5. FUTURE TRENDS
State-of-the-art improvements in gas turbines are the natural progression for both commercial and military markets as ship owners and operates raise their design and power requirements.
An example of GE's commitment to furthering its gas turbine technology can be found in the LM2500+ gas turbine.
The LM2500+ development extends the available power while maintaining substantial commonality with the current LM2500 (see Figure 3). The LM2500+ is ISO rated at 30.2 megawatts. The marine rating for continuous operation is slightly over 26 megawatts for ambient temperature operation at about 20℃. The engine therefore provides approximately 5 megawatts of additional power for most typical marine applications over the LM2500. The marinized technology of the LM2500 is carried forward in the LM2500+ with a large degree of commonality in components. Long experience in ship operation helps to ensure that LM2500+ is designed for that environment.
5.1 Design of the LM2500+
The increase in power available with the LM2500+ is realized through increased airflow. An increase in operating efficiency is also achieved through a small increase in firing temperature. What follows is a summary of major upgrades:
Compressor
One additional stage of compressor blades has been added forward of the LM2500s first stage blades. The number of compression stages is increased to 17 (from 16) and the airflow is increased by about 20% relative to the LM2500. Compressor airfoils for stages two and three have increased efficiency. Overall the compressor pressure ratio increases from 18.8 for the LM2500 to 23.1 for the LM2500+.
Hot Section (Combustor and high-pressure turbine)
Improved materials in the hot section result in a more durable configuration with longer repair intervals. Thermal barrier coating is added to the standard combustors, resulting in greater temperature margin than in the LM2500, even though the firing temperature is increased. Materials and coating upgrades in the HPT blades and nozzles plus improvements in cooling will result in longer operating intervals between refurbishments for these items, even at the higher ratings of the LM2500+.
Power turbine
Redesigned power turbine blades and increased disk sizing has been incorporated in the LM2500+ to support the higher torque associated with increased power. These improvements have also increased the low cycle fatigue limits of the power turbine. This is especially important for fast ferry applications, which generally have highly cyclic operating profiles.
5.2 Installation Parameters for Marine Applications
Table 3 compares the specific installation and performance parameters of the LM2500+ to the current LM2500. Increased efficiency and power output are reflected in the table. Of additional interest for ship application are the improvements in power per unit volume and weight that the LM2500+ provides. Because gas turbines are of most interest for ships which are volume limited, i.e. those which carry light density cargo, the improved power density translates directly into additional revenue producing space in commercial vessels. In military vessels the reduction in volume occupied by the propulsion prime mover results in greater combat systems payload.
A likely reduction in cost per unit power makes LM2500+ more attractive on a first cost basis. Installation costs are very close to the LM2500 because the package is essentially the same. This further reduces first cost per unit power for a ship installation because of the increased power available.
5.3 Remote Diagnostics
Reducing manning and improving maintenance while decreasing costs continue to be necessities for both commercial and military marine ship operators and owners. GE's answer is its new on-line remote diagnostics system. The first naval demonstration will be on the U.S. Navy's USS Donald Cook DDG 75 destroyer later this year. The U.S. Navy is integrating GE's on-line remote diagnostics system with its Integrated Condition Assessment System, a condition-based maintenance system. After an evaluation period, the U.S. Navy will determine the potential use of GE's remote diagnostics system elsewhere in its gas turbine fleet.
In early 2000, GE completed the first U.S. Navy testing of this system on a GE LM2500 aeroderivative gas turbine at the land-based engineering site in Philadelphia, Pa.
GE's remote diagnostics capabilities allow for analysis of key operating data for gas turbines located anywhere in the world. This system is currently being successfully used in over 1,000 industrial power and aircraft applications worldwide. By closely monitoring operating data, GE can significantly improve its ability to react to emerging problems and reduce the total cost of ownership.
Table 4 provides an overview of the benefits of the remote diagnostics system which extend to both military and commercial marine applications.
The remote diagnostics system is an extension of GE's service and support activities that enable GE to electronically visit customer sites when necessary, 24-hours-a-day, 7-days-a-week. The system allows GE gas turbine engineers to monitor engine data during the critical on board start-up phase, and from that time on, while the engine is operating. The remote diagnostics service provides an early warning tool that allows diagnosis of developing problems, enabling operators to intervene with a more timely and lower cost repair.
