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FLIGHT POWER. Know basic engine principles. 1. Define a list of terms related to basic engine principles. 2. Describe the mechanical, cooling, and ignition systems of the reciprocating engines. Boyle’s Law. The volume of a gas varies exactly opposite that with the pressure of a gas.
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FLIGHT POWER • Know basic engine principles. • 1. Define a list of terms related to basic engine principles. • 2. Describe the mechanical, cooling, and ignition systems of the reciprocating engines.
Boyle’s Law • The volume of a gas varies exactly opposite that with the pressure of a gas. • A decrease in volume causes an increase in pressure • An increase in volume causes a decrease in pressure Gas Pressure 14.7 psi 29.4 psi 58.8 psi
Charles’ and Gay-Lussac’s Law • The pressure and temperature of a confined gas are directly proportional • Thus, when a gas is compressed, the temperature of a gas is increased 100 500 250 100 500 250 100 500 250 Gas Pressure 14.7 psi 29.4 psi 58.8 psi
Reciprocating Engines Internal or External Combustion?
Mechanical System • Cylinder • Piston • Crankshaft • Connecting Rod • Valves
Mechanical System • Cylinder • Known as the engine’s combustion chamber • Where the power is developed
Mechanical System • Piston • Fits snugly in the hollow cylinder allowing up-and-down linear (straight) motion • Fit will not allow air or fluid in the cylinder
Mechanical System • Crankshaft • The crankshaft and connecting rod allow for the movement of the propeller.
Mechanical System • Connecting Rod • Attached to the throws • With the crankshaft, they change the direction of the pistons into a circular motion
Mechanical System • Valves • A rocker arm regulates the opening and closing of each valve. • Lobes or rings on a camshaft push the rocker arm
Four – Stroke Cycle Step one (First Stroke) is called the intake stroke. Second step (Second Stroke) is the compression process. Third step (Third Stroke) is near the end of the compression stroke, the air and fuel mixture is ignited by an electric spark from the spark plug. The fourth step (Fourth Stroke) is called the exhaust stroke.
Four – Stroke Cycle – Stroke 1 • Called intake stroke • Piston moves down the cylinder creating vacuum • Cam arrangement opens the intake valve • Fuel and air drawn into the cylinder
Four – Stroke Cycle – Stroke 2 • Piston moves up the cylinder • Both valves closed • Air and fuel compressed and pressure rises
Four – Stroke Cycle – Stroke 3 • Air and fuel ignited by electrical spark • Rise in temperature forces piston down
Four – Stroke Cycle – Stroke 4 • Piston moves up forcing burned gas out of cylinder • Burned gas transmitted to exhaust system
Four – Stroke Cycle – Process • Occurs at the same time in all cylinders, but not on the same step • Ignition sequence of the cylinders called the firing order
Cooling System • Engine produces vast amount of heat • Modern aircraft engines use an air cooling system • The liquid cooling system on an aircraft works the same as does the cooling system on most automobiles. • The coolant flows through the engine block and around cylinders. • The liquid circulates through a system of pipes to a radiator.
Ignition System • Must receive an electrical spark originating in the magneto
Types of Reciprocating Engines • In-line Engines • Cylinders are located in a row, one • behind the other • Two classifications: • Upright • Inverted
Types of Reciprocating Engines • Opposed Engines • Two rows or banks of cylinders on each side of the crankshaft • Rows directly opposite each other called horizontal opposed
Types of Reciprocating Engines • V Engine • “V” engine features two rows of cylinders set • at an angle of about 45°
Types of Reciprocating Engines • Radial Engine • Crankshaft with only one throw • Odd number of cylinders in each bank or row • Maximum number of cylinders in each bank is nine http://www.youtube.com/watch?v=KJPf-8p37I0&feature=relmfu
Fuels Used in Reciprocating Engines • Most common form of fuels is hydrocarbons • derived from petroleum • Gasoline and kerosene offer several advantages: • They are volatile • Evaporate quickly • High heat content which means high potential energy to be converted to kinetic energy as the fuel burns • Do not deteriorate when stored over long periods of time
FLIGHT POWER • Know basic engine principles. • 1. Define a list of terms related to basic engine principles. • 2. Describe the mechanical, cooling, and ignition systems of the reciprocating engines.