3D Unsteady Computation of Stall Inception in Axial Compressors

2010 ◽  
Author(s):  
Baofeng Tu ◽  
Jun Hu ◽  
Yong Zhao
Keyword(s):  
Numerical Simulation ◽  
Euler Equations ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Computational Domain ◽  
Stall Inception ◽  
Axial Compressors ◽  
Stall Cells ◽  
Unsteady Numerical Simulation ◽  
Aero Engines

Rotating stall is one of the unsteady phenomena in multistage axial compressors that will damage both of performance and service life of aero engines. Stall inception is a dynamic process including appearance of pre-stall disturbance, evolvement of disturbances into stall cells, and development of stall cells. The main purpose in researching stall inception is to reveal the origins of disturbances and stall cells, investigate the effects of aerodynamic design variations on stall inception, and find the effective ways to prevent engines from turning into rotating stall or surge. Numerical simulation is an economic, reliable and rapid tool to study stall inception. As stall inception is three-dimensional and unsteady, numerical simulation should be capable of describing these aspects. In this paper, a three dimensional unsteady computational model based on the three-dimensional unsteady Euler equations and the three dimensional multi actuator-disks model has been developed. The computational domain can be divided into two kinds. One is blade-free regions, which consist of upstream duct, the axial gaps among blade rows, and downstream duct. The other one is blade rows. The flows in blade-free regions considered inviscid, unsteady, and can be resolved using three-dimensional unsteady Euler equations. The blade rows are replaced by multi actuator-disks with different total-to-static characteristics. By added the correlation functions of inlet and outlet flow angles, we can compute the flow field by combining the Euler equations and the multi actuator-disks model. A two-stage low-speed compressor in NUAA has been investigated, and the predicted results indicates that the second stage comes out stall cell first, and the full developed stall cell rotates at about 40.4% rotor speed, which coincides with the experimental data.

An Unsteady Numerical Investigation on the Hysteresis Stall Loop of a Counter-Rotating Compressor

2011 ◽  
Author(s):  
Zhuoqi Wang ◽  
Wei Yuan ◽  
Qiushi Li ◽  
Yajun Lu
Keyword(s):  
Numerical Simulation ◽  
Recovery Process ◽  
Characteristic Line ◽  
Rotor Speed ◽  
Stall Inception ◽  
Rotating Speed ◽  
Flow Phenomena ◽  
Stall Cells ◽  
Unsteady Numerical Simulation ◽  
Good Agreement

For investigating the flow phenomena in the stall process, a full annular unsteady numerical simulation has been carried out on a low speed counter-rotating compressor. The numerical results are in good agreement with experimental results. According to the CFD results, the stall inception was found in the tip region of the front rotor. The rotating speed of stall cells in the front rotor are about 41% of the rotor speed and the direction is the same with the rotor rotating direction. The stall cells occupies about 20% of the blade span away from the casing wall when the compressor is in deep stall. The flow phenomena is well captured which explained why the compressor characteristic line appears as a hysteresis loop in the stall inception-recovery process.

About the Numerical Simulation of Rotating Stall Mechanisms in Axial Compressors

2006 ◽  
Author(s):  
N. Gourdain ◽  
S. Burguburu ◽  
G. J. Michon ◽  
N. Ouayahya ◽  
F. Leboeuf ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Stall Inception ◽  
Axial Compressors ◽  
Time Frequency ◽  
Flow Phenomena ◽  
Temporal Modes ◽  
Inception Point

This paper deals with the first instability which occurs in compressors, close to the maximum of pressure rise, called rotating stall. A numerical simulation of these flow phenomena is performed and a comparison with experimental data is made. The configuration used for the simulation is an axial single-stage and low speed compressor (compressor CME2, LEMFI). The whole stage is modeled with a full 3D approach and tip clearance is taken into account. The numerical simulation shows that at least two different mechanisms are involved in the stall inception. The first one leads to a rotating stall with 10 cells and the second one leads to a configuration with only 3 cells. Unsteady signals from the computation are analyzed thanks to a time-frequency spectral analysis. An original model is proposed, in order to predict the spatial and the temporal modes which are the results of the interaction between stall cells and the compressor stage. A comparison with measurements shows that the computed stall inception point corresponds to the experimental limit of stability. The performance of the compressor during rotating stall is also well predicted by the simulation.

A Method of Stall and Surge Prediction in Axial Compressors Based On Three-Dimensional Body-Force Model

2021 ◽  
Author(s):  
Hanxuan Zeng ◽  
Xinqian Zheng ◽  
Mehdi Vahdati
Keyword(s):  
Body Force ◽  
Reverse Flow ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Rotating Stall ◽  
The Body ◽  
Force Model ◽  
Computational Domain ◽  
Forward Flow ◽  
Axial Compressors

Abstract The occurrence of stall and surge in axial compressors has a great impact on the performance and reliability of aero-engines. Accurate and efficient prediction of the key features during these events has long been the focus of engine design processes. In this paper, a new body-force model that can capture the three-dimensional and unsteady features of stall and surge in compressors at a fraction of time required for URANS computations is proposed. To predict the rotating stall characteristics, the deviation of local airflow angle from the blade surface is calculated locally during the simulation. According to this local deviation, the computational domain is divided into stalled and forward flow regions, and the body-force field is updated accordingly; to predict the surge characteristics, the local airflow direction is used to divide the computational domain into reverse flow regions and forward flow regions. A single-stage axial compressor and a three-stage axial compressor are used to verify the proposed model. The results show that the method is capable of capturing stall and surge characteristics correctly. Compared to the traditional fully three-dimensional URANS method (fRANS), the simulation time for multi-stage axial compressors is reduced by 1 to 2 orders of magnitude.

scholarly journals Comparison and Sensibility Analysis of Warning Parameters for Rotating Stall Detection in an Axial Compressor

2020 ◽  
Vol 5 (3) ◽  
pp. 16 ◽  
Author(s):  
Gabriel Margalida ◽  
Pierric Joseph ◽  
Olivier Roussette ◽  
Antoine Dazin
Keyword(s):  
Research Work ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Stall Inception ◽  
Axial Compressors ◽  
Sensibility Analysis ◽  
Stall Warning ◽  
Two Parameters ◽  
Unsteady Pressure Measurements

The present paper aims at evaluating the surveillance parameters used for early stall warning in axial compressors, and is based on unsteady pressure measurements at the casing of a single stage axial compressor. Two parameters—Correlation and Root Mean Square (RMS)—are first compared and their relative performances discussed. The influence of sensor locations (in both radial and axial directions) is then considered, and the role of the compressor’s geometrical irregularities in the behavior of the indicators is clearly highlighted. The influence of the throttling process is also carefully analyzed. This aspect of the experiment’s process appears to have a non-negligible impact on the stall warning parameters, despite being poorly documented in the literature. This last part of this research work allow us to get a different vision of the alert parameters compared to what is classically done in the literature, as the level of irregularity that is reflected by the magnitude of the parameters appears to be an image of a given flow rate value, and not a clear indicator of the stall inception.

Effect of Dissipative Terms on the Quality of Two and Three-Dimensional Euler Flow Solutions

2008 ◽  
Author(s):  
Seyed Saied Bahrainian
Keyword(s):  
Euler Equations ◽  
Hyperbolic Conservation Laws ◽  
Three Dimensional ◽  
Strong Shock ◽  
Computational Domain ◽  
Third Order ◽  
First Order ◽  
Proper Values ◽  
Dissipative Terms

The Euler equations are a set of non-dissipative hyperbolic conservation laws that can become unstable near regions of severe pressure variation. To prevent oscillations near shockwaves, these equations require artificial dissipation terms to be added to the discretized equations. A combination of first-order and third-order dissipative terms control the stability of the flow solutions. The assigned magnitude of these dissipative terms can have a direct effect on the quality of the flow solution. To examine these effects, subsonic and transonic solutions of the Euler equations for a flow passed a circular cylinder has been investigated. Triangular and tetrahedral unstructured grids were employed to discretize the computational domain. Unsteady Euler equations are then marched through time to reach a steady solution using a modified Runge-Kutta scheme. Optimal values of the dissipative terms were investigated for several flow conditions. For example, at a free stream Mach number of 0.45 strong shock waves were captured on the cylinder by using values of 0.25 and 0.0039 for the first-order and third-order dissipative terms. In addition to the shock capturing effect, it has been shown that smooth pressure coefficients can be obtained with the proper values for the dissipative terms.

Three-Dimensional Computational Fluid Dynamics Prediction of Turbocharger Centrifugal Compression System Instabilities

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Rick Dehner ◽  
Ahmet Selamet
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Rotating Stall ◽  
Flow Reversal ◽  
Constant Speed ◽  
Local Flow ◽  
Stall Cells

The present work combines experimental measurements and unsteady, three-dimensional computational fluid dynamics predictions to gain further insight into the complex flow-field within an automotive turbocharger centrifugal compressor. Flow separation from the suction surface of the main impeller blades first occurs in the mid-flow range, resulting in local flow reversal near the periphery, with the severity increasing with decreasing flow rate. This flow reversal improves leading-edge incidence over the remainder of the annulus, due to (a) reduction of cross-sectional area of forward flow, which increases the axial velocity, and (b) prewhirl in the direction of impeller rotation, as a portion of the tangential velocity of the reversed flow is maintained when it mixes with the core flow and transitions to the forward direction. As the compressor operating point enters the region where the slope of the constant speed compressor characteristic (pressure ratio versus mass flow rate) becomes positive, rotating stall cells appear near the shroud side diffuser wall. The angular propagation speed of the diffuser rotating stall cells is approximately 20% of the shaft speed, generating pressure fluctuations near 20% and 50% of the shaft frequency, which were also experimentally observed. For the present compressor and rotational speed, flow losses associated with diffuser rotating stall are likely the key contributor to increasing the slope of the constant speed compressor performance curve to a positive value, promoting the conditions required for surge instabilities. The present mild surge predictions agree well with the measurements, reproducing the amplitude and period of compressor outlet pressure fluctuations.

Computations of bladerow stall inception in transonic flows

1999 ◽  
Vol 103 (1025) ◽  
pp. 317-324 ◽  
Author(s):  
L. He ◽  
J. O. Ismael
Keyword(s):  
Three Dimensional ◽  
Rotating Stall ◽  
Navier Stokes ◽  
Flow Conditions ◽  
Stall Inception ◽  
Tip Leakage ◽  
Blade Row ◽  
Inflow Condition ◽  
Shock Oscillation ◽  
Transonic Fan

Abstract A three-dimensional unsteady Navier-Stokes solver has been used to simulate stall inception in a single row ten passage segment of a transonic fan, the NASA rotor-67. At subsonic flow conditions, the 3D results illustrate a rotating stall inception with short scale part-span cells rotating at around 80% rotor speed, similar to that observed in some low speed experiments. However, at a supersonic relative inflow condition, the results show that an isolated blade row tends to stall in a one-dimensional breakdown pattern without first experiencing rotating stall. At near-stall conditions, significant self-excited unsteadiness is generated by the interaction between the tip-leakage vortex and the passage shock wave. Further computations for two-dimensional configurations indicate that it is possible to have a rotating pattern of instability in transonic blade rows associated with circumferential synchronised shock oscillation.

On the Interpretation of Casing Measurements in Axial Compressors

2008 ◽  
Author(s):  
Joshua D. Cameron ◽  
Scott C. Morris ◽  
Sean T. Barrows ◽  
Jen-Ping Chen
Keyword(s):  
Experimental Studies ◽  
Rotating Stall ◽  
Basic Flow ◽  
Tip Clearance ◽  
Stall Inception ◽  
Tip Clearance Flow ◽  
Axial Compressors ◽  
Clearance Flow ◽  
Flow Variables ◽  
Insight Into

Experimental studies of stall inception in axial compressors typically involve the measurement of basic flow variables (often pressure or velocity) with low spatial resolution. These measurements are used to make inferences about the fluid dynamics of stall. This experimental paradigm has been used by many investigators to great effect over the last several decades. However, several limitations remain which restrict the utility of these types of measurements for developing further insight into stall inception physics. Primary among these limitations is the impracticality of making measurements within the rotating blade passages. This is especially troublesome in light of recent computational studies which indicate that the generation of short length-scale rotating disturbances is related to the rotor tip clearance flow. This study utilized the results of a recent full annulus rotating stall simulation to investigate the relationships between the casing pressure field and less observable flow quantities which are believed to be causally related to the generation of rotating disturbances. The CFD results are assumed to represent the true flow physics within the compressor. To the extent that this approximation is true, these results can be used to interpret the meaning of experimental measurements of basic flow variables. These observations not only provide new insight into the interpretation of the large catalog of experimental stall measurements found in the literature, they also give directives for future measurements and numerical simulations.

When are Nonlinearities Important at Stall Inception?

1994 ◽  
Author(s):  
F. E. McCaughan
Keyword(s):  
Three Dimensional ◽  
Numerical Data ◽  
Nonlinear Effects ◽  
Sine Wave ◽  
Rotating Stall ◽  
Stall Inception ◽  
Stall Margin ◽  
Compression System ◽  
And Control ◽  
Recent Experimental Work

Recent experimental work has shown that in some compressors, the nonaxisymmetric disturbance leading to loss of stability appears as a localised phenomena, rather than a travelling sine wave which spans the entire circumference, suggesting that nonlinear effects appear very early in the evolution of the disturbance. In a regime dominated by nonlinear effects, the Fourier modes used to describe the spatial structure of non-axisymmetric disturbances, obtained from either experimental data or numerical data produced by a model, can interact very early in the rotating stall inception process. In this paper, we determine which parameters affect the rate of interaction of the various modes in a study of the Moore-Greitzer (MG) model. The relevant parameters are related back to the physics of compressors. Though the stall inception process may well be three-dimensional and involve physics not captured by the quasi two dimensional MG model, this study is of interest to those who wish to detect and control the magnitude of nonaxisymmetric disturbances, in order to decrease the stall margin in a compression system. Any control strategy which depends on eight detecting devices around the annulus of the compressor can resolve only the first three spatial Fourier modes. If disturbances leading to compression system instability develop as spikes, this approach will be completely unsuccessful at detecting the disturbances while they are still small enough to be controlled. The problem is further exacerbated by temporal nonlinearities, that is, the operating point may be linearly stable, but may lose stability to larger disturbances. It is observed in experiments and the Moore-Greitzer model that the compressor loses stability before the throttle is closed past the peak of the performance curve. Both spatial and temporal nonlinearities are discussed.

Rotating Waves as a Stall inception Indication in Axial Compressors

1991 ◽  
Vol 113 (2) ◽  
pp. 290-301 ◽  
Author(s):  
V. H. Garnier ◽  
A. H. Epstein ◽  
E. M. Greitzer
Keyword(s):  
Growth Rate ◽  
Small Amplitude ◽  
High Speed ◽  
Rotating Stall ◽  
Analytical Models ◽  
Stall Inception ◽  
Axial Compressors ◽  
Spatially Resolved ◽  
Two Stages ◽  
The Waves

Stall inception has been studied in two low-speed compressors (a single-stage and a three-stage) and in a high-speed three-stage compressor, using temporally and spatially resolved measurements. In all three machines, rotating stall was preceded by a period in which small-amplitude waves were observed traveling around the circumference of the machine at a speed slightly less than the fully developed rotating stall cell speed. The waves evolved smoothly into rotating stall without sharp changes in phase or amplitude, implying that, in the machines tested, the prestall waves and the fully developed rotating stall are two stages of the same phenomenon. The growth rate of these disturbances was in accord with that predicted by current analytical models. The prestall waves were observed both with uniform and with distorted inflow, but were most readily discerned with uniform inflow. Engineering uses and limitations of these waves are discussed.

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