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European Workshop on New Aero Engine ConceptsMunich, 30 June – 1 July 2010

Active Surge Control by Tip Injection

NEWAC is an Integrated Project Co-funded by the European Commission within the Sixth Framework Programme(2002-2006) under Thematic Priority 4 Aeronautics and Space.

Sven-Jürgen Hiller, MTU Aero Engines GmbH

Roland Matzgeller, Wolfgang Horn and Michael KernMTU Aero Engines GmbH


SubtitleIdea behind active surge control Motivation• A flow controlled core enables a route to

improve efficiency by reducing stall margin requirements

• Fluidic flow control has already demonstrated benefits and consequently selected

• no degradation at ADP since no obstacles

Pre

ssur

e R

atio


2

• no degradation at ADP since no obstacles are in the flow path (as vortex generators, etc.)

• Usage of compressed air from rear stage(s) (e.g. customer bleeds). �Constraints in mass flow requirements.

Tasks• Stabilization of an multistage aeroengine

compressor by air injections.

• Investigation of the aerodynamics of rotor tip flow w/o tip injection.

Pre

ssur

e R

atio

Mass Flow Rate

acceleration


SubtitleTip injection at front stage of a HPC• Bleed recirculation across multiple

stage

• HP3 customer bleed provides sufficient pressure difference throughout the HPC operating range

• Initial concerns about temperature influence addressed during testing by means of injection with different

shop air HP3 bleed


3

means of injection with different temperature levels

Modification for the rig setup

• External shop air rather than true compressor bleed – virtual link by control valve in both pipes

• External piping rather than casing integration

• Injection air temperature variation by an electrical heater

• Injection port variation (on/off)


SubtitleInjection Test Setup

Close-up of air injection port

• 8 stage HPC compressor, PR=17• 3 variable guide vanes (IGV+2 VGV)• 3D blade design with rotor sweep at front blades• Customer and turbine cooling bleeds• Flow conditions typical for civil aeroengines• Injection nozzles are placed in the casing above the rotor

• Benefit from the Coanda effect

shop air

Manifold

M

heater

standardPipes with

control valve

shop air

Manifold

M

heater

standardPipes with

control valve


44

Close-up of air injection port

NEWAC ASC test setup

• Benefit from the Coanda effectstandardorifices Pipes with

restrictors

Rig

standardorifices Pipes with

restrictors

Rig


SubtitleInstrumentation and equipment

Rig instrumentation• Standard performance rig

• instrumentation and analysis technique

• External heater and metering section

• Standard leading edge instrumentation

• Radial and circumferential traversing


5

• Radial and circumferential traversing (pressure, temperature, FRAP)

• Unsteady wall static pressure transducers in each stageInstrumented rig

Valves + metering sectionsElectric heater Plenum for air distribution between the injection ports (without insulation)


SubtitleTested rig configurations


6

• 3 sets of injection liner

• Baseline

• Liner prepared for PIV measurements

• Modified baseline

• Huge test campaign was performed


SubtitleOverview about the measurement matrix

N/NA [%] 0 1 1.3 2 3 4 5 6 3 5 3 5 2 3 4 575798285889092

94.698100

TINJ = 60^C TINJ=T_Bleed [°C] Sim. Recirculation TI NJ=T_Bleed [°C] rel. injected massflow [%] TINJ = Ambient °


7

• Measurements include• Different speeds• Different VGV-settings for each speedline• Different injected massflows• Different temperatures of injected air

100102104


SubtitleRadial and axial re-matching effects due to the tip injection

no inj

3% inj

WL SL


8

Leading edge instrumentation of stator 1-4: Total pressure (above) and total temperature (below)


SubtitleVariation of injection temperature at stage 1

330K

370K400K

330K 330K

370K

400K

330K

Stage 1

85% speed


9

3% injectionin all cases

baseline baseline

baselinebaseline

Higher injection temperature has no adverse effect on stage 1, although the outer span runs at lower aerodynamic speed.

85% speed

82% speed

82% speed


Measurements – Stage 1 characteristics

tem

pera

ture

rise

incr

ease

d

Tem

pera

ture

rise

coe

ffici

ent [

-]


tem

pera

ture

rise

incr

ease

d

PHI0 AS

PS

I0 A

S

0

1.3

2

3

5

5, 60°C

3, 60°C

Tem

pera

ture

rise

coe

ffici

ent [

Flow coefficient [-]

10


SubtitleMeasurements – Stage 1 characteristics

4.78

5.63

7.49

6.786.56

5.0

6.0

7.0

8.0re

lativ

e st

age

pres

sure

ris

e [%

]0

1.3

2

3

5

3, 60°C

5, 60°C


11

baselinered

baselineredsurgelinered

m

mmPR

)/(

)/()/(

πππ −

=Definition at constant speed:

0.00

2.27

0.0

1.0

2.0

3.0

4.0

realtive injected mass flow [%]

rela

tive

stag

e pr

essu

re r

ise

[%]


SubtitleInfluence of tip injection at 100% speed on compres sor efficiency

m inj=1.5%

Baseline

Isen

trop

ic e

ffici

ency


12

m inj=0%

m inj=1.3%m inj=2%

Reduced mass flow

Isen

trop

ic e

ffici

ency

Isentropic efficiency at N/NA=100% will not be influenced by tip injection.

• Tip injection has no degrading effect on efficiency at design speed.

• Due to a negative effect on fuel consumption and turbine temperatures, mass flow recirculation can only be applied at part speed.


SubtitlePIV measurements I• Special liner design to make optical access feasible• Measurement plane illuminated by lightsheet• Lightsheet was adjusted to make measurements for different radial positions• Unsteady flow captured by PIV measurement


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SubtitlePIV measurements II


14

without tip injection with tip injection

Interaction of blade with injection jet clearly visible.


SubtitleFRAP measurements• Rotor tip injection interacts with rotor flow directly

• FRAP (Fast Response Aerodynamic Probe – ETH Zürich) provides a method to measure the rotor flow

• Measurement of the unsteady pressure field with high spatial resolution (PT, PS, Ma, flow angle)


15

• Measurement performed by Dr.Stadlbauer and Dr.Gründmayer (both MTU Aero Engines GmbH)


SubtitleUnsteady total pressure field downstream of rotor 1 close to surge line


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without injection with 3% injection

Total pressure field of the rotor shows a significant re-organization of the rotor flow field with a local unloading of the blade tip section.


Pulsed injection

• 6 fast modulating valves (company Moog) in combination of a closed-loop control system (company IfTA)

• One valve for each injection port

• Valves modulate mass flow from 0% to 100% at max. 300Hz


17

inj=1.6% core

at max. 300Hz

• Different modulation schemas applicable (e.g. 20% constant injection and modulation from 20% to 100%)

• Control system takes unsteady pressure signal from Kulites mounted above rotor 1

• According the magnitude, frequency and phase of the incoming signal the controller drives each of the six valves individually


Pulsed vs. constant injection

3% constant injection

no injection (baseline)

1.6% puls. injection


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Stage 1 Stage 2

• Hard to detect signatures at low speed (75%-85%) � Large tip flow separation� High injection mass flow needed (3% … 1.6%)

• Clear signatures are detectable at higher speeds (90%-95%) � Distinct flowseparation � Injection mass flow down to 0.6%


Summarized measured compressor map

operating line

reference surge line

surge line by tip injection


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Control Volume

Tip injection has a significant influence on surge line.

75%82%

85%

90%


Summary

• Tip injection is a reliable method to enhance compressor stability.

• Tip injection influences the stage characteristics significantly by changing the radial work distribution.

• Due to the changed stage characteristics an axial re-matching of the whole compressor occurs.


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compressor occurs.

• Hot injection has no degrading effect on the stage characteristic.

• Pulsed injection reduces the averaged injection mass flow.

• FRAP and PIV measurements were applied successfully and unveils important flow details.


Thank you for your attention!


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Thank you for your attention!

10 Active Surge Control by Tip Injection - Home | … · European Workshop on New Aero Engine...

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