Introduction to Gas Turbine Engines Introduction Gas Turbine Engine - Configurations
Gas Turbine Engine Gas Generator Compressor is driven by the turbine through an interconnecting shaft Turbine is driven by heated air from the combustor Compressor Combustor T u r b i n e Gas Generator Heart of Gas Turbine (to supply high-temperature and high-pressure gas to the turbine) Turbojet Exhaust Schematic of a Twin Spool Turbojet
Turbojet with Afterburner Schematic of Turbojet with Afterburner Afterburning Turbojet (Concorde) Sources: http://www.concordesst.com/history/events/sia.html, http://www.concordesst.com/model101/model101detail.html
Turbojet Additional turbine stages may be added to extract more gas energy into mechanical power Less residual exhaust energy Reduced thrust generated by core engine Mechanical power directed to drive: Shrouded fan >>> Turbofan Propeller >>> Turboprop Rotor blades >>> Turboshaft Turbofan 1. Nacelle 2. Fan 3. Low pressure compressor 4. High pressure compressor 5. Combustion chamber 6. High pressure turbine 7. Low pressure turbine 8. Core nozzle Source: http://en.wikipedia.org/wiki/turbofan Turbofans offer: High efficiencies Reduced noise levels
Rolls-Royce Trent XWB Bypass ratio ~ 9.3 Source: Airbus F15, F16 P&W F100 Engine Source: http://en.wikipedia.org/wiki/pratt_%26_whitney_f100 Bypass ratio ~ 0.36
Twin Spool Turbofan Schematic of Unmixed Turbofan (Twin Spool) Turbofan Station Numbering Schematic of Unmixed Turbofan (Twin Spool)
Turboprop & Turboshaft Turbine, through reduction gear box, drives A propeller - turboprop engine Rotor blades turboshaft engine (helicopters) Exhaust gas is not a significant contributor to aircraft thrust Power to drive the reduction gearbox can be extracted either from the same turbine that drives the compressor or from a separate, free-wheeling turbine (Power Turbine) Schematic of Turboprop Turboprop & Turboshaft Schematic of Turboshaft with Power Shaft Driven by Free Power Turbine Source: http://en.wikipedia.org/wiki/turboshaft
Turboprop Propeller typically kept at constant rotational speed (rpm) Propeller blade angle variable and controllable according to speed demands Blade angle can be set to: reverse pitch for reverse thrust Feather to stop engine rotation Photo credit: Soon Kim Tat Turboprop Advantages and limitations of the turboprop are those of the propeller: Excellent performance for low-speed flight and short-field take-off High propulsive efficiency and high thrust at low subsonic speeds Approaching the speed of sound, the propeller/rotor loses its aerodynamic efficiency due to compressibility effects Photo credit: Soon Kim Tat Watch video of C130 Turboprop take-off: http://www.youtube.com/watch?v=nwawxrlzeiw
Turboshaft Rotors kept at constant rpm Rotor blade angle variable and controllable according to demands for lift (collective pitch), or speed and banking (cyclic pitch) Photo credit: Soon Kim Tat See video on how collective and cyclic pitch control works: http://www.youtube.com/watch?gl=sg&hl=en-gb&v=7hbzilti_t4 Ramjet Conceptually the simplest jet engine Inlet combustion chamber nozzle No rotating component Compresses incoming air by decelerating it in the inlet Requires forward motion to produce thrust Schematic of Ramjet Source: http://en.wikipedia.org/wiki/ramjet
Turbo / Ram Jet Engine J58 Engine Source: Rolls-Royce, 1986, The jet engine, 5 th edition, Rolls-Royce plc SCRAMJET Supersonic Combustion RAMJET Hypersonic flights (experimental) Source: Wikipedia http://commons.wikimedia.org/wiki/file:scramjet_operation.png
Summary The heart of the gas turbine engine the gas generator The different gas turbine configurations: Turbojet (including with afterburner) Turbofan or Bypass Engine Turboprop and Turboshaft. The operation of a Ramjet and Scramjet Reflection Question Explain the construction of a turbofan engine and elaborate on its advantages compared to a turbojet.