Feature 6 | SURFACE SHIP PROPULSION
This results in a significant reduction The company believes that other copper wire are expected to be much
in fuel-related operating costs over the cost and reliability advantages will also smaller, lighter and more efficient than
vessel’s lifetime, amounting to many accrue from the use of superconducting current systems, which could reduce the
times the initial cost of the motor. HTS motors. Conventional synchronous cost of wind-generated electricity from
AMSC also notes that HTS propulsion motors use continually adjusted current offshore wind farms. WT
systems can be easily configured according in the rotors, and continual adjustments
to ship type and missions, and can be fatigue rotor windings, adversely affecting
optimised for both in-hull and external, coil life. However, HTS motors are
podded applications. operated at nearly constant temperature,
Synchronous HTS synchronous eliminating a key cause of fatigue
motors are powered using commercially and failure present in non-HTS AC
available adjustable speed drives, synchronous motors. Consequently, HTS
and utilise proven cooling systems. ship propulsion systems are, by design,
HTS motors introduce no special or more reliable than their conventional
untested technologies, claims AMSC, counterparts, AMSC claims.
so maintaining and servicing an HTS rotating machine technology AMSC believes that on vessels such as the
HTS motor aboard ship is no more is also being applied to the renewable US Navy’s LPD 17, the HTS superconducting
complicated than providing service for energy industry. Wind generator motor will provide significant advantages
standard motor technology. systems utilising HTS wire instead of in terms of reduced weight and space.
Fuel control retrofit: reduced costs, enhanced control
GE Marine reports that the US Navy has retrofitted nearly 50 LM2500 marine gas turbines with GE’s Digital Fuel
Control (DFC) kits. The LM2500s power the US Navy’s CG-47 Ticonderoga class cruisers and DDG-51 Arleigh Burke
class destroyers.
The DFC technology kits incorporate new controls for GE LM gas turbines – a technology now standard on new LM2500
and LM2500+ engines. Previous-generation LM2500s use a hydro-mechanical control system.
Noting the benefits of the new system, the US Navy incorporated the DFC retrofit into a concurrent ship system
modernisation programme. Since the first digital fuel controls were installed, the US Navy has accumulated more than
100,000 DFC operating hours on selected DDG-51 and CG-47 class ships. In addition, the US Navy recently purchased
16 DFC kits for four additional ships. GE anticipates continuing this modernisation programme throughout the above-
mentioned ship classes.
Dave DePauw, GE Marine director of services, said: “In 1994, the US Navy installed its first LM2500 equipped with the
DFC technology aboard the Watson class large, medium-speed, roll-on/roll-off ships. The DFC technology – as part
of the standard engine equipment – has also been delivered to international navies for recent LM2500 gas turbines
applications, as well as on a variety of commercial projects where GE gas turbines are used to power cruise ships and
fast ferries.”
In addition, the new LM2500 and LM2500+ gas turbines supplied by GE for US Navy ship programmes, including the LHD
8 Makin Island and the GE-powered LCS, incorporate the engine’s standard DFC technology.
Benefits of the DFC technology are numerous and include:
•
Improved resistance to possible fuel contamination through oil actuation of variable stator vanes (VSV) and the fuel
metering valve
•
Updated control of fuel and air scheduling in the gas turbine, and more accurate fuel/air scheduling through
electrical feedback and closed-loop control. In addition, fuel characteristics and VSV positions can be recalibrated
through the control software inputs
•
Gas turbine control sensor redundancy on compressor discharge pressure, compressor inlet temperature and
pressure, gas generator speed, VSV position, and fuel metering valve position
•
Improved operator signals, alarms and troubleshooting are provided by additional electrical sensors and actuator
feedback. GE DFC kits also offer improved capabilities for data capture and condition monitoring
•
Fuel savings, thanks to better system response and reliability, reducing time required for high-power check-out and
torque balancing after fuel control changes
The primary DFC retrofit kit components include a fuel metering valve and two VSV actuators, both with redundant electronic
feedback. An upgraded engine controller and shipboard wiring changes are also required to incorporate the DFC kit.
34 Warship Technology March 2009
WT_Mar09_p33+34.indd 2 3/4/09 9:41:06 PM
Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36