Numerical Modeling of Some Parameters for Performance Prediction of Centrifugal Impellers

2000 ◽  
Author(s):  
JongSik Oh ◽  
KoonSup Oh
Keyword(s):  
Turbulent Flows ◽  
Performance Prediction ◽  
Effective Means ◽  
Three Dimensional ◽  
Cfd Analysis ◽  
One Dimensional ◽  
Engineering Models ◽  
Time Marching ◽  
And Diffusion ◽  
Marching Method

The numerical results of a CFD analysis for 5 impellers are presented and discussed to generate simple correlations for the slip factors and the aerodynamic exit blockages of centrifugal compressors. The purpose of the analysis and modeling is to supply an effective means of estimating both parameters used in the meanline performance prediction stage, only in the agile engineering sense. A finite volume time marching method was used in the analysis of three dimensional compressible turbulent flows. To generate one dimensional representative values from the three dimensional results, a mass-averaged concept was used on each impeller exit plane. The Wiesner’s slip factor was found to fail to predict accurate level of values and also the trend of variation, when the flow rate was changed, especially in case of backswept impellers. Aerodynamic blockage at the impeller exit was also found to vary with the flow rates, the blade exit angle and diffusion ratio. Some useful engineering models of both parameters were suggested to improve the current level of prediction for the impeller exit performance.

Calculation of the Quasi Three-Dimensional Flow in a Turbomachine Blade Row

1977 ◽  
Vol 99 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Jean-Pierre Veuillot
Keyword(s):  
Finite Difference ◽  
Three Dimensional ◽  
Three Dimensional Flow ◽  
Through Flow ◽  
Blade Row ◽  
Time Marching ◽  
Space Discretization ◽  
Finite Volume Approach ◽  
Marching Method ◽  
Finite Difference Techniques

The equations of the through flow are obtained by an asymptotic theory valid when the blade pitch is small. An iterative method determines the meridian stream function, the circulation, and the density. The various equations are discretized in an orthogonal mesh and solved by classical finite difference techniques. The calculation of the steady transonic blade-to-blade flow is achieved by a time marching method using the MacCormack scheme. The space discretization is obtained either by a finite difference approach or by a finite volume approach. Numerical applications are presented.

Improving a one-dimensional centrifugal compressor performance prediction method

2005 ◽  
Vol 219 (8) ◽  
pp. 653-659 ◽  
Author(s):  
E Swain
Keyword(s):  
Centrifugal Compressor ◽  
Performance Prediction ◽  
Fluid Dynamic ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Prediction Method ◽  
Compressor Cascade ◽  
One Dimensional ◽  
Compressor Performance ◽  
Cfd Analyses

A one-dimensional centrifugal compressor performance prediction technique that has been available for some time is updated as a result of extracting the component performance from three-dimensional computational fluid dynamic (CFD) analyses. Confidence in the CFD results is provided by comparison of overall performance for one of the compressor examples. The extracted impeller characteristic is compared with the original impeller loss model, and this indicated that some improvement was desirable. The position of least impeller loss was determined using a traditional axial compressor cascade method, and suitable algebraic expressions were derived to match the CFD data. The merit of the approach lies with the relative ease that CFD component performance currently can be achieved and adjusting one-dimensional methods to agree with the CFD-derived models.

Theoretical design of MoO3-based high-rate lithium ion battery electrodes: the effect of dimensionality reduction

2014 ◽  
Vol 2 (45) ◽  
pp. 19180-19188 ◽  
Author(s):  
Fengyu Li ◽  
Carlos R. Cabrera ◽  
Zhongfang Chen
Keyword(s):  
Density Functional ◽  
Three Dimensional ◽  
Lithium Ion ◽  
High Rate ◽  
Functional Theory ◽  
One Dimensional ◽  
Theoretical Design ◽  
Different Dimensions ◽  
Li Adsorption ◽  
And Diffusion

By means of density functional theory computations, we systematically investigated the behavior of lithium (Li) adsorption and diffusion on MoO3 with different dimensions: including three-dimensional (3D) bulk, two-dimensional (2D) double-layer, 2D monolayer and one-dimensional (1D) nanoribbons.

ACOUSTIC ATTENUATION CHARACTERISTICS OF STRAIGHT-THROUGH PERFORATED TUBE SILENCERS AND RESONATORS

2008 ◽  
Vol 16 (03) ◽  
pp. 361-379 ◽  
Author(s):  
Z. L. JI
Keyword(s):  
Performance Prediction ◽  
Transmission Loss ◽  
Three Dimensional ◽  
Geometrical Parameters ◽  
Mean Flow ◽  
Acoustic Attenuation ◽  
One Dimensional ◽  
The One ◽  
Attenuation Characteristics ◽  
Perforated Tube

The one-dimensional analytical solutions are derived and three-dimensional substructure boundary element approaches are developed to predict and analyze the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators without mean flow, as well as to examine the effect of nonplanar waves in the silencers and resonators on the acoustic attenuation performance. Comparisons of transmission loss predictions with the experimental results for prototype straight-through perforated tube silencers demonstrated that the three-dimensional approach is needed for accurate acoustic attenuation performance prediction at higher frequencies, while the simple one-dimensional theory is sufficient at lower frequencies. The BEM is then used to investigate the effects of geometrical parameters on the acoustic attenuation characteristics of straight-through perforated tube silencers and folded resonators in detail.

Numerical Analysis of Internal Flow Field in an Impeller with the Time Marching Method

2011 ◽  
Vol 94-96 ◽  
pp. 1476-1480
Author(s):  
Cai Hua Wang
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Internal Flow ◽  
Centrifugal Impeller ◽  
Three Dimensional Flow ◽  
Vector Distribution ◽  
Time Marching ◽  
Marching Method

Centrifugal compressors are power machineries used widely. Fully understanding of the complex three-dimensional flow field is very important to design higher pressure ratio, higher efficiency centrifugal compressor. In this paper, time marching method is adopted to solve the three-dimensional viscous N-S equations under the relative coordinate system. The internal flow field of the “full controllable vortex” high speed centrifugal impeller is analyzed and the medial velocity vector distribution and the development of the velocity of each section in the impeller are showed. From the figures, it can be seen that the “wake” phenomenon, such as Ecckart described, caused by the curvature, Coriolis force and the boundary layer is exist

Experimental assessment of fractal scale similarity in turbulent flows. Part 2. Higher-dimensional intersections and non-fractal inclusions

1997 ◽  
Vol 338 ◽  
pp. 89-126 ◽  
Author(s):  
RICHARD D. FREDERIKSEN ◽  
WERNER J. A. DAHM ◽  
DAVID R. DOWLING
Keyword(s):  
Turbulent Flows ◽  
Three Dimensional ◽  
Local Scale ◽  
Scalar Dissipation ◽  
Experimental Assessment ◽  
One Dimensional ◽  
Higher Dimensional ◽  
Scale Similarity ◽  
Data Points ◽  
Simple Average

Results from an earlier experimental assessment of fractal scale similarity in one-dimensional spatial and temporal intersections in turbulent flows are here extended to two- and three-dimensional spatial intersections. Over 25000 two-dimensional (2562) intersections and nearly 40 three-dimensional (2563) intersections, collectively representing more than 2.3 billion data points, were analysed using objective statistical methods to determine which intersections were as fractal as stochastically scale-similar fractal gauge sets having the same record length. Results for the geometry of Sc [Gt ]1 scalar isosurfaces and the scalar dissipation support span the range of lengthscales between the scalar and viscous diffusion scales λD and λν. The present study finds clear evidence for stochastic fractal scale similarity in the dissipation support. With increasing intersection dimension n, the data show a decrease in the fraction of intersections satisfying the criteria for fractal scale similarity, consistent with the presence of localized non-fractal inclusions. Local scale similarity analyses on three-dimensional (643) intersections directly show such intermittent non-fractal inclusions with characteristic lengthscale comparable to λν. These inclusions lead to failure of the relation among codimensions Dn≡D−(3−n) when applied to simple average dimensions, which has formed the basis for most previous assessments of fractal scale-similarity. Unlike the dissipation support geometry, scalar isosurface geometries from the same data were found not to be as fractal as fractional Brownian motion gauge sets over the range of scales examined.

Rationalization of Empirical Loss Coefficients and Their Application in One Dimensional Performance Prediction Procedures for Centrifugal Compressors

1978 ◽  
Author(s):  
A. Whitfield
Keyword(s):  
Performance Prediction ◽  
Essential Feature ◽  
Three Dimensional ◽  
Separated Flow ◽  
General Assumption ◽  
Centrifugal Compressors ◽  
Loss Mechanism ◽  
One Dimensional ◽  
Adiabatic Flow ◽  
Dimensional Flow

The flow through centrifugal compressors is often highly separated and fully three-dimensional. Modern computing techniques have not yet provided the ability to predict this three-dimensional separated flow. The design engineer has the need of a relatively simple performance prediction procedure in order to assess the potential of any proposed design. Consequently, a number of performance prediction procedures, with the general assumption of one-dimensional adiabatic flow, have been published. A common and essential feature of all these procedures is the use of empirical parameters in order to expand the one-dimensional flow into a description of the fully three-dimensional flow. These empirical parameters usually describe the loss mechanism and the flow deviation in any duct. Presented in footnote is a one-dimensional procedure which separated the fundamental gas dynamics from the empiricism used. Consequently, it is a relatively simple matter to apply alternative empirical parameters, and, more importantly, it is also possible for the design engineer to readily apply empirical relationships built up from his own experience. Unfortunately, numerous techniques are used to define the losses, and it may be necessary for the design engineer to redefine his own data in terms compatible with the computer program available to him.

scholarly journals Turbulence in the interstellar medium

2014 ◽  
Vol 21 (3) ◽  
pp. 587-604 ◽  
Author(s):  
D. Falceta-Gonçalves ◽  
G. Kowal ◽  
E. Falgarone ◽  
A. C.-L. Chian
Keyword(s):  
Cosmic Rays ◽  
Magnetic Fields ◽  
Interstellar Medium ◽  
Turbulent Flows ◽  
Molecular Clouds ◽  
Three Dimensional ◽  
Interstellar Turbulence ◽  
The Stability ◽  
Observational Techniques ◽  
And Diffusion

Abstract. Turbulence is ubiquitous in the insterstellar medium and plays a major role in several processes such as the formation of dense structures and stars, the stability of molecular clouds, the amplification of magnetic fields, and the re-acceleration and diffusion of cosmic rays. Despite its importance, interstellar turbulence, like turbulence in general, is far from being fully understood. In this review we present the basics of turbulence physics, focusing on the statistics of its structure and energy cascade. We explore the physics of compressible and incompressible turbulent flows, as well as magnetised cases. The most relevant observational techniques that provide quantitative insights into interstellar turbulence are also presented. We also discuss the main difficulties in developing a three-dimensional view of interstellar turbulence from these observations. Finally, we briefly present what the main sources of turbulence in the interstellar medium could be.

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