1. Gas Turbine Applications
LM 2500,
Allison 501,
The Plant

2. Objectives
LM 2500 Gas Turbine Engine - specific components, specifications, systems
Allison 501 Gas Turbine Generator Set - purpose and operation
Interrelationship of supporting systems and operations
Engineering plant lineups

3. Gas Turbine Power Plants
Gas generator section
Compressor
Combustion chamber
Gas generator turbine
Power section
Power turbine

4. LM 2500 In DDG’s and CG’s, have 4 engines In FFG’s, have 2 engines
Engines are shock mounted to minimize noise and allow for protection
Advantages of LM 2500
Compact & light
Easy to maintain & repair
Quick start time (~ 1 min)

5. LM 2500

6. LM 2500 Components Starter Compressor
Pneumatic - driven by pressurized air
Compressor
16-stage, axial flow (17:1 compression ratio)
Has some controllable pitch vanes to provide proper air flow and prevent stall

7. LM 2500 Components
Combustion Chamber
Annular design
30 fuel nozzles

8. LM 2500 Components Gas Generator Turbine Power Turbine HP Element only
High speed
Power Turbine
Split shaft to allow varying output speeds while maintaining constant generation of energy
6 sets of nozzles and blades
Lower speed than GGT

9. LM 2500 Engine Control Gas Generator Turbine Power Turbine
Produces energy available for power turbine
Controlled by throttles - alters fuel flow
Runs at set continuous RPM
Power Turbine
Speed depends on quantity of exhaust gases from gas generator turbine & propulsion load
Double helical, double reduction, locked train reduction gears

10. LM 2500 Characteristics Stage efficiency = 92.5%
R&D: 30,000+ hrs of op-testing
Two versions available:
LM (22,500 shp)
LM (30,000 shp) – USN warships

11. LM 2500 Engine Control Speed Governor Overspeed Trip
Used to prevent power turbine from exceeding speed limit (104%)
Reduces fuel to gas generator section which reduces gases to power turbine
Overspeed Trip
If governor fails, trip secures fuel to LM 2500 to shut it down (108%)

12. CRP Propeller & Propulsion Shafting
Shaft is hollow to provide flow of oil to propellers
LM 2500 cannot operate at < 5,000 RPM (corresponds to ~11 kts for DDG)
Pitch of blades controlled hydraulically through pistons and gears
Pitch must be adjusted to go slower than 11 kts

13. CRP Propeller & Propulsion Shafting
In order to go faster than 11 kts, shaft RPM increased
In order to go astern, pitch varied to reverse flow
Overall purpose
Controllable pitch to improve efficiency
Reversible to allow for ahead/astern flow with single direction rotation of shaft

14. Plant Lineups Disadvantage of gas turbine
VERY poor partial load fuel economy
LM 2500’s connected to reduction gears via pneumatic clutch
Three possible lineups
Full Power
Split Plant
Trail Shaft

15. Plant Lineups Full Power Lineup Split Plant Lineup Trail Shaft Lineup
2 turbines/shaft with 2 shafts (4 turbines)
Max speed > 30+ kts
Split Plant Lineup
1 turbine/shaft with 2 shafts (2 turbines)
Max speed = 30 kts
Trail Shaft Lineup
1 turbine/shaft with 1 shaft (1 turbine)
Other shaft windmilling
Max speed = 19 kts

16. Air Intake & Exhaust Must minimize space and weight
Must keep air inlet losses to a minimum to ensure maximum performance
Intake has screens/filters to ensure clean, filtered air at all times

17. Air Intake & Exhaust Exhaust generates thermal and acoustic problems
Possible damage to personnel & equipment
Increased detection & weapons guidance from heat (IR signature)
Silencers and eductor nozzles used to silence and cool exhaust

18. Air Intake & Exhaust

19. Allison 501 Gas Turbine Generator Set (GTGS)
Used to generate electricity
Three 2000KW GTGS
Any two can supply electrical needs of ship
Separated by 3 water-tight bulkheads to minimize potential battle damage
Single Shaft
Waste Heat Boiler
Uses heat of exhaust to generate low pressure steam for auxiliary purposes

20. Allison 501

21. Safety Features Automatic Shutdown on: Battle Override High Vibration
Cooling System Failure
Module Fire (UV Flame Detection)
High Turbine Inlet Temp
Low Lube Oil Pressure
Power Turbine Overspeed
Battle Override

22. Ship Layout

23. Operating Stations

24. Propulsion Plant Comparisons

25. Introduction
Overall, various different propulsion designs - to choose, must consider:
Operational requirements
Construction requirements
Manpower requirements
Thermodynamic efficiency

26. Design Considerations
Minimal size and weight
Reliable & easy to maintain
Cost efficiency & budget
Fuel efficiency over wide power range
Shock resistant to handle stress
Quiet & safe
Manpower & training

27. Conventional Steam Plant
Advantages:
cruising speeds
Reliability
Good partial loading
Usefulness for auxiliary functions
Disadvantages
Large & bulky w/ large manpower req’s
Long start-up time
Large fuel storage & low endurance

28. Nuclear Power Plant Advantages Disadvantages
Endurance, reliability, speed
No air required for combustion
No NBC warfare problem
Disadvantages
High costs & weight for shielding
Long startup time
Manpower & training requirements
Radiological problems

29. Diesel Plant Advantages Disadvantages High efficiency @ all loads
Low initial cost and specific fuel cost (SFC)
Reliability
Few operators needed
Disadvantages
Capacity limitations & space considerations
High maintenance & overhaul
High lube oil consumption
Noise

30. Gas Turbine Plant Advantages Disadvantages Light weight & compact
Short startup time
Reliable & quiet
High full-load efficiency
Disadvantages
Large quantities of air (NBC problems)
Large fuel storage
Low partial loads

31. Hybrid Plants
Overall goal: small, more fuel efficient engines for normal ops while retaining ability to shift to high power units when needed
Examples:
CODAG, CODOG: (Diesel and/or GT)
COGAS (RACER): (GT & Steam )
CODAS: (Diesel & Steam)

32. Summary Diesel plant is a hacker!
Most efficient
Easy to construct and operate
Good versatility
Gas Turbine with CRP screws is a winning combo
Efficient and reliable
Good for mass-production “missile sponges”

33. Summary Most versatile is nuclear plant
Tremendous endurance overcomes inefficiency
Saves space and energy
If you consider fuel storage for other plants, it is actually lighter & less expensive

34. Questions?