Influences of cavity leakage on the design of low flow coefficient centrifugal impeller

2011 ◽  
Vol 54 (2) ◽  
pp. 311-317 ◽  
Author(s):  
ZhiHeng Wang ◽  
Guang Xi
Keyword(s):  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Low Flow Coefficient

Numerical Investigation on the Labyrinth Seal Design for a Low Flow Coefficient Centrifugal Compressor

2010 ◽  
Author(s):  
Zhiheng Wang ◽  
Liqun Xu ◽  
Guang Xi
Keyword(s):  
Centrifugal Compressor ◽  
Labyrinth Seal ◽  
Flow Coefficient ◽  
Low Flow ◽  
Design Parameters ◽  
Centrifugal Impeller ◽  
Computational Domain ◽  
Cfd Simulations ◽  
Isentropic Efficiency ◽  
Low Flow Coefficient

The leakage flow across the shroud of a centrifugal compressor impeller has an important effect on the compressor’s performance, in particular, in the low flow coefficient compressor. This paper presents the three-dimensional CFD simulations and the Radial Basis Function (RBF) model to investigate the aerodynamic performance of the labyrinth seal as well as the low flow coefficient centrifugal impeller. The CFD simulations are performed on the computational domain consisting of the labyrinth seal and the impeller. The relationship between the leakage loss coefficient and the isentropic efficiency is indicated. With the application of the RBF model, the global sensitivity analysis to the seal geometric design parameters is carried out, and the geometry of the labyrinth seal is optimized. The leakage of the optimized labyrinth seal is reduced remarkably and the impeller’s isentropic efficiency improved by 2% in a wide operating range.

Radial Impeller Forces Using CFD: Part II — A Comparison Between Compressible and Incompressible Flows

2002 ◽  
Author(s):  
Daniel O. Baun ◽  
Ronald D. Flack
Keyword(s):  
Mach Number ◽  
Flow Rate ◽  
Incompressible Flows ◽  
Lateral Force ◽  
Magnetic Bearing ◽  
Flow Coefficient ◽  
Low Flow ◽  
Working Fluid ◽  
Centrifugal Impeller ◽  
Cfd Model

Lateral centrifugal impeller forces are calculated using the CFD model developed in Part I of this paper. The impeller forces are evaluated by integrating the pressure and momentum profiles at both the impeller inlet and exit planes. Direct impeller lateral force measurements were made using a magnetic bearing supported pump rotor. Comparisons between the simulated and measured forces are first made for both average and transient impeller forces with water as the working fluid. Air was then substituted as the working fluid in the validated CFD model and the effect of impeller Mach number and Reynolds number on the static impeller lateral forces was investigated. The non-dimensional lateral impeller force characteristics as a function of normalized flow coefficient are similar in character between the incompressible and compressible case. At the matching point flow coefficient the non-dimensional impeller force magnitude was the same for all compressible and incompressible simulations. For any normalized flow rate other than the matching point flow rate, the magnitude of the non-dimensional impeller force increased as the Mach number increased. As the choke condition was approached the magnitude of the impeller force increased exponentially. As the Mach number increased the transition of the force orientation vector from the low flow asymptote to the high flow asymptote occurred over a progressively smaller range of flows.

Reynolds Number and Roughness Effects on Turbocompressor Performance: Numerical Calculations and Measurement Data Evaluation

2020 ◽  
Author(s):  
Fabian Dietmann ◽  
Michael Casey ◽  
Damian M. Vogt
Keyword(s):  
Reynolds Number ◽  
Measurement Data ◽  
Theoretical Models ◽  
Design Flow ◽  
Flow Coefficient ◽  
Low Flow ◽  
Roughness Effects ◽  
Flow Channels ◽  
Compressor Performance ◽  
Low Flow Coefficient

Abstract Further validation of an analytic method to calculate the influence of changes in Reynolds number, machine size and roughness on the performance of axial and radial turbocompressors is presented. The correlation uses a dissipation coefficient as a basis for scaling the losses with changes in relative roughness and Reynolds number. The original correlation from Dietmann and Casey [6] is based on experimental data and theoretical models. Evaluations of five numerically calculated compressor stages at different flow coefficients are presented to support the trends of the correlation. It is shown that the sensitivity of the compressor performance to Reynolds and roughness effects is highest for low flow coefficient radial stages and steadily decreases as the design flow coefficient of the stage and the hydraulic diameter of the flow channels increases.

scholarly journals Numerical characteristics of a centrifugal compressor with a low flow coefficient

2019 ◽  
Vol 140 ◽  
pp. 06010 ◽  
Author(s):  
Aleksey Yablokov ◽  
Ivan Yanin ◽  
Nikolay Sadovskyi ◽  
Yuri Kozhukhov ◽  
Minh Hai Nguyen
Keyword(s):  
Centrifugal Compressor ◽  
Numerical Study ◽  
Flow Coefficient ◽  
Ultrahigh Pressure ◽  
Low Flow ◽  
Classical Type ◽  
Numerical Characteristic ◽  
Wall Cell ◽  
Low Flow Coefficient ◽  
Near Wall

The study presents the simulation results of the viscid gas flow in low flow coefficient centrifugal compressor stages. The problem is solved in a stationary formulation using the Ansys CFX software package. The numerical simulation is carried out on three ultrahigh-pressure model stages; two stages have blades of the classical type impeller and one stage is of the bodily type. The value of the conditional flow coefficient is 0.0063 to 0.015. As part of the study, block-structured design meshes are used for all gas channel elements, with their total number being equaled as 13–15 million. During the calculations a numerical characteristic was validated with the results of tests carried out at the Department of Compressor, Vacuum and Refrigeration Engineering of Peter the Great St. Petersburg Polytechnic University. With an increase of inlet pressure as a result of a numerical study, it was found that for a given mathematical model the disk friction and leakage coefficient (1 + βfr + βlk) is overestimated. The analysis of flow in labyrinth seals has shown an increase of total temperature near the discs by 30–50 °С, nevertheless this fact did not influence gas parameters in the behind-the-rotor section. The calculation data obtained with finer design mesh (the first near-wall cell was 0.001 mm) is identical to those obtained with the first near-wall cell 0.01 mm mesh.

Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1995 ◽  
Vol 117 (4) ◽  
pp. 585-592 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncˇl
Keyword(s):  
Development Program ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Disk Friction ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development program for centrifugal compressors are presented. Six-stage configurations with low flow coefficient were tested. The stages had channel width parameter b2/D2 = 0.01 and 0.03. For each value of the width parameter, three different impellers with inlet hub to outlet diameter ratio do/D2 = 0.3, 0.4, and 0.5 were designed. Test rig, instrumentation, and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing, and disk friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with deswirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

scholarly journals Experimental Investigation and Performance Analysis of Six Low Flow Coefficient Centrifugal Compressor Stages

1994 ◽  
Author(s):  
J. Paroubek ◽  
V. Cyrus ◽  
J. Kyncl
Keyword(s):  
Rotating Stall ◽  
Development Programme ◽  
Diameter Ratio ◽  
Flow Coefficient ◽  
Low Flow ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Return Channel ◽  
And Performance ◽  
Low Flow Coefficient

Some results of a research and development programme for centrifugal compressors are presented. Six stage configurations with low flow coefficient were tested. The stages had channel width parameter bo/D2=0.01 and 0.03. For each value of the width parameter three different impellers with inlet hub to outlet diameter ratio do/D2=0.3, 0.4 and 0.5 were designed. Test rig, instrumentation and data analysis are described. Special attention was devoted to probe calibrations and to evaluation of the leakage, bearing and disc friction losses. Aerodynamic performance of all tested stages is presented. Slip factors of impellers obtained experimentally and theoretically are compared. Losses in both vaneless diffuser and return channel with de-swirl vanes are discussed. Rotating stall was also investigated. Criteria for stall limit were tested.

Automatic computational fluid dynamics-based procedure for the optimization of a centrifugal impeller

2005 ◽  
Vol 219 (7) ◽  
pp. 549-557 ◽  
Author(s):  
F Martelli ◽  
S Pazzi ◽  
V Michelassi
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
New Technologies ◽  
Geometric Constraints ◽  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Geometrical Parameters ◽  
Design Point ◽  
Blade Thickness

A typical centrifugal impeller characterized by a low flow coefficient and cylindrical blades is redesigned by means of an intelligent automatic search program. The procedure consists of a feasible sequential quadratic programming algorithm (Fletcher, R. Practical Methods of optimization, 2000 (Wiley)) coupled to a lazy learning (LL) interpolator 1 to speed-up the process. The program is able to handle geometric constraints to reduce the computational effort devoted to the analysis of non-physical configurations. The objective function evaluator is an in-house developed structured computational fluid dynamics (CFD) code. The LL approx-imator is called each time the stored database can provide a sufficiently accurate performance estimate for a given geometry, thus reducing the effective CFD computations. The impeller is represented by 25 geometric parameters describing the vane in the meridional and s-0 planes, the blade thickness, and the leading edge shape. The optimization is carried out on the impeller design point maximizing the polytropic efficiency with nearly constant flow coefficient and polytropic head. The optimization is accomplished by maintaining unaltered those geometrical parameters which have to be kept fixed in order to make the impeller fit the original stage. The optimization, carried out on a cluster of 16 PCs, is self-learning and leads to a geometry presenting an increased design point efficiency. The program is completely general and can be applied to any component which can be described by a finite number of geometrical parameters and computed by any numerical instrument to provide performance indices. The work presented in this paper was done under the METHOD EC funded project for the implementation of new technologies for optimization of centrifugal compressors.

Application of a CFD-Based Program for the Optimization of a Centrifugal Impeller

2003 ◽  
Author(s):  
Simone Pazzi ◽  
Francesco Martelli ◽  
Marco Giachi ◽  
Michela Testa
Keyword(s):  
New Technologies ◽  
Leading Edge ◽  
Computational Effort ◽  
Flow Coefficient ◽  
Low Flow ◽  
Centrifugal Impeller ◽  
Geometrical Parameters ◽  
Design Point ◽  
Blade Thickness ◽  
Geometrical Constraints

A typical centrifugal impeller characterized by a low flow coefficient and cylindrical blades is redesigned by means of an intelligent automatic search program. The procedure consists of a Feasible Sequential Quadratic Programming (FSQP) algorithm [6] coupled to a Lazy Learning (LL) interpolator [1] to speed-up the process. The program is able to handle geometrical constraints to reduce the computational effort devoted to the analysis of non-physical configurations. The objective function evaluator is an in-house developed structured CFD code. The LL approximator is called each time the stored database can provide a sufficiently accurate performance estimate for a given geometry, thus reducing the effective CFD computations. The impeller is represented by 25 geometrical parameters describing the vane in the meridional and s-θ planes, the blade thickness and the leading edge shape. The optimisation is carried out on the impeller design point maximizing the polytropic efficiency with more or less constant flow coefficient and polytropic head. The optimization is accomplished keeping unaltered those geometrical parameters which have to be kept fixed in order to make the impeller fit the original stage. The optimisation, carried out on a cluster of sixteen PCs, is self-learning and leads to a geometry presenting an increased design point efficiency. The program is completely general and can be applied to any component which can be described by a finite number of geometrical parameters and computed by any numerical instrument to provide performance indices. The work presented in this paper has been developed inside the METHOD EC funded project for the implementation of new technologies for optimisation of centrifugal compressors.

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