MAE 5350: Gas Turbines

1. MAE 5350: Gas Turbines Lecture 1: Introduction and Overview Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk

2. LECTURE OUTLINE • Introduction • What is an air-breathing engine • Key questions • Propulsion Options • Rocket Propulsion Overview and Basic Operation • Air-Breathing Propulsion Overview and Basic Operation • Momentum Exchange Physics • Air-Breathing Engine Components • Nomenclature • Component Functionality • Engine Types • Turbojet (+ afterburner), Turbofan, Turboprop, Ramjet, Scramjet • Examples of Current Aircraft Engines • Introduction to Propulsion Performance Parameters

3. Take mass stored in a vehicle and throw it backwards → Use reaction force to propel vehicle All fuel and oxidizer are carried onboard the vehicle Capture mass from environment and set that mass in motion backwards → Use reaction force to propel vehicle Only fuel is carried onboard Oxidizer (air) is ‘harvested’ continuously during flight ROCKET VS. AIR-BREATHING PROPULSION

4. AIR-BREATHING PROPULSION • Gas turbine engines power every modern aircraft and will for foreseeable future • Gas turbines used for land-based power application, rocket engine turbo-pumps, marine applications, ground vehicles (tanks), etc. • Many technical challenges to be addressed (Fuel Economy, Emissions, Noise) • Fluid mechanics, thermodynamics, combustion, controls, materials, etc. • One of most complicated, parts, extreme environment device on earth • Enormous market: vast research and development $$ • Development time of engine > development time of aircraft (5:3) • Market is so competitive that engines are sold for a loss

5. FUEL CONSUMPTION TREND • U.S. airlines, hammered by soaring oil prices, will spend $5 billion more on fuel this year or even a greater sum, draining already thin cash reserves • Airlines are among the industries hardest hit by high oil prices, which have jumped 38 percent in just 12 months. • Airline stocks fell at the open of trading as a spike in crude-oil futures weighed on the sector JT8D Fuel Burn PW4084 JT9D Future Turbofan PW4052 NOTE: No Numbers 1950 1960 1970 1980 1990 2000 2010 2020 Year

6. FUEL COST DRIVEN EXAMPLE • With fuel now largest component of operating costs, air carriers are turning to fuel-saving measures that once seemed hardly worthwhile • Upswept wingtips to increase range and improve aerodynamics • Taxi to and from runway on one engine to save fuel • Does it make sense to actually fly slower? • Do you polish an airplane or paint it? • Airlines have new program to wash their aircraft/engines • Other cost saving measures • 1st and 2nd bag check fee (and many others new fees…) • Remove all pillows from MD-80’s

7. CHEMICAL EMISSIONS

8. GREENHOUSE GAS EMISSIONS

9. AIRCRAFT NOISE

10. AIRCRAFT AND ENGINE NOISE

11. COMMERCIAL ENGINES 707 757 727 767 737 777 747 787

12. TRENDS TO BIGGER ENGINES 1995: Boeing 777, FAA Certified 1958: Boeing 707, United States' first commercial jet airliner Similar to PWJT4A: T=17,000 lbf, a ~ 1 PW4000-112: T=100,000 lbf , a ~ 6

13. VARIOUS NUMBER OF ENGINE CONFIGURATIONS 2 Engines 3 Engines 4 Engines 6 Engines

14. SR-71: J-58 TURBO RAMJET

15. Electric vs. Gas Turbine: Drones

16. X-51

17. LAND-BASED POWER GENERATION

18. LARGEST GAS TURBINE ENGINE: SGT5-8000H • Power 340 MW • Extrapolated mass flow based on SGT100-SGT1000 series: 900 kg/s • Average of SGT100-SGT1000, Assume pc: 15 • Assumed tc (isentropic, g=1.35): 2 • Assume 24 burners (consistent with SGT5-series) • Combustor total CFM: 216,000 • CFM per burner: 9,000 • Full-scale, single-burner testing can be accomplished • Trends: • If combustor inlet temperature is lower, CFM is lower • If combustor inlet pressure is higher, CFM is lower http://www.powergeneration.siemens.com/en/products/gasturbinesseries/largescale/sgt5_8000h/index.cfm

19. GE 9H: HOW LARGE IS THE DEVICE?

20. FURTHER EXAMPLES

21. WHY “AIR-BREATHING” PROPULSION • Propulsion Goal: Create a Force to Propel a Vehicle (N.S.L) • 2 ‘Choices’ for Propulsion • Take mass stored in a vehicle and throw it backwards → Use reaction force to propel vehicle • Rocket Propulsion (MAE: 4262) • All fuel and oxidizer are carried onboard vehicle • Capture mass from environment and set that mass in motion backwards → Use reaction force to propel vehicle • Air-Breathing Propulsion (MAE: 4261) • Only fuel is carried onboard • Oxidizer (air) is ‘harvested’ continuously during flight Airplanes are very sensitive to environment in which they operate Rockets are highly insensitive to operational environment

22. HOW ALL ROCKET WORKS F Chemical Energy Rocket Propulsion: Produces thrust by ejecting stored matter • Propellants combined in combustion chamber where chemically react to form high T&P gas • Gases accelerated and ejected at high velocity through nozzle, imparting momentum to engine • Thrust force is reaction experienced by structure due to ejection of high velocity matter • Same phenomenon pushes garden hose backward as water flows from nozzle, gun recoil QUESTION: Could a rocket engine exert thrust while discharging into a vacuum (with not atmosphere to “push against”)? Thermal Energy Kinetic Energy

23. HOW AN AIRCRAFT ENGINE WORKS Chemical Energy Kinetic Energy Thermal Energy • Flow through engine is conventionally called THRUST • Composed of net change in momentum of inlet and exit air • Fluid that passes around engine is conventionally called DRAG

24. SUMMARY: ESTIMATES FOR THRUST • Points to remember: • Mass flow for rocket is propellant carried onboard (fuel + oxidizer) • Mass for air-breathing engine is fuel carried onboard and air harvested from environment as airplane flies • Rockets usually require far higher thrust levels than airplanes • Airplanes usually fly for far greater durations than rockets Rocket Air-Breathing Engine

25. ENGINE OVERALL LAYOUT

26. CROSS-SECTIONAL EXAMPLE: GE 90-115B Compressor Nozzle Fan Turbine Combustor Inlet • Why does this engine look the way that it does? • How does this engine push an airplane forward, i.e. how does it generate thrust? • What are major components and design parameters? • How can we characterize performance and compare with other engines?

27. EXAMPLE OF MILITARY ENGINE:TURBOJET OR LOW-BYPASS RATIO TURBOFAN Extreme Temperature Environment Compressor Combustor Turbine Afterburner

28. MAJOR GAS TURBINE ENGINE COMPONENTS • Inlet: • Continuously draw air into engine through inlet • Slows, or diffuses, to compressor • Compressor / Fan: • Compresses air • Generally two, or three, compressors in series • Raises stagnation temperature and pressure (enthalpy) of flow • Work is done on the air • Combustor: • Combustion or burning processes • Adds fuel to compressed air and burns it • Converts chemical to thermal energy • Process takes place at relatively constant pressure

29. MAJOR GAS TURBINE ENGINE COMPONENTS • Turbine: • Generally two or three turbines in series • Turbine powers, or drives, the compressor • Air is expanded through turbine (P & T ↓) • Work is done by the air on the blades • Use some of that work to drive compressor • Next: • Expand in a nozzle • Convert thermal to kinetic energy (turbojet) • Burning may occur in duct downstream of turbine (afterburner) • Expand through another turbine • Use this extracted work to drive a fan (turbofan) • Nozzle: • Flow is ejected back into the atmosphere, but with increased momentum • Raises velocity of exiting mass flow

30. 2. COMPRESSORS: WHERE IN ENGINE? PW2000 Fan Compressor Purpose of fan is to increase efficiency of turbojet engine Much of air bypasses core of engine

31. TURBOFAN ENGINES Engine Core

32. TURBOFAN ENGINES Bypass Air Core Air Bypass Ratio, B, a: Ratio of by pass air flow rate to core flow rate Example: Bypass ratio of 6:1 means that air volume flowing through fan and bypassing core engine is six times air volume flowing through core

33. TRENDS TO BIGGER ENGINES 1995: Boeing 777, FAA Certified 1958: Boeing 707, United States' first commercial jet airliner Similar to PWJT4A: T=17,000 lbf, a ~ 1 PW4000-112: T=100,000 lbf , a ~ 6

34. HOW LARGE IS THE 777-300 ENGINE? 11 ft 7 in (3.53 m) 11 ft 3 in (3.43 m) Engine is largest and most powerful turbofan built (11 ft 3 in (3.43 m) in diameter) In this case, 737 cabin is a mere 3% wider than 777 engine

35. 2 SPOOL DEVICE: PW2000 Low Pressure Compressor (wlow) High Pressure Compressor (whigh)

36. 3. COMBUSTOR (BURNERS): LOCATION Commercial PW4000 Combustor Military F119-100 Afterburner

37. 4. TURBINES: LOCATION Low Pressure Compressor (wlow) High Pressure Compressor (whigh) High and Low Pressure Turbines

38. NOISE SUPPRESSION

39. 5. NOZZLES: PW119 (F22 ENGINE)

40. MILITARY ENGINES: P&W F119

41. AFTERBURNER TESTING

42. COMMERCIAL AND MILITARY ENGINES(APPROX. SAME THRUST, APPROX. CORRECT RELATIVE SIZES) GE CFM56 for Boeing 737 T~30,000 lbf, a ~ 5 P&W 119 for F- 22, T~35,000 lbf, a ~ 0.3

43. THRUST VS. PROPULSIVE EFFICIENCY Important for both fighter and commercial aircraft T/W usually more important for military aircraft (maneuverability) Large mass flow means high W Fighter → DV Extremely important for commercial aircraft, much less so for fighter Efficiency critical for commercial Low DV, high mass flow Conflict

44. ENGINE STATION NUMBERING CONVENTION 2.0-2.5: Fan 3: Combustor 0: Far Upstream 1: Inlet 4: Turbine 2.5+: Compressor 5: Nozzle One of most important parameters is TT4: Turbine Inlet Temperature Performance of gas turbine engine ↑ with increasing TT4 ↑

45. Combustor Inlet Compressor Turbine Nozzle MAE 4261 REPRESENTATION OF AN ENGINE Freestream 0 1 2 5 3 4

46. TYPICAL PRESSURE DISTRIBUTION THROUGH ENGINE

47. BOEING 747-400 AT TOUCHDOWN

48. BOEING 747-400 AT ROLLOUT Thrust Reverse on Landing

49. y a x Thrust Reverser Vane SIMPLE THRUST REVERSE MODEL: HOMEWORK #2

50. TWO OTHER LAYOUTS GTF: Geared Turbofan http://www.flug-revue.rotor.com/FRHeft/FRHeft07/FRH0710/FR0710a.htm UDF: Unducted Fan Concept http://www.aerospaceweb.org/question/propulsion/q0067.shtml