Regional Gliding School Types of Reciprocating Engines QThere are three main types of piston engines in current use: –Horizontally Opposed –Radial –In-Line

Regional Gliding School

Types of Reciprocating Engines

There are three main types of piston engines in current use:

– Horizontally Opposed

– Radial

– In-Line


Horizontally Opposed• Two banks of cylinders

which lie directly opposite to each other in the horizontal plane.

• Four, six or eight cylinders.

• Design is flat with small frontal area (good visibility) and low drag production.

• Most commonly used in general aviation.


Radial• Cylinders arranged radially.

• Always an odd number of cylinders.

• Crankshaft is short, compact and light.

• Produces tremendous horsepower.

• Poor shape increases parasite drag and reduces forward visibility.


In-Line• Cylinders are arranged

side by side in a row.• Practical limit is six.• Any more cylinders and

V, X or H-type in-line engines are used.

• Two crankshafts side by side.

• Some are inverted for better visibility.

• Little drag but heavier engine and size limited.

Confirmation Stage

NOTE: You must use the buttons in the Confirmation Stage


Aero EnginesAero EnginesBasic construction and the four stroke cycleBasic construction and the four stroke cycle

A

B

C

D

Radial

In Line

Horizontally Opposed

V6

Let's try a few review questions on Aero Engines:

Question #1 - What type of engine is the most commonly used in general aviation?

I’m afraid that answer is incorrect

Let's try again...

Flying Scholarship Program


Let's try again...



Let's try again...



That answer is correct.

Let's move on...

Regional Gliding School (Atlantic)

Horizontally Opposed• Two banks of cylinders

which lie directly opposite toeach other in the horizontalplane.

• Four, six or eight cylinders.

• Design is flat with smallfrontal area (good visibility)and low drag production.

• Most commonly used ingeneral aviation.



A

B

C

D

Poor visibility

Short crankshaft

Size is limited


Question #2 - What is an disadvantage of using a radial engine?

Heavy crankshaft


Let's try again...



Let's try again...



Let's try again...




Let's move on...


Radial• Cylinders arranged radialy.

• Always an odd number ofcylinders.

• Crankshaft is short, compactand light.

• Produces tremendoushorsepower.

• Poor shape increases parasitedrag and reduces forwardvisibility.


Construction of a Reciprocating Engine

• Piston - Cylinder shaped object that moves up and down.

• Piston Rings - wrap around the piston and provide a seal between the piston and cylinder.

• Connecting Rod - joins the piston to the crankshaft, which turns the propeller.

• Cylinder Head - contains the inlet (intake) valve, exhaust valve and two spark plugs.


Construction of a Reciprocating Engine

• Camshaft - turned by the crankshaft and operates the push rods and rocker arms. It turns at half the speed the crankshaft turns.

• Magnetos - provide electrical current to ignite the Fuel/Air mixture through the distributor.

• Intake Valve Ports - allow air to enter the cylinder and is connected to the carburetor where the air and fuel are mixed.

• Exhaust Valve - connected to the exhaust pipe, which vents the exhaust fumes away from the cabin.


Piston

Spark Plugs

Cylinder

Intake Valve

ExhaustValve

Connecting Rod

Crankshaft

Major Engine Components


The Four Stroke Cycle Most piston engines operate on the four stroke cycle. The piston moves through four strokes, two up and

two down, to complete the cycle. The crankshaft makes two complete revolutions. The four strokes are:

the induction (or intake) stroke, the compression stroke, the power (or combustion) stroke, and the exhaust stroke.


The Induction (or Intake) Stroke

Intake valve is open.

Piston moves down.

Fuel/air mixture drawn into combustion chamber through intake valve.

Exhaust valve remains closed.


The Compression Stroke

Both valves are closed.

Piston moves up.

Mixture is compressed.

Compression ratio is comparison of volume of mixture with piston at the bottom and volume with piston at the top.


The Power (or Combustion) Stroke


Compressed mixture is ignited by spark plug.

Burning gas expands forcing piston down.

Energy drives other three strokes as well as useful work (i.e.. turn propeller).


The Exhaust Stroke

Exhaust valve is open.

Piston moves up.

Burnt gas is pushed out through exhaust valve.

Intake valve remains closed.


Timing The purpose of timing is to improve the

performance of the engine.

Valves take time to open and close.

Therefore they are timed to open early and close late in order not to waste any of the induction or exhaust stroke.


Timing the valve to open early.

Timing the valve to close late.

Allowing both valves to remain open at the same time.

Valve Lead

Valve Lag

Valve Overlap


Valve Clearances

Valve clearance, or tappet clearance, is a space that must be provided between the valve stem and rocker to allow for heat expansion of the metal.

Clearances too wide cause a loss of power and excessive wear.

Clearances too close can warp the valves.

Confirmation Stage

NOTE: You must use the buttons in the Confirmation Stage



A

B

C

D

Power

Compression

Exhaust


Question #3 - Name the second stroke in the four stroke engine?

Intake


Let's try again...



Let's try again...



Let's try again...




Let's move on...


The Four Stoke CycleMost piston engines operate on the four stroke cycle.

The piston moves four strokes, two up and two down, to complete the cycle.

The crankshaft makes two complete revolutions.

The four strokes are: the induction (or intake) stroke,

the compression stroke,

the power (or combustion) stroke, and

the exhaust stroke.



A

B

C

D

Power

Compression

Exhaust


Question #4 - During which stroke do the spark plugs fire?

Intake


Let's try again...



Let's try again...



Let's try again...




Let's move on...


The Power (or Combustion) Stroke


Compressed mixture is ignited by spark plug.

Burning gas expands forcing piston down.

Energy drives other three strokes as well as useful work (i.e.. turn propeller).



A

B

C

D

Valve closes late

Both valves remain open

Both valves remain closed


Question #5 - What is the definition of valve lag?

Valve closes early


Let's try again...



Let's try again...



Let's try again...




Let's move on...


Timing the valve to open early.

Timing the valve to close late.

Allowing both valves to remainopen at the same time.

Valve Lead

Valve Lag

Valve Overlap


Congratulations!!

You have now completed the Basic Construction and the Four Stroke Cycle lesson of the Aero Engines Module. Of course, this lesson is always available to you for future reference if required.

You are now ready to move along to the next Aero Engines lesson you have not completed or to any other module you wish. You can advance to the Self Test Module if you feel ready to challenge the final exam.

Good Luck!


Documents

Regional Gliding School Types of Reciprocating Engines QThere are three main types of piston engines in current use: –Horizontally Opposed –Radial –In-Line