3
Paper for Oil&Field
2
Final review
1
Preliminary review
Tech. report.20/11
0
Prediction of centrifugal
compressor performances
Paganini Di Febo 13/05/2014
E
9/9
rev
description
prepared checked approved date
language sheets
figure 4
figure 5
Figure 4.
Centrifugal compressor design performances
comparison to calculated performances (discharge
temperature).
Project : Pro 250 - CMap
PREDICTION OF CENTRIFUGAL
COMPRESSORS PERFORMANCES
AND APPLICATIONS FOR TEST,
SURGE PROTECTION AND
MACHINERY DIAGNOSTIC
TR 20/11 Paper Cmap rev 3
3
Paper for Oil&Field
2
Final review
1
Preliminary review
Tech. report.20/11
0
Prediction of centrifugal
compressor performances
Paganini Di Febo 13/05/2014
E
10/10
rev
description
prepared checked approved date
language sheets
figure 6
In the previous pictures it can be noted how the curves almost overlap: the maximum error
calculated is less than 0.2 % (polytropic work at maximum speed). Measured errors have
been considered tolerable for the purpose of the evaluation of compressor field
performance.
This case study confirms the capability of the proposed method to predict compressor
performances aligned with design ones.
An important application of these proposed methods is on surge protection systems and
on diagnostic purposes
The actual centrifugal compressors protection systems are based on simplified algorithms
that use basically the inlet flow, suction and discharge pressures and temperatures. These
actual algorithms, are based on a basic surge locus equation obtained under simplified
hypothesis such as the ideal gas law, validity of hydraulic affinity laws, reference gas mix
and inlet conditions. These algorithms are consequently completly dependent on the
suction thermodynamic parameters (pressure, temperature and gas mix composition): the
protection action is than rigidly linked to design suction parameters and remains valid only
for the design specified gas mix. Therefore these systems provide a limited surge
protection valid in a small operative range around the design conditions. The compressor
protection is not correctly active when inlet conditions move to off design values, especially
when approaching the high pressures range where introduced errors do not allow to
provide enough accurate predictions for more severe applications
Figure 5.
Centrifugal compressor design performances
comparison to calculated performances (polytropic
efficiency).
Actual centrifugal compressor protection systems
being reliant on simplified algorithms that use suction
thermodynamic parameters, the protection action is
rigidly linked to design suction parameters and remains
valid only for the design specified gas mix. Therefore,
these systems provide a limited surge protection valid
in a small operating range around the design conditions.
The compressor protection is not correctly active when
inlet conditions move to off design values, especially
when approaching high pressure range.
Conclusion
The methods proposed and described in this article can
allow operators to:
n
Predict the performances of a centrifugal
compressor under varying thermodynamic
conditions of the inlet gas. The prediction of
compressor performances is accurate even at high
pressures, where the ideal gas theory commonly
used introduces considerable errors.
n
Analyse the performance of the compressor during
operation and compare them with those expected
(provided by the manufacturer).
n
Implement advanced protection from surge,
overcoming limits of the current technology.
n
Having useful indications of the health of the
compressor (diagnostics) based on the capability to
analyse the performances and efficiency of the
machine in a simple and immediate way.
n
Support decisions and planning of predictive
maintenance and activities.
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