scholarly journals Energy Loss and Radial Force Variation Caused by Impeller Trimming in a Double-Suction Centrifugal Pump

Entropy ◽  
2021 ◽  
Vol 23 (9) ◽  
pp. 1228
Author(s):  
Qifan Deng ◽  
Ji Pei ◽  
Wenjie Wang ◽  
Bin Lin ◽  
Chenying Zhang ◽  
...  
Keyword(s):  
Energy Loss ◽  
Entropy Production ◽  
Flow Separation ◽  
Incidence Angle ◽  
High Energy ◽  
Radial Force ◽  
Production Theory ◽  
Pump Head ◽  
Radial Forces ◽  
Force Variation

Impeller trimming is an economical method for broadening the range of application of a given pump, but it can destroy operational stability and efficiency. In this study, entropy production theory was utilized to analyze the variation of energy loss caused by impeller trimming based on computational fluid dynamics. Experiments and numerical simulations were conducted to investigate the energy loss and fluid-induced radial forces. The pump’s performance seriously deteriorated after impeller trimming, especially under overload conditions. Energy loss in the volute decreased after trimming under part-load conditions but increased under overload conditions, and this phenomenon made the pump head unable to be accurately predicted by empirical equations. With the help of entropy production theory, high-energy dissipation regions were mainly located in the volute discharge diffuser under overload conditions because of the flow separation and the mixing of the main flow and the stalled fluid. The increased incidence angle at the volute’s tongue after impeller trimming resulted in more serious flow separation and higher energy loss. Furthermore, the radial forces and their fluctuation amplitudes decreased under all the investigated conditions. The horizontal components of the radial forces in all cases were much higher than the vertical components.

Optimal hydraulic design of an ultra-low specific speed centrifugal pump based on the local entropy production theory

2019 ◽  
Vol 233 (6) ◽  
pp. 715-726 ◽  
Author(s):  
Hucan Hou ◽  
Yongxue Zhang ◽  
Xin Zhou ◽  
Zhitao Zuo ◽  
Haisheng Chen
Keyword(s):  
Entropy Production ◽  
Centrifugal Pump ◽  
Orthogonal Design ◽  
High Energy ◽  
Geometrical Parameters ◽  
Production Theory ◽  
Local Entropy ◽  
Hydraulic Design ◽  
Low Specific Speed ◽  
Specific Speed

The ultra-low specific speed centrifugal pump has been widely applied in aerospace engineering, metallurgy, and other industrial fields. However, its hydraulic design lacks specialized theory and method. Moreover, the impeller and volute are designed separately without considering their coupling effect. Therefore, the optimal design is proposed in this study based on the local entropy production theory. Four geometrical parameters are selected to establish orthogonal design schemes including blade outlet setting angle, wrapping angle volute inlet width, and throat area. Subsequently, a 3D steady flow with Reynolds stress turbulent model and energy equation model is numerically conducted and the entropy production is calculated by a user-defined function code. The range analysis is made to identify the optimal scheme indicating that the combination of local entropy production and orthogonal design is feasible on pump optimization. The optimal pump is visibly improved with an increase of 1.08% in efficiency. Entropy production is decreased by 16.75% and 6.03% in impeller and volute, respectively. High energy loss areas are captured and explained in terms of helical vortex and wall friction, and the turbulent and wall entropy production are respectively reduced by 3.82% and 14.34% for the total pump.

The Effect of Taylor Vortex Flow on the Radial Forces in an Annulus Having Variable Eccentricity and Axial Flow

1978 ◽  
Vol 100 (2) ◽  
pp. 210-214 ◽  
Author(s):  
J. E. R. Coney ◽  
J. Atkinson
Keyword(s):  
Vortex Flow ◽  
Outer Cylinder ◽  
Axial Flow ◽  
Reynolds Numbers ◽  
Radial Force ◽  
Taylor Vortex ◽  
Eccentric Annulus ◽  
Taylor Vortex Flow ◽  
Radial Forces ◽  
Force Variation

Results are presented in dimensionless form as obtained in an experimental study of the resultant radial force variation in an eccentric annulus formed by a stationary outer cylinder and a rotating inner cylinder, through which an axial flow of oil may be pumped. Two eccentricity ratios, 0.5 and 0.9, and three axial Reynolds numbers for the flow of the fluid in the annulus, 0, 25, and 50, are considered. It is shown that the onset of Taylor vortex flow has a marked effect on the magnitude and direction of the resultant radial force. The resultant forces and attitude angles are compared with those derived from Sommerfeld’s journal bearing theory. Comparisons are also made between critical Taylor numbers for the present investigation and those available in the literature.

Energy Loss Analysis of Novel Self-Priming Pump Based on the Entropy Production Theory

2019 ◽  
Vol 28 (2) ◽  
pp. 306-318 ◽  
Author(s):  
Hao Chang ◽  
Weidong Shi ◽  
Wei Li ◽  
Jianrui Liu
Keyword(s):  
Energy Loss ◽  
Entropy Production ◽  
Production Theory ◽  
Loss Analysis

Energy loss analysis of the double-suction centrifugal pump under different flow rates based on entropy production theory

2020 ◽  
Vol 234 (20) ◽  
pp. 4009-4023
Author(s):  
Hongyu Guan ◽  
Wei Jiang ◽  
Jianguo Yang ◽  
Yuchuan Wang ◽  
Xinghai Zhao ◽  
...  
Keyword(s):  
Energy Loss ◽  
Entropy Production ◽  
Centrifugal Pump ◽  
Optimization Design ◽  
Flow Region ◽  
Main Flow ◽  
Production Theory ◽  
Flow Rates ◽  
Loss Analysis ◽  
The Difference

The investigation of energy loss of pump is of great significance for energy conservation and structural optimization design. And traditional methods have great limitations in researching the distribution of energy losses. In this paper, the entropy production theory is utilized to analyze the energy loss of the double-suction centrifugal pump. The numerical simulation results verified by experiments indicate that the difference in total entropy production under different flow rates is mainly affected by the entropy production in the main flow region. Moreover, the entropy production of the volute has the greatest impact on the entropy production in the main flow region, and even the proportion of entropy production in the volute at 1.2 QD operating point reaches 96%. Besides, the Q-criterion is applied to study the morphology of the vortex core in the volute. In the volute inlet region, it is found that the stable double-vortex flow has a better flow field and less energy loss than the scattered wake vortex.

Monte Carlo Modelling of Secondary Electron Yield from Rough Surfaces

1990 ◽  
Vol 48 (1) ◽  
pp. 422-423
Author(s):  
John C. Russ
Keyword(s):  
Monte Carlo ◽  
Energy Loss ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Analytical Calculation ◽  
Mean Free Path ◽  
Single Scattering ◽  
High Energy ◽  
Secondary Electron Yield ◽  
Electron Yield

Monte-Carlo programs are well recognized for their ability to model electron beam interactions with samples, and to incorporate boundary conditions such as compositional or surface variations which are difficult to handle analytically. This success has been especially powerful for modelling X-ray emission and the backscattering of high energy electrons. Secondary electron emission has proven to be somewhat more difficult, since the diffusion of the generated secondaries to the surface is strongly geometry dependent, and requires analytical calculations as well as material parameters. Modelling of secondary electron yield within a Monte-Carlo framework has been done using multiple scattering programs, but is not readily adapted to the moderately complex geometries associated with samples such as microelectronic devices, etc.This paper reports results using a different approach in which simplifying assumptions are made to permit direct and easy estimation of the secondary electron signal from samples of arbitrary complexity. The single-scattering program which performs the basic Monte-Carlo simulation (and is also used for backscattered electron and EBIC simulation) allows multiple regions to be defined within the sample, each with boundaries formed by a polygon of any number of sides. Each region may be given any elemental composition in atomic percent. In addition to the regions comprising the primary structure of the sample, a series of thin regions are defined along the surface(s) in which the total energy loss of the primary electrons is summed. This energy loss is assumed to be proportional to the generated secondary electron signal which would be emitted from the sample. The only adjustable variable is the thickness of the region, which plays the same role as the mean free path of the secondary electrons in an analytical calculation. This is treated as an empirical factor, similar in many respects to the λ and ε parameters in the Joy model.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

Influence of Rim Run-Out on the Nonuniformity of Tire-Wheel Assemblies

1994 ◽  
Vol 22 (2) ◽  
pp. 99-120 ◽  
Author(s):  
T. B. Rhyne ◽  
R. Gall ◽  
L. Y. Chang
Keyword(s):  
Finite Element ◽  
Radial Force ◽  
Membrane Model ◽  
Model Experiments ◽  
Force Variation ◽  
One To One ◽  
The One

Abstract An analytical membrane model is used to study how wheel imperfections are converted into radial force variation of the tire-wheel assembly. This model indicates that the radial run-out of the rim generates run-out of the tire-wheel assembly at slightly less than the one to one ratio that was expected. Lateral run-out of the rim is found to generate radial run-out of the tire-wheel assembly at a ratio that is dependent on the tire design and the wheel width. Finite element studies of a production tire validate and quantify the results of the membrane model. Experiments using a specially constructed precision wheel demonstrate the behavior predicted by the models. Finally, a population of production tires and wheels show that the lateral run-out of the rims contribute a significant portion to the assembly radial force variation. These findings might be used to improve match-mounting results by taking lateral rim run-out into account.

EXEELFS (Extended Electron Energy Loss Fine Structure) Study of Tin Grown by the DC Sputtering Technique.

2000 ◽  
Vol 6 (S2) ◽  
pp. 226-227
Author(s):  
Duarte-Moller A. ◽  
F. Espinosa-Maganña ◽  
R. Martínez-S´anchez ◽  
O. Contreras
Keyword(s):  
Energy Loss ◽  
Direct Current ◽  
Physical Vapor Deposition ◽  
Standard Procedure ◽  
High Energy ◽  
Structure Study ◽  
Voltage Source ◽  
Titanium Target ◽  
High Voltage Source ◽  
Mechanical Pump

Titanium nitride coatings were grown in a physical vapor deposition system assisted by a direct current reactive magnetron sputtering technique. The vacuum chamber was evacuated with a mechanical pump and cryopump to a base pressure of 10-7 Torr. The Sputtering was performed with a direct current high voltage source (0-1 Kev and 1 A) on a titanium target (99.98% purity). The titanium target was sputtered with a high purity argon -nitrogen mixture. The films were deposited on monocrystalline silicon (mc-Si) (111) substrates at different nitrogen partial pressures from 0.08 mTorr to 1.5 mTorr. Total pressure, power applied to target and substrate temperature were keep constant in all the experiments.EXEELFS analysis were done using the standard procedure [1,2]. In this case, we are find that the atomic concentration is in good agreement with the respective established stoichioinetry N/T=0.99. Figure 1 shows the window of high energy loss where appears their respective N K-edge and Ti -L23.

scholarly journals ‘Pave-and-crack’ technique for the recanalization of severely calcified occlusive aorto-ilio-femoral disease in type-III Leriche syndrome: a case report

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Sorin Giusca ◽  
Andrej Schmidt ◽  
Grigorios Korosoglou
Keyword(s):  
External Iliac Artery ◽  
Covered Stent ◽  
Radial Force ◽  
Covered Stents ◽  
Leriche Syndrome ◽  
Step Procedure ◽  
Technical Advances ◽  
Radial Forces ◽  
Endovascular Approach ◽  
The Right

Abstract Background  Leriche syndrome is the result of the atherosclerotic occlusion of the distal aorta that may also involve pelvic arteries. The standard treatment for this condition is considered surgical with various techniques available for establishing appropriate flow to both limbs. However, due to the technical advances in the last decades, endovascular approaches are now also capable to tackle such lesions. The ‘pave-and-crack’ technique enables the treatment of severely calcified lesions. This two-step procedure consists of firstly placing a covered stent prothesis (VIABAHN) into the severely calcified segment, which is afterwards aggressively dilated with high-pressure balloons. Subsequently, an interwoven nitinol SUPERA stent with high radial forces is placed within the prothesis. Case summary  Herein, we describe the case of an 81-year-old male patient, who presented with critical limb-threatening ischaemia of his right leg. Doppler ultrasound revealed a long occlusion of the right external iliac artery, common femoral, superficial femoral, and deep femoral artery. The lesion was successfully tackled using antegrade and retrograde punctures and the ‘pave-and-crack’ technique. Discussion  The ‘pave-and-crack’ technique is an endovascular approach for the treatment of severe circumferential calcified lesions. Based on this technique covered stents are initially placed to prevent vessel rupture, which might occur during the aggressive balloon dilatation. Subsequently, the covered stents are relined by interwoven Supera stents, which provide high radial force preventing recoil and restenosis.

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