Результаты исследования нестационарных процессов на электрической модели в зависимости от способа исполнения гидросистем

Abstract

UK: Представлены исследования и рисунки в виде осциллограмм исследования гидравлических ударов на электрической модели в зависимости от способа исполнения гидравлических систем.

EN: Problem. Investigations of mine air conditioning systems situated in deep mines of Donbas by electric model were performed. Hydraulic impact values depending on the hydrosystems completion method were illustrated in the pictures.

Literature review. No scientific research has been done in the field of hydraulic impacts in vertical pipelines before. D. K. Smirnov and L. B. Zubov were engaged with the problem of hydraulic impact in Ostankino television tower, Moscow. However, they had to stop the pump, whereas therein HI with flow overlapping is described. In case the pump is stopped, the first amplitude goes down (discharging, pressure reduction), whereas in case the flow is lapped with the valve — the first amplitude – pressure increase takes place and the first harmonic goes up.

Aim. Investigation of HI depending on the hydrosystem completion method and in the vertical pipeline.

The following variants of the pipeline have been considered:

1. According to the type of pump protection:

a) The pump is protected with the damper;

b) The pump is protected with a return valve.

2. According to the pipeline design:

a) The pipeline location is asymmetrical comparing to the valve;

b) The pipeline location is asymmetrical comparing to the valve.

3. According to the use of kinetic energy of fluid during pipeline closure:

a) Fluid energy is dissipated in the pipeline;

b) Fluid energy is partially absorbed by the working load acting simultaneously with the hydraulic distributor. Its value corresponds to the pipeline parameters.

For the mentioned variants, Picture 1 shows strain oscillograms in the perturbation pit of the

ransitional process GN.-8, corresponding to the pipeline section prior to the valve. This implies that the presence of matched load enables to reduce the amplitude of the first pressure wave by 1,4 times. At the same time, maximum pressure surge for both symmetrical and non-symmetrical pipeline with any type of pump protection is around 2,0 MPs (n* = 200 m). This value is relatively large. This variant corresponds to the non-symmetrical pipeline (relative to the perturbation pit); the pump is protected by the damper τ3 / Тн = 1.

That is why there was an idea to perform the control object in such a way that it did not miss a direct current level but would let the alternating component (in kind it should not let the fluid in but it would let the pressure wave in, thus quenching oscillations. In the model it can be applied with the help of large capacity condenser which would be parallel to the electronic key. In kind it is performed with the help of the damper, parallel to the valve whose principal scheme is fully similar to the damper scheme that is parallel to the pump.

The present variant was performed with the help of the model. Strain oscillograms in the perturbation pit of the transitional processes GN-8 and GN-9 are given in рicture

3. After their close examination it can be clearly observed that stain oscillations in these sections are fully eliminated. The same is true for all pits of the model. The present variant corresponds to the symmetrical pipeline (relative to the perturbation pit); the pump is protected with damper; τ3 / Тн = 1.

Consequently, working with hydraulic distributor with the damper parallel to it the pressure down the entire pipeline passes from one steady-state value to the other one smoothly, without jumps (h* = 0). At the same time no special protection of the pump is needed, the design of units that protect it from accidental pressure jumps can be simpler, the possibility of cavitation is eliminated; impact energy is transformed into potential energy of deformed damper materials, and can at least partially return to the system with the opening of the valve.

Conclusion.

1. The application or Racc for a non-symmetrical model in a strict branch leads to the decrease of stress amplitude in the first harmonic component by 42 % during the first one-half period, by 57% during the second one-half period, further harmonic components are even more decreased. In the reverse branch such decrease is 31 % and 49 % respectively (curves 1, 2, рic. 1, 2)

2. The application or Racc for a symmetrical model leads to the decrease of stress amplitude in the first harmonic component by 41 % during the first one-half period, by 81 % during the second one–half period of a strict branch. In the reverse branch such decrease is 40 % and 77 % respectively (curves 3, 4, 5, рic. 3, 4, 5).

3. The time of transitional process in a non-symmetrical model with the presence of Racc is decreased by 2,6 times.

4. The time of the main transitional period in a symmetrical model is decreased by 6,8 times. Thus, according to both parameters symmetrical model is a more favorable one. A satisfactory explanation is that there is a progressive wave, transferring energy brought by branches into Racc load. Similarly, in the pipeline, a progressive wave supplying energy of the halted liquid in the pipeline into effective load. Without Racc during interruption of the circuit in the model (like in full-scale hydraulic system) stationary waves are initiated whose energy is used for traction.

With the application of the proposed hydraulic distributor and cold bearer distribution system in the system of mine air conditioning, heat economy will be approximately 30–40 %.

With the application of the proposed hydraulic distributor in the system of mine air conditioning, technical effect lies in the elimination of hydraulic impacts, mine air conditioning system becomes more simplified and reliable.