EFFECTS OF ANTI-ICING SYSTEM OPERATION ON GAS TURBINE ...€¦ · LABORATORY OF THERMAL...

LABORATORY OF THERMAL TURBOMACHINES NATIONAL TECHNICAL UNIVERSITY OF ATHENS

ASME TURBO EXPO 2001 - Land, Sea, & Air, The 46th ASME International Gas Turbine & Aeroengine Technical Congress New Orleans, Louisiana, USA, June 4-7, 2001

2001-GT-0211

EFFECTS OF ANTI-ICING SYSTEM OPERATION ON GAS TURBINE

PERFORMANCE AND MONITORING

K. Mathioudakis, A. Tsalavoutas,

Laboratory of Thermal Turbomachines National Technical University of Athens


Effects Of Anti-Icing System Operation On Gas Turbine Performance And Monitoring 01-021

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Effects Of Anti-Icing System Operation On Gas Turbine Performance And Monitoring

• Effects on Performance

• Impact on Monitoring

o Measurement observation

o Derived parameters

• Propose a way to improve diagnostic capability

• Present supporting data from an industrial gas turbine

• Discussion-Conclusions



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Hot bleed anti-icing

Anti-icing with compressor delivery air. Compressor Bleed air



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Effects of hot-bleed anti-icing on performance. Mechanisms: - air extracted from compressor delivery - compressor inlet temperature > ambient

Shift of operating line because of compressor delivery (additional) bleed.

45 50 55 60 65 70 75 80Corrected Mass Flow Rate (kg / sec)

4

6

8

10

12

14

16

Pres

sure

Rat

io

Normal ConditionIncrease of Compressor Bleed by +5%



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Change of the interrelations between operating parameters.

Effect of hot bleed anti-icing operation on EGT versus load dependence.

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

50 55 60 65 70 75 80 85 90 95 100

Load %

T5-T

5nom

(oC

)

Normal operation Anti-Icing Activated

(when variation of operating parameters is monitored, their change may be misinterpreted as indication of a malfunction)



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Effects On Monitored Parameters

I. Methods based on measurements observation "Signatures" of measurement deviations from nominal values are used to monitor performance and diagnose malfunctions "Signatures" can be estimated using engine models

1

41 3

2 5 4

bW

2W m

1W m

C PTCT

G

Engine subdivision into components for simulation of hot bleed anti-icing operation.



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Performance Parameters Deviations,

( In function of bleed air amount)

-3

-2

-1

0

1

2

3

4

5

6

7

8

0% 1% 2% 3% 4% 5%

bleed %

diff

eren

ce %

EGT

TIT

WaN1

CDPCDT

ΔY=(Y-Yo)/Yo X 100

Differences formed for operation at the same engine inlet temperature, which is not necessarily equal to ambient temperature.



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"Signature" of compressor delivery bleed, on measurements

(a) simple bleed

-0.6-0.4-0.2

00.20.40.60.8

11.21.41.6

N1 W CDP CDT Wf TIT EGT

Dev

iatio

n (%

)

(b) bleed redirected to inlet for anti-icing

-2

-1

0

1

2

3

4

N1 W CDP CDT Wf TIT EGT

Chan

ge (%

)

Constant load operation



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Effects On Monitored Parameters

II. Model Based Methods Technique used "ADAPTIVE MODELLING" "HEALTH INDICES" Compressor

( ) ( )refPTWPTWf 2222221 //)/= ,

refCCf ,2 /ηη= Gas Generator Turbine

( ) ( )refPTWPTWf 4444445 ///= ,

refGGTGGTf ,6 /ηη= Power Turbine

( ) ( )ref

PTWPTWf 1.41.41.41.41.41.47 /// ⋅⋅=

refPTPTf ,8 /ηη= Measurements collected from the engine operating with the anti-icing system activated, fed to the adaptive model, without altering the layout to reflect the presence of a bleed, produce health parameters different form their nominal values.



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"Signatures" of extra bleed on health indices

(different amounts of bleed )

.

-4

-2

0

2

4

6

8

10

df1 df2 df5 df6 df7

Perc

enta

ge D

evia

tions

(%)

1% 2% 3% 4% 5%

Bleed presence ≈ increase in turbines flow capacity, drop of compressor turbine efficiency.



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TEST data from a gas turbine with anti-icing in operation.

.

Inlet pressure, Temperature

CDP,CDT

EGT N1

Airflow

Load

NPT

Gas turbine Layout and quantities measured for monitoring Inlet anti-icing when ambient temperature drops below 4 oCr. The amount of air designed to increase inlet temperature by approximately 5 oC



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Operating conditions, including operation with anti-icing

9180

9200

9220

9240

9260

9280

9300

9320

4:00 8:00 12:00 16:00 20:00 0:00Time (hours)

N1

(rpm

)

80

85

90

95

100

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

Load

(%)

0

2

4

6

8

10

12

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

T (C

)

Tin Tamb

Anti-Icing Activation

Anti-Icing Deactivation



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Effect of anti-icing operation on performance

(a) compressor related performance variables

0.95

0.96

0.97

0.98

0.99

1

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

W2

(ref

erre

d)

0.92

0.93

0.94

0.95

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

CD

P (r

efer

red)

0

2

4

6

8

10

12

14

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

CD

T-C

DT n

om

- compressor delivery temperature ↑ - compressor delivery pressure ↓ -air mass flow drops ↓ In agreement with trends predicted by the engine model



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Effect of anti-icing operation on performance

(b ) exhaust gas temperature.

0

5

10

15

20

25

30

35

40

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

EGT-

EGTn

om

(c) Estimated quantities

0

5

10

15

20

25

30

35

40

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

TIT-

TIT n

om

-2

-1

0

1

4:00 8:00 12:00 16:00 20:00 0:00

Time (hours)

Δ(T

herm

al E

ffici

ency

) %



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Anti-icing operation and performance parameters interrelations

EGT - Load (operation with and without anti-icing)

-10

-5

0

5

10

15

20

95 100 105

Load (%)

EGT-

EGTn

om (ο

C)

Normal

Anti-Icing

EGT gets values larger than expected for given load. Could lead to a false alarm. Turn-off the EGT checking function, when the anti-icing system is in operation.



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Time evolution of health indices

(anti-icing operation no taken into account)

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df1%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df2%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df5%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df6%

01234567

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df7%

Anti-icing Deactivation

Anti-icing Activation

-Flow capacity of power turbine changes by about four times the change in compressor turbine -Actual turbine problem could be overshadowed -Behavior in agreement with prediction



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Accounting For Anti-Icing Operation In Monitoring

Bleed air fraction estimation Full mixing assumed

bb hWhWhW ⋅+⋅=⋅ 1122

bb WWWWWb +== 122,/

Bleed air fraction:

13

12

13

12

TTTT

hhhhb

−−

≈−−

=

-Evaluated from ambient, compressor inlet and compressor delivery temperatures -Applicable for a steady state condition

1 2

bW

2W m

1W m

C



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Direct Observation Method

Measurement Changes when anti-icing is activated.

Comparison of measured to estimated values.

-2

-1

0

1

2

3

4

5

6

N1 CDP CDT EGT

Cha

nge

(%)

Measurements Predictions

Expected changes of measured quantities can be calculated from the known amount of anti-icing bleed



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Time evolution of health indices

Anti-icing bleed incorporated into model.

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df1%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df2%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df5%

-2

-1

0

1

2

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df6

%

01234567

0:00 4:00 8:00 12:00 16:00 20:00 0:00

df7

%



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Signature of -1.5 OC bias on CDT reading,

-1-0.8-0.6-0.4-0.2

00.20.40.60.8

1

f1 f2 f5 f6 f7

D (%

)

Derived by adaptive modelling the twin shaft engine



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Remarks on General Applicability of Procedure A known alteration during operation should be modeled, otherwise possible incorrect conclusions

A procedure to isolate faults in the presence of altered configuration.

ADAPTIVE ENGINE MODEL

Quantities Measured for Monitoring

Inlet Conditions Setting Variables

Health indices

Engine and Component Parameters

(including bleeds)

• Effect of parameters alteration separated from effect of faults..

• Requirement for successful implementation: correct modeling.

• Other types of alteration: variable customer bleeds, VGV’s etc.

• Using an adapted engine model gives an additional advantage: § data for unmeasured quantities (e.g. TIT), § additional information on overall performance (e.g thermal efficiency)



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Summary - Conclusions

• Effects of hot bleed anti-icing on the performance of

an industrial gas turbine examined • Behavior of different performance variables can be

predicted using an engine performance model • Influence of anti-icing operation on monitoring

procedures analyzed. Uunless appropriate provisions are taken, difficulties may be introduced to the diagnosis and false alarms are possible

• A method to eliminate such possible shortcomings was

introduced: information for altered configuration introduced into a supporting engine model

• Data from an industrial gas turbine, used to

substantiate observations

• Generality of such an approach discussed. Approach useful for other types of altered configuration.

EFFECTS OF ANTI-ICING SYSTEM OPERATION ON GAS TURBINE ...€¦ · LABORATORY OF THERMAL...

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