of Rotor-Stator in Axial-Flow Turbines and Compressors*downloads.hindawi.com/journals/ijrm/1998/787468.pdf · 2019-08-01 · InternationalJournalofRotating Machinery 1998, Vol. 4,

International Journal of Rotating Machinery1998, Vol. 4, No. 4, pp. 217-231

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Printed in India.

Experimental Investigation of Rotor-Stator Interactionin Axial-Flow Turbines and Compressors*

HEINZ E. GALLUS

Institut fiir Strahlantriebe und Turboarbeitsmaschinen, RWTH Aachen (Aachen University of Technology),52062 Aachen, Germany

(Received 3 April 1997," In finalform 10 July 1997)

Detailed results of unsteady flow measurements in a stator-rotor-stator assembly of anaxial-flow turbine as well as an inlet guide vane-rotor-stator formation of an axial-flowcompressor are presented in this paper.The measurements include the time-dependent 3-D velocity vector fields in the axial gaps

between the blade rows by means of triple-hot wire-technique, furthermore the total pressurefield downstream of the blade rows by means of semiconductor total pressure probes and theunsteady flow field determination in the rotor passages by LDV-technique. Special semi-conductor pressure measurements along the casing all over the rotor tip clearance permitdetailed discussion of the rotor tip clearance flows.The conclusion of the measured data provides a new and very instructive view of the

physics of the unsteady blade-row interaction in axial-flow turbines and compressors.

Keywords." Experiments, Compressor flow, Turbine flow, Secondary effects, Periodic interaction

1. INTRODUCTION

Most of the present analysis and design methods inturbomachinery are based on steady aerodynamics,although it is well known that the unsteady flowassociated with blade row interaction has a majorinfluence on the flow field, boundary layers, turbu-lence intensities, flow separation, blade vibration,noise, and heat transfer. The demand for higherperformance in aircraft as well as heavy duty gasturbine design results in a close axial spacing of theblade rows, lower aspect ratios and a reduced

This paper was originally presented at ISROMAC-6.Fax: 0241-8888-229.

217

number of blades. This requires more sophisticateddesign methods, including the possibility to cali-brate numerical methods and their turbulencemodelling. There is a strong need to gain a betterunderstanding of the three-dimensional unsteadyflow in a blade row including the upstream anddownstream influence of rotor-stator interactions.

Gallus et al. (1982) investigated the influence ofblade number ratio and blade row spacing on axial-flow compressor stator blade dynamic load andstagesound pressure level. By variation ofthe param-eters blade number ratio and blade row spacing in

218 H.E. GALLUS

an annular wind-tunnel they found experimentallyas well as by numerical approaches the resultsshown in Figs. 1-3. Since the measurements andcalculations were done for the midspan sectionthese results are valid only for the flow at midspan.

Figure shows the fluctuation of the localpressure coefficients compared with the local pneu-matically measured mean values. The results reveala much stronger increase of the dynamic pressurefluctuations with decreasing rotor-stator blade

number ratio than with decreasing axial spacingAxis. Nevertheless, low blade number ratio Z./Zstand low axial spacing results in highest dynamicblade loads.

Figure 2 represents a comparison ofthe potential-theoretic and the wake interactions as a function ofthe axial distance between the blade rows. It isobvious that the fluctuation amplitudes (plotted forthe first harmonic) of the potential-theoretic inter-action (computed after Lienhart, 1973) decrease

zt?/ZM-72/24

dx -SmmMx/s=O,128)

Sr=l,5

ZR/ZM=I24Sr:/,2

n=7OOOmin-1zlx=2OmmMx/s=0,320)

FIGURE Fluctuation of the local pressure coefficients Cp compared with the local mean values.

ROTOR-STATOR INTERACTION 219

02O

OJO

10 20 30 0 mmaxial distance

FIGURE 2 Comparison of the potential-theoretic and wakeinteractions as a function of the axial distances between theblade rows.

more rapidly with increasing axial distance thanthe wake interaction amplitudes calculatedaccording to Henderson (1972).

Figure 3 is also taken from Gallus et al. (1982)and compares computed and measured "stimuli"

(representing dynamic blade forces to the static

ones) as a function of the axial distance between theblade rows. The computed curves were gained byLienhart’s prediction method for the potential-theoretic interaction alone. They show that thedynamic forces due to upstream interaction are

higher than those due to downstream interaction.The experimental values measured only in thedownstream blade row contain also the dynamic

|

|

|

20 4x lmrnl 8 35 8 20 x lmml /,8

rotor stalorFIGURE 3 Computed and measured "stimuli" as a function of the axial distance between the blade rows.

220 H.E. GALLUS

forces due to wake interaction and are much higherthan the potential-theoretic results which is in goodagreement with the information in Fig. 2.For the design of bladings in axial-flow turbo-

machines these blade row interaction effects haveto be considered. That means unsteady flow effectsdue to rotor-stator interactions do change the realflow compared with a pure steady design. Forexample, due to the fact that in the wakes of anaxial-flow compressor rotor the exit flow angle fluc-tuates strongly in that way that the time-averagedincidence angle to the following stator is higherthan that of the steady design for the core flowbetween the blades. That means, the wake effects incompressor blade rows result in a higher turning ofthe following blade row. It can easily be shown thatthe wakes in turbines reduce the time-averagedturning of the downstream blade row.The above discussion of the rotor-stator inter-

action concerned at first the time-averaged loadingof the blade rows. On the other hand, the profilepressure fluctuation due to rotor-stator interac-tion strongly influences the behaviour of profile aswell as side wall boundary layers. The periodicallyfluctuating boundary layer behaviour leads dodifferent positions of the onset and length oftransition as well as boundary layer separation.These effects take strong influence on the lossesand the efficiency, respectively. Investigations inannular cascades and real stages showed, that theflow through the blade passages and on the bladesuction side surfaces is highly three-dimensional.That means midspan investigations are no longerrepresentative for the blade row behaviour in a

machine. That is why the investigations reportedon in this paper were carried out measuring theqow field over the full span.

2. EXPERIMENTAL INVESTIGATION OFTHE THREE-DIMENSIoNAL FLOW INAN ANNULAR COMPRESSOR CASCADE

The annular compressor stator cascade mentionedin the introduction was investigated with respect

to the three-dimensional flow field at variousincidence angles by Schulz and Gallus (1988). Theinlet swirl was provided by variable inlet guidevanes far upstream of the stator cascade. Majorobjectives were the studies of corner stall and losseswith increasing incidence angle. In order to checkthe influence ofrotor-stator interaction on the 3-Dflow field in the annular compressor cascade,Schulz et al. (1990) simulated the unsteady effectsofa bladed rotor by using cylindrical spokes insteadof blades. The swirl was further on provided by thevariable inlet guide vanes in front. Figure 4 demon-strates the different boundary layer and corner stallbehaviour on the blade suction surface withincreasing incidence. The left column shows theoil-flow visualization on the blade suction sidewithout rotor and in the right column with rotor. Itbecomes obvious, that due to the rotor-statorinteraction the extent of the corner stall region hasbeen extremely reduced. Figure 5 confirms thesefacts by a photo taken from the flow visualizationon the hub surface. By total pressure measurementsdownstream of the annular cascade the authorsfound remarkable results about the loss behaviour.Figure 6 shows the loss distribution with increasingincidence. The left hand side demonstrates thecircumferentially averaged losses at midspan,where the profile losses are dominating and sidewall flow influences are comparatively small. Inthis case, the midspan losses are increased byrotor-stator interaction due to an earlier profileboundary layer transition. The right hand side ofFig. 6 shows the overall losses averaged circumfer-entially and from hub to tip as a function ofincidence angle. In the whole incidence range theoverall losses are lower due to rotor-statorinteraction causing a higher turbulence level andstronger energy transport from the core flow to thelow energy side wall flow.

It should be mentioned here, that these results ofrotor-stator interaction on loss behaviour wereachieved for an aspect ratio of only 0.86 explainingfor the fact that the reduction of the overall lossesby rotor-stator interaction is due to the strong lossreduction near the sidewalls that overcompensates

ROTOR-STATOR INTERACTION

(-- 54.6

57. 6-

w i t bout roto wit h

FIGURE 4 Oil flow visualization on the, blade suction side.

221

222 H.E. GALLUS

thout Rotor Wi th Rotor

FIGURE 5 Hub and blade suction side flow visualization (O2--44.2).

2

midsp.n overallFIGURE 6 Loss distribution with increasing incidence.


the increase of the profile losses along a small bladeheight.

These measurements have been supported byfurther studies on the 3-D boundary layer behaviourand flow field. Due to the complete documentationof data this test case served various authors asvalidation of their computation codes (Gallus et al.,1990; Lticke et al., 1995; Melake, 1995).

3. ROTOR-STATOR INTERACTION INA HIGH SPEED AXIAL-FLOWCOMPRESSOR

The research machine is a single-stage axial-flowcompressor with an inlet guide vane row as shownin Fig. 7. The main design parameters of thecompressor are listed in Table I.The objective ofthe project was to study unsteady

flow effects in a high speed compressor. Therefore,the compressor was equipped with various unsteadyflow measuring techniques.The three-dimensional flow field at rotor inlet

and outlet was determined with 3-D hot-wire

probes. For the unsteady total pressure field down-stream of the rotor a probe with a single Kulite

type (XB-X-062) semiconductor pressure trans-ducer mounted under a pneumatic tube was used.These probe measurements were taken at midspac-ing of IGV and stator,respectively. The unsteadypressure at the casing above the rotor-blade tipswas detected by a single Kulite (XCQ-062) pressuretransducer at 21 axial positions spaced 3.5 mm. Toinvestigate the unsteady transition process of theperiodically disturbed profile boundary layers on

the suction sides of IGV and stator blades glue-onhot films were used. The IGV and stator bladeswere in addition provided with semiconductortransducers to measure the unsteady blade pressuredistribution. Detailed information on data acquisi-tion and data reduction can be taken from Galluset al. (1995).

In the following essential results from these inves-

tigations with respect to rotor-stator interactionshall be presented. To start with, the tip clearancemeasurements revealed strong tip clearance flow asis shown in Figs. 8 and 9. Figure 8 represents thepressure distribution above the rotor (ensemble

FIGURE 7 Cross-section of the research compressor.

224 H.E. GALLUS

TABLE Design parameters of the compressor

Nominal speedTotal pressure ratioDesign corrected mass flowRotor tip speedTip diameter

17,000 rpm1.313.4kg/s345 m/s387 mm

IGV Rotor Stator

Number of bladesSpacing/chord ratio (tip)Aspect ratio

38 25 401.0 1.0 1.02.7 1.7 2.4

IIIIIIIIIIIIIIIIII IIIIIIIIIIIIIII llllllffllllllllll[llllllllllHlllll]llll IIIII IHIIIUItlIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIt IIIIIit I1IIIIIIIIIIIIII:IIIIIIII-IIIIIIIII IIIIIIIIIIIIIII lllllllYtllllllll,,llllllllllllllllllllll I l.lllllllIllllllllllllllllllllll tttltIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIFHIHI.IN

tlHHIII [llllHllltllll IkllllllllllllllllllllllllltllP;__ ;,IIIIIIIINtII.I.IIIIIIII[ II[1/IIIIIIIIIIIIIIIIIIII"IIIIII IIIIIIIIIII II,IIIIIIIIIIIIIIIIIIIIIIII """"’IIIIII IIIII’""IIIIIIIIIIIIIIIIIItllilil I/1tll ().(J(10

". :;2; 0.880

2-7: -’2 ,)j] .--........_.??.. 0.720

(;t; ::::-"" " 0.740

.o(<.:.,<.v.-- I ;.?

ttt 0.840

0.9000.020

0.940

periodic fluctuations0.90

1.000

FIGURE 8 Unsteady pressure distribution above the rotor (ensemble-average data).

averaged data) whereas Fig. 9 shows the RMSdata. Due to the strong interaction of tip leakageflow and main flow in the tip region the pressureminimum (see Fig. 8) is no longer at the bladesuction side surface and the leakage flow vortex isstrongly directed to the pressure side of theneighbouring blade. The concentration of highRMS data indicates the location of very intensiveinteraction of leakage flow and main flow. The

strength of the tip leakage vortex can also bedetected by hot-wire measurements of thesecondary flow distribution downstream of therotor exit as is shown in Fig. 10.A very interesting information can be derived

from the unsteady pressure distribution measure-ment at midspan on the suction sides of IGV andstator shown in Fig. 11. The unsteady pressuredistributions are plotted in the same scale. Thus, it


[Pa]

:, <:--..,xYui:. UX;-m, ’,> .<... < ,. ..,. ._. oo.o.-ZZ i /

ll0O.0

-/’i ;-,:+,d- ’/’,.":-: 18o0.0

3000.0’J()o.o

34oo.o

stochastic fluctuations .,,,00.,,

4000.0

FIGURE 9 Unsteady pressure distribution above the rotor (rms data).

130.0133.0t36.0

178.0181.0184.0187.0

-10.0 1-8.0

-4.0.":: -,0

0.02.04.00.0

lo.o1ZO14.010.0aoeo.o2ZO4.o.on,o

mial wloaxial velocity total pressure[m/s] ratio

1.24

1.310

1.3141.3171.31.325

FIGURE 10 Time dependent development at rotor exit (50% spacing stator, absolute frame).

226 H.E. GALLUS

IGV, 50% span, SS

0.020

-0.040

Stator, 50% span, SS0.040

-0.020

-0.040

’’’ 0.020

-0.040

o.o40

"J>.-0.020

-0.040

o.o,oj,,,

-0.020

0.000 0.172 0.3,14 0.516 0.688 0.860

"’ 0.040

=’ 0.020

.j-,,j

-0,040

0.000 0.172 0.344 0.516 0.688 0.860[m,]

FIGURE 11 Unsteady pressure distribution at midspan on suction side of IGV and stator.

is obvious that the potential-theoretic upstreaminteraction of the rotor on the IGV vanes is muchstronger than the downstream interaction on thestator blades comosed of potential-theoretic andwake interaction. Similar effects have been men-

tioned already in the introduction of this paper.Along with the before described pressure fluc-

tuation on the blade surfaces of IGV and stator thestudy of the boundary layer behaviour is most

important with respect to the effect of unsteadinesson the position and axial extent of boundary layertransition as well as its influence on loss develop-ment. Figures 12 and 13 allow to compare theboundary layer development at midspan on thesuction sides of IGV and stator blades, respec-tively. Comparing first the ensemble averaged datain the left columns of both figures we recognizeagain that also the glue-on hot-wire films showmuch stronger values of the real time dataupstream of the rotor on the IGV surface thandownstream on the stator. The frequency spectraare plotted in the middle column and show inagreement with the ensemble averaged data quiteanother boundary layer behaviour for the IGV

frequency spectra

0.04

0.00

pwlodlo

.toclmllc

20

16.0

50%,

FIGURE 12 Boundary layer development at midspan onsuction side of IGV.


frequency pctra

10+

DN 0.20 0.40 O.&0 0.,80 1.1)0

FIGURE 13 Boundary layer development at midspan onsuction side of stator.

than for the stator. Figure 12 shows an increase ofthe amplitudes of the ensemble averaged data as

well as frequency spectra up to sensor 6 immedi-ately followed by a relative minimum at sensor 7and a relative maximum shortly downstream atsensor 8. Figures 12 and 13 describe from the left tothe right the periodic ensemble average signals, theaffiliated frequency spectra and the time averagedvalues. Here, the normalized dc-voltages and thetime-averaged random and periodic fluctuationsare plotted over the associated steady pressure dis-tribution. For a general impression of the transi-tion process in the boundary layer the plots have tobe viewed side by side.During the acceleration the dc-voltages go down

continuously until sensor 7 lying slightly behindthe suction side pressure minimum. In the front

part the boundary layer is laminar. Before thepressure minimum is reached the random fluctua-tions start to increase rapidly to their maximum atabout 70% chord (sensor 8) which can also be seen

in the frequency spectra. The boundary layerdecelerates, grows instable and thus more sensitiveto fluctuations in the core flow. Parallel herewiththe distribution of the time-averaged periodicfluctuations got. a minimum at sensor 7 betweentwo maxima. Referring to Schr6der (1989) andHourmouziadis et al. (1986) this is characteristicfor a transition via a separation bubble. The bubbleoscillates with blade passing frequency and its

extension depends on it (Dong and Cumpsty, 1989).Both the beginning and the end of transition differsin time with rotor-stator position. The wholetransition takes place over ca. 30% chord. Notuntil sensor 9 the boundary layer is completelyturbulent.The profile boundary layer of the stator is

influenced by the rotor wakes (Fig. 13). The ampli-tudes are smaller in comparison with the IGV. The

ensemble-average-signal of sensor 3 indicates thatthere the flow is already affected by the transition

although the normalized dc-voltages reach theirminimum behind the measured steady pressureminimum at sensor 4. A similar second maximumwas observed by Dong and Cumpsty (1989). It is

caused by the faster travelling wakes in the freestream. Sensor 4, where in contrast to the IGV bothmaxima of random and periodic fluctuations are

situated, is lying in the transition zone all the time.A so-called "bypass"-transition takes place. Thewhole transition is stretched until sensor 6. This is

more than 30% chord.

4. STATOR-ROTOR-STATORINTERACTION IN AN AXIAL-FLOWTURBINE AND ITS INFLUENCE ONLOSS MECHANISMS

Detailed measurements have been performed in a

subsonic, axial flow turbine stage to investigate thestructure of the secondary flow field and the loss

228 H.E. GALLUS

Posidon 2

0.02.04.0

B.OI0.0

14.0

18.020 02.0

Position

20.0 m/s

h/H 72.7 %

FIGURE 14 Secondary flow and turbulence intensity in the turbine rotor (at 72.7% span).

generation (Zeschky and Gallus, 1993). The datainclude the static pressure distribution on rotorblade passage surfaces and radial-circumferentialmeasurements of the rotor exit flow field usingthree-dimensional hot-wire and pneumatic probes.The flow field at the rotor outlet is derived fromunsteady hot-wire measurements with high tem-poral and spacial resolution. The above-mentionedpaper presents the formation of the tip clearancevortex and passage vortices which are stronglyinfluenced by the spanwise nonuniform statoroutlet flow. The experimental results of the un-

steady flow velocity and turbulence measurementsdemonstrate the influence of the periodic statorwakes onto the rotor flow.

Figure 14 shows the cross flow patterns insidethe rotor blade passages. The arrows represent thedifference between the local velocity vector and therelative velocity field in the rotor. According tothe reduced frequency two stator wakes are simul-taneously present in each rotor passage. Due to the

cut stator wakes and secondary vortices from thestator the turbulence level is increased. Similarresults were obtained by Binder (1985). The higheracceleration at the blade suction sides causes adistortion of the stator wakes. Nevertheless, cross

flow components are still observed close to thetrailing edge and downstream of the rotor.The relative flow angles and turbulence inten-

sities inside the rotor passage in snap shots for fourrotor-stator positions are shown in Fig. 15. Thedistributions show the angle and turbulence condi-tions over the blade height at an axial position of

x/bp--13.9%. At rotor position 2 higher flowangles occur in the corner between pressure sideand casing representing a cross flow towards thesuction side. The reasons for this are the lowervelocity and the underturning in the high loss areaof the stator exit flow. Turbulence spots associatedwith the stator loss cores appear. At position 4 thestator wake is visible over the entire span with

strong distortions at h/H= 15 and h/H= 85%. Due


Position 4

Position 6

Position 8

SS PS,’-/" ii

o.o 2.04.0

8.0lO.O12..014.0

18.0:?.0.0.0

FIGURE 15 Flow angle distribution and turbulence intensity inside the rotor passage for four different stator-rotor positions.

to the higher absolute flow angles the wake in thetip region and the loss cores are passing earlier. Atposition six the flow angles decrease after thepassing of the wake. Position 8 shows the undis-

turbed flow field with a reduced turbulence level.The blade to blade gradient is caused by thedifferent turning and acceleration at the pressureand suction side.

230 H.E. GALLUS

The measurements show that the rotor secondaryflow is mainly caused by the radial nonuniformstator exit flow and the periodically unsteadytransport of the stator wakes through the rotorpassages. The endwall boundary layer at the rotorinlet are very thin which is a result of the transportmechanisms and the acceleration in the stator.Therefore, the highest overturning d3es not occurclose to the side walls but at 15% and 85% span.

5. CONCLUSIONS

The measurements of the unsteady three-dimen-sional flow fields in compressors and turbinesdemonstrated quite different behaviour of thesecondary flow and loss production. Inside theturbine stator strong passage vortices are generatedby the endwall boundary layers. The lowmomentumfluid of the boundary layers is accumulated insidethese two vortices. Therefore, the endwall boundarylayers at the rotor inlet are very thin. They con-tribute only in a small scale to the rotor secondaryflow.The secondary flow field in a compressor blade

row is much more complicated. The endwallboundary layers do not have the major and domi-nant influence as it was observed in the turbinetests, since the pressure gradient from blade toblade is lower. The intensity of the secondary flowsdue to leakage, profile boundary layer centrifuga-tion, nonuniform blade circulation, is of the samemagnitude. On the other hand flow separations likecorner stall and rotor blade tip stall are present.Furthermore, the wake decay takes place in anadverse pressure field so that higher turbulencelevels are generated inside the wake.The measuring results demonstrated that the total

pressure losses of compressor cascades with lowaspect ratios (< 1.0) decreased in unsteady flowcompared to those obtained in an undisturbed flowfield (without rotor). This tendency has beenobserved at various incidence angles. Althoughthe profile losses at midspan increase due to theearlier onset of boundary layer transition in the

case with rotor, the overall losses decrease. Thiscan be related to the significant loss reduction dueto a smaller hub corner stall region. Intensiveturbulent mixing in the wakes is believed todiminish the hub corner stall.Comparing the influence of the rotor-stator

interaction in compressor and turbine flow com-

pletely different mechanisms of loss re-distributioncan be observed. In the turbine rotor a distinct shiftof the loss cores occurring downstream of thestator towards midspan can be observed. There-fore, the dominant mixing effect in the turbinestage is caused by the intensive secondary flow.

References

Binder, A. (1985) Turbulence production due to secondaryvortex cutting in a turbine rotor, Journal of Engineering forGas Turbine and Power, 107.

Dong, Y. and Cumpsty, N.A. (1989) Compressor bladeboundary layers, Part and Part II, ASME 89-GT-50, ASME89-GT-51.

Gallus, H.E., Grollius, H. and Lambertz, J. (1982) The influenceof blade number ratio and blade row spacing on axial-flow-compressor stator blade dynamic load and stage sound pres-sure level, Journal of Engineeringfor Power, 104, 633-641.

Gallus, H.E., Schulz, H.D. and Hah, C. (1990) Experimentaland numerical investigation of three-dimensional viscousflows and vortex motion inside an annular compressor bladerow, ASME Paper 90-GT- 155.

Gallus, H.E., Pieper, S., Schulte, J. and Hoynacki, A. (1995)Unsteady flow behaviour in a high speed axial-flowcompressor, International SYMKOM ’95, Lodz, Polen.

Henderson, R.W. (1972) The unsteady response of an axial-flowturbomachine to an upstream disturbance, Ph.D. Thesis,University of Cambridge.

Hourmouziadis, J., Buckl, F. and Bergmann, P. (1986) Thedevelopment of the profile boundary layer in a turbineenvironment, ASME 86-GT-244.

Lienhart, W. (1973) Berechnung der instationfiren Str6mungdurch gegeneinander bewegte Schaufelgitter und der instatio-nfire Schaufelkrfifte, VDI-Bericht No. 193.

Lticke, J., Benetschik, H., Lohmann, A. and Gallus, H.E. (1995)Numerical investigation of three-dimensional separatedflows inside an annular compressor cascade, InternationalSYMKOM ’95, Lodz, Polen.

Melake, A. (1995) Numerische Simulation der Str6mung imradialen Schaufelspalt axialer Turbomaschinen, DissertationRWTH Aachen.

Schulz, H.D. and Gallus, H.E. (1988) Experimental investiga-tion of the three-dimensional flow in an annular compressorcascade, Journal of Turbomachinery, 110, 467-478.

Schulz, H.D., Gallus, H.E. and Lakshminarayana, B. (1990)Three-dimensional separated flow field in the endwall regionof an annular compressor cascade in the presence of rotor-stator interaction. Part I: "Quasi-steady flow field andcomparison with steady-state data". Part II: "Unsteady flowand pressure field", Journal of Turbomachinery, 110.


Schr6der, Th. (1989) Measurements with hot-film probes andsurface-mounted hot-film gauges in a multistage low-pres-sure-turbine, Proceedings European Propulsion Forum: ModernTechniques and Developments in Engine and ComponentTesting, Bath, UK, pp. 15.1-15.27.

Zeschky, J. and Gallus, H.E. (1993) Effects of stator wakes andspanwise nonuniform inlet conditions on the rotor flow of anaxial turbine stage, Transaction of the ASME, 115.

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of Rotor-Stator in Axial-Flow Turbines and Compressors*downloads.hindawi.com/journals/ijrm/1998/787468.pdf · 2019-08-01 · InternationalJournalofRotating Machinery 1998, Vol. 4,