Five-hole differential pressure airspeed tube

Abstract

The present invention relates to the field of measuring flight parameters such as airspeed and attitude angle during the flight of low-altitude aircraft. Specifically, it is a five-hole differential pressure type airspeed tube, which includes a probe. The probe includes a first conical surface section provided at the end of the probe and a second conical surface section axially connected to the first conical surface section along the probe. The cone angle of the first conical surface section is greater than that of the second conical surface section, so that the flow velocity of the air increases in the area where the first conical surface section is connected to the second conical surface section; a central hole is provided on the end face of the first conical surface section, and the center line of the central hole coincides with the axis of the probe; four side holes are evenly arranged along the circumferential direction of the conical surface of the second conical surface section. Under the action of the rapid increase in air flow velocity, the present invention can enable sundries such as mosquitoes and dust to quickly pass by without entering the four side holes on the second conical surface during the process of flowing backward along the two conical surfaces of the probe, thus playing a role in preventing blockage.

Description

Technical Field

[0001] The present invention relates to the field of measuring flight parameters such as calibrated airspeed (CAS), angle of attack (AOA), and angle of sideslip (AOS) during the flight of low-altitude aircraft, and specifically relates to a five-hole differential pressure type airspeed tube. Background Art

[0002] Among the many airborne sensors configured in aircraft, the instrument used to measure airspeed is a basic equipment, which provides the most important guarantee for flight control and safety. The airspeed tube technology is currently the most mature and widely used flight airspeed measurement technology, so the airspeed tube is still an important means for aircraft airspeed measurement until now. The types and characteristics of commonly used airspeed tubes are as follows:

[0003] Pitot tube type: It consists of a double-layer casing with an opening at the front end. It measures the total pressure of the airflow through the opening at the front end, measures the static pressure through the static pressure holes opened on the tube wall, and then uses an air data computer to calculate and obtain the airspeed of the aircraft. This type of airspeed tube has a simple structure and low manufacturing difficulty, but has a large measurement error when the aircraft makes large-angle maneuvers.

[0004] External wind vane type: Its main form is the same as that of the pitot tube type airspeed tube, and an external wind vane type angle of attack sensor and sideslip angle sensor are provided, which can measure airspeed and attitude angles simultaneously. This type of airspeed tube can measure the flight attitude angles of the aircraft, but is affected by the "cylindrical wake" phenomenon and generates data jitter during maneuvers in the opposite direction of the angle of attack and sideslip angle sensors.

[0005] Total pressure tube type: It consists of an independent total pressure tube and a static pressure hole array arranged on the fuselage. The independent total pressure tube only measures the total pressure of the airflow, and cooperates with the static pressure collected by the static pressure hole array arranged on the fuselage, and uses an air data computer to calculate and obtain the airspeed of the aircraft. This type of airspeed tube has a high measurement accuracy, but has high requirements for the design of the static pressure hole array on the fuselage. At the same time, small aircraft are limited by the fuselage size and it is not easy to arrange the static pressure hole array.

[0006] Five-hole differential pressure type: Its head is hemispherical or conical, with five holes opened on it for measuring the airflow velocity and pressure in different directions; multiple static pressure holes are opened on the tube wall to measure the static pressure, so as to provide more comprehensive flight data. This type of airspeed tube has less limitations and performs well in low-speed, subsonic, and even supersonic flights, and can more accurately measure the aerodynamic parameters of the aircraft during flight. However, due to the large number of holes opened on the head and the need to limit the aperture due to structural and weight requirements, there is a risk of blockage of the intake holes by mosquitoes, dust, etc. during low-altitude and low-speed flights of the aircraft. Summary of the Invention

[0007] In view of the defects of the existing technologies of various types of pitot tubes, especially the five-hole differential pressure type pitot tube with comparative advantages, the present invention provides a five-hole differential pressure type pitot tube, which includes a first cone angle, a second cone angle of the probe, and different aperture designs of the central hole and the four side holes opened on the second conical surface. It focuses on improving the probe of the traditional five-hole differential pressure type pitot tube, and solves the problem that the intake holes are easily blocked during the low-altitude and low-speed flight of the aircraft through the design of variable cone angles and multiple apertures, while ensuring a compact structure, reducing weight, and guaranteeing the measurement accuracy.

[0008] To achieve the above object, the technical solution provided by the present invention is a five-hole differential pressure type pitot tube, which includes a probe. The probe includes a first conical surface section provided at the end of the probe, and a second conical surface section axially connected to the first conical surface section along the probe.

[0009] The cone angle of the first conical surface section is greater than the cone angle of the second conical surface section, so that the flow velocity of the air flow increases in the area where the first conical surface section is connected to the second conical surface section.

[0010] A central hole is opened on the end surface of the first conical surface section, and the center line of the central hole coincides with the axis of the probe.

[0011] Four side holes are evenly opened along the circumferential direction of the conical surface of the second conical surface section.

[0012] Further, the cone angle range of the first conical surface section is 45° to 65°, and the cone angle range of the second conical surface section is 35° to 55°.

[0013] Further, the cone angle of the first conical surface section is 62°; the cone angle of the second conical surface section is 43°.

[0014] Further, the center line of the side hole is perpendicular to the conical surface of the second conical surface section.

[0015] Further, the aperture of the central hole is larger than the aperture of the side hole.

[0016] Further, the aperture of the central hole is φ4mm; the apertures of the four side holes are all φ1.5mm.

[0017] Further, the five-hole differential pressure type pitot tube includes a pitot tube body connected to the probe. The interior of the pitot tube body is sequentially provided with a front cavity, a middle cavity and a rear cavity along the direction away from the probe. The central hole is communicated with the front cavity. A total pressure acquisition head and a drainage hole are arranged in the front cavity, and a static pressure hole is opened in the middle cavity.

[0018] Further, a base is provided at one end of the pitot tube body away from the probe. A pressure guiding pipe joint and a wire joint are provided on the base. A heating wire is provided on the inner wall of the front cavity, and the heating wire is connected to the wire joint through a wire.

[0019] Further, the side holes are connected to a pressure guiding pipe, and the pressure guiding pipe is connected to the pressure guiding pipe joint.

[0020] Further, the side holes are connected to a pressure guiding pipe, and the diameter of the pressure guiding pipe is equal to the diameter of the side holes.

[0021] The beneficial effects of the present invention are as follows: A probe is provided, and the probe has a variable cone angle structure. Specifically, the probe includes two mutually connected conical surface segments with different cone angles, and transitions from the first conical surface segment with a larger cone angle to the second conical surface segment with a smaller cone angle. With such a setting, on the one hand, the measurement performance of the five-hole differential pressure type pitot tube can be more excellent during the flight of the aircraft in a wider speed range such as low speed, subsonic speed, and supersonic speed. On the other hand, by using the principle of aerodynamics, after the airflow passes through the conical surface of the first conical surface segment during flight, the speed increases rapidly at the connection between the first conical surface segment and the second conical surface segment, and reaches the maximum at the connection between the bottom of the second conical surface segment and the pitot tube body. With such a setting, under the action of the rapid increase in airflow speed, when mosquitoes, dust and other sundries flow backward along the two conical surfaces of the probe, they can quickly pass over and will not enter the four side holes on the second conical surface, thus playing a role in preventing blockage. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of a five-hole differential pressure type pitot tube in an embodiment of the present invention;

[0023] Figure 2 is a schematic structural diagram of a probe in an embodiment of the present invention;

[0024] Figure 3 is a side view of a probe in an embodiment of the present invention;

[0025] Figure 4 is a sectional view of a five-hole differential pressure type pitot tube in an embodiment of the present invention;

[0026] Figure 5 is Figure 4 a partial enlarged view of the probe area in;

[0027] Figure 6 is a simulation schematic diagram of the airflow velocity distribution of three forms of probes at 0.6Ma in an embodiment of the present invention;

[0028] Figure 7 is Figure 6 a partial enlarged view of part Ⅰ in;

[0029] Figure 8 is Figure 6 a partial enlarged view of part II in

[0030] Figure 9 is Figure 6 a partial enlarged view of part III in

[0031] Figure 10 a simulation schematic diagram of the air flow velocity distribution of three forms of probes in an embodiment of the present invention;

[0032] Figure 11 is Figure 10 a partial enlarged view of part I in

[0033] Figure 12 is Figure 10 a partial enlarged view of part II in

[0034] Figure 13 is Figure 10 a partial enlarged view of part III in

[0035] Figure 14 a simulation schematic diagram of the surface pressure of the combined side holes with two cone angles of 65° and 55° in an embodiment of the present invention;

[0036] Figure 15 a simulation schematic diagram of the surface pressure of the combined side holes with two cone angles of 45° and 35° in an embodiment of the present invention;

[0037] Figure 16 a simulation schematic diagram of the surface pressure of the combined side holes with two cone angles of 62° and 43° in an embodiment of the present invention;

[0038] Figure 17 a velocity vector diagram at the corner position of the combined side holes with two cone angles of 62° and 43° in an embodiment of the present invention;

[0039] Figure 18 a comparison diagram of the boundary layer thickness at the key position after the corner of the combined side holes with two cone angles of 62° and 43° in an embodiment of the present invention;

[0040] In the figure:

[0041] 100, probe; 110, first conical surface section; 111, end face; 1111, central hole; 112, first conical surface; 120, second conical surface section; 121, second conical surface; 1211, side hole,

[0042] 200, airspeed tube body; 210, front cavity; 211, total pressure acquisition head; 212, heating wire; 213, drain hole; 220, middle cavity; 221, static pressure hole; 230, rear cavity; 231, wire; 240, pressure guiding tube,

[0043] 300, Base; 310, Pressure guiding pipe joint; 320, Wire joint. Detailed implementation mode

[0044] To make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation mode of the present invention will be given in conjunction with the accompanying drawings. Many specific details are set forth in the following description to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0045] As Figure 1 shown, a schematic structural diagram of a five-hole differential pressure type airspeed tube in an embodiment of the present invention includes a probe 100, an airspeed tube body 200, and a base 300. One end of the airspeed tube body 200 is provided with a probe 100, and the other end of the airspeed tube body 200 is provided with a base 300. The probe 100 is a variable cone angle and multi-aperture structure for collecting air flow pressure. The airspeed tube body 200 is internally provided with a front cavity 210, a middle cavity 220, and a rear cavity 230. The front cavity 210 is used for collecting the total air flow pressure (Pt), ablating mosquitoes, and deicing and draining water. The middle cavity 220 is used for collecting the static air pressure (Ps). The rear cavity 230 is connected to the base 300, and the pressure guiding pipe joint 310 and the wire joint 320 at the rear end of the base 300 can be connected to the air data host.

[0046] See Figure 2 , the probe 100 includes a first conical surface section 110 provided at the end of the probe, and a second conical surface section 120 axially connected to the first conical surface section 110 along the probe 100. The cone angle of the first conical surface section 110 is greater than the cone angle of the second conical surface section 120, so that the air flow velocity increases in the area where the first conical surface section 110 and the second conical surface section 120 are connected. That is, the air flow pressure suddenly and significantly decreases, and the air flow velocity suddenly and significantly increases. A central hole 1111 is opened on the end surface of the first conical surface section 110, and the center line of the central hole 1111 coincides with the axis of the probe 100. Four side holes 1211 are evenly opened along the circumferential direction of the conical surface of the second conical surface section 120.

[0047] The above five-hole differential pressure airspeed tube is provided with a probe 100, and the probe 100 has a variable cone angle structure. Specifically, the probe 100 includes two conical surface segments with different cone angles that are connected to each other, and transitions from the first conical surface segment 110 with a larger cone angle to the second conical surface segment 120 with a smaller cone angle. With such a setting, on the one hand, the five-hole differential pressure airspeed tube can have better measurement performance during the flight of the aircraft in a wider speed range such as low speed, subsonic speed, and supersonic speed. On the other hand, by using the principle of aerodynamics, after the airflow passes through the conical surface of the first conical surface segment 110 during flight, the speed increases rapidly at the connection between the first conical surface segment 110 and the second conical surface segment 120, and reaches the maximum at the connection between the bottom of the second conical surface segment 120 and the airspeed tube body 200. With such a setting, under the action of the rapidly increasing airflow speed, when mosquitoes, dust and other sundries flow backward along the two conical surfaces of the probe 100, they can quickly pass over without entering the four side holes 1211 on the second conical surface 121, thus playing the role of the first layer of anti-blocking. Refer to Figure 4 , in a preferred embodiment, the cone angle of the first conical surface segment 110 is 62°, and the cone angle of the second conical surface segment 120 is 43°. Refer to Figure 16 , in this embodiment, the results of the side hole pressure simulation show that the 0 pressure line is exactly located at the side hole 1211, and its measurement accuracy is the best. The two cone angles in this embodiment can not only achieve the anti-blocking effect but also ensure the measurement accuracy. Therefore, 62° and 43° are the optimal combination of cone angles.

[0048] Combined with refer to Figure 2 and Figure 3 , in a specific embodiment, the first conical surface segment 110 is arranged at the end of the probe 100, and it includes an end face 111 and a first conical surface 112. The central hole 1111 is opened at the center of the end face 111; the second conical surface segment 120 includes a second conical surface 121, and four side holes 1211 are opened on the second conical surface 121 and are evenly distributed.

[0049] As Figure 3 shown, specifically, the central hole 1111 opened at the top center of the end face 111 of the first conical surface segment 110 is 2 holes, the two side holes 1211 opened in the vertical direction of the second conical surface 121 are holes 1 and 3, and the two side holes 1211 opened in the horizontal direction are holes 4 and 5. The functions of the five holes on the probe 100 are to collect the airflow pressure during the flight of the aircraft. The total pressure (Pt) collected by hole 2 minus the static pressure (Ps) collected by the static pressure hole 221 on the wall of the middle cavity 220 can be used to calculate the dynamic pressure (Qc), and the flight airspeed (CAS) of the aircraft can be calculated by solving formulas such as the Bernoulli equation; the flight angle of attack (AOA) is calculated through the pressure difference collected by holes 1 and 3, and the flight sideslip angle (AOS) is calculated through the pressure difference collected by holes 4 and 5.

[0050] In order to further enhance the anti-clogging effect, in one embodiment, the centerline of the side hole 1211 is perpendicular to the conical surface of the second conical surface section 120. With such a setting, since the four side holes 1, 3, 4, and 5 are opened in the normal direction, the projected area of the four side holes 1211 facing the oncoming flow direction (the axis of the five-hole differential pressure airspeed tube) becomes smaller, thereby playing a role in the second layer of anti-clogging.

[0051] As Figure 3 shown, in one embodiment, the aperture of the central hole 1111 is larger than that of the side holes. Specifically, in one embodiment, the aperture of the central hole 1111 is φ4mm; the apertures of the four side holes 1211 are all φ1.5mm.

[0052] In the above five-hole differential pressure airspeed tube, since the central hole 1111 is opened in the high-pressure area at the very front end of the probe 100, according to the principle of aerodynamics, the air flow velocity will stagnate to 0 at the orifice of the central hole 1111. If the aperture of the central hole 1111 is too small, it will cause mosquitoes and other sundries to block the hole. In this embodiment, the aperture is designed to be φ4mm, which enables mosquitoes to smoothly enter the front cavity 210 of the airspeed tube and be discharged through methods such as heating ablation and drainage; at the same time, a total pressure acquisition head 211 is provided in the front cavity 210 of the airspeed tube, and a pressure guiding tube 240 with the same diameter as the four side holes 1211 is used, thereby ensuring the measurement accuracy. In addition, according to the principle of aerodynamics and engineering practice, if the holes of the pneumatic probe are opened small, or the projected area of the holes facing the oncoming flow is small, it will improve the resolution of the entering air, enhance the sensitivity of the measurement, and thus improve the measurement accuracy of the attitude angle (AOA, AOS); at the same time, the small intake holes can be connected with small-diameter pressure guiding tubes 240, thereby reducing the overall diameter of the airspeed tube as a whole, making the structure more compact and lighter in weight. Therefore, the apertures of the four side holes 1211 are designed to be φ1.5mm, which not only adds another layer of anti-clogging design on the basis of the existing variable cone angle anti-clogging, but also ensures the measurement accuracy and makes the airspeed tube structure more compact and reduces the weight.

[0053] In order to reduce the overall diameter and weight of the airspeed tube, the present invention provides a total pressure acquisition head 211 in the front cavity 210 of the airspeed tube. The total pressure acquisition head 211 is circumferentially provided with intake holes on the side to collect the total pressure (Pt) (which also plays an anti-clogging role). The diameter of the pressure guiding tube 240 connected behind the total pressure acquisition head 211 is the same as the diameter of the pressure guiding tube 240 connected behind the four side holes 1211. Thus, the overall diameter of the airspeed tube will not increase due to the enlargement of the diameter of the central hole 1111, ensuring the compactness of the airspeed tube structure and the control of the weight. At the same time, due to the control of the aperture, the measurement accuracy of the airspeed (CAS), angle of attack (AOA), and sideslip angle (AOS) of the aircraft by the airspeed tube is ensured.

[0054] See Figure 1 and Figure 4, in one embodiment, the five-hole differential pressure airspeed tube includes an airspeed tube body 200 connected to the probe 100. Inside the airspeed tube body 200, a front cavity 210, a middle cavity 220, and a rear cavity 230 are sequentially formed in the direction away from the probe. The central hole 1111 communicates with the front cavity 210. A total pressure collection head 211 and a drain hole 213 are provided in the front cavity 210, and a static pressure hole 221 is formed in the middle cavity 220.

[0055] Specifically, referring to Figure 4 , in order to clean and discharge sundries such as mosquitoes and dust entering through the central hole 1111, in one embodiment, a base 300 is provided at one end of the airspeed tube body 200 away from the probe 100. A wire connector 320 is provided on the base 300, and a heating wire 212 is provided on the inner wall of the front cavity 210. The heating wire 212 is connected to the wire connector 320 through a wire 231. With this setting, mosquitoes can smoothly enter the front cavity 210 of the airspeed tube and be discharged through methods such as heating and ablation by the heating wire 212. Referring to Figure 1 , the drain hole 213 is provided on the airspeed tube body 200 and communicates with the front cavity 210. The heating and ablation are completed in the front cavity 210. The entering mosquitoes will be ablated into ashes and then discharged through the drain hole 213. Additionally, in the absence of water, the ablated dust and impurities can also adhere to the surface of the heating wire.

[0056] Continuing to refer to Figure 4 , in one embodiment, a pressure guiding pipe joint 310 is provided on the base 300. A side hole 1211 is connected to a pressure guiding pipe 240, and the pressure guiding pipe 240 is connected to the pressure guiding pipe joint 310.

[0057] It should be noted that the probe 100 is provided with five holes, which are respectively connected to the pressure guiding pipes 240 for collecting the air flow pressure. Specifically, the central hole 1111 is equivalent to the opening of the front cavity 210, and the total pressure collection head 211 is arranged inside the front cavity 210. The total pressure collection head 211 is connected to the central pressure guiding pipe 240. The four side holes 1211 are respectively connected to one end of the four pressure guiding pipes 240, and the other ends of the four pressure guiding pipes 240 are connected to the pressure guiding pipe joints 310 provided on the base 300. The connection methods include but are not limited to welding.

[0058] In one embodiment, a side hole 1211 is connected to a pressure guiding pipe 240, and the diameter of the pressure guiding pipe 240 is equal to the diameter of the side hole 1211.

[0059] Referring to Figures 7 - 9 , Figures 11 - 13 As shown, in order to explore and verify the feasibility, scientificity, and rationality of the improved design of the variable cone angle of the present invention, two air flow velocities of 0.6 Ma and 0.3 Ma are selected to perform aerodynamic simulations on three forms of probes, where Figure 7, Figure 11 It is in the form of a single-cone-angle probe. Figure 8 , Figure 12 It is in the form of a variable-cone-angle probe. Figure 9 , Figure 13 It is in the form of a hemispherical probe. From the simulation results of the air flow velocity of 0.6Ma, the high-pressure area of the air flow of the single-cone-angle probe is located at holes 1, 3, 4, and 5, and the low-pressure area is located at the connection between the bottom of the conical surface and the tube body, that is, the air flow velocity at holes 1, 3, 4, and 5 is relatively low, and it is easy to block the four side holes with sundries such as mosquitoes and dust; the location of the high-pressure area of the air flow of the hemispherical probe is similar to that of the single-cone-angle probe, and its low-pressure area is in front of the connection between the bottom of the arc and the tube body, and there is also a risk of blocking the four side holes 1, 3, 4, and 5 with sundries such as mosquitoes and dust; the high-pressure area of the variable-cone-angle probe is located at the connection between the first and second conical surfaces, in front of holes 1, 3, 4, and 5, and the low-pressure area is located at the connection between the bottom of the second conical surface and the tube body, that is, the air flow velocity increases in a gradient manner starting from the connection between the first and second conical surfaces, and sundries such as mosquitoes and dust will cross holes 1, 3, 4, and 5 with the increase of the air flow velocity, thereby reducing the risk of blocking the four side holes 1211. From the simulation results of the air flow velocity of 0.3Ma, the air flow velocity change situations of the single-cone-angle probe, the hemispherical probe, and the variable-cone-angle probe are the same as those in the 0.6Ma speed condition; the difference is that due to the relatively low air flow velocity, the pressure change between the high- and low-pressure areas is small, and the increase in the air flow velocity is not as obvious as that in the 0.6Ma speed condition, but the design of the variable cone angle of the probe also plays a role in preventing blockage because the forward movement of the high-pressure area makes the air flow velocity increase in advance. In summary, the design of the variable-cone-angle probe of the five-hole differential pressure type airspeed tube meets the expectations and can achieve the invention purpose of preventing blockage under the conditions of low altitude and low speed of the aircraft.

[0060] In the present invention, the cone angles of the first conical surface section and the second conical surface section include, but are not limited to, the combination of 62° and 43°, see Figure 14 , Figure 15 and Figure 16 . The cone angle range of the first conical surface section 110 is 45° to 65°, and the cone angle range of the second conical surface section 120 is 35° to 55°.

[0061] See Figure 14 , Figure 15 , Figure 16 As shown, in order to explore and verify the feasibility of the selection of the cone angle ranges of the two conical surface sections of the present invention and the rationality of the optimal cone angle value, three forms of cone angle combinations of 65° and 55°, 45° and 35°, and 62° and 43° are selected for aerodynamic calculation and simulation. After calculation, the dynamic pressure value ranges of the above three cone angle combinations are as follows:

[0062] Example 1: The cone angle of the first conical surface section is 65°, and the cone angle of the second conical surface section is 55°; the dynamic pressure value range (Pa) is 5469.48 to 5613.41;

[0063] Example 2: The taper angle of the first conical surface section is 45°, and the taper angle of the second conical surface section is 35°; the dynamic pressure value range (Pa) is 6620.95 - 6764.88;

[0064] Example 3: The taper angle of the first conical surface section is 62°, and the taper angle of the second conical surface section is 43°; the dynamic pressure value range (Pa) is 6189.15 - 6333.08.

[0065] See Figure 17 As shown, in the aerodynamic simulation results under the combination of 62° and 43°, vortices with a maximum Q - criterion value of 0.38 are generated at the corner position, and heavy impurities and blockages can be thrown out of the side - hole measurement range by the vortex separation effect.

[0066] See Figure 18 As shown, in the aerodynamic simulation results under the combination of 62° and 43°, the original boundary - layer thickness is thinned after the corner position, reduced to 15% of the single - conical - surface structure thickness, effectively reducing the thickness of the low - speed area and the number of impurities in low - speed flow.

[0067] In Example 3, the taper angle of the first conical surface section is greater than that of the second conical surface section. The taper angle of the first conical surface section is 62°, and the taper angle of the second conical surface section is 43°. By reducing the taper angle by 19°, the dynamic pressure on the surface of the second conical surface section is increased by 15.2%, facilitating the faster removal of light impurities from the side - hole measurement position by the air flow;

[0068] There is a corner structure between the first conical surface and the second conical surface, generating vortices within a controllable range during use, and heavy impurities can be separated from the side - hole range by the vortex. When the combination is 62° for the first conical surface and 43° for the second conical surface, the vortex strength is a Q - criterion value of 0.38;

[0069] The taper angle of the first cross - section is greater than that of the second cross - section. The low - speed air flow in the central hole of the first cross - section is better concentrated on the surface of the first cross - section, reducing the thickness of the low - speed boundary layer on the surface of the second cross - section, reducing the probability and quantity of light impurities in the low - speed - area boundary layer, and improving the side - hole measurement accuracy of the second cross - section. When the combination is 62° for the first conical surface and 43° for the second conical surface, the boundary - layer thickness after the corner of the second conical surface is reduced to 15% of that of the single conical surface.

[0070] Since the air flow velocity on the surfaces of the four side holes is negatively correlated with the probe angle (i.e., the larger the probe cone angle, the smaller the air flow velocity on the side hole surface; conversely, the smaller the probe cone angle, the larger the air flow velocity on the side hole surface), taking the dynamic pressure value range (5459.67~5620.25) Pa of the commonly used 60° single cone angle in engineering as a reference, the dynamic pressure value range of Example 1 is equivalent to that of the 60° single cone angle, indicating that even if the cone angle of the first cone section is greater than 60°, due to the design that the cone angle of the second cone section is smaller than that of the first cone section, a comparable dynamic pressure value can still be achieved, that is, it can also play the role of increasing the air flow velocity on the side hole surface and achieving the effect of preventing blockage; see Figure 14 , the results of the side hole pressure simulation in Example 1 show that the 0 pressure line starts to deviate partially relative to the side hole, which will have a certain impact on the measurement accuracy. Therefore, the two cone angles in Example 1 can be regarded as the maximum values of the cone angle of the first cone surface section and the cone angle of the second cone surface section.

[0071] The dynamic pressure value of Example 2 is the largest, that is, the air flow velocity on the side hole surface is the largest, and theoretically the anti-blocking effect is the best, but from Figure 15 the results of the side hole pressure simulation, the 0 pressure line also starts to deviate relative to the side hole, which will also have a certain impact on the measurement accuracy. Therefore, the two cone angles in Example 2 can be regarded as the minimum values of the cone angle of the first cone surface section and the cone angle of the second cone surface section.

[0072] The dynamic pressure value of Example 3 is between the dynamic pressure values of Example 1 and Example 2, that is, the air flow velocity on the side hole surface is also between these two combinations, and the anti-blocking effect is also very obvious; see Figure 16 , the results of the side hole pressure simulation in Example 3 show that the 0 pressure line is exactly located at the side hole, and its measurement accuracy is the best. Therefore, the two cone angles in Example 3 can not only achieve the anti-blocking effect but also ensure the measurement accuracy, and 62° and 43° are the optimal value combinations.

[0073] It should be noted that the design of the variable cone angle of the pitot tube probe of the present invention, as well as the design of the normal opening of holes 1, 3, 4, and 5 on the second cone surface, will increase the manufacturing and processing difficulty to a certain extent and will cause a small increase in the manufacturing cost. In addition, although the variable cone angle pitot tube probe can be used to measure the airspeed and attitude angle of an aircraft under low-speed, subsonic, and supersonic working conditions, supersonic working conditions generally occur in high-altitude environments. At the same time, due to the high air flow velocity, an air film will be formed on the surface of the pitot tube, so the intake holes generally do not have blockage problems, and it is often a suitable choice to use a single cone angle probe. Therefore, the design of the variable cone angle of the pitot tube probe of the present invention is more suitable for the low-altitude and low-speed flight conditions of an aircraft.

[0074] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0075] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0076] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0078] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation.

Claims

1. Five-hole differential pressure airspeed tube, characterized in that: It includes a probe, The probe includes a first conical section provided at the end of the probe and a second conical section axially connected to the first conical section along the probe; The cone angle of the first conical section is greater than that of the second conical section, so that the flow velocity of the air flow increases in the area where the first conical section is connected to the second conical section; A central hole is provided on the end face of the first conical section, and the central axis of the central hole coincides with the axis of the probe; Four side holes are evenly provided along the circumferential direction on the conical surface of the second conical section; The cone angle range of the first conical section is 45° - 65°, and the cone angle range of the second conical section is 35° - 55°; The five-hole differential pressure airspeed tube includes an airspeed tube body connected to the probe, Inside the airspeed tube body, a front cavity, a middle cavity and a rear cavity are sequentially provided along the direction away from the probe, The central hole is communicated with the front cavity, and a total pressure acquisition head and a drain port are provided in the front cavity, A static pressure hole is provided in the middle cavity.

2. The five-hole differential pressure type airspeed tube according to claim 1, characterized in that: The cone angle of the first conical section is 62°; the cone angle of the second conical section is 43°.

3. The five-hole differential pressure type airspeed tube according to claim 1 or 2, characterized in that: The central axis of the side hole is perpendicular to the conical surface of the second conical section.

4. The five-hole differential pressure type airspeed tube according to claim 1 or 2, characterized in that: The aperture of the central hole is larger than that of the side hole.

5. The five-hole differential pressure type airspeed tube according to claim 4, wherein: The aperture of the central hole is φ4mm; the apertures of the four side holes are all φ1.5mm.

6. The five-hole differential pressure type airspeed tube according to claim 1, wherein: One end of the airspeed tube body away from the probe is provided with a base, and a pressure guiding pipe joint and a wire joint are provided on the base, A heating wire is provided on the inner wall of the front cavity, and the heating wire is connected to the wire joint through a wire.

7. The five-hole differential pressure type airspeed tube according to claim 6, characterized in that: The side hole is connected with a pressure guiding pipe, and the pressure guiding pipe is connected with the pressure guiding pipe joint.

8. The five-hole differential pressure type airspeed tube according to claim 1 or 2, characterized in that: The side hole is connected with a pressure guiding pipe, and the diameter of the pressure guiding pipe is equal to the diameter of the side hole.

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