Abstract
Most production technologies require a uniform flow path of liquid from pressure distribution pipelines. To achieve this goal, it is proposed to introduce polymer additives into the liquid flow or to use converging distribution pipelines with a continuous longitudinal slot in the wall. To reduce the uneven operation of the distribution pipeline during discrete liquid dispensing, it is proposed to use cylindrical output rotary nozzles with a lateral orthogonal entry of the jet into the nozzle. The problem is the lack of methods for accurate hydraulic calculation of the operation of distribution pipelines. Adequate calculation methods are based on differential equations. Finding the exact solution of the differential equation of fluid motion with variable path flow rate for perforated distribution pipelines is urgent, because it still does not exist. The available calculation methods take into account only the right angles of separation of the jets from the flow in the distribution pipeline. These methods are based on the assumption that the coefficient of hydraulic friction and the coefficient of resistance of the outlets are constant along the flow. A calculation method is proposed that takes into account the change in the values of these resistance coefficients along the distribution pipeline. The kinematic and physical characteristics of the flow outside the distribution pipeline are also taken into account. The accuracy of calculating the value of the flow rate of water distributed from the distribution pipeline has been experimentally verified. The error in calculating the water consumption by the method assuming that the values of the resistance coefficients are unchanged along the distribution pipeline reaches 18.75 %. According to the proposed calculation method, this error does not exceed 6.25 %. However, both methods are suitable for the design of pressure distribution pipelines, provided that the jet separation angles are straight. Taking into account the change from 90° to 360° of the angle of separation of the jets from the flow in the distribution pipeline will expand the scope and accuracy of calculation methods.
Highlights
Pressure distribution pipelines (DP) is common in many processes
The hydraulic calculations of the water flow rate for the remaining length of the DP according to formulas (8), (9) [25] for pressure DP with jet diversion angles β=90° practically coincide with the experimental data and differ by 25, 0–39.7 % of the calculation results according to the method [8]
With the study of DP, work is being carried out to improve the design of pressure collecting pipelines [32, 33]. The latter require an approach similar to that used for calculating pressure distribution pipelines [29, 33], which is reflected in the works [1, 30]
Summary
Pressure distribution pipelines (DP) is common in many processes. In irrigation, they form the basis of sprinkler, drip (Fig. 1) and subsurface irrigation systems. Based on the design scheme (Fig. 5) of the pressure flow with jet separation, the author of [25] supplemented the differential equation of fluid motion with variable flow rate (2) with the term pout (dQ/v) Nx εω hole ω – pore volume (perforai−k tion) of DP in the calculated section i-k; εi‐k – coefficient of compression of the jet in the outlet (nozzle); poout – fluid (or air) pressure outside the DP; λ(xi ) – hydraulic coefficient of friction (Darcy coefficient); λ(x) is calculated using known formulas depending on the flow regime and the values of the Reynolds criterion Re(xi ). – to compare the calculation results of pressure distribution pipelines with experimental data
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