Propulsion Systems Aircraft, Rocket, Space © 2011 Project Lead The Way, Inc.Aerospace Engineering

Types of Propulsion Systems 1.Propeller –Reciprocating Engines 2.Turbines 3.Rocket –Liquid + Solid 4.Space

Engine Operations All engines must perform four basic operations. –Intake: Fuel and air must be brought into the engine –Compression: Fuel-air mixture must be compressed –Power: Fuel-air mixture must be ignited for the gases to provide engine power –Exhaust: Gases must be cleared for the next cycle

Engine Categories A.Reciprocating (contains pistons)Reciprocating 1.Gasoline-powered 2.Diesel-powered (not typical in aircraft) B.TurbineTurbine 1.Turbojet 2.Turbofan 3.Turboprop 4.Afterburning turbojet

Turbojet Simplest and earliest gas turbine Air flows continuously through engine 1.Intake 2.Compression 3.Power (combustion) 4.Exhaust Intake Compression Power Exhaust

Turbojet Example SR-71 Engine

Turbofan Modern military and commercial aircraft Combines best of high and low speed and altitude performance Two airstreams – Center core of air sent through process similar to basic turbojet –Some air passes around this center turbojet –Ratio of two streams is bypass ratio

Turbofan Boeing 767 Engine Boeing 777 Engine

Turboprop Turbine engine turns propeller Propellers develop thrust by moving large mass of air through small change in velocity Used in low speed transport aircraft and small commuter aircraft

Turboprop Example

Afterburning Turbojet Most military fighter jet engines (turbojet and turbofan) use afterburners Helps exceed drag close to sound barrier Nozzle extended and fuel injected in hot gases for extra thrust Inefficient burn uses a lot of fuel

Engine Placement Engine arrangements Under wing –Engine weight close to lift generation –Reduces wing structure Rear-fuselage Mixed under wing and rear fuselage

Produces thrust by ejecting stored matter Rockets can be classified by propulsion –Liquid –Solid Other classifications –Expendable or reusable –Number of stages –Size of payload –Manned or unmanned Rocket Propulsion

Liquid Fuel Rocket Fuel mixed with oxidizer and burned Gases escape out nozzle to generate thrust

Solid Fuel Rocket Fuel burned to generate gases Gases escape out nozzle to generate thrust

Model Rocket Engine Design

Space Propulsion Space is frictionless Small forces result in movement –Venting gas from spacecraft can cause spinning or undesired movement Spacecraft frequently adjust direction with small pulses Each pulse uses fuel

Many different types of Space Propulsion Cold Gas Solid Fuel Liquid Fuel Monopropellant Bipropellant Dual Mode Hybrid Electric Nuclear Solar Moment Exchange Tethers Electrodynamic Tethers Ion Drive Orion Future Types