SU1478063A1 - Dynamometric towing arrangement - Google Patents

Abstract

The invention relates to technical means of experimental hydrodynamics and can be used to measure the forces of resistance to the motion of models. The purpose of the invention is to expand the range of measured forces. The dynamometer towing device contains a towing knife with a model fixed on it and a measuring element associated with the model. The device comprises a sleeve hinged on a horizontal axis, which includes horizontal and vertical parts, and a rod with a weight mounted on it with the possibility of movement. The rod is fixed to the horizontal part of the fork, which is rigidly connected to the towing knife. The measurement element is designed as an elastic element connected to the vertical parts of a fork by means of flexible connections and an electrical sensor including two fixed inductors and a core rigidly connected to the elastic element. 3 il.

Description

 The invention relates to technical means of experimental hydrodynamics and can be used to measure the forces of resistance to the motion of models.

The purpose of the invention is to expand the range of measured forces.

Figure 1 shows the device; figure 2 - node 1 in figure 1; Fig. 3 shows the operating characteristic of the elastic element.

The device comprises a plug 1 consisting of vertical parts 2 and 3 and horizontal part 4. Height h

the vertical part is determined by the expression

h}

X MIN

where 1

- the length of the towing but-, a 5; Rv - minimum allowed

And № p

load on measuring element 6 (limit of sensitivity), determined by passport or by calibration; the magnitude of the resistance force determined at the lowest possible rate R

min

-U j

00

O5 00

3 1478063

the towing speed of model 7, for a given towing speed and fluid density depends on the model we are and its position relative to the surface of the liquid.

In particular, for bodies of revolution, a sphere, a cylinder, an ellipsoid) located at a depth, where D is a di10

n K to in with in e r

body meter, the value of Rx M is calculated by the formula

D

 ALI

-G. With RLUUDI,

 2;

where C

v

min

resistance coefficient} determined by reference data;

the area of the midsection of the body;

fluid density; The lowest possible towing speed model. The size of the horizontal part 4 of the fork 1 is determined by the horizontal dimension of the elastic element 6, the fork 1 is pivotally fixed on the horizontal axis 8 "mounted on the towing carriage 9. On the horizontal part 4 of the fork 1, the rod 10 is fixed with the load 11 installed on it ,

The rod 10 has a cylindrical shape and is fixed on the horizontal part 4 of the plug 1 by means of a threaded joint, which allows changing the position of the rod 10. The axis of the rod 10 is located horizontally and intersects the axis of rotation of the two shoulders at an angle of 90 °. The load 11 is connected to the rod 10 by means of a threaded joint that secures the load 11. Moreover, the load 11 is made in the form of two identical cylinders. Such an embodiment makes it possible to securely fix its position on the rod 10, since one of the cylinders is a lock nut for the other. In addition, the position of the adjacent bases of the cylinders is used to determine the coordinate of the center of the weight and weight of the load.

The rod 10 is mounted on the horizontal part 4 on the side of the vertical part 2 (the resistance force Rx has the direction indicated in FIG. 1). In this position stock mouth

0

5 Q

five

0

When the resistance force, K, the movement of the model 7 imposes a load on the elastic element 6 that exceeds the value corresponding to the working section of its characteristics. If the magnitude of the force RK is not sufficient to create a load that is required according to the characteristic of the elastic element b, the rod is 10 meters from the side of the vertical part 3.

The towing knife 5 is positioned vertically and rigidly fixed on the horizontal part 4 forks 1 The lower end of the knife 5 is rigidly connected to the model 7,

The elastic element 6E, fixedly mounted on the carriage 9 and connected to the vertical parts 2 and 3 of the fork 1 by means of flexible links 12, is made in the form of a parallelogram containing a movable 13 and a fixed 14 base, connected by elastic bars 15. The elastic element can be made in the form of an elastic rod or membrane. The fixed base 4 of the elastic element 6 is rigidly fixed on the towing carriage 9. The movable base 13 is connected to the vertical parts 2 and 3 of the forks 1 by flexible connections 129 which ensures the freedom of vertical movements of the mobile base 13 of the elastic element 6 when the vertical parts 2 and 3 deviate from the initial position In the variant shown on, one of the ends of the flexible connection 12, made in the form of a plate spring} is pressed into the groove 16 of the vertical part 2 (3). Its other end rests on the movable base 13 of the elastic element 6.

The katuiki 17 inductance of the electric sensor 18 is fixedly mounted on the towing carriage 9. The core 19 of the sensor 18 is rigidly connected to the elastic element 6. When performing a flexible connection according to FIG. 2, the core 19 is fixed on the movable base 13 of the elastic element 6. The fastening of the elements of the sensor 18 is carried out with the help of brackets 20. The windings of inductors 17 are connected to an electrical measuring instrument (not shown).

Example The fork is made of duralumin. The height of the vertical parts is 30 mm, the horizontal part has

length 115 mm. The width of all parts is 65 mm. The thickness of the vertical parts of 15 mm, the horizontal part of 35 mm. Bearings are installed in the center of the lateral surfaces of the horizontal part in holes with a diameter of 30 mm. The rod has a cylindrical shape, its diameter is 10 mm, length 150 mm. A graduation scale with a step of 0.1 mm is plotted along the stem axis. Rod and weight are made of brass. The load is made in the form of two identical 75 mm cylinders with a height of 10 mm. The weight of each cylinder is 300 g.

The towing knife is made of stainless steel in the form of a 300 mm long hollow wing. The bases of the elastic element are 75 mm long and 65 mm wide. Base thickness 5 mm. Vertical beams of rectangular section, 5-1.5 mm, 50 mm long, are located at the corners of the bases. The elastic element is made of hardened steel. As an electric sensor, an acceleration sensor DU-5C is used, which is part of the equipment VI6-6TN (VI-02-B8TU).

Flexible communications are made in the form. flat steel plates 40-10 mm with a thickness of 0.2 mm. The free ends of the plates are rounded along the radius of 0.1 mm. The axis is made of brass. The length of the axis is 250 mm. The central part is 65 mm long and has a diameter of 10 mm for bearing installation. The diameter of the end parts of 7 mm.

The mounting brackets for the electrical sensor are made of duralumin, they are rods of 30-5zh x3 mm with bases of 10-10-3 mm.

The towing carriage is an H-shaped structure made of three steel plates 10 mm thick bonded to each other. The two side plates are trapezoidal with bases of 300 and 200 mm and a height of 350 mm. The horizontal plate mm is set at a distance of 100 mm from the upper edges of the side plates. In the upper part of each side plate, the axles of two wheels having a diameter of 100 mm are strengthened. The distance between the axles is 150 mm. Wheels mounted on one of the plates have V-shaped grooves. The rail head has a groove-shaped shape that prevents 780636

No possibility of horizontal displacement; lower carriage.

The device works as follows.

Before starting measurements, calibration is performed. According to the results of calibration, a graph of the dependence of the output signal of 1 electric sensor .JQ (current) on the load R on the towing knife is plotted

five

0

0

I f (Rx.

Such a relationship for this example is shown in FIG. 3. On the working. The characteristic of the measuring element (R) is distinguished from three characteristic areas (Fig. 3): a - a section of low sensitivity due to the presence of friction in connection between the elements of the device; $ - working area; e - section of the overload corresponding to the position of the core, at 5 of which one of the air gaps in the magnetic systems of the sensor is zero (further movement of the core is impossible).

Before starting the measurements, a series of control measurements of the resistance force is made to determine the value of the required initial load on the measuring element created by the load-rod system. For this, the rod 10 is installed on the side of the vertical part 3 of the plug 1. The arrow of the electrical measuring device is outputted to O. The weight 10 is mounted on the stem 10. At the same time, the force of the load G of the load 11 creates an initial load on the elastic element 6. The magnitude of this load is recorded by an electrical measurement. device. The shoulder t of the strength of the body of G of the load 11 choose

. according to the initial reading of the 1D electric-5 "measuring device and the calibration graph so that the initial load on the elastic element 6 corresponds to the working section Y of the characteristic (Rx) (vol. A, fig. 3):

t Rx 1n

15

where Rx ddii is the value of the resistance force corresponding to the lower boundary of the working section of the characteristic (Rx) (FIG. 3);

five

0

0

714

1C - the length of the towing knife 5;

G is the weight of the load 11. Thus, they exclude the section a of low sensitivity and ensure the operation of the measuring element in the working linear section of its characteristics.

If, during the control measurement, the resistance force of the model 7 (instrument reading) exceeds the values corresponding to the working area & the characteristics of the measuring element, the rod 10 is installed on the fork 1 from the side of the vertical part 2, After the arrow of the electrical measuring device is mounted on O, a load 11 is installed on the rod 10. In this case, the moment of gravity G of the load 11 is directed opposite to the moment of resistance

lazy Ry and partially compensates for his action when moving the model.

In this case, the reverse polarity is preset at the terminals of the electrical measuring instrument, since when the position of the rod 10 is changed, the direction of displacement of the core 19 relative to the coils 17 of the electric sensor 18 and the direction of the current in the sensor circuit change.

The magnitude of the arm 1 of the force G is determined by the equation

1. €. 5khl1 l111l 1 g

G

five

Ie, A, on the working section of the characteristic (Rx) is the extreme left position, with decreasing resistance value Kx (the speed decreases) - the extreme right one.

After the preparatory stage for carrying out the measurement of the resistance force, the carriage 9 is set in motion. The resultant force of resistance Rx to the movement of the model 7 is perceived by the towing knife 5. Under the action of the moment of force R, the fork 1 rotates on the horizontal axis 8 and its vertical parts 2 and 3 deviate from the initial position by an angle proportional to the magnitude of the moment.

The deviation of the vertical parts 2 and 3 causes a displacement of the flexible connection 12, under the action of which the movable part 13 of the elastic element 6 is displaced relative to its fixed part 14. As a result of the deformation of the elastic element 6, the air gaps in the magnetic systems of the electric sensor 18 change. sensor 18 is recorded by an electrical measuring device.

0 The value of the measured resistance force is determined in accordance with the expression

0

R., R

, and C,

where R.

K LLSTSKs

the magnitude of the resistance force corresponding to the upper boundary of the working section of the characteristic (Rx) (Fig. 3, the calibrated graph does not change when the direction of the loading force changes to the measuring element 6). The control measurement is repeated as many times as necessary until the load on the measuring element corresponds to the working section of the characteristic (Rx) (i.e., FIG. 3). In this case, the shoulder 1 of the force G is increased each time by an amount determined by the above equation. The length of the shoulder 1 set on the rod 10 on the graduation scale.

With an increase in the resistance value RX from measurement to measurement (the speed of the model increases) the most preferred position

five

where i

0

- electric meter reading during testing j

RX () is the corresponding value of the resistance force determined by the operating characteristic (Rx) (Fig. 3),

moreover, in the formula the sign is put - if the rod 10 is installed on the side of the vertical part 3 of the plug 1, and the sign +, if the rod 10 is installed on the side of the vertical part 2.

Claims (1)

Invention Formula A dynamometer towing device containing a towing knife with a model fixed on one of its ends and a measuring element connected to the other end of the towing device, characterized in that, in order to rub the range of measured forces, the device contains a fork hinged on a horizontal axis, including horizontal and vertical parts and a rod with a load mounted on it with the ability to move, while the rod is fixed on the horizontal part of the fork, which is rigidly connected on 1B 20 2 ° / " with the towing knife, and the measuring element is designed as an elastic element connected to the vertical parts of the fork by means of flexible couplings, and an electric sensor including two fixedly mounted inductors and a core rigidly connected to the elastic element. Fi.g. 7 Yu gO 30 40 50 60 Fig.Z FIG. 2