🔍 Key Concepts

• Fuel atomization – how finely the fuel is broken into small droplets as it leaves the injector nozzle • Penetration – how far the fuel spray travels into the compressed air in the cylinder • Relationship between droplet size, spray cone shape, and air–fuel mixing in a diesel cylinder

💭 Think About

• Think about what happens when fuel is broken into very fine droplets versus large droplets – which travels farther into the air charge? • How does a finer spray affect the contact area between fuel and air, and what does that do to the spray’s ability to ‘push’ deeply into the cylinder? • Consider how injection pressure and nozzle design change both atomization and the distance the spray can reach.

✅ Before You Answer

• Be clear on the difference between atomization (droplet size) and penetration (spray distance) – they are not the same thing. • Visualize a spray nozzle: as you increase fineness of the spray, what happens to spray momentum and thus to how far it can penetrate? • Eliminate any choice that says atomization and penetration are identical processes or completely unrelated; focus on how one typically affects the other.