Air pressures receiver

FIELD: aircraft engineering.

SUBSTANCE: device is a body, limited by portion of surface of body of special shape 1, with central 2 and peripheral 3, 4 apertures in it, meant for determining direction and value of speed of gas flow and cutting plane of parallel axis of specific body, on which aperture 5 is placed for determining Mach number and static pressure.

EFFECT: higher precision, lower interference.

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The invention relates to the field of measurement technology and can be used to measure parameters of flat flow of gaseous media or for determining motion parameters of rigid bodies, aircraft, missiles, etc. relative to the air environment.

Known cylindrical receiver pressure, designed to measure the magnitude and direction of velocity two-dimensional gas flows and the Mach number (see, for example, Petunin A.N. Methods and techniques of measuring parameters of a gas stream. M:. The engineering. - 1996. - P. 166.). The receiver is made in the form of a cylindrical tube, which on the surface in the plane of the cross section are the receiving holes: Central and two peripheral to measure the pressure used to determine the direction and amount of the gas flow rate. The receiver has the greatest sensitivity to the angle of bevel of the stream, measuring the velocity direction).

The disadvantage of the receiver is that when using it to measure the static pressure is measured with considerable error that is associated with a large angular sensitivity of the receiver and, as a consequence, displacement of a point on the surface of the receiver, in which the pressure is static, changing direction as the flow velocity or the change in elevation is th position of the receiver. The disadvantages of the receiver can be attributed to the error of measurement of Mach number and value of the velocity of the gas stream at high subsonic and supersonic speeds, which is associated with the phenomenon of stabilization of local Mach numbers. With Mach numbers M>0.75 loss of receiver sensitivity to the magnitude of the velocity and the Mach number is not restored.

The reason preventing people from getting in a known technical solution required technical result is that on the surface of the cylindrical receiver is not strong acceleration of the gas flow, resulting in it already with Mach numbers M≈0,75 local supersonic zones, which, in turn, cause significant loss of receiver sensitivity and decrease the accuracy of the measurement value of the flow velocity and Mach number, and the high sensitivity to the angle of the bevel makes it unsuitable for measuring the static pressure due to the displacement of the point where the pressure is static, changing the angular position of the receiver relative to gas flow.

The closest to the invention by the combination of essential features is the receiver air pressure, represents the cylindrical body (see patent of Russia №1723879, G 01 L 19/00 from 02.01.90 - prototype). The receiver is designed to measure the magnitude and direction of velocity PLO is such flows, gas, and also to measure the static pressure and Mach number. On the part of the cylindrical surface of the receiver, which is part of the lateral surface of a circular cylinder, are the receiving holes of the Central and peripheral used to determine the direction and magnitude of the flow velocity. On the verge of a cylindrical surface, which is at the measurements on the leeward side, there is a receiving hole (bottom)designed to measure the Mach number and static pressure.

The disadvantage of the receiver is that the bottom of the receiving hole is in the area of stall area intensive mixing of gas, education reciprocating circulation flow and pressure pulsations, carrying random character, which leads to increased errors of measurement of static pressure and Mach number. The disadvantage of the receiver is that it creates a significant disturbance in the gas flow, as it has prohealthcare form the upper flat base facing the stream intersects the cylindrical surface with the formation of sharp edges, which is one of the conditions of functioning of the prototype, while well-streamlined body (body aerodynamic shape) - little disturbing thread should have smooth edges (see, for example, drawings of similar - Petunin A.N. Methods and techniques of measurements n the parameters of the gas stream. M:. The engineering. 1996. S).

The reason preventing people from getting in a known technical solution required technical result is that the ratio by which calibration are based receiver intended for receiving relationship pressures, perceived receiving holes, with parameters of the air flow, contain the pressure, perceived bottom receiving hole, which is in the area of stall, which is characterized by random fluctuations of the pressure, resulting in averaging of pressure at different time intervals view calibration curves will depend on the averaging period of the pulsations. The instability of the calibration curves and associated with strong perturbations of the stream, carrying random character created by the upper base of the prototype, facing the stream. The presence of the upper flat base leads to the formation of additional spatial vortex structures, which destroy the stable (non-random) two-dimensional patterns. The above reasons and ultimately lead to increased errors of measurement of static pressure and Mach number.

The invention is directed to solving the problem of increasing the accuracy of measurement of static pressure and Mach number in a flat gas flows, and n is the reduction of disturbances, generated by receiver pressure in the gas stream.

The technical result consists in increasing the accuracy of measurement of static pressure and Mach number in a flat gas flows, and reduction in disturbance generated by the receiver, by giving him this model is well streamlined.

The technical result is achieved by the fact that in the known receiver air pressure, representing the body, a limited part of the surface of rotation with the location of the Central and peripheral receiving holes designed to determine the direction and magnitude of the flow velocity, and intersecting the surface of the rotation plane parallel to the axis of rotation surface, which has a feed opening that is designed to measure the Mach number and static pressure, the portion of the surface of rotation of the receiver is made as part of the surface of the body arched form.

Description body having the form of a revived, can be found, for example, in the book: Petunin A.N. Methods and techniques of measuring parameters of a gas stream. M:. - Engineering. - 1996. - S.

1 shows a General view of the receiver air pressure.

Figure 2 shows the density field to the air stream, flowing the claimed receiver pressure. The receiver section in the plane of arrangement of the receiving holes is redstavlena position 1. Position 2 indicated vortices formed at a bottom surface of the receiver included in the track of his Pocket.

Figure 3 shows the density field (contours density) of air flowing across the prototype, whose cross section is in the vertical plane of symmetry of the cylinder, represented by item 1. Position 2 the designated centre spatial vortex structure formed on the upper base of the cylinder.

The inventive receiver air pressure (see figure 1) is a body, a limited part of the surface of the body arched form 1, which has a Central 2 and the peripheral 3 and 4 receiving apertures designed to determine the direction and magnitude of the flow velocity and the plane 6, which has a feed opening 5 (bottom), designed to measure the Mach number and static pressure, the receiver has a base 7, which it is fastened to the holder or to the object, and to reduce the perturbations introduced into the air stream, the top of the receiver 8 may be rounded.

The receiver pressure is as follows.

First, for the inventive device to establish the relationship between pressure, perceived receiving holes, with parameters a flat air (or gas) flow: the angles of the bevel, the Mach number, static galleriesprostate blowdown receiver in a wind tunnel, the results of which are calibration dependence. In the General case, the proposed receiver air pressure and prototype calibration dependencies can be determined on the basis of the same formula. For example, the desired flow parameters can install the following dependencies:

for bevel angle

for Mach number

for static pressure

where P_i- pressure; i - number of the receiving holes (see figure 1); ε - the angle of the bevel; M is the Mach number; P_cm- static pressure.

Then, when determining the parameters of the air flow or in the determination of motion parameters of rigid bodies, aircraft, missiles, etc. relative to the air environment, using found by the above (or any other) formulas calibration dependence solve the inverse problem on the measured pressures are the angles of the bevel, the Mach number, static pressure, and on detected values of the Mach number and static pressure - flow rate.

Consider the features wrap prototype and the proposed receiver air pressure and show why the implementation of the receiver according to figure 1 allows to achieve the claimed technical result. Consider the case is, when the receiver pressure is not fastened to the holder, and to a flat substrate, such as a turbine blade or aircraft.

As follows from the above formula, the total for the prototype and the proposed receiver, they all contain the pressure P₅perceived bottom receiving hole, and therefore the accuracy of measurements of parameters of the air flow receivers containing a receiving hole in the area of stall, largely determined by the accuracy of the measurement pressure P₅.

Only stability and randomness of the obtained calibration curves can provide a high accuracy of determination of parameters of the air (gas) flow at measuring the pressure in the bottom region is the area of the stall. For prototype - shortened cylindrical body cannot get in the bottom region for stable - not changing randomly in time parameters (velocity, density, pressure). For settings, changing a non-random, can be obtained for a cylindrical body of a large extend with the value of the ratio of the height of the receiver to the diameter, for example, more than 10. With this ratio of height to diameter of perhaps getting in the bottom region of the flow close to flat (two-dimensional), having a form of non-random vortex structures is - track Pocket. But such execution receivers pressures for flat threads is unacceptable, because high altitude receivers will lead to blockage of the flow, resulting in the receiver will make a significant perturbations in the flow, having a large aerodynamic drag. One of the basic requirements for receivers of air pressure, the minimum transverse (relative flux) dimensions and minimum wind resistance, so when you (at a small value of the ratio of height to diameter), the structure of the gas flow in the bottom region of the prototype will be a completely different space. This is due to the fact that at relatively low altitude of the prototype nature of the flow in the base region has a significant (determines) the influence of top facing the flow, the base of the receiver, which in this case leads to the formation of additional vortex bundles.

Thus, due to the flat top of the base of the transition from two-dimensional flow to three-dimensional (spatial), as a stable two-dimensional patterns in this case are destroyed due to short-wave instability (see Belotserkovsky O.M. Numerical simulation in continuum mechanics. - M.: Nauka. - 1984. - P.93). Figure 3 shows the density field (isol the Sri density) for air flow, flowing the prototype. The prototype is installed on a flat base-plate, the stream runs to the left, the Mach number M=0,9. The cross section of the prototype in the vertical plane of symmetry represented by the position 1. As follows from figure 3, with the receiver having a ratio of height to diameter equal to three, there is no track of the Pocket, and at a height of about flat top face is formed vortex structure, the center of which is indicated by the position 2. Below is a zone of back-circulating flow. When constructing calibration curves with this structure, the flow of their appearance will depend on the initial turbulent flow, turbulence, turbulence scale), from the time of formation of the vortex structure and turbulent flow in the receiver itself. The wind tunnel have different degree of turbulence, which, in turn, is higher than in the free atmosphere under normal conditions. Therefore calibration based, built on formulas involving pressure, measured in the base region will be unstable and will be different for different wind tunnels and the free atmosphere. The difference in the measured pressure in the bottom region due to the pulsation of the pressure will be provided by another period (time interval) T, during which the measured pressure, i.e. the time t₂-t ₁during which determined the average pulse pressure valuein the field of turbulent flow:

For the prototype nature of the generated turbulent flow (and hence the averaging period pressure) depends on the initial turbulence of the flow and can be set uniquely in the calibration.

The prototype of its base, facing the stream, and creates a strong disturbance in the flow of air (gas) in height, including through the formation of additional vortex structure, the center of which is located at the Foundation level. Presented on figure 3 contours of the density of the air show that perturbations generated by the prototype, go up steeply.

In the case of the performance of the proposed receiver pressure as part of the body arched form (figure 1), which has no upper flat base (like a cylinder), facing the stream, but due to the curvature of the generatrix revived the side surface of the receiver may be closer in size to a cylindrical, it is possible to keep the current in the base region close to flat - type track Pocket. Figure 2 shows calculated using the method of large particles (see Belotserkovsky O.M., Davydov, Y.M. Method of large particles in gas dynamics. - M.: Nauka, 1982. - 392 S.) field of platnost is for air flow, flowing the claimed receiver pressure. The Mach number, the incident on the receiver to the left of the air flow, M=0,9. The receiver section in the plane of arrangement of the receiving holes is represented by item 1. The receiver pressure is set on a flat base and has a ratio of height to base diameter equal to 2.8. Position 2 indicated vortices formed at a bottom surface of the receiver included in the track of the Pocket. Only figure 2 presents 10 vortices whose intensity diminishes as the distance from the receiver. The Pocket track is sustainable education, its parameters depend little on the initial turbulent flow: the degree of turbulence, turbulence scale. For different wind tunnels and for the free atmosphere under normal conditions the period of the formation of the vortices is determined mainly by the speed of incoming air flow (Mach number). In this regard, the calibration based, built on formulas involving pressure, measured at the bottom area will be for the proposed receiver air pressure is stable and will not be different for different wind tunnels and the free atmosphere. The period (time interval) T, during which it should be measured the pressure, i.e. be averaged pressures for the proposed receiver can be installed easily on the basis of the ODA is dividing the period of the formation of individual vortices.

Reducing the perturbations introduced in the air flow indicated by the air receiver pressure is a matter of running it as a part of the body arched form. In this case, perturbations propagating in the direction of the height of the receiver is small, because of the well-known property of thin bodies with smooth edges, to make a minimum of disturbance to the stream. The reduction of the disturbances introduced into the air stream of the inventive receiver, in the direction perpendicular to the plane, which has a feed opening that is designed to measure the Mach number and static pressure, due to the significant decrease in cross-sectional area of the body arched form compared to cylindrical with the same values of the heights and areas of the grounds.

As shown by calculations, body arched form provide sustainable education track Pocket for the whole range subsonic speeds and ranges transonic and supersonic speeds (for example, to the value of the Mach number M=2).

Thus, performance of the proposed receiver air pressure in the form of body arched form, is installed across the flow, will increase the accuracy of the measurement of static pressure and Mach number, as well as to reduce the perturbations introduced by the receiver in the air (or gases which th) stream, compared with the receiver in the form of a cylindrical body.

Receiver air pressure, representing the body, a limited part of the surface of rotation with the location of the Central and peripheral receiving holes designed to determine the direction and magnitude of the flow velocity, and intersecting the surface of the rotation plane parallel to the axis of rotation surface, which has a feed opening that is designed to measure the Mach number and static pressure, characterized in that the portion of the surface of rotation of the receiver is made as part of the surface of the body arched form.