Annulus Wall Boundary Layers in Axial Compressor Stages

1963 ◽  
Vol 85 (1) ◽  
pp. 55-62 ◽  
Author(s):  
J. H. Horlock
Keyword(s):  
Boundary Layers ◽  
Guide Vane ◽  
Axial Compressor ◽  
Axial Flow ◽  
Velocity Profiles ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Blade Row ◽  
Layer Velocity ◽  
Flow Compressor

An analytical and experimental study is made of the development of secondary vorticities through the successive blade rows of a turbomachine. Whereas in cascade experiments the streamwise vorticity is usually zero at entry to the cascade, in the turbomachine this vorticity is in general nonzero and must be taken into account in the calculation of the secondary vorticity at exit from a blade row. In the calculation of boundary layer velocity profiles through an axial flow compressor stage, the variations in the exit air angles from the rows are computed first, from estimates of the secondary vorticities. There will always be overturning at the exit from the guide vane tip section, but tracing of the vorticity vectors through the machine shows that there may be underturning at rotor and stator tip. The exit air angles obtained from the analysis of these secondary flows may be used, together with actuator disk theory, to calculate axial velocity profiles in the boundary layers. It is suggested that this method of calculating the flow in the regions near the annulus walls should be used in the design of axial flow compressors.

Wall Boundary Layer Development Near the Tip Region of an IGV of an Axial Flow Compressor

1984 ◽  
Vol 106 (2) ◽  
pp. 337-345
Author(s):  
B. Lakshminarayana ◽  
N. Sitaram
Keyword(s):  
Boundary Layer ◽  
Guide Vane ◽  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Inlet Guide Vane ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Boundary Layer Development ◽  
Flow Compressor

The annulus wall boundary layer inside the blade passage of the inlet guide vane (IGV) passage of a low-speed axial compressor stage was measured with a miniature five-hole probe. The three-dimensional velocity and pressure fields were measured at various axial and tangential locations. Limiting streamline angles and static pressures were also measured on the casing of the IGV passage. Strong secondary vorticity was developed. The data were analyzed and correlated with the existing velocity profile correlations. The end wall losses were also derived from these data.

Effect of Stator Variability on Axial Compressor Performance

2019 ◽  
Author(s):  
Kirubakaran Purushothaman ◽  
N. R. Naveen Kumar ◽  
Vidyadheesh Pandurangi ◽  
Ajay Pratap
Keyword(s):  
Guide Vane ◽  
Flow Analysis ◽  
Axial Compressor ◽  
Axial Flow ◽  
Low Pressure ◽  
Inlet Guide Vane ◽  
Jet Engines ◽  
Stator Blade ◽  
And Performance ◽  
Flow Compressor

Abstract Variability in stator vanes is a widely used technique to improve the stability and efficiency of axial flow compressor in gas turbine engines. Most of the modern aircraft jet engines use variable stator vanes in both low pressure and high pressure compressors primarily for off-design performance. This study discusses in detail about the effect of stator variability in a three stage low pressure axial compressor at design and off-design conditions. Computational flow analysis were carried out for the three stage low pressure compressor with variability in inlet guide vane and first stage stator blade. Detailed investigation on flow physics was carried out in rotor blade passages with stator variability. At off-design speeds, the reduction in flow velocity is lower than the reduction in blade tip speed. This leads to mismatch in flow angles and inlet blade angles causing high incidence and large flow separation in blade passage. This results in poor aerodynamic stability of the axial compressor at off-design speeds. In this study, aerodynamic performance of compressor is evaluated from 70% to 100% design speeds with different stagger angle setting of inlet guide vane at each speed. Further, to improve 2nd stage rotor performance, variability was introduced in 1st stage stator blade and performance was evaluated. Compressor test results are compared with CFD data for design and off-design speeds.

Improving Efficiency of a High Work Turbine Using Non-Axisymmetric Endwalls: Part II—Time-Resolved Flow Physics

2008 ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Axial Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Time Resolved ◽  
Flow Physics ◽  
High Work

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one-and-half stage high work axial flow turbine. The first part covered the design of the endwall profiling as well as a comparison with steady probe data, this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that lead to a total-to-total stage efficiency improvement of Δηtt = 1.0% ± 0.4%. The investigated geometry is a model of a high work (Δh/U2 = 2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a Fast Response Aerodynamic Probe (FRAP). The paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the non-axisymmetric endwall profiling cases. The flowfield at exit of the first stator is improved considerably due to non-axisymmetric endwall profiling and results in reduced secondary flow and a reduction of loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction of secondary flows mainly at the hub. At the rotor exit the flow field with non-axisymmetric endwalls is more homogenous due to the reduction of secondary flows in the two rows upstream of the measurement plane. This confirms that non-axisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption the time-resolved data is used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The non-axisymmetric endwall profiling of the first nozzle guide vane show reductions of dissipation and streamwise vorticity due to reduced trailing shed vorticity. This smaller vorticity explains the reduction of loss at mid-span, which is shown in the first part of the two part paper. This leads to the conclusion that non-axisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.

An Experimental Study of the Inception of Rotating Stall in a Single-Stage Low-Speed Axial Compressor

2007 ◽  
Author(s):  
Alexander K. Simpson ◽  
John P. Longley
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Rotating Stall ◽  
Single Stage ◽  
Predictive Tool ◽  
Stall Inception ◽  
Low Speed ◽  
Blade Row ◽  
Flow Compressor ◽  
Critical Incidence

There are two established mechanisms, spike and modal inception, by which rotating stall is initiated in an axial flow compressor. Whilst the “Critical incidence hypothesis” and the “Zero slope criterion” are useful ideas in explaining the different stability boundaries for spikes and modes they do not provide the designer with a predictive tool. A detailed experimental investigation utilising a single-stage low-speed compressor is presented in which the aerodynamic environment of a rotor blade row is changed (rotor geometry is held fixed) so that it exhibited both spike and modal inception upon throttling into stall. The dominant mechanism of stall inception was found to be dependent on both the inlet flowfield and the downstream stator. The measurements are analysed and show that the meridional acceleration across the tip region of the rotor influences the mechanism by which rotating stall is incepted. This research is presented as a contribution towards the prediction of the stall inception mechanism.

Spanwise Mixing in Axial-Flow Turbomachines

1982 ◽  
Vol 104 (1) ◽  
pp. 97-110 ◽  
Author(s):  
G. G. Adkins ◽  
L. H. Smith
Keyword(s):  
Secondary Flow ◽  
Boundary Layers ◽  
Axial Flow ◽  
Separated Flow ◽  
Secondary Flows ◽  
Main Stream ◽  
Flow Measurements ◽  
Mixing Coefficient ◽  
Blade Row ◽  
End Wall

Flow measurements taken in multistage axial-flow turbomachines suggest that substantial spanwise mixing of flow properties often occurs. In addition, measured blade row turnings often show considerable deviation from two-dimensional cascade theory, particularly in the end-wall regions. An approximate method is presented with which both of these effects can be included in design through-flow calculations. The method is based on inviscid, small-perturbation secondary flow theory. Frictional effects are not directly included but secondary flows caused by annulus wall and blade boundary layers are included in an approximate way. The secondary flow model includes effects of 1) main-stream nonfree-vortex flow, 2) end-wall boundary layers, 3) blade end clearances, 4) blade end shrouding, and 5) blade boundary layer and wake centrifugation. The spanwise mixing phenomenon is modeled as a diffusion process, where the mixing coefficient is related to the calculated spanwise secondary velocities. Empirical adjustments are employed to account for the dissipation of the secondary velocities and interactions with downstream blade rows. The induced blade row overturnings are related to the calculated cross-passage secondary velocities. The nature of the assumptions employed restricts the method to design-point-type applications for which losses are relatively small and significant regions of separated flow are not present.

scholarly journals Experimental Study and Theoretical Prediction of Secondary Flows in a Transonic Axial Flow Compressor

1982 ◽  
Author(s):  
F. Leboeuf ◽  
F. Bario ◽  
G. Boris ◽  
K. D. Papailiou
Keyword(s):  
Secondary Flow ◽  
Vortex Motion ◽  
Axial Compressor ◽  
Axial Flow ◽  
Inviscid Flow ◽  
Secondary Flows ◽  
Tip Clearance ◽  
Axial Distance ◽  
Axial Flow Compressor ◽  
Flow Compressor

Detailed time-mean measurements have been realized on a transonic axial flow compressor. Flow quantities in the secondary flow regions have been obtained. The purpose of this paper is to present some essential features which drive the secondary following development in axial compressor among others, the strong influence of secondary vortex motion on the energy transfer between the flow and the blading is displayed. Also, we study the effect of tip clearance and axial distance between blade row. A secondary flow model is used for comparisons with theoretical computations. Very good comparisons have been obtained which show the validity of the theoretical model, in particular, the decomposition of the secondary flow into a viscous part and a vortical part, using an inviscid flow as a basis.

scholarly journals Propagation of Steady Circumferential Distortion Through an Axial Compressor Rotor

1985 ◽  
Author(s):  
Zhang Hui Min ◽  
Hu Jun
Keyword(s):  
Axial Compressor ◽  
Axial Flow ◽  
Flow Equations ◽  
Compressor Rotor ◽  
Differential Flow ◽  
Crucial Effect ◽  
Blade Row ◽  
Time Marching ◽  
Flow Compressor ◽  
The Stability

In this paper, a time marching method is proposed to predict the propagation of steady inlet circumferential distortion through an axial flow compressor rotor (or stator). This method also adopt the “Semi-actuator disk” concept to replace the rotor. It is assumed that the flow fields outside of the disk are described by a set of ideal, compressible and unsteady quasi-linear partial differential flow equations. Furthermore, the unsteady response of rotor is also taken into account. This method can be easily developed to a stage or extended to investigate the effect of transient disturbance on the stability of a compressor. Through numerical experiments, it has been found that distortion amplitude, rotation of the rotor, the chord length and especially the characteristic curves of the blade row have crucial effect on the attenuation behavior of the rotor.

Experimental Study of Casing Boundary Layers in a Multistage Axial Compressor

1991 ◽  
Vol 113 (2) ◽  
pp. 240-244
Author(s):  
S. Venkateswaran
Keyword(s):  
Shear Stress ◽  
Skin Friction ◽  
Boundary Layers ◽  
Axial Compressor ◽  
Axial Flow ◽  
Two Dimensional ◽  
Law Of The Wall ◽  
The Law ◽  
Flow Compressor ◽  
Two Dimensional Flows

Measurements of the casing boundary layers were obtained in a four-stage, low speed axial flow compressor, to verify the ‘law of the wall’ applicability to these complex flows. Some of the available shear stress models of the two-dimensional flows have been examined towards the quantitative assessment of skin friction. The shear stress prediction obtained from the Ludwieg-Tillmann relation applied to the streamwise or untwisted profile agreed closely with the measured shear stress by the hot wire. The skin friction was fairly constant for rotor and stator flows and was close to the flat plate values. The boundary layer profiles exhibited a well pronounced semi-logarithmic region with the universal constants of the law of the wall far removed from the standard two dimensional values, especially for rotor flows. Stator flows showed signs of similarity to two dimensional flows.

Improving Efficiency of a High Work Turbine Using Nonaxisymmetric Endwalls—Part II: Time-Resolved Flow Physics

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
P. Schüpbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Guide Vane ◽  
Axial Flow ◽  
Fast Response ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Time Resolved ◽  
Flow Physics ◽  
High Work

This paper is the second part of a two part paper that reports on the improvement of efficiency of a one and a half stage high work axial flow turbine. The first part covered the design of the endwall profiling, as well as a comparison with steady probe data; this part covers the analysis of the time-resolved flow physics. The focus is on the time-resolved flow physics that leads to a total-to-total stage efficiency improvement of 1.0%±0.4%. The investigated geometry is a model of a high work (Δh/U2=2.36), axial shroudless HP turbine. The time-resolved measurements have been acquired upstream and downstream of the rotor using a fast response aerodynamic probe (FRAP). This paper contains a detailed analysis of the secondary flow field that is changed between the axisymmetric and the nonaxisymmetric endwall profiling cases. The flowfield at the exit of the first stator is improved considerably due to the nonaxisymmetric endwall profiling and results in reduced secondary flow and a reduction in loss at both hub and tip, as well as a reduced trailing shed vorticity. The rotor has reduced losses and a reduction in secondary flows mainly at the hub. At the rotor exit, the flow field with nonaxisymmetric endwalls is more homogenous due to the reduction in secondary flows in the two rows upstream of the measurement plane. This confirms that nonaxisymmetric endwall profiling is an effective tool for reducing secondary losses in axial turbines. Using a frozen flow assumption, the time-resolved data are used to estimate the axial velocity gradients, which are then used to evaluate the streamwise vorticity and dissipation. The nonaxisymmetric endwall profiling of the first nozzle guide vane show reductions in dissipation and streamwise vorticity due to the reduced trailing shed vorticity. This smaller vorticity explains the reduction in loss at midspan, which is shown in the first part of the two part paper. This leads to the conclusion that nonaxisymmetric endwall profiling also has the potential of reducing trailing shed vorticity.

Three-Dimensional Flows and Loss Reduction in Axial Compressors

1987 ◽  
Vol 109 (3) ◽  
pp. 354-361 ◽  
Author(s):  
Y. Dong ◽  
S. J. Gallimore ◽  
H. P. Hodson
Keyword(s):  
Three Dimensional ◽  
Axial Compressor ◽  
Axial Flow ◽  
Tracer Gas ◽  
Suction Surface ◽  
Axial Compressors ◽  
Small Clearance ◽  
Oil Flow ◽  
Stator Blade ◽  
Flow Compressor

Measurements have been performed in a low-speed high-reaction single-stage axial compressor. Data obtained within and downstream of the rotor, when correlated with the results of other investigations, provide a link between the existence of suction surface–hub corner separations, their associated loss mechanisms, and blade loading. Within the stator, it has been shown that introducing a small clearance between the stator blade and the stationary hub increases the efficiency of the stator compared to the case with no clearance. Oil flow visualizaton indicated that the leakage reduced the extensive suction surface–hub corner separation that would otherwise exist. A tracer gas experiment showed that the large radial shifts of the surface streamlines indicated by the oil flow technique were only present close to the blade. The investigation demonstrates the possible advantages of including hub clearance in axial flow compressor stator blade rows.

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