront are perpendicular to each other, and the tangent direction of any point on the sound ray represents the propagation direction of the sound signal. Specifically, for a supersonic vehicle, a high-altitude aircraft can be regarded as a point sound from a macroscopic scale. source, when the aircraft is in supersonic flight, the propagation direction of the sonic boom signal is perpendicular to the Mach cone. According to the parameters of the flight Mach number, flight height, and attitude angle, the propagation direction of the sonic boom signal of the supersonic aircraft at any time and the specific transmission to the ground are calculated. position, according to which the measurement position of the ground sonic boom signal is obtained.

Then, according to the characteristics of the sonic boom signal and the characteristics of the test, the best measurement system composition scheme is selected. Among various types of sound pressure measurement sensors, capacitive microphones have the advantages of high sensitivity, wide dynamic range, and good frequency response characteristics, and because the energy of the sonic boom signal is mainly concentrated in low frequencies, the capacitive low-frequency microphone is selected in the present invention. , choose the preamplifier and the data collector, the low-frequency microphone and the preamplifier can be connected through an adapter, the preamplifier and the data collector can be connected by a cable, and the data collector and the portable computer can be connected through a network cable. The data collector is powered by a battery, and a portable computer is used to control the collector and store the measurement data of the sonic boom signal in real time.

Finally, according to the specific flight conditions and the environmental conditions of the measurement area, the measurement equipment is reasonably arranged to collect and store the ground sonic boom signal data of the supersonic vehicle. At each measurement point, four condenser-type low-frequency microphones are used and preamplifiers are configured respectively, which are connected to a four-channel data collector through four cables, and the data collector is connected to a portable computer through a network cable. . According to the battery life of the measurement equipment, data collection is started before the aircraft reaches the sky above the measurement area, and data collection is stopped after the sonic boom signal is successfully measured, and the measured sonic boom signal is analyzed and processed from the time period of data collection.

Example 2

A method for measuring the sonic boom signal in a flight test is as follows: First, the measurement position of the ground sonic boom signal is calculated according to the flight parameters of the supersonic aircraft. According to the flight Mach number M (M>1), the Mach angle a can be calculated and obtained. The calculation formula is as follows:

According to the basic theory of geometric acoustics, the sound ray and the Mach cone are perpendicular to each other. From the flight height h and the Mach angle a, the horizontal distance x of the sonic boom signal generated by the supersonic vehicle at a certain position at a certain time can be calculated. The formula is as follows:

Therefore, the measurement position of the ground sonic boom signal corresponding to the sonic boom signal generated by the supersonic aircraft at this position at this moment is obtained, that is, the ground sonic boom signal measurement position is increased by x distance along the flight direction on the basis of the ground coordinates of the aircraft at this moment. .

Then, according to the characteristics of the sonic boom signal and the characteristics of the test, the best measurement system composition scheme is selected. Since the energy of the sonic boom signal is mainly concentrated in the low frequency, a capacitive low-frequency microphone is selected as the ground sonic boom signal measurement sensor. The low-frequency microphone and the preamplifier are connected through an adapter, and the low-frequency microphone is wrapped with a wind cover to reduce wind noise. influences. The microphone is connected with the data collector through a cable, and the data collector is connected with the portable computer through a network cable. The data collector is powered by a built-in battery, and a portable computer is used to control the collector and store the measurement data of the sonic boom signal in real time.

Finally, according to the specific flight conditions and the environmental conditions of the measurement area, the measurement equipment is reasonably arranged to collect and store the ground sonic boom signal data of the supersonic vehicle. According to the geographical location and environmental conditions of the measurement area, the location and number of measurement points should be reasonably selected. At each measurement point, four condenser-type low-frequency microphones are used and preamplifiers are respectively configured to form a microphone array, which is connected to a four-channel data collector through four cables, and the data collector is connected to a portable device through a network cable. When the computer is connected, the four microphones can be arranged on a flat plate with a large enough area, or a bracket can be used to fix the four microphones at a certain height from the ground. According to the battery life of the measurement equipment, data collection is started before the aircraft reaches the sky above the measurement area, and data collection is stopped after the sonic boom signal is successfully measured, and the measured sonic boom signal is analyzed and processed from the time period of data collection.

Claims (2)

1. A flight test sonic boom signal measurement method is characterized by comprising the following steps: the measuring device comprises capacitance type low-frequency microphones, a preamplifier, a data collector and a portable computer, wherein a plurality of capacitance type low-frequency microphones are adopted at each measuring point, the preamplifiers are respectively configured to form a microphone array, the microphone array is electrically connected with the data collector, the data collector is electrically connected with the portable computer, the data collection is started before an aircraft reaches the upper space of a measuring area, the data collection is stopped after the sonic boom signal is successfully measured, and the sonic boom signal obtained by measurement is analyzed and processed in the data collection time period.

2. The method for measuring the sonic boom signal in the flight test according to claim 1, characterized in that: the specific calculation method for the measurement position of the ground sonic boom signal is as follows: according to the flight Mach number M, M is larger than 1, the Mach angle a is obtained through calculation, and the calculation formula is as follows:

according to the basic theory of geometric acoustics, the acoustic ray is perpendicular to the Mach cone, the horizontal distance x of the acoustic explosion signal generated by the supersonic aircraft at a certain position at a certain moment and transmitted to the ground is calculated according to the flight altitude h and the Mach angle a, and the calculation formula is as follows:

therefore, the ground sonic boom signal measuring position corresponding to the sonic boom signal generated by the supersonic aircraft at the position at the moment is obtained, namely the ground sonic boom signal measuring position is obtained by increasing the x distance along the flight direction on the basis of the ground coordinate of the supersonic aircraft at the moment.

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