UDC:621.313.333 - Toshkent davlat texnika universiteti xalqaro ilmiy-texnik anjuman

МЕЖДУНАРОДНАЯ НАУЧНО-ТЕХНИЧЕСКАЯ КОНФЕРЕНЦИЯ
АКТУАЛЬНЫЕ ПРОБЛЕМЫ ЦИФРОВИЗАЦИИ ЭЛЕКТРОМЕХАНИЧЕСКИХ И
ЭЛЕКТРОТЕХНОЛОГИЧЕСКИХ СИСТЕМ
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suction pipeline. This method of regulating the water flow of the pump unit is mainly
used to eliminate unstable pump operation and is considered most appropriate in terms of
energy efficiency only for pumps with a specific speed coefficient (n) greater than 300,
where an increase in the pump unit's supply leads to a decrease in power on its shaft. In
centrifugal pumps with a lower specific speed coefficient, regulating the pump unit's
performance by diverting water leads to an increase in the pump's power. Consequently, it
causes an overload of the pump unit's drive motor. Despite improving the pump's
cavitation properties, this regulation method contributes to a decrease in its efficiency,
complicates the communication system, and increases the amount of equipment and the
overall size of the pump installation.
A more economical method than throttling is the regulation of the pump unit's supply
by admitting air into the suction pipeline. This method can be applied in cases where the
pump unit operates on an unbranched pressure network that does not require special
devices to remove air, and the actual suction head for a particular pump model is
significantly less than the allowable value.
By introducing air into the suction pipeline, the pump's flow-head characteristic is
shifted downwards, while maintaining the values of the H characteristic, and the
intersection points determine the operating mode of the pumping unit. Thus, by varying
the amount of air entering the suction pipeline, it is possible to select the pump operating
mode that corresponds to the required delivery values of the pump unit. However, with an
increase in air content, despite the improved power consumption indicators of the pump
unit, its efficiency deteriorates due to the drop in head developed by the pump, and it also
provides a limited range of water delivery regulation, determined by the reduction in the
pump's cavitation qualities.
The method of regulating the delivery of the pump unit by trimming the pump
impeller on the outer diameter without changing the shape of its blades is mainly used in
pumping stations of machine water lifting systems equipped with identical pump
equipment, where there is a need to use a pump of this type with a lower power
consumption while providing the required delivery according to the pumping station
coverage schedule. Typically, the maximum impeller trimming, taking into account its
speed coefficient, is no more than 11-15%, and in the practice of operating pumping
stations of machine water lifting systems, it is quite common to equip identical pump
units with pump equipment with different impeller diameters.
The considered method of regulating pump performance compared to throttling
provides significant power savings, has relatively high efficiency, and is most effective
for regulating the supply of a pump station in water lifting systems. However, regulating
the performance of a centrifugal pump by trimming its impeller diameter externally has
the drawback of fixing the pump supply at a constant level for a long period of time (until
the next overhaul period of the pump unit), as well as a limited range of flow rate
adjustment for the pump unit. Adjusting the performance of a pump unit by changing the
angle of the impeller blades is most effective in systems with low static head and is
mainly implemented in axial and diagonal flow pumps. An analysis of the applied
methods of quantitative performance regulation of centrifugal pumps has shown that
throttling or direct pump intervention leads to a significant reduction in the energy
performance of the pump unit and sometimes complicates its design, shortens the service
life of the hydraulic equipment, and hinders the possibility of automating the water supply
process.