© frank kameier - fluid mechanics and acoustics 1 frank kameier professor for fluid mechanics and...

© Frank Kameier - Fluid Mechanics and Acoustics

1

Frank KameierProfessor for Fluid Mechanics and Acoustics

Unsteady Aerodynamics in Turbomachines

• Rotating Stall and Surge

• Rotating Instabilities and Blade Vibrations (Flow-induced Vibrations)

• The „Demonstrator“ of FH Düsseldorf


2

Operating Map (Compressor)– non dimensional

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

-0,05 0 0,05 0,1 0,15 0,2 0,25

j

y

Rotating Instabilities

Rotating Stall

Surge

Design Conditions


3

Flow Separation in a Turbomachine(Compressor)

NGV Dresden

y

j

„Abrupt Stall“


4

Surge Conditions

High Pressure Compressor A pressure wave with an amplitude of several bar propagates from rear to front stages.

Damage of the rotor blades after app. 1000 surge cycles.

y

j


5

Instrumentation – Wall Pressure Transducers - Kulite XT190

4 mm

Piezo-resisitive

(DC up to 30 kHz)


6

Surge Test Nhrt=60%

Expansion

Wall pressureTemperature


7

Wall Pressure Fluctuations at Surge Conditions


8

Wall Pressure Fluctuations at Bang-Test-Conditions

s 45.12 45.122 45.124 45.126 45.128 45.13 45.132 45.134 45.136 45.138

kPa

-1

-0.5

0

0.5

Pressure

B0215A1 (RIG302_2/D2on190896t01 [B])

B0215B1 (RIG302_2/D2on190896t01 [B])

B0215C1 (RIG302_2/D2on190896t01 [B])

RIG 302_2 Bang Test

Kameier/Holste ET-24pak2 21.10.96 10:44

Event: 19.08.96 19:07h

2 ms

axial shot = plane wave


9

Wall Pressure Fluctuations at Bang-Test-Conditions

lateral shot = non plane wave


10

Surge Analysis in a 10-Stage Compressor

-1

0

1

2

3

4

5

6

7

8

9

B0206B1 B0215A1 B0223A1 B0231A1 B0239A1 B0247A1 B0255A1 B0263B1 B0271B1 B0279A1

Pressure transducers along 10-stage compressor

Ord

er

of

reac

tio

n

NHrt 100%

Shock amplitude sign


11

Rotating Instabilities – a Periodic Vortex Shedding?

Flow around a cylinderR.Feynman, Lectures on Physics, 1974


12

Kármán Vortex Separation Causes Mechanical Damage

Ferrybridge, England 1965

Ref.: Sahlmen, Niemann http://www.aib.ruhr-uni-bochum.de/


13

Kármán Vortex Separation Causes “Stall Flutter”

s

m19c


14

Rotating Instabilities – a Wall Shear Stress Fluctuation?

Schlichting, Boundary Layer Theory


15

Rotating Instabilities and Blade Vibrations

Wall pressure fluctuations- fixed frame of reference -

Blade vibrations- rotating frame of reference -

BAUMGARTNER, KAMEIER, HOURMOUZIADIS, ISABE Conference, Melbourne, 1995

Restricted speed range


16

Rotating Instabilities and Blade Vibrations

Wall pressure fluctuations- fixed frame of reference -

Blade vibrations- rotating frame of reference -


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Tip Clearance Effect of an Axial Flow Machine

Hysterese-sprung


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10 Stage High-Speed Compressor N =13200 rpm (83 %)

110

130

150

170

190

0 2000 4000 6000 8000 10000 12000 14000 16000

f [ Hz ]

Lp [dB]

1.BPF

2.BPF

RI

1.BPF + RI

1.BPF - RI

DLR Low-Speed Compressor N =1400 rpm (Point of maximum efficiency)

50

70

90

110

130

150

0 200 400 600 800 1000 1200

f [ Hz ]

Lp [dB]

1.BPF

2.BPF

RI

1.BPF + RI

1.BPF - RI

High pressure compressor13200 U/min

Low speed fan1400 U/min


19

High Pressure Compressor – Speed Variation

f[Hz]

t[s]

p[Pa]


20

Acoustic Resonances – Aero Engine Occurence

Speed of sound is the speed of propagation• Helmholtz-Resonator

• Standing waves and orifice resonance

• Self-induced acoustical resonances - „Parker Modes“ – Orgen-pipe resonances

Vd

L

daf

4

4

01 4

1f

L

af 02 4

3f

L

af bzw.

Sharp peak!

[Hz]


21

“Acoustic Resonance” Downstream of a Flat Plate in Flow

Quelle: Parker, Aeroacoustics, International Journal of Fluid Dynamics, 1997http://www-vhost.monash.edu.au/elecpress/ijfd/1997_vol1/paper1/Parker.Flow.html


22

Wall Pressure Fluctuations Upstream Rotor 1(HPC)

y

j

Operating conditions on secondary characteristics

Rotating stall


23

Wall Pressure Fluctuations Upstream Rotor 1(HPC)

y

j

Operating conditionsclose to design

Transonic flow in the blade tip region


24

Rotor 1 Redesign - Wall Pressure Fluctuations

y

j

Operating conditions close to surge margin

Redesign


25

Circumferential Distribution of Rotating Instabilities

Wall Pressure Fluctuations

Power spectrum

Coherence

Phase spectrum


26

Rotating Stall as a Special Case of Rotating Instabilities

jj tcosAt,p QQQ

tFQ

FQ jj

jj tcosAt,p F

QQFF

FQ

QF

RF

FQ

F RQ

R

0Q „Rotating Stall“


27

Rotating Stall in a Compressor Blade Row

RSR rp+

p-

U = r

.


28

Negative Frequencies and Rotating Stall

RRS

RRS F

RSFRS

RF

RF


29

Rotating Stall – Part Span Stall

Turbotech II - Teilvorhaben Nr. 1.244

Fixed frame

Rotor frame


30

Historical Review: „Instabilities“ in the Atmosphere of the Earth

(Chen, Haupt, Rautenberg, Uni Hannover, 1987)

A circumferential propagating Kármán vortex street: Rossby-wave


31

Rotating Stall in a Centrifugal Impeller

Quelle: Bohl, Strömungsmaschinen, 1994


32

Sound Generation by Rotating Stall in Centrifugal Turbomachines

Inlet Duct Impeller Blade

Rotating Instability

(Mongeau, Pennsylvania State University, 1991)


33

Rotating Instability Waves in a Ducted

Axial Fan

(Krane, Bent, Quinlan, AT&T Bell Laboratories, 1995)


34

Rotating Instabilities in a Steam Turbine (Low Pressure Stage)

Power spectrum Coherence along circumference

vgl.: Truckenmüller, Gerschütz, Stetter, Hosenfeld, Uni Stuttgart, ImechE, London 99


35

Rotating Instabilities - Periodical Unsteady Flow Field Within aRotor Blade Row of an Axial Compressor (TU Dresden)

vgl.: Mailach, Vogler, Lehmann, TU Dresden, ASME Montreal 2007


36

Rotating Stall Rotating Instabilities

RS

D

separated flow randomised behaviour turbulent frequencies are not related to the number of rotor blades

separated flow discrete behaviour periodical frequencies are related to the number of rotor blades

PitchBladeZ

DD

RI

FR

FRS 6.0...4.0 F

RFRI Z6.0...4.0


37

Correlation of Vibration and Pressure Fluctuations – Measurements on the Demonstrator of FH Düsseldorf (Co-op Rolls-Royce Germany)


38

Unsteady Instrumentation – Fixed Frame of Reference

Transducers

- 16 ¼‘‘ MicrofonesMicrotech MK301.

- Accelerometer B&K 4371

- Polytec Laservibrometer

Transducer positions

- 84 circumferential positions, = 4.285°.

- 6 positions in the rotor wake region, = 60°.


39

Unsteady Instrumentation – Rotating Frame of Reference

Blades with transducers

Transducer

- 4 Pressure transducersKulite LQ-47 und LQ125

- Strain Gages HBM

- Rotating 8-chanel amplifier unitDLR Berlin,4 x Kulites, 4x Strain Gage

- 10 – chanel slip ring unit


40


Strain Gage

Pressure Transducers LQ-47, LQ125

Transducer


- Strain Gages HBM




41


8-Channel amplifier unit (rotating)

10-Channel Slip-ring

Transducer


- Strain Gages HBM




42

Continuous Throttle Procedure n=1000min-1 – Wall Pressure

Excitation of Modes = 20 ... 9

0.060.100.15 0.05j

0.18 0.17 0.14 0.13 0.12 0.11 0.090.16 0.060.100.15 0.05j

0.18 0.17 0.14 0.13 0.12 0.11 0.090.16

Fixed Frame of Reference, = 60°, 1000min-1, f = 1Hz Rotating Frame of Reference, = 60°, 1000min-1, f = 1Hz


43

Continuous Throttle Procedure n=1000min-1 - Rotating Frame of Reference (Strain Gauge) -

Soft Blade feigen ~ 69Hz

0.060.100.15 0.05j

0.17 0.16 0.14 0.13 0.12 0.11 0.09 0.060.100.15 0.05j

0.17 0.16 0.14 0.13 0.12 0.11 0.09

Stiff Blade feigen ~ 97Hz

Excitation of Modes = 20 ... 9


44

Continuous Throttle Procedure n=1000min-1 - Increased Blade Loading - Fixed Frame of Reference –

Excitation of Modes = 5, 6, 6.5 und 7

0.050.17

j

0.20 0.19 0.16 0.15 0.10

Rotating Stall


45

Statistical Analysis of Rotating Instability and Rotating Stall

Rotating Stall

2

2

2

2

1)(

x

exf

Gauß Distribution

Rayleigh Distribution

2

2

22

c

x

ec

xxf

RI-Frequenzen

Umgebungsrauschen

Histogram of Rotating Stall amplitudes

6 8 10 12 14 16 18 200

0.02

0.04

0.06

0.08

0.1

0.12

0.14Wahrs cheinlichkeits funktion gewichtet der RS -Frequenz (4Hz), 800 1/min, P hi = 0,17, M19 R 355, 1500 S pektren

[Pa]

f(x)

23Anz.Klas s en =

0.519Klas s enbreite =

12.524 =

12.6482 =

1.772 =

3.1392 =

9.992c =

0.042S chiefe =

-0.074Wölbung =

Gaus s -Vert. Rayleigh-Vert

Histogram of Rotating Instability amplitudes

0 5 10 15 20 25 30 350

0.02

0.04

0.06

0.08

0.1

0.12Wahrscheinlichkeits funktion gewichtet e iner RI-Frequenz (72Hz), 800 1/min, P hi = 0,17, M19 R 355, 1500 Spektren

[Pa]

f(x)

23Anz.Klas s en =

1.422Klass enbreite =

11.580 =

12.9212 =

5.733 =

32.8642 =

9.240c =

0.395Schiefe =

-0.303Wölbung =

Gaus s -Vert. Rayleigh-Vert


46

Rotating Stall and Rotating Instabilities

„primary“ - Characteristics

Stall region

Rotating Instabilities(Schematical Sketch)

Rotating Stall(Schematical Sketch)


47

Flow Field with RIFlow visualization -

Single stage compressor along throttling procedure

Tip Clearance Flow

Quelle: Kameier 1994.

Small Gap Large Gap

j

c

c

Rotorblade

Starting Hypothesis

Small Gap Large Gap

Small Gap Large Gap

No secondary flow region, no separated boundary layer

Secondary flow region

Point of separation


48

Low Flow Rate

Separated Flow RegionSeparated Flow Region

High Flow Rate


49

High Flow Rate Low Flow Rate

Separated Flow RegionSeparated Flow Region


50

Tip Clearance s*= 0%, Low Flow Rate

Tip Clearance VariationTip Clearance s*= 2%,

Low Flow Rate


51

Summary

Stufe 1

Stufe 1

Stufe 1

.redm

RS

RS+RI

RI


52

Rotating Instabilities

Rotating instabilities occur in radial and axial flow machines.

RI is explained as a pulsating separated flow region which is rotating relative to the rotor in rotor direction (slip condition).

It is impossible to predict a rotating instability.

A numerical model is not known yet.


53

Fluid Mechanics and Acoustics at FH DüsseldorfInstitute of Sound and Vibration Engineering (in the course of formation)

• CAE of centrifugal flow machines (funded by BMBF)

• Low noise design (Outflow Valve Boeing 787)

• Flow induced vibrations (funded by BMW AG)

• Steady state CFD for localising unsteady mechanisms (funded by BMW AG)

• Combustor resonances (funded by Weishaupt GmbH)

• Noise reduction of roots compressors (funded by Lufttechnik KG)

• Optimisation of vacuum cleaner (Aeroacoustics) (funded by Miele)

Current Research and Development

© frank kameier - fluid mechanics and acoustics 1 frank kameier professor for fluid mechanics and...

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