scholarly journals Effect of Rotor–Stator Interaction on Impeller Performance in Centrifugal Compressors

1999 ◽  
Vol 5 (2) ◽  
pp. 135-146 ◽  
Author(s):  
K. Sato ◽  
L. He
Keyword(s):  
Navier Stokes ◽  
Test Case ◽  
Steady Flows ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Rotor Stator Interaction ◽  
Flow Through ◽  
And Performance ◽  
Unsteady Effects ◽  
Blade Row Interaction

A 3-D unsteady thin-layer Navier-Stokes code has been used to calculate the flow through a centrifugal compressor stage. The validation of the code for steady flows in centrifugal compressors was conducted for the Krain’s impeller with a vaneless diffuser as a test case and the numerical results were compared with the experimental results. The predicted flow field and performance agreed well with the experimental data. An unsteady stage solution was then conducted with this impeller followed by a generic low-solidity vaned-diffuser to examine the unsteady effects on the impeller performance. The computational results showed a stabilising effect of the blade row interaction.

Numerical Study of Deterministic Fluxes in Compressor Passages

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Navier Stokes ◽  
Design Stage ◽  
Reynolds Stresses ◽  
Mean Flow ◽  
Radial Profiles ◽  
And Performance ◽  
Stage Matching ◽  
Unsteady Effects

Computational fluid dynamics (CFD) has been widely adopted in the compressor design process, but it remains a challenge to predict the flow details, performance, and stage matching for multistage, high-speed machines accurately. The Reynolds Averaged Navier-Stokes (RANS) simulation with mixing plane for bladerow coupling is still the workhorse in the industry and the unsteady bladerow interaction is discarded. This paper examines these discarded unsteady effects via deterministic fluxes using semi-analytical and unsteady RANS (URANS) calculations. The study starts from a planar duct under periodic perturbations. The study shows that under large perturbations, the mixing plane produces dubious values of flow quantities (e.g., whirl angle). The performance of the mixing plane can be considerably improved by including deterministic fluxes into the mixing plane formulation. This demonstrates the effect of deterministic fluxes at the bladerow interface. Furthermore, the front stages of a 19-blade row compressor are investigated and URANS solutions are compared with RANS mixing plane solutions. The magnitudes of divergence of Reynolds stresses (RS) and deterministic stresses (DS) are compared. The effect of deterministic fluxes is demonstrated on whirl angle and radial profiles of total pressure and so on. The enhanced spanwise mixing due to deterministic fluxes is also observed. The effect of deterministic fluxes is confirmed via the nonlinear harmonic (NLH) method which includes the deterministic fluxes in the mean flow, and the study of multistage compressor shows that unsteady effects, which are quantified by deterministic fluxes, are indispensable to have credible predictions of the flow details and performance of compressor even at its design stage.

Evaluation of Unsteady CFD Methods by Their Application to a Transonic Propfan Stage

2001 ◽  
Author(s):  
S. Schmitt ◽  
F. Eulitz ◽  
L. Wallscheid ◽  
A. Arnone ◽  
M. Marconcini
Keyword(s):  
Numerical Methods ◽  
Navier Stokes ◽  
Test Case ◽  
Flow Angle ◽  
Laser Measurements ◽  
General Flow ◽  
Blade Row ◽  
Flow Features ◽  
Blade Row Interaction ◽  
Good Agreement

The accuracy in predicting the unsteady aerodynamic blade-row-interaction of two state-of-the-art Navier-Stokes codes is evaluated within the current paper. The general flow features of the test case — a transonic research propfan stage — are described in brief as far as necessary to understand the detailed comparisons. The calculated unsteady velocity and flow angle distributions at various axial planes of the stage are compared to data from unsteady laser measurements. The general flow features of the propfan are very well reproduced by the numerical methods and a good agreement is also obtained in comparison to the measured data. One important outcome of the comparison is the good agreement of both numerical methods with the unsteady fluctuations measured in the experiment.

A Simulation of the Unsteady Interaction of a Centrifugal Impeller With its Vaned Diffuser: Flows Analysis

1994 ◽  
Author(s):  
W. N. Dawes
Keyword(s):  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Centrifugal Impeller ◽  
Vaned Diffuser ◽  
Time Resolved ◽  
High Loss ◽  
Swirl Angle ◽  
Unsteady Interaction ◽  
Unsteady Effects

The aim of this paper is to help advance our understanding of the complex, three-dimensional, unsteady flow associated with the interaction of a splattered centrifugal impeller and its vaned diffuser. A time-resolved simulation is presented of the Krain stage performed using a time-accurate, 3D, unstructured mesh, solution-adaptive Navier-Stokes solver. The predicted flowfield, compared with experiment where available, displays a complex, unsteady interaction especially in the neighbourhood of the diffuser entry zone which experiences large periodic flow unsteadiness. Downstream of the throat, although the magnitude of this unsteadiness diminishes rapidly, the flow has a highly distorted three-dimensional character. The loss levels in the diffuser are then investigated to try and determine how time-mean loss levels compare with the levels expected from “equivalent” steady flow analysis performed by using the circumferentially averaged exit flow from the impeller as inlet to the diffuser. It is concluded that little loss could be attributed directly to unsteady effects but rather that the principle cause of the rather high loss levels observed in the diffuser is the strong spanwise distortion in swirl angle at inlet which initiates a strong hub/comer stall.

scholarly journals Simulations of Aeroelasticity in an Annular Cascade Using a Parallel 3-Dimensional Navier-Stokes Solver

2002 ◽  
Author(s):  
Ivan McBean ◽  
Feng Liu ◽  
Kerry Hourigan ◽  
Mark Thompson
Keyword(s):  
Unsteady Flow ◽  
Flow Model ◽  
Standard Test ◽  
Navier Stokes ◽  
Test Case ◽  
Turbine Cascade ◽  
3 Dimensional ◽  
Flow Through ◽  
The Stability ◽  
Annular Cascade

A parallel multi-block Navier-Stokes solver with the k-ω turbulence model is developed to simulate the 3-dimensional unsteady flow through an annular turbine cascade. Results at mid-span are compared with the experimental results of Standard Test Case 4. Comparisons are made between 3-dimensional and 2-dimensional, and inviscid and viscous simulations. The inclusion of a viscous flow model does not greatly affect the stability of the configuration.

Assessment of Laminar-Turbulent Transition Models for Turbomachinery Flow Computations

2005 ◽  
Author(s):  
L. Cutrone ◽  
P. De Palma ◽  
G. Pascazio ◽  
M. Napolitano
Keyword(s):  
Incompressible Flows ◽  
Navier Stokes ◽  
Test Case ◽  
Bypass Transition ◽  
Turbine Cascade ◽  
Turbulent Transition ◽  
Complex Test ◽  
Flow Through ◽  
Transition Models ◽  
Intermittency Factor

This paper provides a thorough comparison of different laminar-to-turbulent bypass transition models. The models are based on combinations of two transition-onset correlations and three intermittency factor models. They have been embedded in a Reynolds averaged Navier–Stokes solver employing a low-Reynolds number k–ω turbulence model. The performance of the transition models have been validated by computing three well documented incompressible flows over a flat plate, namely, test T3A, T3B, and T3C2 of ERCOFTAC SIG 10, with different free-stream conditions, the latter being characterized by non-zero pressure gradient. Finally, a more complex test case, namely the two-dimensional compressible flow through a linear turbine cascade, has been considered, for which detailed experimental data are available in the literature.

scholarly journals Deterministic Stress Modeling for Multistage Compressor Flowfields

2013 ◽  
Author(s):  
Stefan Stollenwerk ◽  
Edmund Kügeler
Keyword(s):  
Gas Turbines ◽  
Transport Model ◽  
Navier Stokes ◽  
Transonic Compressor ◽  
Wide Range ◽  
Multistage Compressor ◽  
Aero Engines ◽  
Unsteady Effects ◽  
Stress Models ◽  
Blade Row Interaction

Unsteadiness is one of the main characteristics in turbomachinery flows. Local unsteady changes in static pressure must exist within a turbo-machine in order for that machine to exchange energy with the fluid. The primary reason for unsteady effects lies in the interaction between moving and stationary blade rows. The industrial design process of aero-engines and gas turbines is still based on Reynolds-averaged Navier-Stokes (RANS) techniques where the coupling of blade rows is carried out by mixing-planes. However, this methodology does not cover deterministic unsteadiness in an adequate way. For standard aero-optimization, detailed unsteadiness is not essential to the designer of turbomachines but rather its effect on the time averaged solution. The time averaged deterministic unsteadiness can be expressed in terms of deterministic stresses. The present paper presents two different modeling strategies for deterministic stresses that constitute an improvement of the conventional steady mixing-plane approach. Whilst one of the presented models operates with deterministic flux terms based on preliminary unsteady simulations, the other one, a novel transport model for deterministic stress, is a stand-alone approach based on empirical correlations and a wide range of numerical experiments. A 4.5 stage transonic compressor is analyzed regarding blade row interaction effects and their impact on the time averaged solution. The two models are applied to the compressor and their solutions are compared to conventional mixing-plane, time accurate and experimental data. The results for the speedline, the wake shapes, the radial distributions and the rotor blade loadings show that the deterministic stress models strongly improve the RANS solution towards the time accurate and the experimental methods.

Evaluation of Flow Field Approximations for Transonic Compressor Stages

1996 ◽  
Author(s):  
Daniel J. Dorney ◽  
Om P. Sharma
Keyword(s):  
Flow Field ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Loosely Coupled ◽  
Transonic Compressor ◽  
Blade Row ◽  
Flow Through ◽  
And Performance ◽  
Computer Resources ◽  
Fully Coupled

The flow through gas-turbine compressors is often characterized by unsteady, transonic and viscous phenomena. Accurately predicting the behavior of these complex multi-blade-row flows with unsteady rotor-stator interacting Navier-Stokes analyses can require enormous computer resources. In this investigation, several methods for predicting the flow field, losses and performance quantities associated with axial compressor stages are presented. The methods studied include, 1) the unsteady fully-coupled blade row technique, 2) the steady coupled blade row method, 3) the steady single blade row technique, and 4) the loosely-coupled blade row method. The analyses have been evaluated in terms of accuracy and efficiency.

Application of Low Solidity Vaned Diffusers to Prevent Rotating Stall in Centrifugal Compressors: Experimental Investigation

2003 ◽  
Author(s):  
A. Cellai ◽  
M. De Lucia ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
Stall Inception ◽  
And Performance

Rotating stall is a key problem in centrifugal compressors especially for high-pressure applications. Among the several solutions proposed to prevent this problem, low solidity vaned diffusers (LSDs) have been successfully applied. The aim of this research is to find an optimized LSD configuration in terms of stall inception and performance for the tested compressor. The influence of the vane leading and trailing edge radii, maintaining the same solidity and null deflection were investigated. The geometrical parameters of tested configurations were methodically chosen in order to achieve a design of experiment (DOE) analysis. In view of the above, a series of tests on five low solidity vaned diffuser configurations were carried out. Tests allowed determination of 2 different LSDs that showed the best behavior in terms of working range and performance. These LSDs were then compared with the standard and the reduced-width vaneless diffuser to better understand the best solution to the stall problem.

Numerical Simulation of the Flow Through the Rotor of a Radial Inflow Turbine

1997 ◽  
Author(s):  
V. Amedick ◽  
H. Simon
Keyword(s):  
Viscous Flow ◽  
Mass Flow ◽  
Incidence Angle ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Viscous Forces ◽  
Flow Through ◽  
Radial Inflow Turbine ◽  
Comparison Of The Results ◽  
Unsteady Effects

An existing Navier-Stokes solver to simulate the turbulent transonic flow using block-structured grids has been used to optimize the guide vanes of radial inflow turbines. The code has been extended to calculate the flow in the rotating parts of turbomachines and is now used to simulate the turbulent flow through the rotor of a radial inflow turbine. The results of three calculations are presented (inviscid and viscous flow without tip clearance, viscous flow with tip clearance). The flowfield is investigated at design conditions where a large incidence angle exists at the entrance of the rotor. Unsteady effects are neglected. The comparison of the results of the inviscid and viscous simulations shows the strong influence of the viscous forces. Strong secondary flow patterns are found in the vicinity of the blades and the walls. Special attention has been paid to the analysis of the flow through the gap between the casing and the blades. The determination of the mass flow rate through the gap shows that mass is transported from the suction towards the pressure side of the blade at the beginning of the blade (6.1% of the blade length). Thereafter, the mass flow through the gap changes its direction.

scholarly journals Comparative Study on Steady and Unsteady Flow in a Centrifugal Compressor Stage

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Changhee Kim ◽  
Changmin Son
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Compressor ◽  
Industrial Development ◽  
Navier Stokes ◽  
Compressor Stage ◽  
Common Procedure ◽  
Vaned Diffuser ◽  
Centrifugal Compressor Stage ◽  
Rans Simulation ◽  
And Performance

Steady Reynolds-averaged Navier-Stokes (RANS) simulation with the mixing-plane approach is the most common procedure to obtain the performance of a centrifugal compressor in an industrial development process. However, the accurate prediction of complicated flow fields in centrifugal compressors is the most significant challenge. Some phenomena such as the impeller-diffuser flow interaction generates the unsteadiness which can affect the steady assumption. The goal of this study is to investigate the differences between the RANS and URANS simulation results in a centrifugal compressor stage. Simulations are performed at three operating points: near surge (NS), design point (DP), and near choke (NC). The results show that the RANS simulation can predict the overall performance with reasonable accuracy. However, the differences between the RANS and URANS simulation are quite significant especially in the region that the flows are highly unsteady or nearly separated. The RANS simulation is still not very accurate to predict the time-dependent quantities of the flow structure. It shows that the URANS calculations are necessary to predict the detailed flow structures and performance. The phenomena and mechanisms of the complex and highly unsteady flow in the centrifugal compressor with a vaned diffuser are presented and analyzed in detail.

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