Cross beam straight rod type airspeed tube

Abstract

The invention belongs to the technical field of aircrafts, and particularly relates to a cross beam straight rod type airspeed tube. The airspeed tube comprises a probe body and a mounting base connected with the probe body, the probe body is of an isometric structure, the interior of the probe body is hollow to form a gas collection cavity, the probe body is an arc-shaped front face right facing the airflow direction, and more than one total pressure hole is formed in the arc-shaped front face; more than two static pressure holes are formed back to the airflow direction. According to the airspeed tube / probe, the aerodynamic basic principle that flowing in a leeward area of an object is relatively stable is utilized, the total pressure hole design and the redundant backup design of the total pressure hole and the static pressure hole are considered, and the reliability and safety of the airspeed tube / probe are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aircraft, and in particular relates to a cross-beam straight-rod type pitot tube. Background Art

[0002] The atmospheric data system is an indispensable measuring device used by aircraft to sense the flight environment, measure flight speed, flight attitude, and flight altitude in real time during actual flight. It is of great significance and indispensable for ensuring the flight safety of aircraft and improving flight quality. Pitot tubes and wind vanes are specific manifestations of the sensing equipment and design methods of the atmospheric data system.

[0003] As we all know, the pitot tube (also called probe) in the aircraft measures the total pressure P0 and static pressure P∞ data during flight, and then calculates the flight speed V (airspeed), flight altitude H (pressure altitude based on static pressure P∞); it can even calculate the flight attitude (angle of attack, sideslip angle). Among them, the measurement of the total pressure P0 of the pitot tube is relatively convenient, but because there is only one total pressure hole, the total pressure value may not be obtained or may be inaccurate due to blockage. The static pressure P∞ data measured by the pitot tube is easily affected by various factors and may result in errors or large fluctuations, which in turn leads to deviations in the subsequent data processing results.

[0004] Most pitot tubes are installed on the left and right sides of the front area of ​​the aircraft. The static pressure they measure is the data after the disturbance and interference of the front body of the aircraft, rather than the actual static pressure P∞ of the incoming flow; and after the disturbance, the obtained data fluctuates greatly, which is not conducive to subsequent data processing.

[0005] This phenomenon Figure 1 , Figure 2 Explain. Even if it is the same pitot tube, when it is installed on aircraft of different shapes or in different positions on the same aircraft, the static pressure felt by the pitot tube is different. When the flight attitude of the aircraft changes, the flow pattern of the airflow on the aircraft surface will also be different, and the measured static pressure will inevitably be different. This characteristic is not conducive to the stable and accurate measurement of the static pressure information of the incoming air.

[0006] To solve this problem, scientists have explored a pitot tube design method: aerodynamic compensation pitot tube design method. The method / idea is: for a certain aircraft shape and its specific position (the position is the actual installation position of the pitot tube), the pitot tube shape is repeatedly optimized and designed, and finally the static pressure measured by the pitot tube is the same as the static pressure of the incoming flow. Figure 3 The appearance drawings of several pitot tubes after aerodynamic compensation design are given.

[0007] Depend on Figure 3It can be seen that the aerodynamic shapes of pitot tubes designed by the aerodynamic compensation method are different. The more prominent contradiction is that the pitot tube designed by this method can only be used for a specific aircraft and its specific installation position; it cannot be easily and reliably transplanted to other aircraft or other positions on the same aircraft, and its technology has poor portability and versatility. This defect limits the development of this method. At present, the use of aerodynamic compensation method to design pitot tubes is no longer the mainstream technology.

[0008] How to design a widely applicable pitot tube / probe so that the static pressure it measures can remain basically stable over a relatively wide range of angles of attack and the total pressure it measures is accurate is an issue that needs to be addressed urgently. Summary of the invention

[0009] The purpose of the present invention is to overcome the defects of the prior art and propose a crossbeam straight rod type pitot tube.

[0010] In order to achieve the above-mentioned object, the present invention provides a beam straight rod type pitot tube, comprising: a probe body and a connected mounting base, wherein:

[0011] The probe body is of an iso-rectangular configuration, with a hollow interior to form a gas collecting cavity, an arc-shaped front facing the airflow direction, and more than one total pressure hole is arranged on the arc-shaped front; more than two static pressure holes are arranged opposite to the airflow direction.

[0012] Preferably, the air collecting chamber includes a total pressure pipe and a static pressure pipe, wherein the total pressure pipe is used to gather pressure data collected by multiple total pressure holes and output an averaged total pressure data value; the static pressure pipe is used to gather pressure data collected by multiple static pressure holes and output an averaged static pressure data value.

[0013] Preferably, the curved front surface is designed using a von Karman curve, satisfying the following formula:

[0014]

[0015] ψ=arccos(1-2x / B)

[0016] Among them, y is the vertical axis coordinate of the curve, x is the horizontal axis coordinate of the curve, ψ is the intermediate variable, and A and B are both constants.

[0017] Preferably, a concave cavity is formed opposite to the airflow direction.

[0018] Preferably, the arrangement of the total pressure holes on the arc-shaped front side is: arranged at equal intervals along the cylindrical axis; or arranged at equal intervals along the perpendicular to the cylindrical axis; or there are no less than 5 total pressure holes arranged in a cross shape, and one side of the cross is parallel to the cylindrical axis, and the other side is perpendicular to the cylindrical axis, and each total pressure hole is equally spaced; or there are n×n total pressure holes, arranged at equal intervals in n rows and n columns, n≥3.

[0019] Preferably, the static pressure holes facing away from the airflow direction are arranged equidistantly along the cylinder axis to obtain stable static pressure data.

[0020] Preferably, the pitot tube realizes the expansion and contraction states of the probe body by adding a motion mechanism to the mounting base.

[0021] On the other hand, the present invention provides an aircraft, comprising the above-mentioned cross-beam straight rod type pitot tube.

[0022] Compared with the prior art, the advantages of the present invention are:

[0023] The present invention provides a new design method and design object of a cross-beam pitot tube / probe that is different from the traditional forward-extending type. The invention utilizes the basic aerodynamic principle that the flow in the leeward area of ​​an object is relatively stable, takes into account the design of the total pressure hole, and the redundant backup design of the total and static pressure holes, so as to improve the reliability and safety of the pitot tube / probe. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a diagram of airflow passing over the surface of an object. Figure 1 ;

[0025] Figure 2 It is a diagram of airflow passing over the surface of an object. Figure 2 ;

[0026] Figure 3 This is a schematic diagram of the pitot tube after aerodynamic compensation design;

[0027] Figure 4 It is a schematic diagram of the flow pattern at the bottom of the object;

[0028] Figure 5 This is a schematic diagram of the flow pattern at the bottom and inner cavity of the object. Figure 1 ;

[0029] Figure 6 This is a schematic diagram of the flow pattern at the bottom and inner cavity of the object. Figure 2 ;

[0030] FIG. 7( a ) is a schematic diagram of the windward surface of the crossbeam straight rod type pitot tube of the present invention;

[0031] FIG7( b ) is a schematic diagram of the leeward side of the crossbeam straight rod type pitot tube of the present invention;

[0032] Figure 8 It is a schematic diagram of the "physical average" method of pressure measurement;

[0033] Fig. 9 This is a schematic diagram of the von Karman curve on the front of the probe;

[0034] Fig.10This is a schematic diagram of another arrangement of total pressure holes;

[0035] Fig.11 This is a schematic diagram of the third arrangement of total pressure holes; Fig.12 This is a schematic diagram of the fourth arrangement of total pressure holes; Fig.13 It is the total pressure data comparison;

[0036] Fig.14 This method obtains the installation form and two states of the pitot tube;

[0037] Fig.15 It is the static pressure data of the leeward area. DETAILED DESCRIPTION

[0038] Basic principle:

[0039] According to the basic theory of aerodynamics, when air flows over a deflected object, expansion waves will appear (Prandt-Meyer flow theory). Figure 4 As shown in the figure, a relatively stable "recirculation zone" or "dead water zone" will be formed at the rear of the bend; the airflow in this area is relatively stable and the pressure is also relatively stable. Using this characteristic, a pitot tube / probe for stable static pressure measurement is designed.

[0040] There is similar experience from previous aerodynamic tests. The flow in the inner cavity of an object is often stable to a certain extent; the bottom pressure measurement data is relatively stable. Figure 5 , Figure 6 shown.

[0041] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0042] Example

[0043] The embodiment of the present invention discloses a cross-beam and straight-rod type pitot tube, the configuration of which is shown in FIG. 7( a ) and FIG. 7( b ).

[0044] Its specific form and technical ideas are described as follows:

[0045] 1. The probe body has an arc-shaped front (designed to face the incoming flow) and an equal straight body configuration; the interior is hollow to form a gas collecting cavity, which includes a total pressure pipe and a static pressure pipe.

[0046] 2. The arc surface of the probe faces the incoming flow. The arc surface should be designed to make the airflow flow more stable on this surface without flow separation, so as to facilitate the stable measurement of total pressure. Three total pressure holes are designed on this arc surface (the number is not necessarily strictly limited to 3, 2 or 4 is also OK; but not 1), and finally a total pressure data value is output through the physical averaging method. The purpose of this is: ① to perform "physical averaging" of pressure data, such as Figure 8 As shown. Data from multiple pressure measuring holes are integrated into a total pressure pipe, and finally a pressure data value is output. After the data is averaged, the accuracy of the data is ensured to a certain extent; the output total pressure value will not be invalid or distorted due to abnormal data from a certain measuring hole; ② Redundant backup design. Even if a hole is blocked or fails, there is still a total pressure hole that can work normally to ensure that credible and reliable data is obtained.

[0047] The curved front of the probe is designed using the von Karman curve. Fig. 9 As shown, the equation is as follows:

[0048]

[0049] ψ=arccos(1-2x / B)

[0050] In the formula: A = constant 1, B = constant 2.

[0051] The characteristic of the von Karman curve is that it has the advantage of better reducing air resistance and aerodynamic load. This method uses the von Karman curve to design the front of the probe.

[0052] A concave cavity is formed facing away from the airflow direction. It is sunken inward to form a certain dead water area, which is convenient for stable airflow and accurate measurement.

[0053] As a derivative form of the total pressure hole design method, the longitudinal arrangement form is different from the transverse arrangement form shown in Figure 7, and also has its unique advantages. Fig.10 From the figure on the right, it can be imagined that when the probe flies with the aircraft at a changing angle of attack, the middle hole is the conventional total pressure hole, and the upper and lower holes are not total pressure holes. However, when the angle of attack increases (positive increase or negative increase) to a certain angle, the total pressure detection capability of the conventional total pressure hole will inevitably decrease, and at this time the upper hole (or lower hole) can take on the role of continuing to detect the total pressure. In this way, the angle of attack range of total pressure detection is expanded. This feature is very important for aircraft that need to fly at high angles of attack. Furthermore, in one embodiment, there are at least 5 total pressure holes arranged in a cross shape, and one side of the cross is parallel to the axis of the cylinder, and the other side is perpendicular to the axis of the cylinder, and each total pressure hole is equidistant, such as Fig.11 This design takes into account the horizontal axis of the cylinder (the horizontal arrangement in Figure 7) and Fig.10Further, in one embodiment, the cross-shaped total pressure holes are expanded to 3 rows and 3 columns or more rows and more columns, that is, n rows and n columns, and each total pressure hole is equally spaced, such as Fig.12 shown.

[0054] Depend on Fig.13 It can be seen that compared with the measurement results of the traditional "single total pressure hole", the total pressure measurement data of this method has a larger angle of attack range of the "data platform", namely: -α2—α2; this "data platform" is the total pressure data available during flight.

[0055] 3. Five static pressure holes are designed on the back of the probe (the number is not limited to 5, but should be greater than 2). These 5 holes are equidistantly arranged along the axis of the cylinder. The pressure data collected by multiple static pressure holes are converged through the static pressure tube to output an averaged static pressure data value. The basis or purpose of this design: ① As described in the third part "Basic Principles", the flow in the leeward area is relatively stable, which is conducive to obtaining stable pressure data; ② As described in 2 above, the "physical averaging" and redundant design of pressure data are performed;

[0056] 4. This type of probe can also be further designed to be easy to expand and contract to adapt to more flight scenarios and environments. Fig.14 In one embodiment, the pitot tube is equipped with a motion mechanism on the mounting base to realize the expansion and contraction of the probe body, which can be applied to stealth requirements, hypersonic flight and other scenarios.

[0057] 5. From the test data, if Fig.15 As shown in the figure, the static pressure data Cp~α pressure curve at the back of the model (leeward area) basically does not change with the change of the angle of attack; and when Ma<1.0, the data change amplitude is not drastic with the change of Ma. This shows that the pressure value measured by the designed static pressure measuring point is not sensitive to the change of flight attitude and flight speed. This feature is beneficial to the stable measurement of static pressure in flight, which is also the original intention of the design.

[0058] 6. Explain the significance and role of accurately measuring static pressure during flight:

[0059] a. To calculate the flight airspeed V, static pressure data is required

[0060] As can be seen from the following formula, when calculating airspeed, it is necessary to obtain both the total pressure and static pressure data at the same time. Only by accurately obtaining the pressure data of both can the accurate flight airspeed be obtained (this is also the origin of the name of the pitot tube).

[0061]

[0062] Where: V is airspeed; P0 is total pressure; P∞ is static pressure; ρ is air density;

[0063] b. To calculate the flight altitude (pressure altitude), static pressure data is required

[0064] As can be seen from the following formula, pressure altitude is a function of static pressure. Only by accurately obtaining static pressure data can accurate pressure altitude be obtained.

[0065]

[0066] Where: H p is the pressure altitude; P∞ is the static pressure.

[0067] Summarize:

[0068] 1. The present invention provides a new design method and design object of a beam-type pitot tube / probe, which is different from the traditional forward-extending type;

[0069] 2. The core idea is to use the basic principle of aerodynamics that the flow in the leeward area of ​​an object is relatively stable to carry out this design work;

[0070] 3. Take into account the design of total pressure hole, as well as the redundant backup design of total and static pressure holes to improve the reliability and safety of the probe;

[0071] 4. Can be designed into a retractable structure;

[0072] 5. As a further optimization, the leeward area can be designed as an arc. The core idea is to make the flow in this area relatively stable, reduce the volatility of pressure data, and improve the accuracy and stability of data measurement.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A beam straight rod type pitot tube, characterized in that: include: The probe body and the attached mounting base, where: The probe body is of an iso-rectangular configuration, with a hollow interior to form a gas collecting cavity, an arc-shaped front facing the airflow direction, and more than one total pressure hole is arranged on the arc-shaped front; more than two static pressure holes are arranged opposite to the airflow direction.

2. The crossbeam straight rod type pitot tube according to claim 1, characterized in that: The gas collecting chamber includes a total pressure pipe and a static pressure pipe, wherein the total pressure pipe is used to gather pressure data collected by multiple total pressure holes and output an averaged total pressure data value; the static pressure pipe is used to gather pressure data collected by multiple static pressure holes and output an averaged static pressure data value.

3. The beam straight rod type pitot tube according to claim 1, characterized in that: The curved front is designed using the von Karman curve, satisfying the following formula: ψ=arccos(1-2x / B) Among them, y is the vertical axis coordinate of the curve, x is the horizontal axis coordinate of the curve, ψ is the intermediate variable, and A and B are constants.

4. The beam straight rod type pitot tube according to claim 1, characterized in that: The cavity is formed opposite to the airflow direction.

5. The cross beam straight rod type pitot tube according to claim 1, characterized in that: The arrangement of the total pressure holes on the arc-shaped front side is: arranged at equal intervals along the cylindrical axis; or arranged at equal intervals along the perpendicular line of the cylindrical axis; or there are no less than 5 total pressure holes arranged in a cross shape, and one side of the cross is parallel to the cylindrical axis, and the other side is perpendicular to the cylindrical axis, and each total pressure hole is equally spaced; or there are n×n total pressure holes, arranged at equal intervals in n rows and n columns, n≥3.

6. The beam straight rod type pitot tube according to claim 1, characterized in that: The static pressure holes facing away from the airflow direction are arranged equidistantly along the axis of the cylinder to obtain stable static pressure data.

7. The beam straight rod type pitot tube according to claim 1, characterized in that: The pitot tube realizes the expansion and contraction state of the probe body by adding a motion mechanism to the mounting base.

8. An aircraft, characterized in that: It comprises a cross beam straight rod type pitot tube as described in any one of claims 1-7.

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