Gas Turbine Applications LM 2500, Allison 501, The Plant

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

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

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)

LM 2500

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

LM 2500 Components Combustion Chamber Annular design 30 fuel nozzles

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

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

LM 2500 Characteristics Stage efficiency = 92.5% R&D: 30,000+ hrs of op-testing Two versions available: LM 2500-20 (22,500 shp) LM 2500-30 (30,000 shp) – USN warships

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%)

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

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

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

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

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

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

Air Intake & Exhaust

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

Allison 501

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

Ship Layout

Operating Stations

Propulsion Plant Comparisons

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

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

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

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

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

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 efficiency @ partial loads

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)

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”

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

Questions?