Gas Turbine Gas Turbine ApplicationsApplications

LM 2500,LM 2500,

Allison 501,Allison 501,

The PlantThe Plant

ObjectivesObjectives

• 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 Gas Turbine Power PlantsPlants

• Gas generator Gas generator sectionsection• Compressor• Combustion chamber• Gas generator turbine

• Power Power sectionsection• Power

turbine

LM 2500LM 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 2500LM 2500

LM 2500 ComponentsLM 2500 Components• Starter

• 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 ComponentsLM 2500 Components

• Combustion Chamber• Annular design • 30 fuel nozzles

LM 2500 ComponentsLM 2500 Components• Gas Generator

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 LM 2500 Engine ControlControl

• Gas Generator 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 LM 2500 CharacteristicsCharacteristics

• 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 LM 2500 Engine ControlControl

• Speed Governor• 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 & CRP Propeller & Propulsion ShaftingPropulsion 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

• 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

CRP Propeller & CRP Propeller & Propulsion ShaftingPropulsion Shafting

Plant LineupsPlant Lineups

• Disadvantage of gas turbine• VERYVERY 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 LineupsPlant Lineups

• Full PowerFull Power Lineup• 2 turbines/shaft with 2 shafts (4 turbines)• Max speed > 30+ kts

• Split PlantSplit Plant Lineup• 1 turbine/shaft with 2 shafts (2 turbines)• Max speed = 30 kts

• Trail ShaftTrail Shaft Lineup• 1 turbine/shaft with 1 shaft (1 turbine)• Other shaft windmilling• Max speed = 19 kts

Air Intake & ExhaustAir 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 & ExhaustAir 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 & ExhaustAir Intake & Exhaust

Allison 501 Gas Allison 501 Gas Turbine Generator Set Turbine Generator Set

(GTGS)(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 501Allison 501

Safety FeaturesSafety Features

• Automatic Shutdown on:• High Vibration• Cooling System Failure• Module Fire (UV Flame Detection)• High Turbine Inlet Temp• Low Lube Oil Pressure• Power Turbine Overspeed

• Battle Override

Ship LayoutShip Layout

Operating StationsOperating Stations

Propulsion Plant Propulsion Plant ComparisonsComparisons

IntroductionIntroduction

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

Design ConsiderationsDesign 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 Conventional Steam PlantPlant

• 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 PlantNuclear Power Plant• Advantages

• 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 PlantDiesel Plant• Advantages

• 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 PlantGas Turbine Plant• Advantages

• 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 PlantsHybrid 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)

SummarySummary

• 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”

SummarySummary

• 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?Questions?