Toshkent davlat texnika universiteti xalqaro ilmiy-texnik anjuman

МЕЖДУНАРОДНАЯ НАУЧНО-ТЕХНИЧЕСКАЯ КОНФЕРЕНЦИЯ 
АКТУАЛЬНЫЕ ПРОБЛЕМЫ ЦИФРОВИЗАЦИИ ЭЛЕКТРОМЕХАНИЧЕСКИХ И
ЭЛЕКТРОТЕХНОЛОГИЧЕСКИХ СИСТЕМ
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• Application of scientifically justified and technically feasible, progressive specific 
power consumption standards for the pump station of machine water-lifting systems. 
By the present time, in the practice of machine water lifting, only unregulated electric 
drives are used as the drive for the pumping unit. In order to coordinate the water supply 
mode of the pumping station with the water consumption schedule, the only practically 
used method of regulating its performance at the moment is the adjustment of the number 
of operating units, which provides for a stepped (per unit) regulation of the flow rate. In 
most operating irrigation pumping stations, there is a mismatch between the actual water 
consumption schedule and its coverage provided by the operation of the machine water 
lifting system pumping station. Therefore, typically, in order to avoid crop yield losses of 
field and garden crops, the machine water lifting pumping stations deliberately operate 
with an inflated covering schedule, which in turn leads to unjustified overconsumption of 
water resources and electrical energy. Another feature of the operation of the machine 
water lifting system pumping station is their conversion to a regulated electric drive 
instead of an unregulated one, which will undoubtedly allow for the efficient use of 
electrical energy and irrigation water, implement the transition to comprehensive 
automation of the technological processes of water supply of pumping stations, increase 
the flexibility of managing the load of electrical equipment, and increase the overall 
operational resource of the energy and hydromechanical equipment of the pump unit. 
In pump engineering practice, there are two fundamentally different methods of 
regulating the performance (delivery) of a pumping unit: 
• Quantitative – with constant speed (frequency) of the pump impeller, by changing 
the characteristics of the discharge pipeline, the geometry of the pump flow passages, the 
flow kinematics at the impeller inlet, etc.; 
• Qualitative – by changing the speed (frequency) of the pump impeller. 
The following methods of quantitative delivery regulation of the pumping unit can be 
applied at the pump station of machine water lifting systems: 
a) by using a throttling valve (throttling); 
b) by diverting part of the water from the discharge pipeline to the suction 
pipeline; 
c) by introducing air into the suction pipeline; 
d) by changing the diameter of the impeller; 
e) by adjusting the impeller blades or the guide apparatus. 
It should be noted that the listed methods can only achieve pump performance 
regulation mainly below its nominal delivery value. 
Among the quantitative methods of pump delivery regulation mentioned by us, 
throttle flow control has gained the widest application in the operation of small pumping 
stations for machine water lifting systems, where it is necessary to regulate its 
performance for a short period. 
The advantages of throttle flow control include its simplicity, lack of need for 
additional equipment, and the possibility of smoothly regulating the pump delivery within 
the range from to zero. 
The main disadvantages of throttling are its uneconomical nature due to increased 
non-productive energy costs, a significant reduction in the efficiency of pumping 
equipment, and accelerated wear of the valve, especially when the water contains a 
sufficient amount of abrasive particles in suspension and has a predominant turbidity, 
which is typical for rivers and channels in most regions of our republic. 
The regulation of the pump unit's supply by diverting a portion of the water can be 
achieved by adjusting the opening of a valve installed on the bypass pipeline, through 
which the required liquid flow is achieved by diverting it from the pressure pipeline to the 

МЕЖДУНАРОДНАЯ НАУЧНО-ТЕХНИЧЕСКАЯ КОНФЕРЕНЦИЯ 
АКТУАЛЬНЫЕ ПРОБЛЕМЫ ЦИФРОВИЗАЦИИ ЭЛЕКТРОМЕХАНИЧЕСКИХ И
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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. 

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