RU2660305C2 - Device for demonstration the bernoulli equation with respect to the closed flows - Google Patents

Abstract

FIELD: hydraulic equipment.

SUBSTANCE: invention relates to the devices for training on the "Hydraulics" engineering course when carrying out the laboratory works. Essence of the invention consists in that the device, which comprises the pressure tank with the water supply, inside which the drainage funnel is provided in order to maintain the water level, and the pipeline, on which the piezometers are installed in order to record the pressure along the length of the pipeline, can change the deviation angle of the pipeline. In order to change during the experiments the angle of inclination of the pipeline, it is connected via the flexible hose to the pressure tank.

EFFECT: device is proposed for demonstrating the Bernoulli equation with respect to the closed flows.

1 cl, 1 dwg

Description

The invention relates to devices for training in the engineering course "Hydraulics" during laboratory work.

A device is known (in the hydraulic laboratory of Voronezh State Technical University), consisting of a pressure tank, which is studied at a pipe section inclined at a constant angle to the horizon in the form of a Venturi flowmeter with piezometers and full pressure pipes (Pitot tubes) installed in them in appropriate places, in the form of communicating vessels from transparent tubes, with which you can determine all the components that make up the Bernoulli equation, and use them to build a piezometric and pressure lines.

The disadvantage of this device is the constant angle of inclination of the investigated area to the horizon, and, therefore, the impossibility of visual observation of the transition of one type of specific energy to others during the experiments when the angle of the studied area changes and the water supply is not stopped during the experiments.

The invention is intended for visual (visual) observation during experiments of a change in all components making up the total specific energy according to the Bernoulli equation, when, for example, the pipe slopes change, without stopping the flow of water to the experimental setup.

The technical result consists in providing the possibility of visual observation of the transition of one type of specific energy to another during the experiments when the angle of the investigated section changes, without stopping the water supply during the experiments.

This is achieved by the fact that a pressure tank with a water supply, an overflow funnel in the tank to maintain the water level, and a pipeline on which piezometers are installed to record pressure along the length of the pipeline are included in the device. To change the angle of inclination of the pipeline during the experiments, the pipeline through a flexible hose is connected to the pressure tank.

In FIG. 1 shows a front view of the proposed device. The device consists of a pressure tank 2 with a supply of water 1. Inside the tank there is an overflow device 3 in the form of a funnel to maintain a constant level of 4.

Using the flexible hose (or a special hinge) 5, the test pipe section 6 is connected to the pressure tank. The full pressure tubes (Pitot tubes) 7 and piezometers 8 are installed in three sections at the test section. At the end of the test section, there is a tap 9. Values of required parameters ( the position of the liquid levels in all tubes and piezometers) are determined using the coordinate scale printed on the shield 10, constantly fixed relative to the horizontal reference plane 0-0 11.

The device operates as follows. When raising the end of the investigated section of the pipe 7 to the water level in the pressure tank 2, the movement of water along the studied section will stop, i.e. the water level in all full pressure pipes and in piezometers is equal to the water level in the tank, as in communicating vessels.

As soon as the end of the studied tube 7 is lowered even by a small amount (to reduce the specific potential energy of the position), a pressure will appear, water will begin to move at a certain speed, i.e. kinetic energy appears proportional to the speed squared and energy loss.

With the lowering of the end of the pipe 6 (decrease in the specific potential position energy), the velocities will increase, and the kinetic energy and energy losses will increase, which are almost proportional to the pressure head (kinetic energy), which is confirmed by the Bernoulli equation.

where Z ₁ and Z ₂ are the specific potential energies of the position for the first and second downstream cross sections relative to the reference plane 0-0 (Fig. 1.);

и

- удельные потенциальные энергии давления в тех же сечениях;

and

- specific potential pressure energies in the same sections;

и

- кинетические энергии там же;

and

- kinetic energies in the same place;

h _f - energy loss due to the viscosity of the liquid U.

When lifting the end of the pipe 6 vertically, everything will be repeated in the reverse order. With an increase in the potential energy of the position, the kinetic energy and its losses will decrease.

Thus, the visually observed pattern of changes in the types of energy during the experiment without stopping the supply of water to the installation may indicate that the Bernoulli equation is not a law of conservation of energy, but rather a law of the transition of one type of energy to another, including its loss.

Claims (1)

A device for demonstrating the Bernoulli equation as applied to closed flows, including a pressure tank with a water supply, an overflow funnel to maintain a water level in the tank, and a pipe on which piezometers are installed to record pressure along the length of the pipeline, characterized in that for changing the angle of the pipeline during experiments , the pipeline through the flexible hose is connected to the pressure tank.

Images