Function of Diesel Engine Injectors
As a critical component of diesel engines, injectors primarily atomize fuel into fine particles and precisely inject them into the combustion chamber. This ensures thorough mixing with air to form a combustible mixture.
The injector's importance lies in ensuring fuel delivery follows the "low-high-low" principle during each injection cycle. Additionally, it must maintain stable injection pressure, appropriate spray range, optimal spray cone angle, and high-quality atomization to prevent dripping.
Types and Structure of Injectors
Currently, closed-type injectors are widely used in diesel engines, with subtypes including orifice-type and needle-valve-type injectors. The core component of a closed-type injector is the nozzle, which consists of a needle valve and needle valve body precisely matched with a clearance controlled between 0.002 and 0.004 mm. This high-precision fit requires meticulous grinding, making interchangeability during use inadvisable. The needle valve is typically manufactured from high-speed steel with excellent thermal stability, while the needle valve body is made from impact-resistant high-quality alloy steel.
Construction of Orifice Injectors
Orifice injectors primarily consist of a needle valve assembly, push rod, pressure-regulating spring, pressure-regulating screw, and injector body. This injector type is particularly suited for diesel engines with direct-injection combustion chambers. The nozzle head is precision-machined with one or more injection holes. Based on the number of holes, they are classified as single-hole, dual-hole, or multi-hole injectors, with hole diameters typically ranging from 0.2 to 0.5 mm.
Structural Characteristics of Axial-Needle Injectors
The shaft-needle type injector differs structurally from the orifice-type injector. Below the sealing cone surface at the lower end of the needle valve, a shaft-needle extends outward. This shaft-needle is either inverted conical or cylindrical in shape. Due to the shaft-needle design, the spray orifice forms a ring-shaped slit. This configuration creates a hollow conical or hollow cylindrical spray pattern during fuel injection.
