Injector nozzles operate under high temperature and pressure conditions, which make them susceptible to deposit formation during long-term engine operation. These deposits gradually accumulate on internal surfaces and spray holes, influencing fuel flow behavior and spray quality.
Nozzle deposits are mainly formed from fuel degradation products and additives. Under high temperature, fuel components may oxidize or polymerize, creating sticky residues that adhere to nozzle surfaces. Incomplete combustion and backflow of hot gases can further accelerate deposit formation at the nozzle tip.
As deposits build up, the effective diameter of spray holes is reduced. This restriction increases flow resistance and alters injection quantity. Reduced hole size also changes spray velocity and penetration, leading to poor fuel atomization and uneven distribution in the combustion chamber.
Deposits may also affect needle movement. Accumulated residues around the needle seat increase friction and disturb sealing behavior. This can result in delayed needle closing or minor fuel dripping after injection, contributing to increased emissions and fuel consumption.
The impact of deposits is particularly noticeable during low-load and cold-start conditions. At low injection quantities, small flow restrictions have a relatively larger effect, causing injection instability and combustion irregularities. Cold starts may be further affected due to reduced fuel volatility and higher fuel viscosity.
Fuel quality plays a significant role in deposit formation. Fuels with poor thermal stability or high impurity levels tend to produce more deposits. The use of detergent additives helps reduce deposit accumulation by keeping nozzle surfaces clean.
To mitigate deposit-related issues, nozzle design may focus on smoother internal surfaces and optimized spray hole geometry to reduce deposit adhesion. Regular maintenance and periodic injector cleaning can help restore nozzle performance.
In summary, deposit formation in injector nozzles is a major factor affecting long-term injection performance. Understanding deposit mechanisms and implementing effective prevention measures are essential for maintaining stable and efficient fuel injection.
