Esempi di
applicazioni
VisSim for Turbine Modeling & Control System
Design
"I was able to use VisSim's intuitive
programming environment to create very complex gas turbine and
compressor models. They were so good that the control systems
that we tested became 'plug-n-play' items in the field. This
is previously unheard of. Many other control system suppliers
deliver 'plug-n-pray' items which are debugged, in the field,
through 'trial and horror' at the customers
expense."
-- Mohan
Thiagarajah, Applications
Consultant,
Honeywell UK
Reference Accounts
- Honeywell UK
- Dresser-Rand
- Penn
State
Honeywell Models
GE Gas Turbine with VisSim
 Author: Mohan Thiagarajah, Applications Consultant, Honeywell
UK
When Honeywell UK won a
contract to retrofit an existing control system on a General
Electric LM2500 gas turbine, they required a simulation package that
had the power and flexibility to model the nonlinearities of a
turbine, as well as evaluate the relationship between the turbine
and the controller. Based on previous experience, Mohan Thiagarajah,
applications consultant at Honeywell, chose VisSim to handle all of
their development and testing needs.
After only a few weeks,
Thiagarajah created a basic model of the gas turbine,
including the compressor, combustor, gas generator turbine,
and power turbine. Several iterations later, the model would
grow to over 2,000 blocks and encompass all the auxiliary
units, including fans, pumps, values, and pipes. According to
Thiagarajah, features like drag-and-drop block placement and
compound blocks streamlined model construction and greatly
improved the readability of the diagram.
General Electric
LM2500 Gas Generator
One of Thiagarajah's prime concerns was
integrating existing GE information into the overall model. In
particular, Thiagarajah wanted to model the starter motor, ignition
system, ventilation fan, and lubrication oil pumps based on GE
specifications. "The map block provided an easy and reliable way to
incorporate this data directly into the simulation," explained
Thiagarajah. "I could perform 1-, 2-, or 3-D table lookups,
depending on how the data was organized."
With a fully functioning model, Thiagarajah
was able to create and validate complicated control algorithms for
start-up sequencing and fuel controls, and stimulate both the
transient and steady-state behavior of the system. He also had a
safe environment in which to test emergency trips and alarms that
would be too costly or dangerous to perform on the physical
system.
In the end, both Honeywell and their customer were
extremely satisfied with Thiagarajah's work. Honeywell found that
VisSim was the most effective and easiest PC-based solution for
developing complex simulation models. Honeywell's customer ended up
with an operational system that met all their
requirements.
"We have a similiar project coming up soon --
an offshore oil rig in Norway that has 10 compressors and 4 Rolls
Royce gas turbines. I fully expect to use VisSim to great effect
again."
Amoco Valhall
Platform
By Mohan Thiagarajah,
Applications Consultant, Honeywell UK
 Amoco Valhall is an oil field which is located on the
maritime border between Norway and UK. It was put into production in
1982, and is currently producing around 100,000 barrels per
day.
Introduction
In 1998, Honeywell in Norway received a $1 million
order to retrofit the turbomachinery control and condition
monitoring systems. The main objective of this retrofit is to
maximise oil production, which in turn requires gas production to be
maximised. This can only be achieved by running both parallel gas
production streams at full load. However, such operations are not
possible with the existing turbomachinery controls, mainly due to
their dated and inflexible designs.
The platform has two 'strings of
compression', each with four compressors stages driven by two
Rolls-Royce Avon gas turbines and a fifth driven by a gas expander.
Both strings are identical and arranged for cascade gas compression.
The diagram below shows a Rolls-Royce Avon driving a two-stage
compressor.
Honeywell also supplied a VisSim
model-based dynamic simulator to test the system thoroughly
during the factory acceptance test (FAT) and thus avoid
unnecessary delays during commissioning. This will be combined
with Amoco's spares to construct a realistic training
aid.
A Rolls-Royce Avon
Driving A Two-Stage Compressor.
VisSim Professional was used to simulate 2
electric motors, 4 Rolls-Royce Avon gas turbines, 10 compressors, 10
re-cycle valves and 10 flow measurement elements. All these models
were linked to Computer Boards I/O cards via VisSim/Real-Time
Pro. This allowed us to test the all the controller / control
modes simultaneously. Thus we were able to start-up any or all of
the turbo-compressors, run them in series / parallel load-sharing
configurations, and then shut them down at will. The result was that
control system became operational at the press of the button. Amoco
was able to start and get machines on-line in a manner that was
unheard of previously.
The VisSim model building exercise
took two months of engineering. It was worth it because the
Amoco Project Manager (Karl Ole Stones) was convinced that the
modelling exercise saved 21 days of off-shore commissioning.
In terms of financial gain, this equates to;
(21 days) x (100,000 barrels per
day) x ($15 per barrels) = $millions
"As a mechanical engineer, my main role at
Honeywell is to solve turbomahinery control problems - not
learn complex programming languages and simulation
environments. So when I was tasked with simulating
turbomachinery to test control systems before they left our
factory, I chose VisSim. All you need is a logical brain and
some knowledge of engineering mathematics. VisSim makes the
rest very simple.
I was able to use its intuitive
programming environment to create very complex gas turbine and
compressor models. They were so good that the control systems
that we tested became 'plug-n-play' items in the field. This
is previously unheard of. Many other control system suppliers
deliver 'plug-n-pray' items which are debugged through 'trial
and horror' at the customers expense."
-- Mohan
Thiagarajah
Conclusion
So
the moral of this story is 'a stitch in time saves nine'.
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VisSim Viewer with Turbine Models
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