A method for measuring sonic boom signals in flight tests

Abstract

The invention discloses a method for measuring a sonic boom signal in a flight test, which comprises the following steps: obtaining a measurement position of a ground sonic boom signal according to parameters of a flight Mach number, a flight altitude and an attitude angle, reasonably selecting the position and number of measurement points, and the measuring equipment comprising a capacitive low-frequency microphone, a preamplifier, a data collector and a portable computer. At each measurement point, a plurality of capacitive low-frequency microphones are used and respectively configured with preamplifiers to form a microphone array, the microphone array electrical signal is connected to the data collector, the data collector electrical signal is connected to the portable computer, data collection starts before the aircraft arrives above the measurement area, data collection stops after the sonic boom signal is successfully measured, and the measured sonic boom signal is analyzed and processed within the data collection time period. The invention can realize accurate measurement of ground sonic boom signals of supersonic aircraft.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation aerodynamic flight test, and in particular relates to a flight test sonic boom signal measurement method. Background Art

[0002] The new generation of environmentally friendly supersonic civil aircraft has become a hot research field for the world's aviation powers. The sonic boom problem caused by aircraft flying at supersonic speeds has always been a key technical problem that has plagued 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 for studying sonic boom problems, namely numerical simulation, wind tunnel tests and flight tests. Flight tests that can study sonic boom characteristics under real atmospheric conditions are a direct means of verifying sonic boom prediction technology. They are of great significance to the development of supersonic civil aircraft aerodynamic theory, the establishment of high-precision sonic boom prediction technology, and the exploration of sonic boom suppression methods.

[0003] The measurement research of sonic boom in flight test usually includes two aspects: one is to use detection aircraft or tethered balloon as a platform to measure in the near field, mid-field or far field of supersonic aircraft before the sonic boom signal propagates to the ground; the other is to use acoustic measurement equipment to measure near the ground 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 its destructiveness to ground buildings, it is urgent to invent a method for measuring the ground sonic boom signal of supersonic aircraft. Summary of the invention

[0004] In view of the above shortcomings, the present invention proposes a flight test sonic boom signal measurement method, which can achieve accurate measurement of the ground sonic boom signal of a supersonic aircraft.

[0005] The technology adopted by the present invention is as follows: a flight test sonic boom signal measurement method is as follows: the measurement position of the ground sonic boom signal is calculated according to the parameters of the flight Mach number, the flight altitude and the attitude angle, the measurement point position and the number of the measurement points are reasonably selected, the measurement equipment includes a capacitive low-frequency microphone, a preamplifier, a data collector and a portable computer, at each measurement point, a plurality of capacitive low-frequency microphones are used and respectively configured with preamplifiers to form a microphone array, the microphone array electrical signal is connected to the data collector, the data collector electrical signal is connected to the portable computer, data collection starts before the aircraft arrives above the measurement area, and data collection stops after the sonic boom signal is successfully measured, and the measured sonic boom signal is analyzed and processed within the data collection time period.

[0006] 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, the Mach angle a is calculated and the calculation formula is as follows:

[0007]

[0008] According to the basic theory of geometric acoustics, the sound ray is perpendicular to the Mach cone. Given the flight altitude h and the Mach angle a, the horizontal distance x that the sonic boom signal generated by a supersonic aircraft at a certain position at a certain moment propagates to the ground can be calculated. The calculation formula is as follows:

[0009]

[0010] Thus, the ground measurement position corresponding to the sonic boom signal generated by the supersonic aircraft at this moment and this position is obtained, that is, on the basis of the ground coordinates of the aircraft at this moment, increasing the distance x along the flight direction is the ground measurement position of the sonic boom signal.

[0011] The advantages and beneficial effects of the present invention are: according to the flight parameters, the propagation direction of the sonic boom signal of the supersonic aircraft at any moment and the specific position where it propagates to the ground can be calculated, and the accurate measurement of the ground sonic boom signal of the supersonic aircraft is realized. Brief Description of the Drawings

[0012] Figure 1 is a schematic diagram for calculating the ground measurement position of the sonic boom signal of a supersonic aircraft;

[0013] Figure 2 is a schematic diagram of the system solution for measuring the ground sonic boom signal of a supersonic aircraft;

[0014] Figure 3 is a composition diagram of the sensors for measuring the ground sonic boom signal of a supersonic aircraft;

[0015] 1. Supersonic aircraft, 2. Flight direction, 3. Sound ray, 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 Embodiments

[0016] The following further describes the present invention in detail with reference to the attached drawings and examples.

[0017] Example 1

[0018] As Figures 1-3As shown, a method for measuring sonic boom signals in a flight test is as follows: First, the measurement position of the ground sonic boom signal is calculated based on 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 supersonic aircraft, from a macroscopic scale, the aircraft flying at high altitude can be considered as a point sound source. When the aircraft is flying at supersonic speed, the propagation direction of the sonic boom signal is perpendicular to the Mach cone. According to the parameters of the flight Mach number, flight altitude, and attitude angle, the propagation direction of the sonic boom signal of the supersonic aircraft at any time and the specific position of the propagation to the ground are calculated, and the measurement position of the ground sonic boom signal is obtained accordingly.

[0019] Then, the best measurement system composition scheme is selected according to the characteristics of the sonic boom signal and the test characteristics. Among various types of sound pressure measurement sensors, the capacitive microphone has the advantages of high sensitivity, wide dynamic range, good frequency response characteristics, etc., and because the energy of the sonic boom signal is mainly concentrated in the low frequency, the present invention selects a capacitive low-frequency microphone, and selects a preamplifier and a data collector in matching. The low-frequency microphone and the preamplifier can be connected through an adapter, and the preamplifier and the data collector are connected through a cable. The data collector is connected to a portable computer through a network cable. The data collector is powered by a battery, and the portable computer is used to control the collector and store the sonic boom signal measurement data in real time.

[0020] Finally, the measurement equipment is arranged reasonably according to the specific flight conditions and the environmental conditions of the measurement area to collect and store the ground sonic boom signal data of the supersonic aircraft. At each measurement point, four capacitive low-frequency microphones are used and equipped with preamplifiers respectively. They 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 starts before the aircraft arrives above the measurement area, and stops after the sonic boom signal is successfully measured. The measured sonic boom signal is analyzed and processed during the data collection period.

[0021] Example 2

[0022] A method for measuring sonic boom signals in a flight test is as follows: First, the measurement position of the ground sonic boom signal is calculated based on the flight parameters of the supersonic aircraft. The Mach angle a can be calculated based on the flight Mach number M (M>1), and the calculation formula is as follows:

[0023]

[0024] According to the basic theory of geometric acoustics, the sound ray is perpendicular to the Mach cone. Given the flight altitude h and the Mach angle a, the horizontal distance x that the sonic boom signal generated by a supersonic aircraft at a certain position at a certain moment propagates to the ground can be calculated. The calculation formula is as follows:

[0025]

[0026] Thus, the ground measurement position corresponding to the sonic boom signal generated by the supersonic aircraft at this moment and this position is obtained, that is, on the basis of the ground coordinates of the aircraft at this moment, increasing the distance by x along the flight direction is the ground measurement position of the sonic boom signal.

[0027] Then, select the best measurement system composition scheme according to the characteristics of the sonic boom signal and the test characteristics. 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 is connected to the preamplifier through an adapter. The low-frequency microphone is wrapped with a windscreen to reduce the influence of wind noise. The microphone is connected to the data collector through a cable, and the data collector is connected to a portable computer through a network cable. The data collector is powered by a built-in battery, and the portable computer is used to control the collector and store the sonic boom signal measurement data in real time.

[0028] Finally, reasonably arrange the measurement equipment according to the specific flight conditions and the environmental conditions of the measurement area, and collect and store the ground sonic boom signal data of the supersonic aircraft. According to the geographical location and environmental conditions of the measurement area, reasonably select the measurement point positions and the number of measurement points. At each measurement point, four capacitive 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. The data collector is connected to a portable computer through a network cable. The four microphones can be arranged on a flat plate with a large enough area, or the four microphones can be fixed at a certain height from the ground by a bracket. According to the battery life of the measurement equipment, start collecting data before the aircraft reaches the airspace above the measurement area, stop collecting data after successfully measuring the sonic boom signal, and analyze and process the measured sonic boom signal during the data collection period.

Claims

1. A method for measuring sonic boom signals in flight tests, characterized in that, The measurement method is as follows: Calculate the measurement position of the ground sonic boom signal based on the parameters of flight Mach number, flight altitude, and attitude angle. Reasonably select the measurement point positions and the number of measurement points. The measurement equipment includes a capacitive low-frequency microphone, a preamplifier, a data collector, and a portable computer. 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, and the electrical signals of the data collector are connected to the portable computer. Start collecting data before the aircraft reaches the airspace above the measurement area and stop collecting data after successfully measuring the sonic boom signal. Analyze and process the measured sonic boom signal within the time period of data collection; The specific calculation method of the measurement position of the ground sonic boom signal is as follows: According to the flight Mach number M, where M > 1, calculate the Mach angle a. The calculation formula is as follows: a = arcsin(1 / M) According to the basic theory of geometric acoustics, the sound ray is perpendicular to the Mach cone. From the flight altitude h and the Mach angle a, calculate the horizontal distance x at which the sonic boom signal generated by the supersonic aircraft at a certain position at a certain moment propagates to the ground. The calculation formula is as follows: x = h · tan(a) Thus, the measurement position of the ground sonic boom signal corresponding to the sonic boom signal generated by the supersonic aircraft at this moment and this position is obtained, that is, on the basis of the ground coordinates of the aircraft at this moment, increase the distance x along the flight direction, which is the measurement position of the ground sonic boom signal.

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