Investigation of velocity modes of liquid flows around electric motors of submersible pumps

Abstract

Water supply and wastewater disposal refers to industries with intensive use of pumping equipment, the share of electricity consumed by pumps is more than 50% of the total energy consumption. Therefore, the issue of improving the energy efficiency of water supply is, first of all, the rational operation of pumping equipment.   One of the reasons for the reduction of technical and economic performance of submersible pumping units is the failure of electric pump motors due to overheating during operation. In any electric motor during operation, even with the highest efficiency part of the electrical energy supplied goes to heating, so that the motors do not overheat and do not fail, they need to be cooled. Motors for well pumps unlike surface pumps have a different design, and they do not have a fan, but they also need to be cooled during operation. But in order for the motor to be cooled properly, the necessary fluid velocity must be determined around the motor. This velocity can be provided by means of cooling hoods. This issue is particularly relevant when submersible pumps are used to pump water from tanks, cisterns or open ponds, where the use of cooling covers is mandatory. Manufacturers of submersible pumps specify in their technical data the minimum permissible liquid velocity for cooling the motor casing. If the flow velocity of the pump motor is less than that specified in the technical data of the equipment, it is necessary to determine the minimum permissible velocity of the liquid flow around the pump motor.  In this connection substantiation and development of methods of research and calculation of parameters of liquid flow around the pump motor, is an actual scientific and practical task, having branch importance.  At the same time, at the present stage, the existing methods and two ways of determining the velocity of the fluid flow around the submersible pump motor: calculation - by means of analytical formulae and graphical - by means of charts of rational areas of application of cooling covers do not provide a sufficiently complete solution of the problem of providing a turbulent vortex flow along the motor, preventing the formation of deposits and providing cooling of the motor regardless of the type of formed deposits of minerals, bacteria or metals. The article proposes an improved method of modelling the fluid flow around the electric motor housing of a submersible pump using the SolidWorks software package, which allows to solve the problem of cooling the motor by justifying the design parameters of cooling covers. The aim of the work is to provide conditions of stable cooling of pumping unit motors at which the temperature of electric motor windings will be within permissible limits, which is the main point in the durability of submersible pumps. To achieve this goal, the task of developing a methodology for modelling the turbulent vortex fluid flow along the electric motor of a submersible pump and studying the design parameters of cooling covers is solved. The research methodology included both numerical modelling methods and experimental studies. The obtained results allowed to characterize in detail the fluid velocity fields around the pump unit, to reveal the features of the hydrodynamic behavior of the system and to determine the parameters influencing the durability of submersible pump units.