AVSC 1010 Lecture 10

AVSC 1010 Lecture 10 - Lecture 10 Propulsion Aircraft must...

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Lecture 10 Propulsion Aircraft must have some type of propulsion to move the air over the airfoils and create lift. Whether this propulsion comes from an internal combustion piston engine, or turbojet, or even human power, it is an essential ingredient of flight. Propulsion in powered aircraft comes from the powerplant. The powerplant includes the engine, the generator or alternator which obtain electrical power from the engine, batteries, and all other accessories necessary to provide thrust for the aircraft and power to run instruments, lights, radios, and other important functions. Engines can be very simple or complex. They can be engines that put out less than 50 horsepower for an ultralight aircraft or that put out tens of thousands of pounds of thrust, as those found on heavy transport category aircraft. Even rockets have engines. All of these engines have one thing in common--they convert kinetic or stored energy into the force vector of thrust. Thrust is one of the four forces of flight discussed in the previous chapter essential for flight. Engines can also differ greatly in cost. Some light aircraft engines may cost less than several thousand dollars. Heavy jet turbines cost millions. All of them are wonders of engineering and ingenuity. Piston Engines The piston engine is the most common type of engine found on light aircraft. It is a type of internal combustion engine, where fuel is burned with air inside a combustion chamber, which forces a rapid expansion of gases. This burning process is harnessed to turn a crankshaft in the piston engine, which eventually turns a propeller. The piston engine contains cylinders, where fuel, air, and a sparked charge are introduced in a well timed sequence. The burning of the fuel and production of gases causes a piston within the cylinder to move. The controlled firing and introduction of fuel and gases causes expansion and contraction of gases and an up and down movement of the piston. The engine produces power. In aircraft engines which are attached to propellers, the power produced is measured in horsepower. Horsepower is a unit of mechanical power equal to 33,000 foot-pounds of work done in one minute or 550 foot-pounds of work done in 1 second. I've had the opportunity several times while working with farm equipment as a boy to see these pistons move up and down to move an attached crankshaft. It is a remarkable device. Even farm equipment older than 100 years demonstrates the genius of the timing of the burn. Most automobiles operate with piston engines, but you won't see the pistons under their protective engine shell unless you spend hours at a repair shop that specializes in engine overhaul. The piston engine has a four cycle series of events which you should learn: The intake stroke begins with the piston at the top of the cylinder. A vacuum is created in the cylinder chamber as the crankshaft forces the piston downward. This vacuum causes a mixture of fuel and air to enter the cylinder. The compression/ignition stroke begins as the crankshaft forces the piston up in the cylinder,
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AVSC 1010 Lecture 10 - Lecture 10 Propulsion Aircraft must...

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