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Lecture 3b: Aircraft Engines. 1903- 1940s: Propeller + Piston Engines Era. From 1903 (Wright bros.) until the Early 1940s , all aircraft used the piston engine combined with propeller as their propulsion system. Piston engine is just similar with car engine except with several different.
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1903- 1940s: Propeller + Piston Engines Era • From 1903 (Wright bros.) until the Early 1940s, all aircraft used the piston enginecombined with propelleras their propulsion system. • Piston engine is just similar with car engine except with several different. • A propeller is essentially a type of fan which transmits power by converting rotational motion into thrust to propel the aircraft (move forward). • Piston engineuses the energy produced by burning a mixture of air and fuel to drive the propeller.
The differences between piston aircraft engines and car engines • Crankshaft – The crankshaft in an piston aircraft engine turns a propeller, crankshaft in car engine is used to move the wheels of the car. • Weight – the piston aircraft engine must be lightweight compare to car engine. • Power demand to run the engines- the piston aircraft engine demands high power for very long times compare to car engines • Numbers of engine parts - an aircraft engine has at least two sets for every parts, including ignition system (spark plugs and magnetos) and fuel pumps compare to car engine that only have one set. • Operating environment different- an aircraft engine no need radiator for air-cooling compare to the car.
Propeller + PistonEngine Aircraft • Very efficient for low speed flight. • Lower load capacity compared to similar sized jet powered aircraft. • Consumes less fuel, thus cheaper and much more economic than jets. • Quiet, but fly at lower speeds. • The best option for people who need to transport a few passengers and/or small amounts of cargo. • Best choice for pilots who wish to own their own aircraft. • Propellers are not used on high speed aircraft.
Jet Engine History • 1931: 1st turbojet engine designed 1930 by Sir Frank Whittle • 1939: The 1st jet aircraft (Heinkel He 178) was developed in England and Germany • 1943: The first jet fighter aircraft, Messerschmitt Me 262 went into service in the German Luftwaffe.
History of Aircraft Propulsion • 1944 (After World War 2)-Today : • Airplanes used jet engines to generate thrust. • Jet engines also referred to as Gas Turbine Engines. • Various types (turbo-jet, turbo-prop, turbo-shaft, turbo-fan , ramjet, scramjet) • Messerschmitt Me-262 : 1st operational jet-powered aircraft • German V-1 bomb (pulse jet engine): 1st application for military purposes. • Bell P-59: 1st American aircraft • MiG-15: 1st Soviet jet aircraft.
Jet Engines Jet aircraft make use of turbines for the creation of thrust. Consumes more fuel but provide much more thrust than a piston engine. Fly faster than propeller driven aircraft. Greater weight capacity Example: Airbus A340 and Boeing 777, can carry hundreds of passengers and several tons of cargo, and are able to travel for distances up to 13 thousand kilometers. Noisy, this makes jet aircraft a source of noise pollution.
Newton's 3rd law • The theory of jet propulsion is based on the Newton’s third Law, which state that For every action there is an equal and opposite reaction. • When the jet engine is operating, it draws a lot of air from the front and after air-fuel burns the gas ejects at high speed. • During this process, the engine applies force to the gas and lets the gas accelerate in the backward direction and in the meantime, the gas also gives the engine a reactive force to push the aircraft to move forward.
Turbo-jet Engine Inlet-inlet is the opening at the front of engine, it allows the outside air to enter the engine. Compressor– compressor is made up of fans with many blades, it compress the air and raises the pressure & temperature of the air, the compressed air then is delivered to the burner. Burner – Burning process occur here. Fuel is sprayed to the compressed air .The mixture of the fuel + air will be burned. The results is heated gas with high energy, high pressure and high temperature. Turbine- turbine used some of the heated gas energy to turn the compressor . This energy is transferred through the shaft. Nozzle- The balance of heated gas energy exits through the nozzle at very high speed. This causes thrust. As the jets of gas shoot backward, the engine and the aircraft are thrust forward. (Newton 3rd Law) Thrust Newton's 3rd law: For every action there is an equal and opposite reaction. This is called thrust.
Turbo-prop Engine • The propeller located at the front of engine • The propeller converts the power developed by the engine into thrust as efficiently as possible under all operating conditions. • These aircraft are popular with regional airlines, as they tend to be more economical on shorter journeys. Hercules-1 C130
Turbo-fan Engine • Similar to the turboprop, except a fan replaces the turboprop propeller. • Larger fan at the front provides thrust in the same way as a propeller. • The turbofan engine has a front fan, which runs at the same speed as the compressor and fan turbine located at the back to drive the fan. • Most modern airliners use turbofan engines because of they can produce high thrust, lower fuel consumption and low engine-noise.
Rocket Engine 18 A rocket engine produces thrust by burning a fuel at high pressure and exhausting the gas through a nozzle. The oxygen for combustion is carried with the propulsion system. High temperatures and pressures is built up, the are used to accelerate the exhaust gases through a rocket nozzle to produce thrust. The heavier the rocket , the greater thrust needed to get it off the ground. Newton 3rd Law: “To every action there is an equal and opposite reaction."
Differences between Jet engine and Rocket engine Thrust direction Jet engine is an engine using jet propulsion for forward thrust . Rocket engine is an engine using jet propulsion for upward thrust. Source of oxygen Jet enginesdo not have their own source of oxygen. Outside air is sucked into the engine to act as an oxidizer There is no air in space. Rockets have their own oxygen source, either a liquid tank, or mixed in with the solid fuel for combustion.
Rocket vs Missile Purpose Rocket mission is to send the satellite to outer space. Missile mission is as a weapon to attack high value target. Guidance Rocket no guidance system. Missile has a guidance system.
