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UDC 628.54
Sazonov D. V.
Influence of the pump type on the parameters of the pneumatic-hydraulic aeration system in flotation apparatus
Summary
Flotation has been one of the efficient water treatment technologies. Flotation treatment is based on small gas bubbles generated by different methods, pneumatic-hydraulic, in particular. A case is considered of air feeding before the pump and subsequent water-air mixture passing through the aerator, and air being broken to small bubbles. Possible operation in the presence of air determines the choice of self-priming pumps (centrifugal and vortex). Experiments were carried out on determining two of the most important aeration parameters: bubbling rate and average size of generated air bubbles that determine the efficiency of water flotation treatment. Based on the data obtained it is shown that in most cases centrifugal pumps have the advantages: considerable part of the air entering the pumps is dispersed at the outlet of the aerator to 30–100 μm bubbles; whereas in case a vortex pump is used air bubbles of more than 200 μm size are generated which is ineffective for water flotation. It is stated that for some wastewater types the use of vortex self-priming pumps can be more reasonable.
Key words
water treatment , centrifugal pump , aeration system , pneumatic-hydraulic flotation , aeration intensity , air bubble size
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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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УДК 621.65:62-531.3:628.1/.2
Bagaev Iurii, Karpov N. V., Usachev A. P.
Specific features of frequency regulation of parallel pumps
Summary
One of the options of energy efficient operation of pumping units at the water and sewage pumping stations under pump impeller speed variation with the help of variable-speed electric drives widely used at present time is considered. One variable-speed electric drive is installed either for a group of operating units or on a single pump. Installing a variable-speed electric drive on each operating unit at first sight seems to be a very expensive measure; therefore more often one electric drive is installed for a group of pumps (2–3 units). However, in this case cavitation processes can arise, the dynamic loading on the pump shaft and bearings can increase, the lifting efficiency can decrease, and in the long run the pump energy efficiency can drop. The data of the theoretic and practical substantiation show that installing variable-speed electric drives on each operating pumping unit provides for weakening of the above-mentioned shortcomings, whereas the energy efficiency improves.
Key words
energy efficiency , pumping station , frequency regulation , centrifugal pump , pump capacity
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UDC 621.671
LEZNOV B. S., Vorobiev S. V.
The operation of centrifugal pumps with variable speed
Summary
The technologic aspects of using variable speed drives in pumping units are considered. The operation of centrifugal pumps with variable speed of the impeller is analyzed with account of the impact produced by water mains characteristics on the working parameters of pumping units. It is shown that reducing the pump impeller rotation speed can in some cases result in cavitation, surging, pump rotation speed resonance and resonance of the free lateral vibration of the shaft. Possible pump operation with rotation speed higher than the rated value is considered.
Key words
adjustable electric drive , centrifugal pump , variable speed , pump moment resistance
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UDC 621.671
LEZNOV B. S., Vorobiev S. V.
The operation of centrifugal pumps with variable speed
(The termination, the beginning see here)
Summary
The technologic aspects of using variable speed drives in pumping units are considered. The operation of centrifugal pumps with variable speed of the impeller is analyzed with account of the impact produced by water mains characteristics on the working parameters of pumping units. It is shown that reducing the pump impeller rotation speed can in some cases result in cavitation, surging, pump rotation speed resonance and resonance of the free lateral vibration of the shaft. Possible pump operation with rotation speed higher than the rated value is considered.
Key words
adjustable electric drive , centrifugal pump , variable speed , pump moment resistance
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UDC 621.671:532.528
DOI 10.35776/VST.2024.10.04
Baranchikova N. I., Yepifanov S. P., Kul’kov Viktor
Calculation of cavitation parameters of centrifugal pumps
Summary
The efficient long-lasting operation of pumping units with centrifugal pumps is achieved to a large extent by avoiding cavitation during the operation. To ensure the operation of pumps avoiding cavitation at the design and operation stage is only possible on the basis of correctly performed calculations of the cavitation parameters. By comparing the cavitation parameters with the required ones developing the essential operation modes of the pumping units is possible. Particular attention should be paid to pumping units with variable speed drives, since the recalculation of the cavitation characteristics while changing the rotation frequency of the impeller according to the one available plant characteristic does not always provide for obtaining an adequately changed cavitation characteristic. Therefore, for large pumps and with a sufficiently small cavitation NPSH, a method for recalculating cavitation characteristics using two basic cavitation characteristics of the pump is proposed. While using a pump with a sheared impeller, the cavitation characteristic for the sheared impeller shall be applied that is often just over the characteristic for the rated impeller. Another factor that should be taken into account to avoid cavitation in pumps is gaseous cavitation while determining the available NPSH. A widely used in foreign practice method for recalculating the available permissible NPSH to the actual one with account of the presence of gas cavitation, is given.
Key words
centrifugal pump , NPSH required, vaporous cavitation , vaporous cavitation , gaseous cavitation , head and rate , cavitation characteristic , pump impeller , pump impeller shearing
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UDC 628.1.2:658.26.004.18
Usachev A. P.
Control of centrifugal pump parallel operation
Summary
The problems related to the cable capacity of pumping units during their parallel operation (one with variable-frequency control, another one – without variable-frequency control) are considered. In the traditional control schemes (without variable-frequency control) the problem is solved by throttling of each pump with cable capacity levelling of their drive motors. This function is usually carried out by the operator in manual mode. Based on the conducted analysis an algorithm of pump control was developed that provided for their safe operation in the working area and maximum energy efficiency. It is proposed to carry out controlled throttling of the pump without variable-frequency control by controlling the position of the set point of the pump with variable-frequency control at the working area interface. To ensure failure-free operation of the pumping station in case of the pump with variable-frequency control emergency shutdown it is recommended to change the system of the pump without variable-frequency control for automated pressure maintaining with the help of throttling. To implement the given algorithm the use of a special process controller with the sufficient computing power (STK 500 type) and series SP 200 blocks is proposed.
Key words
power saving , frequency regulation , centrifugal pump , parallel operation , throttling
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DOI 10.35776/VST.2021.06.06
UDC 621.65:628.112.24
Fisenko V. N.
Energy audit of pumps in industrial and municipal systems and labeling of the operational efficiency: systematic approach
(part 1)
Summary
On the basis of a systematic approach, uniform criteria have been developed for estimating the energy efficiency of pumps in real industrial (municipal) systems from the standpoint of environmentally friendly operation in a low-carbon economy. At the same time, the integrated approach of pump manufacturers in tests and designers of real systems with pumps in the process of research and optimization calculations was taken into account. An example is given of estimating the eco-friendly energy efficient operation of a variable-load pump in a municipal system with a time dependent static head component. An example of a typical report of an energy survey is presented based on: the estimation developed for pumps by energy labelling classes for operating conditions in the system, with arbitrary load profiles; a computable structure of the pump design cycle modes with determining the ratio of energy-efficient and energy-consuming operation modes, excess demand energy and taking into account the negative impact on the environment in the form of greenhouse gas emissions in CO2-equivalent. An approach to improving the incentive mechanism for pump operators for the implementation of energy service contracts to reduce the energy intensity of industrial and communal technological processes is considered.
Key words
energy audit , centrifugal pump , system approach , pump load profile , Eco-Efficient Index , labeling of the eco-efficient energy consumption , carbon unit
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