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    TS 4001: Lecture Summary 8: Marine Gas Turbines

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    Venkateswarlu Kolluru
    This document provides information about marine gas turbines. It discusses the advantages and disadvantages of marine gas turbines. It describes the basic components and cycles of gas turbines including compressors, combustors, and turbines. It provides details on commonly used marine gas turbines such as the GE LM2500 and special cycle gas turbines that include recuperators to improve efficiency.

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    TS 4001: Lecture Summary 8: Marine Gas Turbines

    Uploaded by

    Venkateswarlu Kolluru
    75 views27 pages
    This document provides information about marine gas turbines. It discusses the advantages and disadvantages of marine gas turbines. It describes the basic components and cycles of gas turbines including compressors, combustors, and turbines. It provides details on commonly used marine gas turbines such as the GE LM2500 and special cycle gas turbines that include recuperators to improve efficiency.

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    336927531-LM-2500-ppt

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    This document provides information about marine gas turbines. It discusses the advantages and disadvantages of marine gas turbines. It describes the basic components and cycles of gas turbines including compressors, combustors, and turbines. It provides details on commonly used marine gas turbines such as the GE LM2500 and special cycle gas turbines that include recuperators to improve efficiency.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    75 views27 pages

    TS 4001: Lecture Summary 8: Marine Gas Turbines

    Uploaded by

    Venkateswarlu Kolluru
    This document provides information about marine gas turbines. It discusses the advantages and disadvantages of marine gas turbines. It describes the basic components and cycles of gas turbines including compressors, combustors, and turbines. It provides details on commonly used marine gas turbines such as the GE LM2500 and special cycle gas turbines that include recuperators to improve efficiency.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 27

    TS 4001: Lecture Summary 8

    Marine Gas Turbines


    LM2500

    22 February Marine Gas Turbines 2


    Marine Gas Turbines
     Advantages
     Much higher power-to-weight ratio than steam or diesel plants
     Much higher power density (power/volume) than steam or diesel plants
     Short time from start-up to full power
     Highly responsive in tactical maneuvering
     Fuel efficient at rated power
     Ease of operation and maintenance
     Extremely reliable
     Quiet
     Modular installation and replacement
     Disadvantages
     Large intake and uptake volumes
     Poor fuel efficiency at light loading
     High exhaust temperature (IR signature)

    22 February Marine Gas Turbines 3


    Ideal Gas Turbine Cycle

     Simple open cycle based on ideal Brayton cycle


     Isentropic (constant entropy) compression ( - ‚)
     Adiabatic (constant pressure) heat addition (‚ - ƒ)
     Isentropic expansion (ƒ - „)
     Adiabatic cooling („ - )

     Real cycle is non-isentropic due to compressor and turbine losses

    22 February Marine Gas Turbines 4


    Simple Open Cycle Gas Turbine

    Intake
    Combustor

    Power Turbine

    Compressor Turbine Gas Generator Shaft Output Shaft

    HP Turbine

    Exhaust

     Intake air is compressed by compressor turbine


     Compressed air enters combustor where it mixes with fuel and the mixture is burned,
    adding heat to the system
     Combustion gasses enter high pressure turbine, which turns gas generator shaft, which
    powers the compressor turbine
     Combustion gasses then enter power turbine, which turns output shaft, and then are
    exhausted

    22 February Marine Gas Turbines 5


    Gas Turbine Cycles

    22 February Marine Gas Turbines 6


    Simple …

    Exhaust
    Air Intake
    Gas

    Gas Generator
    Turbine
    Compressor
    Output
    Shaft

    Combustion
    Chamber
    Power
    Turbine Fuel

    22 February Marine Gas Turbines 7


    … and ICR Cycles
    Power
    Turbine

    Air Intake

    Gas Generator
    Turbine
    Compressor
    Output
    Shaft

    Combustion
    Chamber

    Fuel Regenerator Intercooler

    Cooling Water
    Exhaust
    Gas

    22 February Marine Gas Turbines 8


    Gas Turbine Shaft Types

     Single Shaft
     One shaft drives both the compressor and the load
     Harder to start since entire engine is mechanically connected to the drive train
     Split Shaft
     Compressor and gas-generator turbine share a common shaft
     Power turbine is decoupled and drives output shaft independently
     Gas generator section not affected by changes in propeller loading
     LM-2500 and Marine Spey Series are split shaft engines
     Twin-Spool
     Two stage compressor, each stage driven by separate turbine
     Gas generator shaft is actually a low pressure shaft turning inside a hollow
    high-pressure shaft
     More complex and larger than split shaft engine
     USCG Hamilton class uses Pratt Whitney FT-4 twin-spool engines

    22 February Marine Gas Turbines 9


    Compressor Types

     Centrifugal
     Single entry or dual-entry impellers
     Air accelerates radially outward from the hub to the diffuser
     Rugged, simple in design, relatively light weight
     Large frontal area, lower efficiency, hard to use more than one stage
     Axial Flow
     Uses several stages of rotor and stator pairs, with decreasing diameter from front to
    rear
     Easy to vary compression ratio by adding or removing stages
     Stators can be fixed or variable pitch
     Most commonly used type for propulsion gas turbines

    22 February Marine Gas Turbines 10


    Axial Flow Compressor

    Simple-cycle, two-shaft design.

    22 February Marine Gas Turbines 11


    Combustion Chamber Types
     Can
     Each fuel nozzle mounted inside an individual chamber or “can”
     Cans are mounted around axis of engine
     Used on engines with centrifugal compressors
     Annular
     Fuel nozzels mounted in single liner around engine
     Holes and slots admit combustion and cooling air
     Very efficient and more compact
     Used on engines with axial compressors
     Can-Annular
     Small annular cans placed around axis of engine
     Outer can contains smaller cans
     Each inner can admits fuel and combustion air
     Greater structural strength, minimal pressure drop due to shorter length
     Used with twin-spool compressors

    22 February Marine Gas Turbines 12


    Annular Combustor Liner

    22 February Marine Gas Turbines 13


    Fuel Consumption

     SFC about 0.38 to 0.40 lb/hp-hr at full rated power, but rises rapidly below
    10,000 BHP
     SFC “map” graphs BHP and SFC vs. power turbine speed (NPT)
     SFC must be corrected to account for intake and exhaust duct losses and inlet
    temperature and pressure

    22 February Marine Gas Turbines 14


    Commonly Used Gas Turbines

     General Electric LM2500


     First used by US Navy on Spruance class destroyers
     Now used in FFG-7, DD-993, CG-47, DDG-51, AOE-6
     Currently rated by the Navy at 29,500 HP
     LM2500-30, LM2500-20, LM500, LM1600, LM5000, LM6000
     Rolls-Royce Marine Spey Series
     Used in UK, Dutch, Japanese navies
     SM-1 rated at about 26,000 bhp
     Allison 570-K/571-K and 501-K
     Used in Navy ship service gas turbine generators
     8,200 bhp for 571-K, up to 7,400 hp for 501-K
     Pratt-Whitney
     FT-4 used in USCG Hamilton class

    22 February Marine Gas Turbines 15


    LM2500 Marine Gas Turbines
     LM2500 most commonly used marine gas turbine
     Almost 500 USN and four commercial US shipboard installations
     Over 350 foreign shipboard installations
     Simple Cycle
     29,500 HP at 3,600 rpm (USN rating @ 100° F and 4/6 inches H20)
     16-stage axial flow compressor, 17:1 pressure ratios
     Variable stators in first six stages
     Split-shaft design
     Annular combustor
     Two-stage HP turbine and six-stage power turbine
     Mounted in enclosure
     Shock, blast, noise, temperature isolation
     Pre-wired, pre-piped, factory tested
     Total weight 44,000 lbs (dry) including enclosure
     312” long x 96” wide x 108” high (1,872 cuft)

    22 February Marine Gas Turbines 16


    LM 2500

    22 February Marine Gas Turbines 17


    LM 2500+

    22 February Marine Gas Turbines 18


    LM 6000

    22 February Marine Gas Turbines 19


    LM2500 Characteristics

    ENGINE SHP

    22 February Marine Gas Turbines 20


    LM2500 Characteristics (cont.)

    Corrections to specific fuel


    consumption for duct losses

    22 February Marine Gas Turbines 21


    LM2500 Characteristics (cont.)

    Corrections for ambient


    temperature

    22 February Marine Gas Turbines 22


    LM2500 Characteristics (cont.)

    Corrections to rating
    for duct losses

    22 February Marine Gas Turbines 23


    Special Cycle Gas Turbines
     Recuperated (Regenerative) Cycle
     Compressed air is ducted through heat exchanger with exhaust, capturing heat
    energy which would otherwise be lost, before entering combustor
     Increases thermal efficiency of cycle
    Recuperator
    Exhaust
    Intake

    Combustor

    Gas Generator Shaft Output Shaft

    HP Turbine Power Turbine

     Intercooled Recuperative (ICR) Cycle


     Adds intercooler between low and high pressure compressors
     Fuel rate can approach that of a diesel engine

    22 February Marine Gas Turbines 24


    Westinghouse WR-21 ICR Engine

     Development
     Navy-funded development program
     Heavy lobbying effort against from GE
     Recuperator troubles have caused delays
     Keystone of Integrated Power System
     Characteristics
     29,050 BHP maximum
     315” long x 104” wide x 180” high (3,413 cuft)
     Recuperator 156” long x 104 “ wide x 76” high and 35,000 lbs
     109,750 lbs (dry) total weight including enclosure and recuperator
     Predicted SFC 17% to 40% lower than simple cycle
     Higher acquisition cost than LM2500

    22 February Marine Gas Turbines 25


    GE LM2500R Recuperative
     Development
     Joint GE/USN development from 1991-1992
     GE continued independently since 1993
     NAVSEA DDG-51/CG-47 LM2500R installation study 1994
     Characteristics
     29,500 BHP maximum @ 3,600 rpm
     Predicted SFC 23% to 37% lower than LM2500
     No changes to compressor
     LM6000 combustor
     Rebladed HP and power turbines
     Variable area fuel nozzles
     Modified casing
     Two-core Solar Primary Surface Recuperator (already 100 in service)
     Recuperator 150” long x 120” wide x 54” high and 25,000 lbs
     69,000 lbs (dry) total weight including enclosure and recuperator

    22 February Marine Gas Turbines 26


    Additional Reading

     1.8.1 DD 963 Power Plant (D. A. Rains).


     1.8.2 Fuel Saving Warship Drives (S. Ashley).

    22 February Marine Gas Turbines 27

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