Gas Turbine

General Electric LM2500

Aircraft Engines

g/W

Turbines

Axial Turbine Stage

Nozzle

Impeller

Dimensionless Coefficients

Degree of Reaction

Flow Coefficient Head Coefficient Specific Speed

Dimensionless Coefficients

Design Coefficients

Nozzle

Isentropic Flow

Nozzle

co

c1

po

p1 , α1 , Ma

+ + +

- - -

p1

δ = α1 – α1s

Impeller

v2

v1

Impuls Turbine (R ~ 0)

Optimum Specific Work / Speed

Yt max;

(α1 ~ 12 – 25o)

Impuls Turbine

Optimum Efficiency

= ho – h1s

α1 ~ 12 – 25o (low)β2 low compared to β1uβ1u – β2 = 0 – 15o

Reaction Turbine (R ~ 0,5)

Optimum Specific Work / Speed

Yt max;

Yt max; uRT ~ 2 uIT

Reaction Turbine

Optimum Efficiency

α1 = β2

φd = φr

CurtisTurbine

Degree of Reaction

co ~c2c1z ~ c2z

Degree of Reaction

Impuls Turbine (R = 0)

Reaction Turbine (R = 0.5)

Main Losses

• Hydraulic (Flow-related)

• Disk Friction

• Ventilation

• Leakage

• Dens gas (Steam Droplets)

• Mechanical

Main Losses

Hydraulic (Flow-related)

Nozzle

Impeller

Annulus

Main Losses

Disk Friction and Ventilation

Disk Friction

Ventilation

Disk Friction and Ventilation

Main Losses

Leakage

Nozzle and Impeller

Reaction Turbine Impuls Turbine

Shaft End

p2 > pk

p2 < pk

Main Losses

Dens Gas Reaction TurbineImpuls Turbine

Mechanical

• Bearings• Seals• Auxiliary Systems

Main Losses

Efficiencies

Hydraulic Losses

Internal Losses

Hydraulic Efficiency

Efficiencies

Internal Efficiency

Hydraulic Losses

Internal Losses

Efficiencies

Total Efficiency

Shaft Power

Shaft Power

Multistage Turbines

Stage efficiency

Internal Efficiency (impeller stage)

Heat Recovery Factor

m ~ 1.03 – 1.04 ; z > 6 stagesm ~ 1.05 – 1.08 ; z > 12 stages

Average Internal Efficiency (turbine)

Multistage Turbines

Efficiency Steam Turbines

Multistage TurbinesNumber of Stages

Impuls Turbine Reaction Turbine

φr = 1.0β1u = β2

Yt IT = 2 Yt RT at fixed u

No of Stages;

Multistage TurbinesNumber of Stages

No of Stages;

Multistage TurbinesNumber of Stages

Reaction Turbine (R = 0.2 – 0.5)

Multistage Turbines

Main Dimensions

Turbines