MDE Unit 5 Q2

Key components to include in your cross-section:

• Injector body: The outer casing that houses the internal components.
• Nozzle holder: The part that holds the nozzle and seals it to the injector body.
• Nozzle: The part with the tiny holes where the fuel is injected.
• Needle valve: The component that controls the opening and closing of the fuel passage.
• Spring: The spring that returns the needle valve to the closed position.
• Hydraulic or electronic actuator: Depending on the injector type, this component controls the needle movement.
• Fuel inlet and outlet ports: The points where fuel enters and exits the injector.
• Cooling channels: If present, these channels help to regulate the injector temperature.

Additional details to consider:

• Nozzle hole shape and number: Indicate the type of nozzle (single-hole, multi-hole, pintle).
• Sac (if present): Some injectors have a small chamber near the nozzle tip to improve atomization.
• Hydraulic lines: If applicable, show the hydraulic lines connecting the injector to the high-pressure pump or common rail.

Remember: The specific components and their arrangement may vary depending on the type of fuel injector (common rail, unit injector, etc.).

By including these components in your cross-section, you will provide a clear representation of a diesel fuel injector’s internal structure and function.

Atomization in the context of diesel engines refers to the process of breaking down liquid fuel into a fine mist of tiny droplets before it’s injected into the combustion chamber. This is a crucial step for efficient combustion.

Why is Atomization Important in Diesel Engines?

• Increased surface area: Smaller droplets have a larger surface area, which promotes faster evaporation and better mixing with air.
• Improved combustion: A well-atomized fuel-air mixture burns more completely, releasing more energy and reducing emissions.
• Reduced ignition delay: Fine fuel droplets ignite more quickly, reducing the time between injection and combustion.

Factors Affecting Atomization:

• Fuel properties: Viscosity, surface tension, and density influence droplet size.
• Injection pressure: Higher pressure leads to finer atomization.
• Nozzle design: The shape and size of the nozzle holes affect the spray pattern and droplet size.
• Ambient conditions: Temperature and pressure in the combustion chamber influence fuel evaporation and droplet formation.

In essence, atomization is a critical factor in determining the efficiency and performance of a diesel engine.

Opens in a new windowwww.researchgate.net

diesel fuel atomization

Penetration in the context of diesel engines refers to the distance the injected fuel spray travels into the combustion chamber before it starts to vaporize and mix with the air.

Factors Affecting Penetration

• Injection pressure: Higher injection pressure results in greater penetration.
• Nozzle geometry: The shape and size of the injector nozzle influence the spray pattern and penetration.   1. (PDF) Effect of injector nozzle geometry of diesel engines on the macroscopic spray characteristics by means of optical techniques – ResearchGate www.researchgate.net
• Fuel properties: Fuel viscosity, density, and surface tension impact how far the fuel travels before breaking up.
• Ambient conditions: Temperature and pressure within the combustion chamber can affect fuel vaporization and penetration.

Importance of Penetration

• Sufficient Mixing: Adequate penetration ensures proper mixing of fuel and air, leading to complete combustion.
• Ignition Delay: Penetration affects the ignition delay, which is the time between fuel injection and the start of combustion.
• Combustion Efficiency: Proper penetration contributes to higher combustion efficiency and lower emissions.

Over-penetration: Excessive penetration can lead to poor mixing, increased ignition delay, and potentially lower combustion efficiency. Under-penetration: Insufficient penetration can result in delayed ignition, increased emissions, and potential engine knocking.