Investigation of a Centrifugal Compressor Stage With Two Volutes and the Same Impeller

2003 ◽  
Author(s):  
Yinghui Dai ◽  
Abraham Engeda ◽  
Michael Cave ◽  
Jean-Luc Di Liberti

Volute scroll, conic diffuser and sudden expansion discharge loss account for 4–6 points of efficiency decrement in a typical centrifugal compressor stage. The flow in a volute is highly complex. It is strongly believed that understanding of the detailed flow structure in a volute will provide insights on minimizing the losses by isolating the mechanisms that contributes to entropy generation. The result will be a more efficient centrifugal compressor product for customers and users and a product at higher profitability levels for manufacturers. This paper presents the experimental and numerical investigation on the matching of two different overhung volutes to the same centrifugal compressor impeller. The experimental data were measured from flange to flange firstly, then three Kiel probes were installed on pinch position circumferentially. At the same time, a detailed numerical simulation of the performance of the two volutes has been carried out. A computational model, using the k-ε turbulence model and the wall function, has been used to predict the internal flow of the both volutes. A good agreement between experimental data and numerical simulation results is found. The overall performance of the two volutes was also discussed in detail.

2013 ◽  
Vol 30 (2) ◽  
pp. 113-121 ◽  
Author(s):  
L. H. Jawad ◽  
S. Abdullah ◽  
R. Zulkifli ◽  
W. M. F. W. Mahmood

ABSTRACTThis paper is a numerical simulation that was made in the three-dimensional flow, carried out in a modified centrifugal compressor, having vaned diffuser stage, used as an auto-motive turbo charger. Moreover, the performance of the centrifugal compressor was dependent on the proper matching between compressor impeller and vaned diffuser, influencing significantly surge and the efficiency of centrifugal compressor stages. In addition, a modified compressor impeller, coupled with vane and vaneless diffuser, has been found to have similar internal flow patterns for both the vaneless and vaned diffuser design. The vaned diffuser effect has been paid particular attention in terms of better analysis where the diffuser was designed for high sub-sonic inlet conditions. Another aim of this research was to study and simulate the effect of vaned diffuser on the performance of a centrifugal compressor. The simulation was undertaken by using a commercial software, the so-called ANSYS CFX, to predict numerically the performance in terms of pressure ratio, poly tropic efficiency and mass flow rate for the centrifugal compressor stage. The results were generated from CFD and were analyzed for better understanding of the fluid flow through centrifugal compressor stage. Conclusively, it was observed that the effect of the vaned diffuser is to convert the kinetic energy into a high static pressure after analyzing the results of the simulation.


Author(s):  
Emanuele Guidotti ◽  
Giovanni Naldi ◽  
Libero Tapinassi ◽  
Valliappan Chockalingam

Numerical tools and test equipments used in the design and validation of modern centrifugal compressor stages need to be at the state-of-the-art. In particular, a big effort is currently made to correctly model secondary flows that play a relevant role in the accuracy of the performance prediction. This paper presents the flow analysis of a high efficiency centrifugal compressor stage using high accurate computational fluid dynamics with a particular attention to the cavity flows modeling. Experimental data were also available and used to validate the numerical results. The key experimental data coming from an advanced FRAPP (Fast Response Aerodynamic Pressure Probe) and traditional probes are presented in the study as overall performance and flow features details. Test data are in fact necessary to validate and continuously improve the numerical techniques. The geometry of the stage including full modeling of the secondary flows cavities were faithfully reproduced in the computational model. The availability of new in-house automated tools for cavity meshing allow compressor aero-designers to accurately resolve leakage flows with a reasonable increase in computational and user time. The results of the computational model were in excellent agreement with the experimental data both in terms of overall performance and main flow field structures. Also details of the flow features inside the cavities matched the test data very well. Only using high accurate geometry modeling including leakage flows was possible to capture important flow features that instead were not correctly simulated with simplified computational models.


2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Daniel R. Grates ◽  
Peter Jeschke ◽  
Reinhard Niehuis

The subject of this paper is the investigation of unsteady flow inside a transonic centrifugal compressor stage with a pipe-diffuser by utilizing unsteady 3D Reynolds-averaged Navier–Stokes simulations (unsteady 3D URANS). The computational fluid dynamics (CFD) results obtained are compared with detailed experimental data gathered using various steady and unsteady measurement techniques. The basic phenomena and mechanisms of the complex and highly unsteady flow inside the compressor with a pipe-diffuser are presented and analyzed in detail.


Author(s):  
Y Dai ◽  
A Engeda ◽  
M Cave ◽  
J-L Di Liberti

The interaction between an impeller with one large and one small overhung volute was investigated by both computational fluid dynamics simulation and experimental methods. The large volute was mainly generated by increasing the small volute axial length. The computational model, with k—∊ turbulence model and wall function, has been used to predict the internal flow of both volutes. The effect of volute tongue on the flow in the impeller was analysed at off-design conditions. The flow structure in the volutes was also investigated in detail. The performance test of the two configurations was carried out in the aero test facility at Solar Turbines Inc. A good agreement between experimental data and numerical simulation results was found on both the whole compressor stage performance and the impeller performance. The largest deviation is close to 10 per cent for the compressor stage performance prediction at high mass flowrate only.


Author(s):  
Daniel R. Grates ◽  
Peter Jeschke ◽  
Reinhard Niehuis

The subject of this paper is the investigation of unsteady flow inside a transonic centrifugal compressor stage with pipe-diffuser by utilizing unsteady 3D Navier-Stokes simulations (unsteady 3D URANS). The CFD results obtained are compared with detailed experimental data gathered using various steady and unsteady measurement techniques. The basic phenomena and mechanisms of the complex and highly unsteady flow inside the compressor with pipe-diffuser are presented and analyzed in detail.


2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Mykola Kalinkevych ◽  
Oleg Shcherbakov

This paper presents the results of numerical investigation of the flow in a vaneless diffuser of centrifugal compressor stage. Simulations were performed using both a commercial CFD package ANSYS CFX and the own-designed computer program. Steady conditions involving SST turbulence model were used for the calculations using CFX. To consider the interaction between impeller and diffuser, not just a diffuser but the whole stage was calculated. The own-designed methodology is based on solving of conservation equations with assumptions that flow in a diffuser is steady state and axisymmetric. The flow area is divided into the flow core and boundary layers. Results of calculation were compared with experimental data.


Author(s):  
Toshiyuki Arima ◽  
Toyotaka Sonoda ◽  
Masatoshi Shirotori ◽  
Yoshihiro Yamaguchi

A two-layer k-ε/algebraic Reynolds stress model (ARSM) has been adopted to the three-dimensional, Reynolds-averaged, Navier-Stokes code to include explicitly the Reynolds stress anisotropy. The code has been used to study the complex flow fields of a transonic axial compressor rotor (i.e., NASA Rotor 37) and a subsonic centrifugal compressor impeller (i.e., the backswept impeller of Krain, first reported in 1988). The computed results have been compared with those from a Baldwin-Lomax model, a low-Reynolds number k-ε turbulence model and actual experimental data. Calculated results for the axial compressor are compared with data reported by Suder in 1994. The suitability of the turbulence model to predict accurately the overall performance of the rotor, spanwise distributions of aerodynamic characteristics, and the wake flow profiles is assessed. Calculations for the centrifugal compressor impeller are compared with the experimental data reported by Hah and Krain in 1989. The usefulness of the turbulence models to predict accurately the overall performance of the impeller, the impeller-exit-velocity profile, and the meridional velocity and flow angle profiles at the cross-channel planes (via L2F measurements) has also been investigated. For modeling the turbulence of both the rotor and the impeller, reasonably good predictions have been obtained with the ARSM and the low-Reynolds number k-ε models, but have not been attainable using the Baldwin-Lomax model. The solutions obtained with the ARSM show better agreement with experimental data than those obtained with the other models. However, in some cases, the predicted differences between the ARSM and the low-Reynolds number k-ε models are not significant. The computed secondary flow and the relative helicity have also been used to investigate the effect of wall curvature and frame rotation on the flow field inside the centrifugal impeller for three operating conditions (i.e., design point, choke, and near surge) and the results are discussed.


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