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ENGINE OVERALL LAYOUT. 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?
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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?
EXAMPLE OF MILITARY ENGINE:TURBOJET OR LOW-BYPASS RATIO TURBOFAN Extreme Temperature Environment Compressor Combustor Turbine Afterburner
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/Burner: • Combustion or burning processes • Adds fuel to compressed air and burns it • Converts chemical to thermal energy • Process takes place at relatively constant pressure
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
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
TURBOFAN ENGINES Engine Core
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
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
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
2 SPOOL DEVICE: PW2000 Low Pressure Compressor (wlow) High Pressure Compressor (whigh)
3. COMBUSTOR (BURNERS): LOCATION Commercial PW4000 Combustor Military F119-100 Afterburner
4. TURBINES: LOCATION Low Pressure Compressor (wlow) High Pressure Compressor (whigh) High and Low Pressure Turbines
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
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
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 ↑
Combustor Inlet Compressor Turbine Nozzle MAE 4261 REPRESENTATION OF AN ENGINE Freestream 0 1 2 5 3 4
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
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
BOEING 747-400 AT ROLLOUT Thrust Reverse on Landing
y a x Thrust Reverser Vane SIMPLE THRUST REVERSE MODEL: HOMEWORK #2
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
HIGH EFFICIENCY TURBINE ENGINE (HETE) FTT50FTA30 • Ideal and non-ideal cycle analysis • Combustor scaling with Da (tflow/tchem), catalyst, porous metal • Detailed component design (variable stators, electric generator, spin test rig, altitude test rig) 1 ft
MICRO TURBOMACHINERY 1 cm
EXAMPLES OF GAS TURBINE COMPONENTS Example of Film-Cooled 1st Turbine Blade Cooling Holes • Why film cooling? • Turbine inlet temperatures > melting temperatures of turbine blade materials • Air provides a thin, cool, insulating blanket along external surface of turbine blade
NASA'S X-43A SCRAMJET BREAKS SPEED RECORD • “NASA's X-43A research vehicle screamed into the record books again Tuesday, demonstrating an air-breathing engine can fly at nearly 10 times the speed of sound. Preliminary data from the scramjet-powered research vehicle show its revolutionary engine worked successfully at nearly Mach 9.8, or 7,000 mph, as it flew at about 110,000 feet.” • “NASA's X-43A scramjet program successfully smashed its own world speed record for aircraft by flying at nearly 10 times the speed of sound. The flight proves its radical, air-breathing engine can function at speeds of nearly 12,000 kilometers per hour.” • “Aviation history was made today as NASA successfully flew its experimental X-43A research vehicle, a forerunner of craft that could well offer alternate access to space in the future.”
AIRCRAFT ENGINE BASICS • All aircraft engines are HEAT ENGINES • Utilize thermal energy derived from combustion of fossil fuels to produce mechanical energy in form of kinetic energy of an exhaust jet • Momentum excess of exhaust jet over incoming airflow produces thrust • Thrust = Force = Time Rate Change of Momentum • In studying these devices we will employ two types of modeling • Fluid Mechanic • Relate changes in pressure, temperature and velocity of air to physical characteristics of engine • Thermodynamic (Cycle Analysis) • Thermal → mechanical energy from thermal is studied using thermodynamics • Study change in thermodynamic state of air as passed through engine • Geometry of engine NOT important, but rather processes are important
ENGINE SURGE EVENT Surge: Violent reverse flow situation: Burning combustion gases driven upstream through compressor and out of engine Usually accompanied by downstream fire Engine must maintain structural integrity and be able to be shut down
ENGINE TESTING: BIRD STRIKE http://100.rolls-royce.com/facts/view.jsp?id=215 http://www.aviationexplorer.com/a6_engine_ingestion.htm
AIRCRAFT ENGINE MANUFACTURERS 3 Major Aircraft Manufacturers in World Today (Commercial and Military) • Pratt and Whitney (USA) • General Electric (USA) • Rolls Royce (GB) • Applications for Gas Turbines • Commercial and Military Aircraft Engines, Helicopters • Chemical Rocket Engines • Industrial (marine turbines, yachts, assault ships, etc.) • Power Plants • Interesting Note: • Companies sell product at a $$ loss • Profit is made many years later on refurbishment, spare parts, maintenance
COMMERCIAL AIRCRAFT ENGINES: JT8D Engine Models JT8D-7/7A JT8D-9/9A JT8D-15/15A JT8D-17/17A JT8D-17R/17AR JT8D-217C JT8D-219 Airplanes Powered Boeing 727 Boeing 737-100/-200 McDonnell Douglas DC-9 Boeing MD-80
COMMERCIAL AIRCRAFT ENGINES: JT8D • P&W introduced JT8D to commercial aviation in February 1964 (Boeing's 727-100) • 8 models of JT8D standard engine family cover thrust range from 14,000 to 17,400 pounds and power 727, 737, and DC-9 aircraft • More than 11,800 JT8D standard engines produced, over one-half billion hours of service operation. New Program emphasis is on compliance with noise regulations • For -200 models, a new low-emissions combustion system, or E-Kit, has been FAR 25 certified. Reduces NOx by 25 percent, unburned hydrocarbons by 99 percent and smoke by 52 percent relative to current models • The -200 is also the exclusive power for the Super 27 re-engining program, in which Pratt & Whitney, in cooperation with Goodrich Aerostructures, is offering 727 operators a solution to achieve Stage 3/Chapter 3 compliance with improved performance. Involves replacing two outboard engines with new JT8D-217C/219 models and adding noise suppression equipment. The Super 27 can increase range up to 1,200 nautical miles and permits carrying up to 30 more passengers or up to 10,000 pounds in additional cargo. • Engine Characteristics • Fan tip diameter: 39.9 - 49.2 in • Length, flange to flange: 120.0 - 154.1 in • Takeoff thrust: 14,000 - 21,700 lb • Bypass ratio: 0.96 - 1.74 • Overall pressure ratio: 15.4 - 21.0 • Fan pressure ratio: 1.92 - 2.21