Monitoring Compressor Efficiency v2

8/6/2019 Monitoring Compressor Efficiency v2

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MONITORING COMPRESSOR

EFFICIENCY FOR MAXIMUM

PERFORMANCE

Presented at PowerGen 2007By Tina L. Toburen, P.E.


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Gas turbines, Compressors

and Air Density

PV=nRT

Increase mass flow by

Increasing Pressure

Increasing Volume

Reducing Temperature

m=PV / ZRT


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Impact of Compressor Performance


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Impact of

1% Lost Compressor Efficiency


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Isentropic Compressor Efficiency

( )kk

processsP

P

T

T

Z

Z1

1

2

2

1

2

1

,

=

Isentropic Process Efficiency

Isentropic Work Efficiency( )

==

2

1

1

2

1

1

2

,,

1

1

Z

Z

T

T

P

P kk

workaworks


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Compressor Efficiency Polytropic Work Efficiency

where

( )

=

=

1

1

1

1

2

1

1

2

1

1

2

,

n

n

k

kor

Z

Z

TT

P

P

p

n

n

workp

=

21

1

TP

TPln

PPln

n2

1

2


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Parameters to Monitor for Compressor

Performance Compressor inlet temperature and pressure

Compressor discharge temperature and pressure

Rotor Speeds (HP and LP, if applicable)

Operating mode of unit (base, part load, T3control, T48 control, etc.)

Auxiliary systems in use (inlet cooling, SPRINT,

bleed heat, etc.)

m=PV / ZRT


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Factors that Impact Compressor

Performance

Inlet temperature

Pressure Ratio Humidity

m=PV / ZRT


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Expected Changes to Compressor

Discharge Temperature

40%

50%

60%

70%

80%

90%

100%

110%

120%

130%

30% 40% 50% 60% 70% 80% 90% 100% 110% 120% 130%

Pressure Ratio (as percent of Design)

ExpectedCOT(aspercentofDesign)

CIT=40

CIT=60

CIT=80


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Compressor Performance Ratio Step 1: Calculate current operating compressor

efficiency

Step 2: Determine expected compressordischarge temperature (CDT) at current operating

conditions Step 3: Determine expected compressor

efficiency based on calculated CDT

Step 4: Calculate compressor performance ratioas measured divided by expected efficiency

Step 5: Trend performance ratio over time


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Using Compressor Efficiency


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Optimizing Water Wash Schedules


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Conclusions Compressor performance has a significant impact

on overall plant performance

There are multiple means of calculatingcompressor efficiency pick one

A real-time performance monitoring system is notrequired to trend compressor efficiency. Planned periodic manual calculations can lead to a greater

understanding of expected efficiencies and fouling rates

Monitoring compressor efficiency can lead tooptimized water washes, resulting in: Higher output Lower heat rate Lower CO2 emissions


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MONITORING COMPRESSOR

EFFICIENCY FOR MAXIMUM

PERFORMANCE

For more information, contact:

Tina L. Toburen, P.E.

[email protected]

425-821-6036

Monitoring Compressor Efficiency v2

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