How a Diesel Engine Works

Summary

This video explains the operating principles of diesel engines used in various vehicles, from cars and pickup trucks to heavy-duty trucks. It details the process where clean air is drawn into the cylinder, compressed, and heated to high temperatures. Fuel is injected at high pressure, igniting spontaneously due to the heat, which powers the engine. The exhaust valve opens to expel gases, and the cycle repeats. The video also contrasts this with conventional gasoline engines, where a fuel-air mixture is ignited by a spark to generate power.

Takeaways

• 😀 Diesel engines rely on clean air being drawn into the cylinder, unlike gasoline engines that use a fuel-air mixture.
• 😀 The air is compressed by the piston, raising its temperature to a high level.
• 😀 Fuel is injected at high pressure into the hot compressed air, creating a fine spray that vaporizes quickly.
• 😀 Spontaneous ignition occurs due to the high temperature, eliminating the need for a spark plug.
• 😀 The combustion of the fuel generates pressure, forcing the piston downward and powering the vehicle.
• 😀 As the piston nears the bottom of its stroke, the exhaust valve opens, allowing the exhaust gases to exit.
• 😀 This exhaust stroke helps expel the spent gases, completing the cycle before it starts again.
• 😀 In contrast to diesel engines, gasoline engines use a fuel-air mixture that is compressed and ignited by a spark.
• 😀 The combustion in gasoline engines also generates pressure that forces the piston down to power the vehicle.
• 😀 Diesel engines typically operate at higher pressure and temperature than gasoline engines due to the nature of their ignition process.

Q & A

What is the main difference between diesel and gasoline engines in terms of their fuel-air mixture?

Diesel engines draw in only clean air, while gasoline engines draw in a mixture of fuel and air.

How is the air in a diesel engine compressed, and what effect does this have?

In a diesel engine, the air is compressed by the piston, which raises the temperature to a high level.

What role does the fuel injector play in a diesel engine?

The fuel injector sprays fuel under high pressure into the cylinder in the form of a fine mist, which vaporizes in the hot air.

Why does spontaneous ignition occur in a diesel engine without the need for a spark?

Spontaneous ignition occurs because the temperature of the compressed air is high enough to ignite the injected fuel as it vaporizes.

How does the combustion process in a diesel engine differ from that of a gasoline engine?

In a diesel engine, combustion occurs through spontaneous ignition, whereas in a gasoline engine, combustion is initiated by a spark.

What happens when the piston in a diesel engine reaches the lowest position?

The exhaust valve opens, and the exhaust stroke expels the spent gases from the combustion chamber.

What is the role of the exhaust stroke in a diesel engine?

The exhaust stroke helps drive out the spent gases from the combustion chamber, preparing the engine for the next cycle.

How does the piston movement contribute to the operation of both diesel and gasoline engines?

In both types of engines, the piston compresses the air-fuel mixture or air, and the pressure generated by combustion forces the piston down to power the vehicle.

What causes the pressure increase inside the cylinder of a diesel engine during combustion?

The rapid expansion of the combusting fuel-air mixture increases the pressure inside the cylinder, forcing the piston down.

What distinguishes the ignition mechanism in gasoline engines compared to diesel engines?

Gasoline engines use a spark to ignite the fuel-air mixture, while diesel engines rely on the high temperature of compressed air to ignite the injected fuel.