CN102692521A - Apparatus for measuring low-speed aircraft airspeed in real time - Google Patents

Abstract

The invention provides a real-time measurement device for air velocity, comprising: a speed-increasing tube, including a static pressure section, a contraction section, a throat and a diffuser section, the static pressure section and the throat are straight tubes, and the cross-sectional area of the static pressure section is The throat is large, the diameter of the constriction section is gradually reduced to connect the static pressure section and the throat, and the diameter of the diffuser section is gradually increased from the diameter of the throat to the diameter of the outlet; connecting pipe; differential pressure sensor. Among them, the static pressure section and the throat have pressure measuring holes respectively, the pressure measuring hole of the static pressure section is connected to the positive pressure measuring end of the differential pressure sensor through a connecting pipe, and the pressure measuring hole of the throat is connected to the negative pressure sensor of the differential pressure sensor through a connecting pipe. Pressure measuring terminal.

Description

Airspeed real-time measurement device for low-speed aircraft

technical field

The invention belongs to the technical field of aviation measurement and control, and in particular relates to a real-time airspeed measurement device for a low-speed aircraft.

Background technique

Low-speed aircraft include aerostats such as airships, buoyant-lifting integrated aircraft, and balloons, as well as aircraft such as helicopters, gliders, powered parachutes, and powered delta wings. The flight performance of low-speed aircraft is greatly affected by the wind, and accurate measurement of airspeed (the speed of the aircraft relative to the atmosphere) is the key to improving flight quality and flight safety. Pitot tubes are used in traditional aviation to measure dynamic pressure, that is, the difference between total pressure and static pressure, because the relationship between dynamic pressure Δp and airspeed V _a satisfies the following formula at low speed:

$\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Then the airspeed can be obtained by formula (1). where ρ is the density of the atmosphere.

Because the flying speed of the low-speed aircraft is small, the dynamic pressure generated is also small. This problem becomes more prominent as the altitude of the flight increases and the density of the atmosphere decreases. For example, at an altitude of 20km, the atmospheric density is only about 7% of that at sea level. The dynamic pressure corresponding to the airspeed of 10 m/s at different heights is shown in Table 1

Table 1 Dynamic pressure (Pa) corresponding to different altitudes and different airspeeds

1(m/s) 2(m/s) 5(m/s) 10(m/s) 20(m/s) 0(km) 0.6125 2.45 15.313 61.25 245 1(km) 0.556 2.224 13.9 55.6 222.4 2(km) 0.5035 2.014 12.588 50.35 201.4 5(km) 0.368 1.472 9.2 36.8 147.2 10(km) 0.207 0.828 5.175 20.7 82.8 20(km) 0.044 0.178 1.1114 4.4455 17.782

At sea level, the dynamic pressure is only 61Pa when the airspeed is 10m/s, and the dynamic pressure is only 15Pa when the airspeed is less than 5m/s. At a height of 20km, the airspeed is only 4.4Pa when the airspeed is 10m/s, and only 1.1Pa when the airspeed is less than 5 meters. In the occasions where the airspeed in a small range needs to be accurately measured, the signal obtained by using the traditional pitot tube is too weak and the noise is large, so it is difficult to accurately extract the airspeed.

Other devices other than aviation instruments, such as ultrasonic anemometers, hot wire/hot bulb anemometers, can also be used for airspeed measurement, but they are expensive, difficult to calibrate and maintain, and have strict requirements on the use environment, usually only used in low altitudes Speed measurement, but cannot be applied at high altitude.

Contents of the invention

The purpose of the present invention is to provide a real-time airspeed measuring device with a large differential pressure signal, which can obtain higher speed measurement accuracy at low airspeed.

The invention provides a real-time measurement device for airspeed, comprising:

1) Speed-increasing pipe, including constriction section, throat and diffuser section, wherein the diameter of the constriction section gradually decreases, the throat is straight, and the diameter of the diffuser section gradually increases from the diameter of the throat to the diameter of the outlet;

2) connecting pipe;

3) differential pressure sensor,

Wherein, the throat has a pressure measuring hole, and the pressure measuring hole in the throat is connected to the negative pressure measuring end of the pressure difference sensor through a communication pipe. The differential pressure sensor is located in the aircraft cabin, and the positive pressure measurement end of the differential pressure sensor is connected to the local static pressure.

According to the airspeed real-time measuring device provided by the present invention, it also includes a straight pipe-shaped static pressure section whose diameter is larger than that of the throat, and which is connected to the end of the constriction section with a larger diameter. The static pressure section has a pressure measuring hole, which is connected to the positive pressure measuring end of the differential pressure sensor through a connecting pipe.

According to the airspeed real-time measuring device provided by the present invention, the constriction section and the diffuser section adopt a streamlined design, or are in the shape of a tapered tube.

The airspeed real-time measuring device provided according to the present invention also includes a barometer and a temperature sensor for providing atmospheric density data, and also includes a microprocessor.

在2～3之间，扩压段的最大直径与收缩段的最大直径的比值在0.85～0.9之间，Airspeed real-time measuring device provided according to the present invention, wherein the scope of the half-cone angle θ of speed-increasing tube shrinkage _section is 19 °～24 °, the half-cone angle scope of diffuser section is 6 °～12 °, the scope of the shrinkage section Ratio of maximum diameter to throat diameter

Between 2 and 3, the ratio of the maximum diameter of the diffuser section to the maximum diameter of the contraction section between 0.85 and 0.9,

According to the airspeed real-time measuring device provided by the present invention, the diameter d ₄ of the pressure measuring hole on the throat of the speed increasing tube is <1.5 mm, and the length l ₂ of the throat is about 4 times the diameter of the pressure measuring hole.

The airspeed real-time measuring device provided by the invention can realize the real-time and accurate measurement of the airspeed at low speed under different atmospheric environments (from the ground to the stratosphere). The device has the following advantages:

1. Simple and reliable, easy to implement and low cost;

2. Compared with the traditional pitot tube airspeed meter, the signal strength at the same airspeed is much higher than

The former, and the signal noise and pulsation are small;

3. Strong applicability, it can be used for both low-altitude speed measurement and high-altitude speed measurement.

Description of drawings

Embodiments of the present invention will be further described below with reference to the accompanying drawings, wherein:

Fig. 1 is a structural schematic diagram of an airspeed real-time measuring device according to the present invention.

Fig. 2 is a structural schematic diagram of the speed-increasing tube of the airspeed real-time measuring device according to the present invention.

Fig. 3 is a schematic diagram of installation on an aircraft of the airspeed real-time measuring device according to the present invention.

Fig. 4 is a physical diagram of an airspeed real-time measuring device according to an embodiment when it is installed.

Fig. 5 is a schematic diagram of the working process of the airspeed real-time measuring device according to the present invention.

Fig. 6 is a schematic block diagram of the measuring method of the airspeed real-time measuring device according to the present invention.

Fig. 7 is a schematic diagram of the key design parameters of the speed increasing tube.

Fig. 8 is a schematic structural diagram of the speed-increasing tube of the simplified airspeed real-time measuring device.

Detailed ways

According to one embodiment of the present invention, a kind of airspeed real-time measurement device (as shown in Figure 1) is provided, comprising:

1) Speed-up tube U2;

2) Differential pressure sensor U1;

3) Microprocessor U4;

4) Barometer and temperature sensor U5;

5) The connecting pipe is used for connecting the speed increasing pipe and the differential pressure sensor.

The structure of the speed-increasing tube U2 is shown in Figure 2, including a static pressure section, a contraction section, a throat and a diffuser section. The static pressure section is a straight tube with a constant diameter, and the contraction section is approximately tapered. Larger static pressure section and throat with smaller cross-sectional area. The throat section is a straight pipe with a constant diameter, and the diameter of the diffuser section gradually increases from the throat diameter to the outlet diameter.

Wherein, the static pressure section and the throat have a pressure measuring hole 101 and a pressure measuring hole 102 respectively, which are respectively connected to the positive and negative pressure measuring ends of the differential pressure sensor through communication pipes.

When the speed-up tube U2 is installed on the airship, as shown in Figure 3, it is required that the speed-up tube is placed parallel to the longitudinal axis of the aircraft, the static pressure section faces the forward direction, and there is no obstruction in front. Fig. 4 shows the physical picture of the airspeed real-time measuring device according to one embodiment of the present invention when it is installed.

The static pressure section in the speed increase tube U2 is used to stabilize the incoming flow and measure the air pressure, the constricted section is used to accelerate the incoming flow, the throat is used to measure the local air pressure after acceleration, and the diffuser section is used to make the static pressure section and the throat The airflow is kept steady to avoid jet disturbances of the airflow at the outlet of the booster tube. When the air flows through the speed increasing tube, the throat air flow accelerates and the pressure drops, creating a pressure difference across the differential pressure sensor.

According to the pressure difference and the design parameters of the speed-increasing tube, the airspeed of the aircraft can be calculated: as shown in Figure 5, record the cross-sectional area of the speed-increasing tube inlet as A ₁ , and the throat cross-sectional area as A ₂ . At low velocities, the gas can be treated as an incompressible flow. From the Bernoulli equation, at the inlet section and the throat section, there are:

${\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Among them, ρ is the local atmospheric density, p ₀ is the total pressure, p ₁ and p ₂ are the inlet section and throat section air pressure, v ₁ and v ₂ are the inlet section flow velocity (i.e. space velocity) and throat section flow velocity, respectively.

From the gas continuity equation, we have:

v ₁ A ₁ =v ₂ A ₂ (3)

Among them, A ₁ and A ₂ are the cross-sectional areas of the inlet section and the throat section, respectively.

The differential pressure measured by the bipolar differential pressure gauge is:

Δp=p ₁ -p ₂ (4)

From formula (2), (3),

$\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; c\&gamma;</span>}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

in

$\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{{<span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

γ≤1 is a correction coefficient that comprehensively considers the effects of air viscosity, friction, and processing. Under ideal conditions γ=1. c is a constant related to the structural parameters of the speed increase tube. Therefore, by measuring the pressure difference Δp and the atmospheric density ρ, the space velocity v ₁ can be calculated according to formula (6).

A schematic block diagram of a measurement method of an airspeed real-time measurement device according to an embodiment of the present invention is shown in FIG. 6 . The pressure difference Δp on the inlet section and the throat section of the speed increasing tube is measured by the differential pressure sensor, and is input into the ADC (Analog-to-Digital Converter) together with the atmospheric density data provided by the atmospheric data sensor, and then calculated by the microprocessor U4, to get the airspeed.

Wherein the atmospheric density ρ data can be obtained by the existing atmospheric data sensor in the aircraft, can also be obtained by the barometer and the temperature sensor U5 included in this airspeed real-time measuring device, can also be obtained by any measurement atmosphere known to those skilled in the art The density method is obtained.

Figure 7 shows the key design parameters of the speed increase tube, where:

The half-cone angle θ ₁ of the contraction section: 19°～24°;

The half-cone angle θ ₂ of the diffuser section: 6°～12°;

2～3；The ratio of the maximum diameter of the constriction to the diameter of the throat

2～3;

：0.85～0.9；The ratio of the maximum diameter of the diffuser section to the maximum diameter of the constriction section

: 0.85～0.9;

The diameter d ₄ of the pressure measuring hole 102 on the throat is <1.5mm, and the length l ₂ of the throat is ≈10d ₄ .

Among them, the static pressure section and the throat are straight pipes. In principle, the constriction section and the diffuser section are best to adopt a streamlined design. However, in order to reduce the difficulty of design and processing, the constriction section and the diffuser section can also be approximated by tapered tubes.

According to an embodiment of the present invention, wherein when the airspeed real-time measuring device according to the present invention is used for a small aircraft, the static pressure section of the speed increase tube can also be removed, only including the constriction section, the throat and the diffuser section to simplify The structure is shown in Figure 8. At this time, the differential pressure sensor is located in the aircraft cabin, and the positive pressure measurement end of the differential pressure sensor is connected to the local static pressure. During the flight, the static atmosphere in the cabin communicates with the outside world, so the differential pressure sensor The pressure on the positive pressure measuring port is still p ₁ .

Due to the influence of factors such as friction, viscosity and heat conduction, the speed calculation correction coefficient of the speed increase tube γ≠1. Before use, the speed-increasing tube needs to be calibrated to determine the correction factor.

Calibration correction coefficient can adopt the following methods:

First, through the wind tunnel test, the pressure difference Δp of the speed-increasing tube at a given incoming flow velocity v is measured, and γ is calibrated by the following formula;

$\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; v</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Second, determine the correction coefficient by comparing it with the Pitot tube.

$\mathrm{<span\; class="notranslate">\; \&gamma;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; f</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}\sqrt{\frac{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

Among them, Δp and Δp' are the pressure difference measured by the speed-increasing tube and the pitot tube respectively, and f is the correction factor of the pitot tube.

Compared with the dynamic pressure signal measured by the conventional pitot tube type airspeed gauge, the differential pressure signal measured by the device is much larger than the former, so that higher speed measurement accuracy can be obtained at low airspeed. The traditional pitot tube airspeed meter directly measures the difference between the total pressure and the static pressure at the inlet section, that is, Δp'=p ₀ -p ₁ . From formula (2), we can get,

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; \&rho;</span>}{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 10</span>}<span\; class="notranslate">\; )</span>$

Therefore, the calculation method of the traditional pitot tube airspeed meter is

${\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; /</span>\mathrm{<span\; class="notranslate">\; \&rho;</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Comparing formula (5) and formula (10), then

$\frac{\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; A</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Let the diameters of the inlet section and the throat section of the speed increasing tube be d ₁ and d ₂ respectively, and let the ratio of the section diameter be

k=d ₁ /d ₂ (13)

but

$\frac{\mathrm{<span\; class="notranslate">\; \&Delta;p</span>}}{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}^{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

That is, under the same airspeed, the theoretical pressure difference measured by the present invention is (k ⁴ -1) times of the theoretical pressure difference of the traditional pitot tube airspeed gauge. Taking k=2 as an example, the theoretical pressure difference measured by the present invention is 15 times that of the traditional airspeed gauge.

Table 2 shows the theoretical pressure difference after using the speed increasing tube (k=2). Comparing Table 1, it can be seen that the pressure difference value at low speed can be significantly improved after the speed increase tube is used.

Table 2 When k=2, the pressure difference corresponding to different altitudes and different airspeeds (Pa)

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than limit them. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims.

Claims (10)

1. air speed real-time measurement apparatus comprises:

1) velocity hooster comprises contraction section, throat and diffuser, and wherein the diameter of contraction section dwindles gradually, and throat is a straight tube-like, and the diffuser caliber increases to outlet diameter gradually by throat diameter;

2) communicating pipe;

3) differential pressure pickup,

Wherein, throat has pressure tap, and the pressure tap of throat connects the negative pressure measuring junction of differential pressure pickup through communicating pipe.

2. air speed real-time measurement apparatus according to claim 1, wherein differential pressure pickup is positioned at the aircraft cabin, and the malleation measuring junction of differential pressure pickup is communicated in local static pressure.

3. air speed real-time measurement apparatus according to claim 1 also comprises the static pressure section of straight tube-like, and its diameter is bigger than throat, and an end bigger with the contraction section diameter is connected.

4. air speed real-time measurement apparatus according to claim 3, the static pressure section has pressure tap, and this pressure tap is connected to the malleation measuring junction of differential pressure pickup through connecting pipe.

5. according to claim 1 or 3 described air speed real-time measurement apparatus, wherein contraction section and diffuser adopt airflow design.

6. according to claim 1 or 3 described air speed real-time measurement apparatus, wherein contraction section and diffuser are Taper Pipe shape.

7. according to claim 1 or 3 described air speed real-time measurement apparatus, also comprise barometer and temperature sensor, be used to provide the atmospheric density data.

8. according to claim 1 or 3 described air speed real-time measurement apparatus, also comprise microprocessor.

9. according to claim 1 or 3 described air speed real-time measurement apparatus, wherein the semi-cone angle θ of contraction section ₁Scope be 19 °～24 °, the semi-cone angle scope of diffuser is 6 °～12 °, the maximum gauge of contraction section and the ratio of throat diameter Between 2～3, the ratio of the maximum gauge of diffuser and the maximum gauge of contraction section

Between 0.85～0.9.

10. according to claim 1 or 3 described air speed real-time measurement apparatus, the wherein diameter d of the pressure tap in the throat ₄＜1.5mm, the length l of throat ₂4 times of diameter that are about pressure tap.

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