Efficiency Extra Edition
BY TINA TOBUREN, P.E.
Compressors -
Revisited
Monitoring Compressor Efficiency for
Maximum Performance
Gas turbine compressors consume more than half of the
power generated in the turbine. It is
therefore imperative to monitor compressor health in order to maximize unit
performance – maximizing generator output while keeping fuel usage and
emissions to a minimum.
A 1% loss in compressor efficiency can lead to more than 2% in lost output,
with a corresponding 2% increase in heat rate. When compressors become fouled, not only do
they take more energy to reach the same discharge pressure, the compressor
discharge temperature will also be elevated.
For units with limits on compressor discharge temperature (such as the
LM6000), this performance loss can be compounded as the unit must back down in
load to maintain the compressor discharge temperature within control system
limits.
There are many options for calculating a compressor
efficiency (Isentropic, Adiabatic and Polytropic efficiencies, to name a
few). All of these methods can be used
to track changes in compressor performance over time. The version of efficiency used is not
important: picking one method and using it to monitor changes in efficiency on
a regular basis is.
When tracking compressor
performance, the following parameters need to be recorded for the compressor:
·
Inlet
temperature and pressure
·
Discharge
temperature and pressure
·
Operating
mode of unit (base, part load, T3, T48, etc.)
·
Auxiliary
systems in use (inlet cooling, wet compression, SPRINT, bleed heat, etc.)
Note: if you have a dual shaft unit, you might want to
trend performance of each compressor section (HP and LP) separately, as well as
trending the overall compressor performance.
Compressor efficiency will vary naturally with load and
air density entering the compressor. The
use of wet compression or SPRINT systems will also have a significant impact on
the measured compressor efficiency.
Curves can be built to determine the expected compressor
discharge temperature which will result from changes in compressor inlet
temperature and pressure ratio at constant compressor efficiency. These curves can be used to determine the
expected compressor discharge temperature under actual operating
conditions. The efficiency calculated
using this expected discharge temperature can then be compared with the
measured compressor efficiency. The
result of this comparison can be used as a compressor performance ratio,
which can be trended over time to determine the fouling rate of the
compressor.
Once the compressor fouling rate is identified, an
economic impact analysis can be completed to determine the break-even time
to perform a water wash; maximizing compressor performance - and the
profitability of your site.
If you have any questions on applying these methods to
your units, please contact me via phone (425-821-6036) or email (tinat@t2e3.com).
Upcoming
Events:
PowerGen 2007 - December 11-13, New Orleans LA
I will be traveling to
New Orleans next week to PowerGen 2007 to give a talk
about Compressor Efficiency. If you
happen to be in the area, please stop by: Tuesday (12/11/07) Plant Performance I; Room
254 - between 1330 and 1530. I hope
to see you there.
LM6000 Performance Seminar
to be held in San Diego next April 3 & 4
Learn about the thermodynamic
relationships behind Gas Turbine performance,
and how to apply this to your units and your site.
Delve into the economics and
application of correction curves - including an understanding of Throttle
Push.
Get an overview of ASME PTC-22,
the standard on gas turbine performance testing.
Learn about performance monitoring programs for gas turbines, what you
need to look out for, and what to do if you think you may have a problem.
Walk away with information
and ideas that you can apply to your operation immediately.
Seminar
to be held in San Diego April 3 & 4, 2008.
Scheduled to compliment attendance
at the 2008 WTUI conference.
Contact TinaT@t2e3.com or see the T2E3 website for
more information:
T2E3 Services for
Power Generators
Analysis Tools & Software – from customized spreadsheets to add-ins for Excel or
complete compiled programs, T2E3 can develop software tools and analyses to
support all your performance monitoring needs, including integrating your
existing tools with available site data systems, to create online systems
providing data and results in real-time.
Training – both public seminars and customized options are available. Highly interactive sessions increase
attendees’ knowledge and understanding of the thermodynamic cycles,
instrumentation and analyses needed to improve equipment performance and
reliability.
Performance Test Support – if your site is
required to perform annual capacity or power purchase performance tests, having
Tina Toburen from T2E3 on site to direct the testing can lead to a smoother
test execution with more consistent performance results. Professional reports can also be produced to
communicate the results to all required parties.
Commercial Program
Design and Evaluation – For sites
interested in a more complete enterprise solution for performance monitoring,
T2E3 can support your program planning and design, including evaluation of the
various commercial products available within the industry for performance
monitoring. Choosing the correct
solution will depend on the specific goals and objectives of your performance
monitoring program.
Unlock the potential of your operation.
Call for more information on how we can work together, today!
T2E3
Tina Toburen’s Energy Efficiency Enterprises
14260 120th PL NE, Kirkland, WA 98034
Phone: 425-821-6036
Fax: 253-550-6992
E-mail: performance@t2e3.com
T2E3
Newsletter Volume 1, Issue 4: 4th
Quarter 2007
HAPPY HOLIDAYS!
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