scholarly journals On the Stability and Surging of Centrifugal Pumps : 3rd Report

1948 ◽  
Vol 14 (48-3) ◽  
pp. 12-17
Author(s):  
Sumiji FUJII
Keyword(s):  
Centrifugal Pumps ◽  
The Stability

Numerical Study of Transient Flow and the Influence of Height and Viscosity in a Cyclonic Chamber in a Distribution System

2017 ◽  
Author(s):  
Carolina C. Rodrigues ◽  
Henrique K. Eidt ◽  
Rafael Dunaiski ◽  
César Y. Ofuchi ◽  
Flávio Neves ◽  
...  
Keyword(s):  
Distribution System ◽  
Transient Flow ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Petroleum Industry ◽  
Wire Mesh ◽  
Intermittent Flow ◽  
Transient Effects ◽  
Centrifugal Pumps ◽  
The Stability

In the petroleum industry, during the production and transportation of oil, multiphase flow occurs, due to the usual mixture of the crude oil, water and gas. This type of flow can be simplified, for study purposes, as a two-phase one, in which the gas is one phase, and a mixture of oil and water is the other. Separation of gaseous and liquid phases at the wellhead level is done by a separator and has innumerous advantages, including avoiding or at least reducing typical problems of multiphase flows such as intermittent flow, severe slugging and hydrates deposition. Another advantage is to increase the efficiency of the submersible centrifugal pumps or other artificial lift process used. A recurrent problem found in exploration and production of oil and gas is the range of the fluid viscosities encountered during exploration and extraction of petroleum, which can greatly vary with the temperature or the composition of the oil being extracted. Thus, it is necessary to understand how this parameter affects the performance of the equipment used. In addition, installation and maintenance of separators are hampered by the large size of this type of equipment. Therefore, a prior distribution system is here proposed, aiming to distribute the flow in more than one branch, in order to decrease the general size of the separation equipment needed, while maintaining the flow rate and separation efficiency. This distribution system has a cyclonic chamber, in which the flow enters through two nozzles tangentially oriented with the wall of the chamber, which performs a pre-separation due to the centrifugal field, and divides the flow into four outlets. This work presents a numerical study on the height influence of the cyclonic chamber in a distribution system. The transient beginning of the flow is analyzed, with the stability of the film being study. This work is focused on the behavior of the liquid phase in this proposed distribution system, so that only single-phase liquid flow at the inlet of the distribution system is considered. A validation was done through comparison with experimental data obtained in a test rig, in which was used one wire mesh sensor with 12 wires in order to evaluate the thickness of the liquid film over time. In addition, different heights and viscosities are studied in order to evaluate their influence on the flow. The parameters investigated are the film thickness, velocity and turbulence kinetic energy fields and flow rates at the outlets, focusing on the stability of the film and the transient effects associated with the beginning of the flow. In order to perform this study, the commercial software ANSYS-CFX 15.0 was used, with a hybrid mesh, for four different heights and two inlet velocities.

scholarly journals Technological assurance of reliability of centrifugal pumps for pumping biomass processing products based on adaptive dampers

2021 ◽  
Vol 2094 (5) ◽  
pp. 052047
Author(s):  
O A Kolenchukov ◽  
E A Kozhukhov ◽  
E A Petrovsky ◽  
V V Bukhtoyarov ◽  
V A Kachaeva
Keyword(s):  
Permanent Magnets ◽  
Hysteresis Loops ◽  
Magnetic Suspension ◽  
Magnetic Bearings ◽  
Optimal Size ◽  
Centrifugal Pumps ◽  
Biomass Processing ◽  
Technological Advances ◽  
The Stability ◽  
Stiffness And Damping

Abstract In almost every mechanical system, moving mechanisms slide over stationary parts, creating friction and, as a result, unwanted energy losses. In engineering, sliding or rolling bearings are most often used as supports. However, any system can benefit from a greater reduction in friction between components. As will be shown in this article, the stability problem can be solved by blocking vibrations in the radial direction. The latest technological advances in the field of manufacturing magnetic materials make it possible to integrate magnetic bearings with permanent magnetization (hereinafter - MBPM) into a larger number of mechanical systems. This blocking of radial movement is carried out without the use of a mechanical sliding bearing, chosen for its simplicity and ease of integration. To facilitate the integration of the MBPM into the overall system of the device, it is important to know the mechanical properties of magnetic bearings, namely stiffness and damping, as well as the performance characteristics and limits of their operation. This article examines the possibility of using an adaptive damper in centrifugal pumps to ensure the technological reliability of the equipment. Alternating permanent magnets in the direction of their movement is the most optimal option, leading to large and smooth hysteresis loops of force - displacement. The proposed arrangement of magnets ensures the adaptability of the device with the determination of its optimal size, and also takes into account the edge and surface effects in the design of the damper. In addition, the article discusses theoretical and technical issues of levitation - free floating of bodies. Magnetic suspension can be used to study only those processes where mechanical connections are undesirable. The use of magnetic suspension for balancing centrifugal pumps during transportation of biomass processing products, supports of mixing devices in reactors in biomass processing reactors and other machine components opens up wide opportunities.

Open discussion

1982 ◽  
Vol 99 ◽  
pp. 605-613
Author(s):  
P. S. Conti
Keyword(s):  
Buenos Aires ◽  
Large Mass ◽  
List Type ◽  
Common Phenomenon ◽  
Open Discussion ◽  
The Stability ◽  
Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

Symmetric Multistep Methods Revisited: II. Numerical Experiments

1999 ◽  
Vol 173 ◽  
pp. 309-314 ◽  
Author(s):  
T. Fukushima
Keyword(s):  
Multistep Methods ◽  
Computational Time ◽  
Integration Time ◽  
Implicit Methods ◽  
Symmetric Methods ◽  
Celestial Bodies ◽  
The Stability ◽  
Predictor Corrector ◽  
Symmetric Multistep Methods ◽  
Integration Errors

AbstractBy using the stability condition and general formulas developed by Fukushima (1998 = Paper I) we discovered that, just as in the case of the explicit symmetric multistep methods (Quinlan and Tremaine, 1990), when integrating orbital motions of celestial bodies, the implicit symmetric multistep methods used in the predictor-corrector manner lead to integration errors in position which grow linearly with the integration time if the stepsizes adopted are sufficiently small and if the number of corrections is sufficiently large, say two or three. We confirmed also that the symmetric methods (explicit or implicit) would produce the stepsize-dependent instabilities/resonances, which was discovered by A. Toomre in 1991 and confirmed by G.D. Quinlan for some high order explicit methods. Although the implicit methods require twice or more computational time for the same stepsize than the explicit symmetric ones do, they seem to be preferable since they reduce these undesirable features significantly.

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