Which statement describes how diesel engines ignite fuel?

Which statement describes how diesel engines ignite fuel?

• A. Compression ignition
• B. Spark ignition
• C. External ignition
• D. Glow plug ignition assist

Answer: (A)

Diesel engines ignite fuel through compression heating of the air. In the cylinder, air is compressed to a high pressure, which raises its temperature to the point that it becomes hot enough to ignite diesel fuel. When fuel is injected into this hot, high-pressure air, it auto-ignites without any spark. This is different from spark ignition engines, which rely on a spark plug to ignite a premixed air-fuel mixture. External ignition isn’t used because there’s no outside energy source providing a flame or spark. Glow plugs can help by warming the cylinder air for easier starting in cold conditions, but they are not the normal ignition method during regular operation. The defining idea is that diesel combustion begins from the heat of compression, not from a spark or external ignition source.

Diesel engines ignite fuel through compression heating of the air. In the cylinder, air is compressed to a high pressure, which raises its temperature to the point that it becomes hot enough to ignite diesel fuel. When fuel is injected into this hot, high-pressure air, it auto-ignites without any spark. This is different from spark ignition engines, which rely on a spark plug to ignite a premixed air-fuel mixture. External ignition isn’t used because there’s no outside energy source providing a flame or spark. Glow plugs can help by warming the cylinder air for easier starting in cold conditions, but they are not the normal ignition method during regular operation. The defining idea is that diesel combustion begins from the heat of compression, not from a spark or external ignition source.