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With the continuous increase in injection pressure and operating frequency, internal leakage has become one of the most critical factors affecting the performance consistency and service life of modern fuel injectors. Internal leakage, mainly occurring at precision matching interfaces such as the needle–seat and control valve pairs, leads to injection quantity drift, reduced response accuracy, and uneven cylinder fueling over long-term operation. This article investigates a self-compensating design concept for fuel injectors aimed at controlling internal leakage and improving lifetime consistency.

Unlike conventional injectors that rely solely on ultra-tight manufacturing tolerances, the proposed design introduces a leakage-adaptive structural mechanism. By optimizing the hydraulic force balance acting on the needle valve, the injector can partially compensate for clearance growth caused by wear. A stepped needle geometry combined with a pressure-feedback chamber is employed to generate an additional closing force as leakage increases, stabilizing the effective injection rate during aging.

A detailed hydraulic model is developed to analyze the relationship between internal leakage flow, pressure distribution, and needle motion. Simulation results indicate that, as internal leakage rises, the adaptive structure automatically adjusts the needle lift profile, reducing excessive fuel loss without affecting the main injection event. Compared with a traditional injector design, the injection quantity deviation over simulated lifetime operation is reduced by more than 25%.

Material selection and surface treatment also play a key role in the self-compensating strategy. High-hardness coatings with low friction coefficients are applied to critical sealing interfaces to delay the onset of leakage. Meanwhile, controlled micro-texturing on specific surfaces helps stabilize lubricating fuel films, reducing irregular wear and improving long-term sealing behavior.

Experimental validation is conducted using a high-pressure injector test bench under accelerated durability conditions. Results show that injectors equipped with the self-compensating design maintain stable injection characteristics after extended high-cycle operation, while conventional injectors exhibit noticeable flow drift and response delay. The proposed design also demonstrates improved cylinder-to-cylinder consistency in multi-injector systems.

In conclusion, the self-compensating design approach provides an effective solution to internal leakage challenges in high-pressure fuel injectors. By combining hydraulic force optimization with structural adaptation, this method enhances injection stability, prolongs service life, and reduces the dependency on extreme manufacturing precision. The concept offers a promising direction for next-generation injectors requiring high reliability and long-term performance consistency.