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JET ENGINE PROPULSION

JET ENGINE PROPULSION. Chapter 4. Types. JET ENGINE TYPES. There are two ways of using the power from a jet engine. By taking as little power from the engine to turn the engine and using most of the power as thrust out of the exhaust.

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JET ENGINE PROPULSION

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  1. JET ENGINE PROPULSION Chapter 4 Types

  2. JET ENGINE TYPES There are two ways of using the power from a jet engine. By taking as little power from the engine to turn the engine and using most of the power as thrust out of the exhaust. Or by taking most of the power from the engine to turn the engine and a drive shaft, which can be used to drive a piece of machinery. i.e. propeller, rotor or pump. The engine designer will look at the requirements and then decide on the best design for the job.

  3. JET ENGINE TYPES Different types: - Turbo Jet Avon, Olympus 593 Bypass Engine Small Bypass Conway, Spey, BR700 Medium Bypass Pegasus, BR715, V2500 Large Bypass RB211, Trent Series Turbo Prop Propeller Dart, Tyne, BR715TP Helicopter Gem Turbo Shaft RN Ships Marine Spey Power Generation Industrial Spey and Trent To understand what is meant by ‘Turbo Jet’, ‘Bypass’, ‘Turbo Prop and ‘Turbo Shaft’ We need to look at the development of Gas Turbine Engines

  4. JET ENGINE TYPES Rolls-Royce AVON Basic Shape and Layout Turbo Jet 17 Stage Compressor driven by: - a 3 Stage turbine With RPM (I.e. Thrust) changes, the airflow velocity does not change in proportion to engine RPM This can cause problems at low RPM. The rear of the compressor cannot cope with all of the air from the front of the compressor.

  5. Turbo Jet This can result in the rear end of compressor ‘choking’ So air blasts forwards JET ENGINE TYPES i.e. NO or insufficient rearward movement of air Flame almost goes out - no power – no thrust This is called: - Compressor SURGE To alleviate this problem we need to get rid of some of the air at the rear of the compressor.

  6. Turbo Jet Air dumped overboard Rearward movement of air restored JET ENGINE TYPES Rear end of compressor ‘unchoked’ Power restored BUT: - air dumped sideways out of the engine (aircraft) produces no thrust This is done through a Bleed Valve.

  7. Turbo Jet ‘Bleed’ valve JET ENGINE TYPES ‘Excess’ air is dumped overboard through a valve

  8. Turbo Jet Air dumped overboard JET ENGINE TYPES Air dumped overboard reduces thrust and wastes fuel So a more efficient system was required Enter - Multiple shaft engines and the Bypass system

  9. Turbo Jet HPC driven by HPT driven by LPC LPT JET ENGINE TYPES Allows front end of compressor to slow down – move less air AND Allows rear end of compressor to speed up – move more air Two shaft layout (Twin Spool System) Compressor surges lessened No wasted energy/thrust

  10. JET ENGINE TYPES Bypass Layout Low Bypass Adour Rolls-Royce Spey BR 710 series Bypass allows air not required in the HPC to flow around the outside of it Known as the core engine.

  11. JET ENGINE TYPES Bypass Layout Medium Bypass Pegasus Two shaft layout – Contra-rotation LP and HP AXIAL Flow Compressors In USAF Service – Harrier series Core flow to ‘Hot’ (rear) Nozzles Bypass flow to ‘Cold’ (front) Nozzles

  12. JET ENGINE TYPES Bypass Layout High Bypass Engine RB211 Series (Trent) Three shaft layout – all rotate same direction LP(Fan) IP and HP AXIAL Flow Compressors Boeing 747 and later series, Airbus A330 and larger a/c

  13. JET ENGINE TYPES The fan produces a large amount of thrust from the volume of air it moves backwards. The core engine has a two stage compressor which receives pressure air from the fan and so improves efficiency. The ratio of the air bypassing the core engine to the air in the core engine gives a dimension to the power split between the fan and the core. A normal bypass ratio is 5 or 4 to 1. i.e. 5 times more thrust from the fan.

  14. JET ENGINE TYPES Rolls Royce Trent

  15. Prop Shaft Reduction Gearbox JET ENGINE TYPES Turbo Prop RR Dart Dart RDa6 = 2 stage turbine Dart RDa7 = 3 stage turbine Turbine drives 2 stage CENTRIFUGAL Compressor and Propeller Over 70 different Marks of Engine – basically different power levels – 15 different aircraft Was in service with RAF – Andover and Argosy Transport Aircraft. Fokker F27, Fairchild F27, Briguet Alize, (and P51 Mustang and Dakota!)

  16. Reduction Gearbox 9 Stage HP Compressor 1 Stage HP Turbine 6 Stage LP Compressor 3 Stage LP Turbine JET ENGINE TYPES Turbo Prop Tyne Prop Shaft (via Reduction Gearbox) C160 Transall, Shorts Belfast, Bristol Britannia, Brequet Atlantic, Avro Lincoln, Canadair CL44, Vickers Vanguard, Aeritalia 222.

  17. Reduction Gearbox Thrust Strut 14 Stage HP Compressor 4 Stage Turbine Air Intake Output Shaft JET ENGINE TYPES Turbo Prop RR Allison T56-A-15 Turbine drives compressor and propeller C130 Hercules, P3 Orion, Lockheed Electra, E2C Hawkeye.

  18. Combining Transmission Rear Rotor Transmission Front Rotor Transmission JET ENGINE TYPES Turboshaft Lycoming T55-GA-714 - with Free Power Turbine Boeing CH47 Chinook

  19. JET ENGINE TYPES Any Questions?

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