advanced turbo machinery

Overview of EAE 138 for Airbreathing Propulsion and MAE 248

for Advanced Turbomachinery

Prof. Roger L. Davis

Department of Mechanical & Aeronautical EngineeringUniversity of California, Davis

2

Overview

• Applications of Gas Turbine Engines

• EAE 138 - Airbreathing Propulsion

• Extensions of the Basic Principles to Other Applications in Rotating Machinery (MAE 248)

• Summary

3

Gas Turbine Applications“Why is EAE 138 Important?”

• Aircraft Jet Engines– Commercial Turbofan– Military Turbojet, Turbofan,

Ramjet, Scramjet• Small Commuter Aircraft

– Turboprop• Helicopters and Tanks

– Turboshaft• Power Generation!!

– Turboshaft, MicroTurbines

4

EAE 138 Airbreathing Propulsion Course Description

• Overview of Gas Turbine Engines• Thermodynamics Review• Compressible Flow Review• Gas Turbine Engines and Components• Ideal Engine Cycle Analysis• Component Performance• Real Engine Parametric Cycle Analysis• Engine Performance Analysis

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High-Bypass Turbofan Engines52-115,000 lbs Thrust Range

Pratt & Whitney 4000General Electric GE90

•76,000 - 115,000 lbs thrust

•Boeing 777

•52,000 - 98,000 lbs thrust

•94 - 112 inch diameter fan

•Airbus A330, Boeing 777

6

Turbojet Engines20-30,000 lbs Thrust

Pratt & Whitney F100

•20,000 - 30,000 lbs thrust

•F15, F16•30,000 lbs thrust

•B-1 Bomber

General Electric F101

F16

7

Turboprop Engines1,800-2,750 Shaft Horsepower

Pratt & Whitney 100

•1,800-2,750 shaft horsepower

•30-70 passenger transport

•1,870 - 1,940 shaft horsepower

•Saab 340, LET L610, Sukhoi S-80

General Electric CT7

8

Turboshaft Engines

General Electric T700

•1,500-2,600 shaft horsepower

•UH-60 Black Hawk, AH-64 Apache, Bell 214ST, Sikorsky 2-70

•1,500-2,500 Shaft horsepower

Rolls-Royce 250

9

Gas Turbine Engine Components

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Inlet

• Inlet Reduces the Entering Air Velocity to a Level Suitable for the Compressor

• Often Considered Part of Nacelle• Critical Factors:

– Mach Number– Mass Flow– Attached Flow

• Subsonic Inlet– Divergent area usedto reduce velocity

• Supersonic Inlet– Shocks often used toachieve reduced velocityand compression

Nacelle

Engine Inlet

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Fan/Compressor

• Axial-Flow Fan• Axial-Flow Compressor

– Low-Pressure – High-Pressure

• Centrifugal Compressor– Mixed Axial/Radial Flow

FanLow-Pressure Compressor

High-Pressure Compressor

From Mattingly

From Mattingly

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Combustor• Designed to Burn a Mixture

of Fuel and Air and Deliver to Turbine– Uniform Exit Temperature– Complete Combustion– Exit Temperature Must Not

Exceed Critical Limit Set By Turbine Metal + Cooling Design

Combustor

From Mattingly

13

Turbine

• Extracts Kinetic Energy form Expanding Gases and Converts to Shaft Horsepower to Drive the Compressor/Fan– Axial Flow Turbine

• High Flow Rates• Low-Moderate Pressure

Ratios– Centrifugal Turbine

• Lower Flow Rates• Higher Pressure Ratio

High-Pressure Turbine

Low-Pressure Turbine

From Mattingly

14

Nozzle

• Increase the Velocity of the Exhaust Gas Before Discharge from the Nozzle and Straighten Gas Flow From the Turbine– Convergent Nozzle Used When Nozzle Pr < 2 (Subsonic Flow)– Convergent-Divergent Nozzle Used When Nozzle Pr > 2

• Often incorporate variable geometry to control throat area– Thrust-Vectoring Nozzles for High-Maneuverability

Nozzle

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Thrust Augmentation

• Thrust Augmentation Through Addition of Heat or Mass– Additional Heat Through Use of Afterburner

• Additional Fuel Injected and Burned Behind Turbine• Usually Used in Military Engines

– Additional Mass Through Water Injection• Water Injected in Compressor or Combustor to Increase Mass

of Flow• Not Used Very Much Due to Added On-Board Weight of Water

and Durability Degradation

Afterburner 16

Gas Turbine Thrust or Power

• A Control Volume Analysis of the Forces Around a Jet Engine Shows that Thrust is:

a

b

c

de

f

g

h

i

j

Vj, AjVo, Ao

( )tion

crossengineinletexitinletexitengine APPVVmThrustsec

)( −+−≅ &

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Gas Turbine Thermodynamics

• Review of Thermodynamics Theory– Work and Heat Interaction– Property, State, Processes– Thermally Perfect Gas, Calorically Perfect Gas– Enthalpy and Stagnation Enthalpy– Gibbs Equation– Entropy, Isentropic Flow and Relationships– Stagnation Pressure and Stagnation Temperature

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Ideal Gas Turbine Thermodynamics

• Brayton Cycle Used in Gas Turbine Engines:

From Mattingly

T or H

S

IDEAL CYCLE

PT0=PT2

PT3

PT4=PT3

PT5= PT9

P0= P9

Compressor Work( )23 ttpc TTcmW −= &&

Turbine Work = Compressor Work

( )54 ttpt TTcmW −= &&

Combustor Heat Addition( )34 ttpc TTcmQ −= &&

Inlet Dynamic Head22

inletV

Exit Dynamic Head22

exitV

( ) engineinletexitinletexitengine APPVVmThrust )( −+−≅ &

Com

pres

sor

Combustor

Turb

ine

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Gas Turbine Compressible Flow

• Review of Compressible Flow Theory– Total Enthalpy and Total

Temperature– Mass Flow Parameter– Area Ratio– Velocity-Area Variation– Wave Propagation– Subsonic, Transonic,

Supersonic, Hypersonic Flow– Normal and Oblique Shock

Relations

Inlet Shocks

Shocks in Turbines

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Losses in Component Performance• “Figures of Merit” are Defined for

Each Component to Describe its Non-Ideal Performance– Inlet and Fan

• Total Pressure Losses Associated with Viscous Flow and Shocks

– Compressor and Turbine• Viscous Flow Total Pressure Losses

Accounted for with Polytropic Efficiency– Combustor and Afterburner

• Total Pressure and Temperature Losses Associated with Incomplete Combustion

• Total Pressure Losses Associated with Viscous Flow Mixing

– Nozzle• Total Pressure Losses Associated with

Viscous Flow and Over/Under Expanded Nozzle and Shocks

Viscous Wakes in Turbine

Over-Expanded Nozzle

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Real Gas Turbine Thermodynamics• Losses Due to

Viscous Flow Effects, Heat Transfer, and Shocks Alter Cycle

From Mattingly

Exit Dynamic Head and Thrust is Smaller than Ideal Due to Losses

S

REAL CYCLE

PT0=PT2

PT3

PT4

PT5i

P0= P9

Compressor Work( )23 ttpc TTcmW −= &&

Turbine Work = Compressor Work

( )54 ttpt TTcmW −= &&

Combustor Heat Addition( )34 ttpc TTcmQ −= &&

Inlet Dynamic Head22

inletV 22exitV

( ) engineinletexitinletexitengine APPVVmThrust )( −+−≅ &

PT3i

PT5

T or H

22

Parametric Cycle Analysis• Equations are Derived for Each

Engine Class to Determine:– Specific Thrust– Specific Fuel Consumption– Fuel/Air Ratio– Thermodynamic, Propulsive, and

Overall Efficiency

With Design Inputs:– Flight Conditions (Mach Number,

Altitude, etc.)– Component “Figures of Merit”– Design Choices (Tradeoffs for Aircraft

Design)

• Tradeoffs are Examined Parametrically with Cycle Design Code

( )

( ) 0

00

1 mFf

mFmmmm

Fm

SC

Cff

&

&&&

&&&

α+=

==

( )( ) ( ) ( )[ ]PRc

in

outT

hgfMaVaVfa

QWnet

211 2

020

219

20

29

20 αα

η

+−++=

=&

&

( )( ) ( ) ( )[ ]( )( ) ( ) ( )[ ]2

02

0192

09

0019090

0

11112

MaVaVfMaVaVfM

WnetVT

outP

αααα

η

+−++

+−++=

=&

( ) ( )

⎥⎦

⎤⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−+−

++

⎥⎦

⎤⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−++−+

+=

19

0

019

0190

0

190

9

0

09

090

0

90

0

111

11111

1

PP

gaVTT

MaV

ga

PP

aVTT

RRfM

aVf

ga

mF

cc

cc

t

c

αα

γα&

23

Cycle Design is Performed for Hypothetical New Aircraft

• New Engine is Designed Using Preliminary Cycle Analysis for Hypothetical New Aircraft– Commercial or Military Application– Design to Required Specific Thrust, Endurance, and Range– Alternate Designs Examined

24

Tour of United Airlines Maintenance Facility

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Tour of United Airlines Maintenance Facility

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Gas Turbine Theory Useful for Applications/Design of Turbomachinery

Radiator Cooling Fan

AirconditioningFan

• Principals Learned in EAE 138 Are Also Basis for Applications in Rotating Machinery (Turbomachinery)

• MAE 248 is Offered for Those Students Interested in Design of Turbomachinery– Gas Turbine Compressor, Fan, Turbine– Airconditioning and Automotive Fans– Electronic Cooling Fans– Centrifugal Pumps, Chillers, and Radial

Turbines

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Summary

• Air-Breathing Propulsion is an Important Subject for MAE Students– EAE 138 Covers the Basic Engineering Principles

• Thermodynamics, Compressible Flow, and Design of Modern Gas Turbine Engines

• Parametric Design of Different Gas Turbine Engines• Fieldtrip to United Airlines Maintenance Facility for “Hands-

On” View of Gas Turbine Components

– Principles are Basis for Any Type of Fluid Machinery Design (Covered in MAE 248)

• Compressors, pumps, fans, turbines, blowers, etc. that add or extract work to a flow