Introducing 

Prezi AI.

Your new presentation assistant.

Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.

Loading…
Transcript

To the First Diesel Four-Stroke

The Citroen 7U (Rosalie) (1933)

Image source: Google Images (16/09/12)

The Diesel Four-stroke

Combustion (Bang)

The four-stroke here is similar to the petrol cycle however in the first stroke it is not an air and fuel mix pulled into the engine; it is only air.

The air is then compressed to a high pressure, thus causing it to reach temperatures of around 600 degrees.

This is the controlled burning of the air and fuel mix in the cylinder.

This is what creates the power to move the flywheel and hence the gearbox and wheels!

The burn pushes the piston down turning the camshaft via the connecting rod (con rod).

Again both valves remain closed.

The exhaust valve remains closed.

Inlet Valve is opened to allow in air and fuel mix.

The piston moves down.

Image source: Google Images (13/09/12)

The Four-Stroke Cycle

The air and fuel mix is compressed to a ratio of 10:1 in the cylinder.

Both valves remain closed.

Easily described as:

Suck,

Squeeze,

Bang,

Blow.

The piston moves up, compressing the air and fuel mix.

Image source: Google Images (13/09/12)

Induction (Suck)

This is the first stroke of a piston in the four-stroke cycle.

It involves the taking in of an air and fuel mix to the cylinder. The inlet valve is opened to allow this to happen.

The cylinder moves down in this stroke.

Thank You

Exhaust (Blow)

The exhaust stroke is the final stroke in the cycle.

It involves blowing out the used gases from the combustion stroke. These gases are what come out of the exhaust.

This piston moves up and pushes the gases out of the open exhaust valve.

The Valves (Poppet Valves)

A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapour flow into an engine. It consists of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide.

Poppet valves date from at least the 1770s, when Watt used them on his beam engines.

Compression (Squeeze)

This second stroke involves the piston moving up and compressing (or squeezing) the air and fuel mix. This energizes the particles causing them to warm up.

Both valves are closed during this stroke.

The exhaust valve is open in this stroke, allowing the waste gases to escape.

The waste gases are pushed out through the open valve.

Image source: Google Images (13/09/12)

The Diesel Four-stroke (cont.)

The Four-Stroke Cycle of the Internal Combustion Engine

At the end of the second (compression) stroke, as the piston reaches top dead centre (TDC), the fuel is injected into the cylinder as a fine mist.

The extreme heat from the compressed air is enough to ignite the fuel and cause the combustion stroke.

The exhaust stroke is then the same as in the SI four-stroke.

Alex Morse

BTEC Communications for Technicians

Or in proper terminology:

Induction

Compression

Combustion (or Power)

Exhaust

The four-stroke cycle

is also known as the

Otto cycle; due to Nicolaus Otto inventing it.

Image source: Google Images (14/09/12)

The First Application of a Four-Stroke in a Car

The Benz Patent-Motorwagen (1886)

Image source: Google Images (16/09/12)

Differences Between SI & CI

SI

CI

Air & fuel mix injected.

Lighter materials can be used.

Petrol is highly volatile.

Compression ratio is around 10:1.

Controlled by quantity of air & fuel.

Only air is injected.

Heavier materials are needed to handle extreme pressures and temperatures.

Diesel is a less volatile substance.

Compression ratios can be up to 23:1.

Controlled by quantity of fuel only.

Variations

A variation of the four-stroke cycle is the diesel four-stroke cycle. This is more commonly known as the compression ignition (CI) as apposed to the sparking ignition (SI) used in petrol four-strokes.

Image source: Google Images (13/09/12)

The spark plug causes the compressed air and fuel mix to ignite and burn rapidly.

Again both the inlet and exhaust valves remain closed.

Image source: Google Images (13/09/12)

Learn more about creating dynamic, engaging presentations with Prezi