Abstract
Development of reliable methods of increasing of centrifugal pump efficiency is a very actual scientific and practical problem. One of ways to increase reliability and efficiency of centrifugal pump is an improvement of constructions of annular seals of running part and methods of their calculation. Now in engineering practice several approaches to research of complicated spiral flow of liquid in the small gaps of annular seals are used. Divergences in the conclusions of researchers are likely to be linked with assumptions that are accepted when solving nonlinear equations of non-stationary motion of liquid in the gap of annular seal. It is necessary to mark that divergences between the calculation values of hydrodynamic characteristics of annular seals and rotor-dynamic characteristics of pump that arise during exploitation are first of all possible to explain by the absence of account of possible change of geometrical parameters of the annular seals, caused by the accepted tolerances in the calculations. Using of probabilistic methods of calculation with existent statistical information got on the stages of design and operating of centrifugal pumps will allow to forecast reliability and efficiency of centrifugal pumps taking into account influence and changing of basic operating factors. Determination of influence of random change of annular seal parameters on flow-rate characteristics and volume efficiency of centrifugal pump is the goal of this research. Dependences to determinate the flow-rate of liquid through the annular seal are got by solving the problem of liquid flow in a cylindrical channel with taking into account the influence of random factors. Influence of random variations of basic geometrical and regime parameters of annular seal on efficiency pump is considered. It is shown on the example of cantilever pump with one impeller, that its efficiency can substantially (up to 1 %) decrease under exploitation. This decrease can be higher in case when pump has more stages.
Highlights
That is why it is necessary to take into account the leakages of the pumped over environment through the annular seals under calculation of centrifugal pump efficiency
Leakages through the annular seal, as well as forces and moments, acting on a rotor from the side of the pumped over environment, depend on the geometrical parameters of seal, character and velocity of movement of sealing surfaces and mode of liquid flow in a gap
On the basis of problem solving of liquid flow in a channel with the internal surface of gap that rotates and precesses, the components of flow-rate through annular seal are determined as functions of basic geometrical and regime parameters
Summary
Annular seals are the most widespread as seals of running part of centrifugal pumps due to the simplicity, low cost and reliability of work in the wide range of pressure drop and rotating frequencies. This fact can destroy all attempts of designers to increase pump efficiency This development of a methodology of centrifugal pump efficiency calculation taking into account the change of basic parameters of annular seals is a new and actual problem of nowadays. In [8] the comparison of experimental data and the results of numerical analysis of liquid motion in the annular seal taking into account the whirling of flow in the inlet of gap is given. The analysis of theoretical and experimental works devoted to the calculation of flow-rate characteristics of annular seals has shown that works in that the random character of change of annular seal parameters is taken into account are practically absent. The determination of influence of random change of annular seal parameters on its flow-rate characteristics and pump efficiency is an important practical problem
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