SU1278721A1 - Method and apparatus for measuring parameters of flow - Google Patents

Abstract

The invention can be used on aircraft and ships to determine their speed and orientation relative to the direction of movement and flight altitude, as well as to diagnose flow fields in ground experimental stands, e. Y / yMjmmV7 / MyMV / y // 7 / y / Vj7 // / Mf Fi.1 I H {and installations. The purpose of the invention is the reduction of measurement errors and the expansion of experimental capabilities. A nozzle, made in the form of a stepped pyramidal body 5.6 with a kink forming, is installed in the flow at a certain installation angle of attack of sliding. At points lying in the same plane at the front and rear of the nozzle, the pressure difference and pressure ratio are measured in pairs. According to the data obtained, local attack angles and bevel sizes are determined. If there are irregularities in the flow, the orientation of the probe is changed relative to the direction of the velocity vector of the external flow and (L repeat measurements. Local irregularities and gradients of the flow parameters are determined. 2 cf f-fla, 4 il. N3 CX5 o

Description

The invention relates to the measurement of pressure, velocity and direction of flow of a liquid or gas, and can be used on aircraft and ships to determine their speed, orientation relative to the direction of movement and flight altitude, as well as to diagnose flow fields in various ground-based experimental stands and installations. .

The aim of the invention is to reduce measurement errors and expand experimental capabilities.

Figures 1 and 2 illustrate device designs that implement a method for measuring flow parameters; in fig. 3 and 4 dependences, explaining the operation of the method and operation of the device.

The device contains a probe 1 fixed on the holder 2 in the suspension 3 connected with the drive 4 of its displacement across the flow and setting the angular position (angles of attack about (and sliding) o. The holder also has the ability to rotate about its longitudinal axis (roll angle). Probe 1 is made in the form of a stepped pyramid body of 5.6 with a fracture of the generatrix. The absolute value of the angle of fracture & cone), and © 2 the rear part of the probe b, respectively. Here the value of the angle of fracture is ± D0 in, -out-.

Zoid 1 for measurements in highly inhomogeneous streams is made in the form of sharp (Fig. 2) and blunt - truncated pyramids 7 and 8 of tetrahedral shape, joined to each other. For numbers M 5-6, the probe is executed with angles of 0.0,. ,

The magnitude of the fracture angle of the generator is selected from the condition of providing a continuous flow around the fracture point.

The sign of the magnitude of the fracture of the generatrix (positive or negative) is specified in accordance with the requirements of providing the necessary accuracy of measurements in the working range of variation of the Mach numbers. For subsonic and small supersonic flow velocities, the ratio of pressures is close to linear at e, 0gla0 0 |, and at high supersonic flow velocities, it is advisable to set, because when using the first version of the probe, the linear dependence of the number M on the ratio of pressures PI / PJ falls and measurement sensitivity. At 0 9, the nature of the curve (Fig. 4) changes to the opposite.

The measurement method is characterized by the following set of actions implemented by the nplH device operation

Calibrations are performed prior to measurements in the stream.

1. Load each of the sensors with pressure and take readings of the absolute values and differences when the sensors are turned on in pairs using a differential circuit.

2. Place probe fixed

at the coordinate, in the pressure chamber, and set the angles of attack and slip relative to the axis that coincides with the axis of the model nozzles (interchangeable or adjustable), and calibrate by the number M of the ratio of pressures measured on the surface of the first and second probe sections. Figures 3 and 4 show, as examples, the character of the change in the ratio of pressure P, / f (M) at © 5 ° on a conical probe for cases of 9.02 and 0.02 i corresponding to 5 °,

. my: 10 °).

J. With several values of the number M ,. „(from the expected range of changes during testing), the dependences of the pressure difference between the windward and leeward sides of each part of the probe ДР, Р, | /СОИ APj Pj / of-X - Pj / are removed oCiO, depending on the angle о (., specified by the coordinate. The calibration of the probe is also carried out in the same way at angles p (slip angle):

L)

LR

 & const, X const.

4. Irregularities of flow rates and their gradients are found by comparing the pressure differences between the symmetric points located on each of the stepped portions of the probe and the differences in nearby points, for example:

dr, rd

Y

40. 2 (0 bo) where S, const, X const.

31

After calibration, the probe is mounted on the mechanism with the help of a holder, connected with the drive of its movement and rotation at the angles of attack and slide. The probe holder is installed in the stream so that its axis coincides with the longitudinal axis of the aircraft (when measured in flight) or the axis of installation (when measured in bench conditions). The probe attached to the holder is placed into the flow at a certain installation angle of attack c / L of slip: Next, all pairwise pressure differences at points lying in the same plane on the front and rear parts of the probe and the ratio of pressures on the indicated areas are measured, the calibration graphs determine the number of Mso, and the remaining parameters are determined by the known gas-dynamic relationships or calibration.

According to the pressure difference in each of the planes, using local calibration charts, local angles of attack are determined for the oL of each part of the probe. The magnitudes of the bevels are found as the difference between S. and installation d angles of attack:. Similarly, bevels are determined in the plane of the slip angles of D. p -,

If the flow is uniform over the length of z.ond, then Dc (L p, lr-r If there is irregularity (yo (Lo / 2), the orientation of the probe relative to the direction of the velocity vector of the external flow, for example, by turning the pressure differences between the windward and leeward sides of one of the probe parts will become equal (or rather close) to zero. The measurements are repeated and local irregularities and gradients of flow parameters, which are between the adjacent drain holes, are found by calculating and using calibrations and said first and second portions of the probe ..

After that, at non-divergence, the probe is moved with the help of a coordinate in the longitudinal or transverse direction and the measurements are repeated.

In the absence of irregularities and flux bevels (or when their values

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irrelevant) measurement of the pressure difference in each of the sections allows unambiguously to determine the angles of attack and slip for one measurement,

and with respect to pressures in the first and second sections, determine all flow parameters (speed or Mach number, velocity head, braking pressure and static pressure, s

the value of which is unambiguously related, to the flight altitude of the aircraft).

Formula. inventions

five

1. A method for measuring flow parameters including inserting a nozzle into a stream, changing its orientation, measuring pressures on the nozzle surface in two mutually perpendicular planes with subsequent determination of the flow parameters by the values obtained, characterized in that, in order to reduce the error measurement and expansion of experimental capabilities, consistently in the direction of the velocity vector deflect the flow by a discrete constant angle relative to the vector

0 speed by changing the inclination angle of the nozzle generator, and the pressure is measured at two pairwise nearby points along the nozzle generator.

5 2. A device for measuring the flow parameters, containing nozzles in the form of a chambered pyramid, on the surface of which the receiving openings are made, located in two

0 mutually perpendicular planes, characterized in that it additionally introduces a truncated four faceted pyramid attached to the base of the sharp four-faceted pyramid, with receiving openings located in two mutually perpendicular planes, while the pyramids are aligned with equal surface areas of the base surfaces. magnitude

 the kink angle of the generatrix of the pyramidal surface satisfies the inequality of 3 ° (6, - L °, where (, ib32 are the angles of inclination of the generating surface to the axis of symmetry, respectively

5 places of a break and after a break.

at

N „

Claims (2)

Claim 1. A method of measuring flow parameters, including introducing a nozzle into the stream, changing its orientation, measuring pressure on the surface of the nozzle in two mutually perpendicular planes with subsequent determination of the flow parameters by the obtained pressure values, characterized in that, in order to reduce the measurement error and expand the experimental possibilities, successively in the direction of the velocity vector, the flow is rejected by a discrete constant value of the angle relative to the velocity vector by changing the angle of inclination of forming nozzle, and the pressure is measured at two pairwise adjacent points along the forming nozzle. 2. A device for measuring flow parameters, containing nozzles in the form of a tetrahedral pyramid, on the surface of which there are receiving openings located in two mutually perpendicular planes, characterized in that a truncated tetrahedral pyramid is attached to the base of the acute tetrahedral pyramid with receiving holes, located in two mutually perpendicular planes, while the pyramids are joined by equally sized bases, and the value of the angle of fracture of the generatrix amide surface satisfies the inequality 5 ° <| G _t - 0 ₂ l <15 °, where <P, and (3 _{2 the} angles of inclination of the generatrix surface to the axis of symmetry, respectively, to the point of break and after the break.