Air pressure gage

FIELD: measuring technique.

SUBSTANCE: air pressure gage is made of round cone (1) and comprises central opening (3) and peripheral receiving openings (4) and (5). Plate (7) abuts against the bottom face of the gage. The area of the plate exceeds the area of the bottom face. Receiving opening (6) for measuring Mach number and static pressure is made in the plate.

EFFECT: enhanced precision.

3 dwg

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 receiver air pressure, represents the cylindrical body (see patent of Russia №1723879, G01L 19/00. - 1990). The receiver is placed across the stream and is designed to measure the magnitude and direction of the flat rate of the gas streams, as well as 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 (bottom end surface), there is a feed opening that is designed to measure the Mach number and static pressure.

The disadvantages of the receiver include the measurement of static pressure and Mach number associated with the presence of his upper flat ground, disturbing the flow, as well as with the fact that when you change the angles of the bevel (flow direction) disruption of the flow is carried out not only with ribs (not odnovremenno with all edges), limiting bottom end surface, which has a receiving hole, but with its side surface, which is a part of the surface of a circular cylinder, and the coordinate of the point of flow separation from the surface of a circular cylinder (in the polar coordinate system associated with the plane of the cross-section of the receiver) is unstable and may change in the angle range 80÷140° (see Aerodynamics of missiles: 2 kN. Book 1. Ed. Mchema, Glassine. - M.: Mir. - 1989. S-265). The disadvantages of the receiver includes an additional error of measurement of speed and direction of flow at subsonic speeds, due to the fact that perturbations caused by flow separation from the surface of the receiver, propagated back through the thread. This leads to pulsations of the velocity and pressure of gas in the area of Central and peripheral receiving holes.

The reason that causes the above mentioned shortcomings, is that the pressure measured bottom receiving hole of the receiver depend on the Reynolds number - viscosity flow and from the initial turbulent flow, because the line of separation of the flow from a portion of the surface of the receiver, which is a part of the surface of a circular cylinder, change their position depending on the specified parameters and surge pressures and gas velocities caused atrivo the flow from the surface of the receiver at subsonic speeds wrapping propagated back through the thread and cover the layout area of the Central and peripheral receiving holes. Wind tunnels are characterized by high (compared to the free atmosphere) the initial level of turbulence, and therefore the received calibration dependencies used to determine the flow parameters will be inaccurate and unstable in the free atmosphere or in streams with a different level of initial turbulence. All these factors ultimately lead to occasional pressure on the bottom end surface of the receiver and in the area of Central and peripheral receiving holes and cause a measurement error of the air parameters.

The closest to the invention by the combination of essential features is the receiver air pressure, representing the body, a limited part of the side surface of a circular cone and intersecting circular cone by a plane, which is the bottom end surface of the receiver (see the patent of Russia №2227906, G01L 19/00. - 2002). The receiver is also located across the stream and is designed to measure the magnitude and direction of the flat rate of the gas streams, as well as to measure the static pressure and Mach number. On part of the surface of the receiver represents part of a side surface of a circular cone in Berlin the wife receiving apertures - Central and peripheral designed to determine the direction and magnitude of the flow velocity. By intersecting the surface of the rotation of the plane on the bottom end surface of the receiver is receiving hole that is designed to measure the Mach number and static pressure.

The disadvantages of the receiver include the error of measurement of Mach number and static pressure associated with the fact that when you change the angles of the bevel (flow direction) disruption of the flow is carried out not only with ribs (not at the same time with all edges), bounding the bottom end surface of the receiver, which has a feed opening that is designed to measure the static pressure and Mach number, but with its side surface, which is part of a lateral surface of a circular cone, and the coordinate of the point of separation of the flow from a portion of the conical surface (in the polar coordinate system associated with the plane of the cross-section of the receiver) and unstable can vary in a wide range of angles (as similar). The disadvantages of the receiver includes the error of measurement of speed and direction of flow, due to the fact that at subsonic speeds the flow disturbances caused by flow separation from the surface of the receiver, propagated backward through the stream that leads to the appearance of the pulse is the second of the velocity and pressure of gas in the area of Central and peripheral receiving holes.

The reason leading to measurement errors, is that the pressure measured bottom receiving hole depend on the Reynolds number - viscosity flow and from the initial turbulent flow, because the line of separation of the flow from the surface of the receiver, which is part of a lateral surface of a circular cone, change their position depending on the specified parameters, which leads to occasional change of pressure in the bottom region and, as a consequence, the measurement errors. In connection with the above obtained for receiver pressure calibration dependencies used to determine the flow parameters will be inaccurate and unstable streams with a different level of initial turbulence. Central and peripheral receiving apertures that are used to determine the direction and magnitude of the velocity of the gas stream at the receiver are in close proximity to the stall area of the gas flow, which leads to the transmission of pulsations of pressure back flow to the Central and peripheral receiving holes at subsonic speeds the flow and, as a consequence, the errors of measurement of speed, direction of flow, 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 the flow of gas moving dozvukovoye, transonic and supersonic speeds, and also the values of the speed and direction of gas flow in the streams moving at subsonic speeds.

The technical result consists in increasing the accuracy of measurement of static pressure and Mach number in the flat flow of gas moving at subsonic, transonic and supersonic speeds, and also the values of the speed and direction of gas flow in the streams moving at subsonic speeds, by giving the receiver forms, ensuring the stability of the position of the lines of separation of the flow from the edges bounding a bottom end surface of the receiver, which is located bottom of the receiving hole, and also by reducing pressure pulsations in the locations of the Central and peripheral receiving holes.

The technical result is achieved in that the air receiver pressure for flat gas streams, representing the body, a limited part of the side surface of a circular cone whose axis is used to set the receiver across the stream located on the surface of the Central and peripheral receiving holes designed to determine the direction and magnitude of the velocity of the gas stream, and the receiving hole, designed to measure the Mach number and static pressure, located adonoy end surface of the receiver, contains plate adjacent to its bottom end surface, the area of which exceeds the area of the bottom end surface and is determined from the condition that the tangent to any part of the side surface of a circular cone, held in the plane of the cross section of the receiver parallel to the ground plane, have a common point with the edge of the plate forms an angle with the line of intersection of the vertical plane of symmetry of the receiver ground plane greater the maximum value of the module of the bevel angle of the stream, and the receiving hole to measure the Mach number and static pressure is made in the plate.

1 shows a General view of the receiver pressure. Figure 2 and figure 3 shows the velocity field of a known and claimed receivers pressure.

The inventive receiver air pressure (see figure 1) is a body, a limited part of the side surface of the circular cone - 1 axis - 2 is designed for installation of the receiver across the stream located on the surface of the Central - 3 and the peripheral - 4, 5 receiving holes designed to determine the direction - ε (bevel angle of flow) and the magnitude of the flow velocity V_∞and the receiving hole - 6, designed to measure the Mach number and static pressure, located on the bottom end surface of the pickup is nick - The ABC. The receiver contains a plate - 7, the area of which exceeds the area of the face formed by the cross-section of a circular cone by a plane, and the magnitude of the square is determined from the condition that the tangent DE (D, E') to any part of the side surface of a circular cone, held in the plane of the cross section of the receiver To parallel to the ground plane - 1, have a common point with the edge of a plate - F (F'), forming an angle of γ line HG crossing the vertical plane of symmetry of the receiver ground plane, the greater the maximum value of the module of the bevel angle of the stream.

Figure 2 shows the velocity eld (contours of velocity in the plane of arrangement of the receiving holes for the receiver air pressure (prototype), whose body is limited to a part of the side surface of the circular cone - 1 for the Mach number of the oncoming left flow M_∞=0,5. Darker spots correspond to the maximum and minimum values of the gas velocity. Position 8 is indicated velocity field at the side surface of the circular cone in the area of one of the spoke receiving holes for the value of the tangential gas velocity V_τ=323 (m/s). Position 9 depicts the velocity field at the side surface of the circular cone in the area of the second peripheral inlet opening for the value of the tangential velocity V _τ=255 (m/s). Position 10 marked the track of the Pocket for a receiver pressure.

Figure 3 shows the velocity field (contours of velocity in the plane of arrangement of the receiving holes for the proposed receiver air pressure, the body of which is limited by the lateral surface of a circular cone, with the adjacent plate 7 for the incident left stream Mach number M_∞=0,5. Darker spots correspond to the maximum and minimum values of the gas velocity. Position 11 is indicated velocity field at the side surface of the circular cone in the area of one of the spoke receiving holes for the value of the tangential gas velocity V_τ=162 (m/s). Position 12 is indicated velocity field at the side surface of the circular cone in the area of the second peripheral inlet opening for the value of the tangential gas velocity V_τ=148 (m/s). Position 13 is indicated velocity field at the edge of a plate, the maximum value of the gas velocity V_τ=246 (m/s). Position 14 is indicated velocity field at the opposite edge of the plate, the value of the tangential gas velocity V_τ=197 (m/s). Position 15 marked the track of the Pocket for a receiver pressure.

The receiver pressure is as follows. First, for the inventive device to the establishment of the relationship of pressure, perceived receiving holes, with parameters a flat air (or gas) flow: the angles of the bevel, Mach numbers, the static pressure of conduct blowdown receiver in a wind tunnel, the results of which are calibration dependencies, which can be the following:

for bevel angle

f_ε(ε)=(P₄-P₃)/(P₅+P₃-2P₆);

for Mach number

f_M(M)=p₃/p₆;

- for static pressure

where P_i- pressure; i - number of the receiving holes (see figure 1); ε - bevel angle of flow; M - Mach number; P_article- 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 the calibration dependence solve the inverse problem on the measured pressures are: bevel angle, 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.

As follows from the above formula, the total is x for the prototype and the proposed receiver, they all contain the pressure P₆perceived receiving hole located on the bottom end surface of the receiver, and therefore, the accuracy of the measurement of the air flow receivers containing a feed opening in the area of separated flow is largely determined by the accuracy of the measurement pressure P₆.

Only stability and not the 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 zone of separated flow. For the prototype, representing the body, limited only part of the circular cone and the face formed by the section of a cone by a plane, unable to get in the bottom region for stable and not changing randomly in time parameters (velocity, density, pressure) due to the fact that the gap flow when changing the angles of the bevel cannot be carried out simultaneously with all edges bounding a face of the receiver, which is located bottom of the receiving hole. The gap flow is carried out, including, and with part of the surface of rotation, and for bodies with clean lines the coordinates of the line of separation of the flow from the surface of the body depend on the parameters flow: Reynolds number, the initial turb is lastnosti (see Aerodynamics of missiles: 2 kN. Book 1. Ed. Mchema, Glassine. - M.: Mir. - 1989. Pp.261-267).

For settings, changing a non-random, can be obtained only for bodies, the shape of which provides a separation of the flow in well-defined places, regardless of the parameters flow (Reynolds number, the initial turbulent flow). The inventive receiver air pressure contains such elements of design - fin plate 7, which will always be the separation lines of the stream, if (see figure 1) tangent DE (D, E') to any part of the side surface of a circular cone, held in the plane of the cross section of the receiver parallel to the ground plane - I, have a common point with the edge of a plate - F (F'), forming an angle of γ line HG crossing the vertical plane of symmetry of the receiver ground plane greater the maximum value of the module of the bevel angle of the thread ε. When performing inequalities γ>|ε| plate 7 (see Fig 1) for any values of the angles of the slant of the thread ε (flow direction) will not be in the wind shadow from the conical body of the receiver, therefore it is all the edges of the plate 7 (not the surface of a circular cone) will be the lines of separation of the air (gas) stream.

Only the presence in the design of the receiver pressures sharp edges at the changing angles of the bevel flow from the windward side allows to obtain stable coordinates of the lines of separation of the flow and, as a consequence, the minimum error in the measurement of pressures in the area of the inlet opening 6 (Fig 1). The measured pressure in this case will depend only on the velocity of the gas stream, and not on its viscosity and the initial turbulence.

The prototype, due to the fact that one edge formed by the cross-section of a circular cylinder by a plane, when you change the angles of the slant of the thread is on the leeward side, i.e., falls into shadow, tear-unstable, which leads to errors of measurement of pressure.

At subsonic flight speeds for the prototype and the claimed receiver pressures are formed vortex structures - track Pocket (see figure 2 and figure 3). Formed in the bottom region for receivers pressure vortices cause pulsations of the velocity and pressure of gas in the area of Central and peripheral receiving holes. But the proposed receiver pressure, these pulsations are significantly less due to the fact that disruption of the flow and turbulence occur at the edges of the plate, the overall transverse dimension that is greater than a corresponding dimension of the body of the receiver pressure, a limited part of the surface of a circular cone. As a result, the measurement accuracy of the air parameters allow jemym receiver pressure is higher, than that of the prototype.

Thus, performance of the proposed receiver air pressure in the form of the body, a limited part of the side surface of a circular cone, with the adjacent plate will improve the measurement accuracy of the air parameters as at subsonic and transonic and supersonic speeds compared to the receiver in the shape of the body, containing only a portion of the surface of rotation without the adjacent plate.

Receiver air pressure for flat gas streams, representing the body, a limited part of the side surface of a circular cone whose axis is used to set the receiver across the stream located on the surface of the Central and peripheral receiving holes designed to determine the direction and magnitude of the velocity of the gas stream, and the receiving hole, designed to measure the Mach number and static pressure, located on the bottom end surface of the receiver, wherein the receiver includes a plate adjacent to its bottom end surface, the area of which exceeds the area of the bottom end surface and is determined from the condition that the tangent to any part of the lateral surface of a circular cone, held in the plane of the cross section of the receiver parallel to the PLO the bones of the base, have a common point with the edge of the plate forms an angle with the line of intersection of the vertical plane of symmetry of the receiver ground plane greater the maximum value of the module of the bevel angle of the stream, and the receiving hole to measure the Mach number and static pressure is made in the plate.