A bidirectional airspeed measurement device and method based on triple differential pressure measurement

Abstract

The present invention discloses a bidirectional airspeed measurement device and method based on triple differential pressure measurement. The device comprises a venturi tube (1), wherein the front straight pipe section, the throat section, and the rear straight pipe section of the venturi tube (1) are all provided with a pressure sampling assembly (2); the pressure sampling assembly (2) comprises a pressure sampling annular gap (21), one end of the pressure sampling annular gap (21) is connected to the venturi tube (1), and the other end is connected to a buffer annular chamber (22), and a pressure sampling port (23) is provided on the buffer annular chamber (22). The present invention avoids the occurrence of blockage of the pressure sampling position through the design of the venturi tube body, and supports airspeed measurement in both forward and reverse directions.

Description

Technical Field

[0001] The invention belongs to the technical field of helicopter airspeed measurement, and relates to a bidirectional airspeed measurement device and method based on triple differential pressure measurement. Background Art

[0002] Among the various parameters of a helicopter, airspeed refers to the speed of the helicopter relative to the surrounding air. It is a basic parameter of helicopter performance and is crucial for helicopters. Accurate airspeed measurement is an important prerequisite for achieving advanced functions such as autonomous navigation, automatic flight, and precise hovering. Currently, commonly used airspeed measurement devices are available. Figure 1 Currently, most fixed-wing and rotary-wing aircraft use the pitot tube principle for airspeed measurement. However, due to the unique configuration of helicopters, the inherent limitations of low flight speeds, and the requirement for low altitudes, the downwash from the rotors can significantly affect airspeed measurements when flying at low altitudes and speeds. This can manifest as rapid and significant jumps in airspeed measurements. Under these circumstances, pilots cannot accurately determine the current flight status, let alone maintain a constant speed cruise.

[0003] In addition to Pitot tube measurement, Wang Cui et al. from the China Helicopter Design Institute (Wang Cui, He Rong. A brief discussion on helicopter low airspeed measurement technology, Military and Civilian Dual-Use Technology and Products, 2018 (4), 29-30.) also introduced an airspeed measurement method based on optical principles. The basic principle is that the laser encounters atmospheric aerosols (solid / liquid particles) and produces a Mie scattering effect. The Doppler frequency shift generated by the received backscattered laser signal is used to measure the atmospheric airspeed. Since 1985, NASA and Ophir have been committed to the research of optical atmospheric data Venturi tube technology. The optical atmospheric data system and molecular optical atmospheric data system based on aerosol particle scattering have been verified. The measurement of atmospheric parameters such as airspeed, angle of attack, and sideslip angle has been effectively solved. The atmospheric data measurement system based on optical measurement eliminates the influence of installation position restrictions and rotor downwash disturbances. Its incomparable advantages and application potential have become a hot topic of concern for atmospheric data researchers. At present, the atmospheric data measurement system based on optical measurement has been installed and verified on fixed-wing aircraft in China. The optical atmospheric data measurement system based on helicopters has a prototype in China, which will be installed and verified after laboratory simulation verification.

[0004] Wang Lidai and others from Tsinghua University (Wang Lidai, Xiong Shenshu, Zhou Zhaoying. Micro airspeed meter based on MEMS pressure venturi tube, Journal of Tsinghua University (Science and Technology), Vol. 45, No. 8, 2005, 1066-1068.) introduced the basic measurement principle of airspeed meter.

[0005] The Venturi tube designed by Wang Lidai and others has the problem of easy clogging at the pressure hole, which will cause the entire airspeed measurement device to fail; during the process of pressure hole clogging, the signal change may be gradual, and the airspeed measurement system is not easy to detect the problem, leading to safety accidents; although there are now means to prevent icing through electric heating protection measures, there is no way to solve the problem from the design of the Venturi tube itself; the existing design methods have not yet found a method to support airspeed measurement in both positive and negative directions. Summary of the Invention

[0006] The purpose of the invention is to provide a bidirectional airspeed measurement device and method based on triple differential pressure measurement. The present invention avoids blockage of the pressure taking position through the design of the venturi tube body, while supporting airspeed measurement in both forward and reverse directions.

[0007] Technical solution: A bidirectional airspeed measurement device based on three differential pressure measurements includes a Venturi tube, and the front straight pipe section, throat section and rear straight pipe section of the Venturi tube are all provided with pressure sampling components; the pressure sampling component includes a pressure sampling annulus, one end of the pressure sampling annulus is connected to the Venturi tube, and the other end is connected to a buffer ring chamber, and a pressure sampling port is provided on the buffer ring chamber.

[0008] In the aforementioned measurement method of the bidirectional airspeed measurement device based on three differential pressure measurements, the air pressures at the pressure sampling ports on the front straight pipe section, throat section, and rear straight pipe section are defined as P1, P2, and P3, respectively, ΔP1=P1-P2, ΔP2=P3-P2, ΔP3=P1-P3; if ΔP3>0, the helicopter is judged to be flying forward; if ΔP3<0, the helicopter is judged to be flying backward.

[0009] In the aforementioned measurement method of the bidirectional airspeed measurement device based on three differential pressure measurements, when ΔP3>0, the airspeed V is calculated as follows:

[0010]

[0011] Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

[0012] In the aforementioned measurement method of the bidirectional airspeed measurement device based on three differential pressure measurements, when ΔP3 < 0, the airspeed V is calculated as follows:

[0013]

[0014] Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

[0015] In the aforementioned measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement, when ΔP3>0, ΔP1=ΔP2+ΔP3.

[0016] In the aforementioned measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement, when ΔP3<0, ΔP2=ΔP1+ΔP3.

[0017] In the aforementioned measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement, the outflow coefficient C is an inherent parameter of the Venturi tube and is calibrated through experiments.

[0018] In the aforementioned measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement, the expansion coefficient ε is obtained by querying the "Expansion Coefficient Table".

[0019] In the aforementioned measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement, the throttling ratio β=d / D; wherein d is the inner diameter of the throat, and D is the inner diameter of the straight pipe section.

[0020] Beneficial effects:

[0021] (1) The present invention can determine the flight direction of the helicopter by means of the positive or negative value of ΔP3. If ΔP3>0, it is determined that the helicopter is flying forward; if ΔP3<0, it is determined that the helicopter is flying backward.

[0022] (2) Compared with conventional technologies, the present invention can achieve spatial filtering through the pressure ring gap and the buffer ring chamber, thereby reducing the influence of the rotor downwash airflow on the measurement of ΔP1, ΔP2, and ΔP3; at the same time, the rotor downwash airflow acts on both the forward and reverse flow sides of the Venturi tube, and the airflows on both sides can be partially offset, further improving the measurement effect of ΔP1, ΔP2, and ΔP3, avoiding large fluctuations in the airspeed measurement results, and helping to improve the control accuracy of the flight control system;

[0023] (3) Based on the three-differential pressure measurement method, it can provide a basis for determining the failure state of the system. ΔP1, ΔP2, and ΔP3 satisfy a certain equivalent relationship. When ΔP3>0, ΔP1=ΔP2+ΔP3; when ΔP3<0, ΔP2=ΔP1+ΔP3. When any of the three signals ΔP1, ΔP2, and ΔP3 fails, it can be calculated from the other two signals, which can achieve one-time fault operation and improve reliability.

[0024] (4) The design of the pressure ring gap can effectively reduce the failure of the measurement system due to ice, foreign matter, etc. Since the two ends of the Venturi tube are connected, foreign matter smaller than the inner diameter of the throat can be discharged from the Venturi tube, improving reliability; BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Diagram of the measurement principle of traditional airspeed meter;

[0026] Figure 2 Schematic diagram of the airspeed measuring device of the present invention;

[0027] Figure 3Illustration of the airspeed measuring device of the present invention. DETAILED DESCRIPTION

[0028] Example 1. A bidirectional airspeed measurement device based on three differential pressure measurements, see Figure 2-3 , aims to avoid the occurrence of blockage at the pressure taking position through the design of the Venturi tube body, and proposes a method for real-time online monitoring of the working status of the Venturi tube based on three differential pressure measurement means, while supporting airspeed measurement in both forward and reverse directions.

[0029] Because helicopters can fly in any direction, the airspeed measurement device mounted on the fuselage may experience both forward and reverse flow. For ease of explanation, the default installation configuration for the differential pressure measurement device is: ΔP1 corresponds to P1 on the high-pressure side and P2 on the low-pressure side; ΔP2 corresponds to P3 on the high-pressure side and P2 on the low-pressure side; and ΔP3 corresponds to P1 on the high-pressure side and P3 on the low-pressure side. This installation configuration is for illustration only and is not intended to be the only one.

[0030] When the flow is positive, the conversion relationship between airspeed and differential pressure signal can be obtained according to Bernoulli equation as follows:

[0031]

[0032] C is the outflow coefficient, which is an inherent parameter of the Venturi tube and can be calibrated through experiments; ε is the expansion coefficient, which can be obtained by looking up the table; β is the throttling ratio, which is equal to d / D; ρ is the atmospheric density; ΔP1 is the differential pressure.

[0033] Similarly, when the flow is reverse, the conversion relationship between airspeed and differential pressure signal is as follows:

[0034]

[0035] The key points of the present invention are as follows:

[0036] (1) The direction of the helicopter's movement can be determined based on the positive or negative sign of the ΔP3 differential pressure signal. If the airspeed measuring device is installed parallel to the fuselage, that is, the flow direction is from the nose to the tail, the P1 corresponding to ΔP3 is the high-pressure side, and P3 is the low-pressure side. If ΔP3 is greater than 0, it means that the helicopter is flying forward; if ΔP3 is less than 0, it means that the helicopter is flying backward;

[0037] (2) Based on the result of the first key point, the airspeed measurement system can automatically determine whether to select ΔP1 or ΔP2 for airspeed measurement. According to the installation method described in the first key point, if ΔP3 is greater than 0, ΔP1 is selected for airspeed calculation; if ΔP3 is less than 0, ΔP2 is selected for airspeed calculation;

[0038] (3) Figure 3The design of the middle pressure ring gap can effectively avoid the easy blockage of the pressure holes in traditional designs. When partial ice occurs, as the pressure ring gap surrounds the pipeline, as long as the pipeline is not completely blocked, it will not cause pressure failure.

[0039] (4) Since the venturi tube adopts a through-hole design, as long as the diameter of the foreign matter is not larger than the inner diameter of the throat, the foreign matter entering the venturi tube can be discharged;

[0040] (5) Since the Venturi tube adopts a through-hole design, the atmospheric environment of the entire Venturi tube is approximately the same. Therefore, the downwash of the rotor and the turbulence around the fuselage have a common mode effect on the Venturi tube. The airflows acting on both ends of the Venturi tube will cancel each other out, preventing the airspeed measurement results from jumping.

[0041] (6) The design of the buffer zone connected to the pressure ring gap can effectively reduce the interference of the rotor downwash airflow on the airspeed through spatial filtering, preventing the airspeed measurement results from jumping;

[0042] (7) The relationship between ΔP1, ΔP2, and ΔP3 can be used to determine whether the airspeed measurement device has failed. According to the installation method assumed above, ΔP1 is approximately equal to the sum of ΔP2 and ΔP3. If the deviation is too large, the airspeed measurement system can be determined to have failed.

[0043] Example 2. A bidirectional airspeed measurement device based on three differential pressure measurements, comprising: Figure 2-3 As shown, it includes a venturi tube 1, and the front straight pipe section, throat and rear straight pipe section of the venturi tube 1 are all provided with a pressure sampling assembly 2; the pressure sampling assembly 2 includes a pressure sampling annulus 21, one end of the pressure sampling annulus 21 is connected to the venturi tube 1, and the other end is connected to the buffer annulus 22, and the buffer annulus 22 is provided with a pressure sampling port 23.

[0044] The aforementioned measurement method of the bidirectional airspeed measurement device based on three differential pressure measurements defines the air pressures of the pressure sampling ports 23 on the front straight pipe section, the throat section, and the rear straight pipe section as P1, P2, and P3, respectively, ΔP1 = P1-P2, ΔP2 = P3-P2, ΔP3 = P1-P3; if ΔP3>0, it is determined that the helicopter is flying forward; if ΔP3<0, it is determined that the helicopter is flying backward.

[0045] When ΔP3>0, the airspeed V is calculated as follows:

[0046]

[0047] Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

[0048] When ΔP3 < 0, the airspeed V is calculated as follows:

[0049]

[0050] Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

[0051] When ΔP3>0, ΔP1=ΔP2+ΔP3.

[0052] When ΔP3<0, ΔP2=ΔP1+ΔP3.

[0053] The outflow coefficient C is an inherent parameter of the Venturi tube and is calibrated through experiments.

[0054] The expansion coefficient ε is obtained by consulting the "Expansion Coefficient Table".

[0055] Throttling ratio β = d / D, where d is the throat diameter and D is the straight pipe section diameter.

Claims

1. A measurement method of a bidirectional airspeed measurement device based on triple differential pressure measurement, characterized in that: The bidirectional airspeed measuring device comprises: a venturi tube (1); a front straight pipe section, a throat section and a rear straight pipe section of the venturi tube (1) are all provided with a pressure sampling assembly (2); the pressure sampling assembly (2) comprises a pressure sampling annular gap (21); one end of the pressure sampling annular gap (21) is connected to the venturi tube (1), and the other end is connected to a buffer annular chamber (22); a pressure sampling port (23) is provided on the buffer annular chamber (22); and a measuring method comprises: defining the air pressures of the pressure sampling ports (23) on the front straight pipe section, the throat section and the rear straight pipe section as P1, P2 and P3 respectively, ΔP1=P1-P2, ΔP2=P3-P2, ΔP3=P1-P3; ΔP3>0, it is determined that the helicopter is flying forward; ΔP3<0, it is determined that the helicopter is flying backward.

2. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 1, characterized in that: When ΔP3>0, the airspeed V is calculated as follows: ； Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

3. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 1, characterized in that: When ΔP3<0, the airspeed V is calculated as follows: ； Where C is the outflow coefficient; ε is the expansion coefficient; β is the throttling ratio; and ρ is the atmospheric density.

4. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 2, characterized in that: When ΔP3>0, ΔP1=ΔP2+ΔP3.

5. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 3, characterized in that: When ΔP3<0, ΔP2=ΔP1+ΔP3.

6. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 2 or 3, characterized in that: The outflow coefficient C is an inherent parameter of the Venturi tube and is calibrated through experiments.

7. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 2 or 3, characterized in that: The expansion coefficient ε is obtained by consulting the "Expansion Coefficient Table".

8. The measurement method of the bidirectional airspeed measurement device based on triple differential pressure measurement according to claim 2 or 3, characterized in that: Throttling ratio β = d / D, where d is the throat diameter and D is the straight pipe section diameter.

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