Hydraulic calculation of group water intakes on underground wells equipped with pumps with variable speed drives

Summary

The use of variable speed drives at group water intakes on underground sources in water supply systems is aimed at saving electricity, ensuring efficient operation modes, improving the management engineering; however, without sufficient justification the desired result is not always effected. One of the reasons is the lack of calculation using an effective mathematical model that describes the movement of water in aquifers, wells, lift pipes and gathering mains, taking into account all the existing limitations, including the mode parameters while using variable speed drives in some or in all submersible pumps. The model is submitted in the form of an optimization task where the target function is the total power input of all the operating submersible pumps. The proposed optimization model provides for describing the modes of the group water intakes operating from the intake external boundary to the tanks. All the limitations of the optimization task can be divided into three non-overlapping groups as follows: balance, technologic, and performance ones. Having calculated the electricity consumption for all significant modes during the year and compared them with the costs at the existing modes without variable speed drives, we can make a reasonable conclusion about the applicability of a variable speed drive in one or more submersible pumps. The proposed model provides for arranging both efficient and technologically allowable operating modes.

Key words

frequency converter , water well , aquifer , submersible pump , hydraulic head , flow distribution task , optimization task , energy input , group water intake

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UDC 628.144:532.542

Yepifanov S. P., Zorkaltsev V. I.

The task of flow distribution with nonfixed junction points of consumption

Summary

A model of flow distribution in the water supply and distribution system with nonfixed junction points of consumption is considered. The model provides for more detailed characteristics of flow distribution both in normal conditions and emergency mode. The suggested junction point flow rate – water head ratios provide for the actual consumption amounts at the consumers’. The flow distribution algorithm in the form of nonlinear algebraic equation system is presented supported with the demonstration of differences in the results of calculating flow distribution with both fixed and nonfixed junction points of consumption.

Key words

water supply , water leaks , pipeline system , flow distribution , nonfixed junction point of consumption , hydraulic head

UDC 628.1/.2:621.65

Yepifanov S. P., Baranchikova N. I., Kurtin A. V.

Mathematical modeling of the joint operation of pumping units including frequency regulated ones

Summary

The use of pumping units with variable speed drives in order to save energy and provide for effective operating modes in water supply and sanitation systems, sometimes without sufficient justification, does not always furnish the desired result. One of the reasons is the lack of a simple mathematical model describing the flow distribution in the process pipelines of pumping stations with account of all the limitations of the operating mode parameters while using variable speed drives in some or all pumping units. The flow distribution task itself should be represented in the form of an optimization problem where the objective function can be the total energy input of all the operating pumping units. Such an optimization model provides for describing the operating modes of both paralleled and compound pumps. Once the electricity costs for all significant modes throughout the year have been determined and compared with the existing modes without the use of variable speed drives, drawing a reasonable conclusion about the applicability of variable speed drives in one or several pumping units becomes possible. The proposed model provides for arranging both effective and technologically acceptable modes. Based on the obtained results of calculating the optimization task for several modes, it is possible to construct approximating functions of the total flow of the pumping station from the head losses in throttling devices and use them in case of the flow meter lack or failure.

Key words

pressure , frequency converter , hydraulic head , centrifugal pump , pumping unit , flow distribution task , optimization task , energy input , parallel and serial operation of pumps

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UDC 628.144:532.542

Baranchikova N. I., Yepifanov S. P., Zorkaltsev V. I., Kurtin A. V., Obuzdin S. Iu.

Flow distribution in water supply and distribution systems with automatic pressure regulators

Summary

The task of flow distribution in general pipeline systems including the systems of water supply and distribution with automatic pressure regulators is considered. To improve the reliability of the system operation pressure regulators are often installed «downstream» (reducing valves) and «upstream» (tank release valves). Pressure regulators manufactured by Bermad have been installed in the water distribution networks of Irkutsk; that provided for reducing and stabilizing the pressure in some zones. However zones exist that are supplied from several water pipelines with different pressure at the connection points, therefore sometimes complete closing of some regulators occurs (more often with small diameters) or flow reversal is possible, and the water flows through the regulator in the opposite direction. In this case the regulator fails to fulfill its function. Mathematical modeling of such situations is very important because it is them which significantly complicate the operation of the water supply and distribution systems. Mathematical models of automatic «upstream» and «downstream» pressure and pressure drop regulators are suggested with account of their version: normally open or normally closed. The mathematical formulation of the problem of flow distribution in the systems of water supply and distribution with pressure regulators is presented. The critical for the practice task of flow distribution in the pipelines with automatic regulators has been solved for the setting that describes different scenarios of the automatic regulators operation. A simple and efficient method of solving the set task of flow distribution that does not require derivation and has rapid enough convergence is suggested. On the basis of the numerical experiments it is fair to assume that the number of iterations moderately depends on the dimension of the problem (number of nodes and semicircular arcs), considerably depends on spread of hydraulic resistance values and to a lesser extent – node selection.

Key words

pressure , mathematical model , pipeline system , flow distribution , hydraulic head , systems of water supply and distribution

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