Classification by Nozzle Structure
This is the primary method for distinguishing diesel engine injectors, mainly categorized into the following two types:
Orifice-type injector: Composed of a needle valve and needle valve body (collectively known as the needle valve assembly), featuring multiple small-diameter orifices on the nozzle face. Characterized by high injection pressure and excellent atomization, it is suitable for direct-injection combustion chambers demanding high spray quality. However, its fine orifices require high fuel cleanliness and exhibit poor self-cleaning capability.
Shaft-needle injector: Features a shaft needle extending from the lower end of the needle valve. Fuel is ejected through the annular gap between the shaft needle and the needle valve body. It has relatively larger orifices and lower injection pressure but offers excellent self-cleaning capability and resistance to clogging. Suitable for swirl chambers or prechambers (also known as partitioned combustion chambers).
Other Classification Methods
Beyond the primary structural classifications above, injectors can be categorized by other characteristics:
By Operating Mode:
Classified as open-type or closed-type. Open-type injectors feature simple construction but are prone to dripping, making them rarely used in modern diesel engines. Closed-type injectors are the most widely adopted, with their needle valves precisely controlling fuel injection start and stop.
By Electromagnetic Coil Resistance Value: Classified as high-resistance (13–16Ω) and low-resistance (2–3Ω). High-resistance types offer slower response but more precise control, suitable for engines requiring accurate fuel consumption regulation; low-resistance types generate stronger magnetic fields and faster needle valve opening, ideal for high-speed engines.
By number of injection holes: Single-hole, dual-hole, and multi-hole types exist. Multi-hole injectors produce a more uniform fuel mist, enhancing combustion efficiency.
By application: Injectors are categorized for use in multi-point injection (MPI) and single-point injection (SPI) systems.
By installation and fuel delivery method: Cylinder-direct injection and external pump-nozzle types, among others.
In summary, orifice-type injectors and needle-valve injectors are the two most common and fundamental types in diesel engines. Their selection primarily depends on the design configuration of the engine combustion chamber.
