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

Abstract

The invention provides an apparatus for measuring low-speed aircraft airspeed in real time, comprising a speedup pipe which comprises a static pressure section, a constricted section, a throat part and a diffusion section, wherein the static pressure section and the throat part are in shapes of a straight pipe, the sectional area of the static pressure section is larger than that of the throat part, the diameter of the constricted section decreases gradually to connect the static pressure section and the throat part, and the pipe diameter of the diffusion section increases gradually from the throat part to reach an exit diameter; a communicating pipe; and a differential pressure transducer. Moreover, the static pressure section and the throat part respectively have a pressure hole, the pressure hole of the static pressure section connected with a positive pressure measuring terminal of the differential pressure transducer through the communicating pipe and the pressure hole of the throat part connected with a negative pressure measuring terminal of the differential pressure transducer through the communicating pipe.

Description

Low-speed operations device air speed real-time measurement apparatus

Technical field

The invention belongs to aviation observation and control technology field, relate in particular to a kind of low-speed operations device air speed real-time measurement apparatus.

Background technology

The low-speed operations device comprises aircraft such as aerostatics such as dirigible, buoyance lift one aircraft, balloon and helicopter, soarer, propeller-parachuting, power dalta wing.The influence of the flying quality wind-engaging of low-speed operations device is very big, and it is the key that improves flight quality and flight safety that air speed (speed of the relative atmosphere of aircraft) is measured accurately.The tradition aviation field adopts pitot tube to measure dynamic pressure, i.e. the difference of stagnation pressure and static pressure is because dynamic pressure Δ p and air speed V during low speed _aBetween satisfy following formula:

$\mathrm{\Δp}=\frac{1}{2}\mathrm{\ρ}{V}_a^2---\left(1\right)$

And then but through type (1) draws air speed.Wherein ρ is an atmospheric density.

Because the flying speed of low-speed operations device is less, the dynamic pressure of generation is also less.Along with the increase of flying height, atmospheric density will reduce, and it is particularly outstanding that this problem becomes.For example on height above sea level 20km height, atmospheric density has only about 7% of sea level.The dynamic pressure of the air speed of 10 meter per seconds correspondence is as shown in table 1 on the differing heights

The different pairing dynamic pressures of air speed (Pa) of table 1 differing heights

	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

On the sea level, have only the dynamic pressure of 61Pa during the air speed of 10m/s, air speed is during less than 5m/s, and dynamic pressure has only 15Pa.And arrived 20km height, and more have only 4.4Pa during the air speed of 10m/s, air speed only has 1.1Pa during less than 5 meters.The occasion of air speed in needs are accurately measured among a small circle, the signal that utilizes traditional pitot tube to obtain is too faint, and noise is bigger, accurately extracts very difficulty of air speed.

Though other outside the instrument for example install ultrasonic wind speed meter, hot line the hot-bulb anemoscope also can be used for air speed and measure; But cost is higher, calibration and difficult in maintenance, and environment for use is required comparatively harsh; Usually can only be used for the low latitude and test the speed, and can't use in the high-altitude.

Summary of the invention

It is big to the purpose of this invention is to provide a kind of pressure difference signal, thereby under low-speed, can obtain higher rate accuracy air speed real-time measurement apparatus.

The invention provides a kind of air speed real-time measurement apparatus, comprising:

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.Differential pressure pickup is positioned at the aircraft cabin, and the malleation measuring junction of differential pressure pickup is communicated in local static pressure.

According to air speed real-time measurement apparatus provided by the invention, also comprise the static pressure section of straight tube-like, its diameter is bigger than throat, and an end bigger with the contraction section diameter is connected.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.

According to air speed real-time measurement apparatus provided by the invention, wherein contraction section and diffuser adopt airflow design, or are Taper Pipe shape.

According to air speed real-time measurement apparatus provided by the invention, also comprise barometer and temperature sensor, be used to provide the atmospheric density data, also comprise microprocessor.

According to air speed real-time measurement apparatus provided by the invention, wherein the semi-cone angle θ of velocity hooster 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,

According to air speed real-time measurement apparatus provided by the invention, the diameter d of the pressure tap in the velocity hooster throat wherein ₄＜1.5mm, the length l of throat ₂4 times of diameter that are about pressure tap.

Air speed real-time measurement apparatus provided by the invention can be realized real-time, the accurately measurement of air speed under the low speed situation at (ground is to stratosphere) under the different atmospheric environments.This device has the following advantages:

1, simple and reliable, be easy to realize, with low cost;

2, compare with traditional pitot tube pitot meter, the signal intensity under the same air speed far above

The former, and signal noise and percent ripple are less;

3, applicability is strong, both can be used for the low latitude and has tested the speed, and also can be used for the high-altitude and tests the speed.

Description of drawings

Followingly the embodiment of the invention is described further with reference to accompanying drawing, wherein:

Fig. 1 is the structural representation according to air speed real-time measurement apparatus of the present invention.

Fig. 2 is the structural representation according to the velocity hooster of air speed real-time measurement apparatus of the present invention.

Fig. 3 be according to air speed real-time measurement apparatus of the present invention at carry-on scheme of installation.

Fig. 4 is the pictorial diagram when installing according to the air speed real-time measurement apparatus of an embodiment.

Fig. 5 is the course of work synoptic diagram according to air speed real-time measurement apparatus of the present invention.

Fig. 6 is the schematic block diagram according to the measuring method of air speed real-time measurement apparatus of the present invention.

Fig. 7 is the synoptic diagram of velocity hooster key design parameter.

Fig. 8 is the structural representation of the velocity hooster of the air speed real-time measurement apparatus after simplifying.

Embodiment

According to one embodiment of present invention, a kind of air speed real-time measurement apparatus (as shown in Figure 1) is provided, has comprised:

1) velocity hooster U2;

2) differential pressure pickup U1;

3) microprocessor U4;

4) barometer and temperature sensor U5;

5) communicating pipe, be used to be communicated with velocity hooster and differential pressure pickup.

Wherein the structure of velocity hooster U2 is as shown in Figure 2; Comprise static pressure section, contraction section, throat and diffuser; The static pressure section is the straight tube-like that diameter remains unchanged, and contraction section connects bigger static pressure section and the less throat of sectional area of sectional area for approximate taper; Throat's section is the straight tube that diameter remains unchanged, and the diffuser caliber increases to outlet diameter gradually by throat diameter.

Wherein, static pressure section and throat have pressure tap 101 and pressure tap 102 respectively, respectively through being connected to the positive and negative pressure measuring junction of differential pressure pickup communicating pipe.

When velocity hooster U2 installs on dirigible, as shown in Figure 3, require velocity hooster and the parallel placement of the aircraft longitudinal axis, the static pressure section is towards the direction of advancing, and the place ahead does not have and blocks.Fig. 4 shows the pictorial diagram when the air speed real-time measurement apparatus is installed according to an embodiment of the invention.

Static pressure section among the velocity hooster U2 is used for steady incoming flow and measures air pressure; Contraction section is used to make incoming flow to quicken; Throat is used to measure the local air pressure after the acceleration, and diffuser is used to make static pressure section and throat's air-flow to keep stable, produces jet disturbance in the velocity hooster exit to avoid air-flow.When airflow during through velocity hooster, throat's air-flow descends because of acceleration pressure, produces pressure reduction at the differential pressure pickup two ends.

According to the size and the velocity hooster design parameter of pressure reduction, can extrapolate the aircraft flight air speed: as shown in Figure 5, note velocity hooster entrance section is long-pending to be A ₁, the throat section is long-pending to be A ₂Under the low speed situation, can be with gas as handling by baric flow.By Bernoulli equation,, have in entrance section and throat section:

$p_1+\frac{1}{2}\mathrm{\ρ}{v}_1^2=p_2+\frac{1}{2}\mathrm{\ρ}{v}_2^2=p_0---\left(2\right)$

Wherein ρ is local atmospheric density, p ₀Be stagnation pressure, p ₁And p ₂Be entrance section, throat section air pressure, v ₁And v ₂Be respectively entrance section flow velocity (being air speed), throat section flow velocity.

By the gas continuity equation, have again:

v ₁A ₁＝v ₂A ₂ (3)

A wherein ₁, A ₂Be respectively the sectional area of entrance section, throat section.

The pressure reduction that ambipolar differential manometer measured is:

Δp＝p ₁-p ₂ (4)

By formula (2), (3),

$\mathrm{\Δp}=\frac{1}{2}\mathrm{\ρ}{v}_1^2(A_1^2/A_2^2-1)=\frac{1}{2}\mathrm{\ρ}{v}_1^2(d_1^4/d_2^4-1)---\left(5\right)$

$v_1=\sqrt{\frac{2\mathrm{\Δp}}{\mathrm{\ρ}(A_1^2/A_2^2-1)}}=\mathrm{c\γ}\sqrt{\frac{2\mathrm{\Δp}}{\mathrm{\ρ}}}---\left(6\right)$

Wherein

$c=\frac{1}{\sqrt{{\left(\frac{A_1}{A_2}\right)}^2-1}}=\frac{1}{\sqrt{{\left(\frac{d_1}{d_2}\right)}^4-1}}---\left(7\right)$

γ≤1 for take all factors into consideration air viscosity, friction and with the correction factor of factor affecting such as processing.γ under the ideal conditions=1.C is the constant relevant with the structural parameters of velocity hooster.Therefore, through measuring pressure differential deltap p and atmospheric density ρ, can calculate air speed v according to formula (6) ₁

The schematic block diagram of the measuring method of air speed real-time measurement apparatus according to an embodiment of the invention is as shown in Figure 6.Measure the entrance section of velocity hooster and the pressure differential deltap p on the throat section through differential pressure pickup, and import ADC (analog to digital converter), calculate through microprocessor U4 then, obtain air speed with the atmospheric density data that air data sensor provides.

Wherein atmospheric density ρ data can obtain through existing air data sensor in the aircraft; Also can obtain, can also obtain through any method of measuring atmospheric density that well known to a person skilled in the art through barometer and the temperature sensor U5 that is included in this air speed real-time measurement apparatus.

Fig. 7 has provided the key design parameter of velocity hooster, wherein:

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

The semi-cone angle θ of diffuser ₂: 6 °～12 °;

The maximum gauge of contraction section and the ratio of throat diameter

2～3;

The ratio of the maximum gauge of diffuser and the maximum gauge of contraction section

: 0.85～0.9;

The diameter d of the pressure tap 102 in the throat ₄＜1.5mm, the length l of throat ₂≈ 10d ₄

Wherein static pressure section and throat are straight tube, and contraction section and diffuser preferably adopt airflow design in principle.But in order to reduce design and difficulty of processing, contraction section and diffuser also can adopt Taper Pipe approximate.

According to one embodiment of present invention, wherein when flying the air speed real-time measurement apparatus according to the present invention when being used for small aircraft, the static pressure section of velocity hooster also can be removed; Include only contraction section, throat and diffuser with simplified structure, as shown in Figure 8, this moment, differential pressure pickup was positioned at the aircraft cabin; The malleation measuring junction of differential pressure pickup is communicated in local static pressure; In the flight course, atmosphere static in the cabin is in communication with the outside, so the pressure on the malleation measuring junction of differential pressure pickup still is p ₁

Owing to have the influence of factors such as friction, viscosity and heat conduction, speed calculation correction factor γ ≠ 1 of velocity hooster.Before the use, need velocity hooster is demarcated, to determine correction factor.

Demarcate correction factor and can adopt following method:

One of which, through wind tunnel test, measure the velocity hooster pressure differential deltap p under the given speed of incoming flow v, calibrate γ by following formula;

$\mathrm{\γ}=\frac{v}{c}\sqrt{\frac{\mathrm{\ρ}}{2\mathrm{\Δp}}}---\left(8\right)$

Two, through and pitot tube contrast, determine correction factor.

$\mathrm{\γ}=\frac{f}{c}\sqrt{\frac{\mathrm{\Δ}{p}^{\′}}{\mathrm{\Δp}}}---\left(9\right)$

Wherein, Δ p and Δ p ' are respectively velocity hooster and the pressure measurement of pitot tube institute is poor, and f is the pitot tube correction factor.

Compare with the dynamic pressure signal that the pitot tube type pitot meter of routine is surveyed, the pressure difference signal that this device is surveyed is much larger than the former, thereby under low-speed, can obtain higher rate accuracy.Tradition pitot tube type pitot meter is directly measured the poor of stagnation pressure and entrance section place static pressure, i.e. Δ p '=p ₀-p ₁Can get by formula (2),

$\mathrm{\Δ}{p}^{\′}=\frac{1}{2}\mathrm{\ρ}{v}_1^2---\left(10\right)$

So the computing method of traditional pitot tube type pitot meter do

$v_1=\sqrt{2\mathrm{\Δ}{p}^{\′}/\mathrm{\ρ}}---\left(11\right)$

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

$\frac{\mathrm{\Δp}}{\mathrm{\Δ}{p}^{\′}}=(A_1^2/A_2^2-1)---\left(12\right)$

If velocity hooster entrance section, place, throat section diameter are respectively d ₁And d ₂, make the diameter of section ratio

k＝d ₁/d ₂ (13)

Then

$\frac{\mathrm{\Δp}}{\mathrm{\Δ}{p}^{\′}}=(k^4-1)---\left(14\right)$

Be under the identical air speed, the measured theoretical pressure reduction of the present invention is the (k of the theoretical pressure reduction of traditional pitot tube type pitot meter ⁴-1) doubly.With k=2 is example, and then the measured theoretical pressure reduction of the present invention is 15 times of traditional pitot meter.

Table 2 has provided, the theoretical pressure difference behind the employing velocity hooster (k=2).Contrast table 1 can be found out, behind the employing velocity hooster, can significantly promote the pressure difference under the low speed.

The different pairing pressure reduction of air speed (Pa) of differing heights during table 2 k=2

It should be noted last that above embodiment is only unrestricted in order to technical scheme of the present invention to be described.Although the present invention is specified with reference to embodiment; Those of ordinary skill in the art is to be understood that; Technical scheme of the present invention is made amendment or is equal to replacement, do not break away from the spirit and the scope of technical scheme of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.

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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