SU128179A1 - Installation for measuring small damping moments when testing models in wind tunnels - Google Patents

Description

There are known installations for measuring small damping moments when testing models in wind tunnels, made in the form of a flat four-link mechanism that sets the angular oscillations of the tested model due to the kinetic energy stored by the flywheel. However, the sensitivity of such installations is insufficient.

In the described installation, in order to increase sensitivity by reducing the intrinsic dissipative forces, the hinges of the four-link mechanism are made in the form of two ball bearings located one inside the other, in which the outer cage of the smaller ball bearing is rotated by a separate electric motor.

FIG. 1 shows the installation; in fig. 2 - hinge.

The installation for measuring small damping moments when testing models in wind tunnels consists of a base 1, a flat four-stage mechanism 2, and a device for measuring angular velocity.

The motor 3 rotates the friction disk 4, from which rotational motion through roller 5 communicates to the flywheel 6 seated on the shaft 7. The rotational motion of the flywheel 6 by means of a four-stage mechanism 2 is converted into oscillatory movement of the shaft 8, to which the tested model 9 is connected. 6, the necessary acceleration of the roller 5 mounted on the lever 10 is brought out of engagement with the flywheel 6 by means of an electromagnet, which continues to rotate by inertia. At the same time, model 9 performs free oscillations with a constant amplitude and a continuously varying (decreasing) frequency, which is caused by the loss of the kinetic energy by the flywheel 6 due to the damping of model 9.

By measuring the angular velocity of the flywheel 6 in a stream flowing in a wind tunnel, with a certain number

No. 128179-2 turns the flywheel 6 in the range of variation of the angular velocity, the magnitude of the loss of kinetic energy, which determine the rotational derivatives that are characteristics of the damping model 9.

The reduction of the installation's own dissipative forces, for example, friction forces, is achieved by the fact that each of the hinges 12 and J3, as well as the hinge 14, is made in the form of a large ball bearing holder 15, the inner ring 16 of which is mounted on the sleeve 17, in which the outer ring 18 of the smaller ball support 19. These sleeves 17, and therefore the sleeves 18, are rotated at a speed much greater than the speeds of rotation of the shafts 7 or 8. The direction of rotation of the sleeves 17 of the hinges 12 is opposite, and for the hinges 13 is the same. The sleeves 17 of the hinges 12 and 14 are driven from the electromotor 3 by means of belt drives 20, and the drive for the hinges 13 from the electric motor 21 via gears 22.

The described installation allows one to determine the aerodynamic characteristics of models in a wide range, regardless of their order, to use aerodynamic pipes with small dimensions of the working part for this purpose and to significantly improve the measurement accuracy.

Subject invention

Installation for measuring small damping moments when testing models in wind tunnels, made in the form of a flat four-link mechanism that sets the angular oscillations of the test model due to the kinetic energy stored by the flywheel, characterized in that in order to increase the sensitivity to reduce its own dissipative forces, The four-link mechanism is made in the form of two pairs, located in one another ball-bearing, in which the outer cages of small sub-bearings are driven into rotation by the division. ny electric motors.

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