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 Pressu

re

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

Gas Pressu

re

14.7 psi

29.4 psi 58.8

psi

100 500

250

100 500

250

100 500

250

Reciprocating Engines

Internal or External Combustion?

Mechanical System

• Cylinder

• Piston

• Crankshaft

• Connecting Rod

• Valves

Mechanical SystemCylinderCylinder

•Known as the engine’s combustion chamber

• Where the power is developed

Mechanical SystemPiston

• Fits snugly in the hollow cylinder allowing up-and-down linear (straight) motion

• Fit will not allow air or fluid in the cylinder

Mechanical SystemCrankshaft

• The crankshaft and connecting rod allow for the movement of the propeller.

Mechanical SystemConnecting Rod

• Attached to the throws

• With the crankshaft, they change the direction of the pistons into a circular motion

Mechanical SystemValves

• A rocker arm regulates the opening and closing of each valve.

• Lobes or rings on a camshaft push the rocker arm

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

• 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 1

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

Four – Stroke Cycle – Process

• 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.

Cooling System

• Must receive an electrical spark originating in the magneto

Ignition System

Types of Reciprocating Engines

In-line Engines

• Cylinders are located in a row, one behind the other

• Two classifications:

• Upright

• Inverted

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

Types of Reciprocating Engines

http://www.youtube.com/watch?v=KJPf-8p37I0&feature=relmfu

• 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

Fuels Used in Reciprocating Engines

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.