Abstract
Long-term durability of fuel injector nozzles plays a critical role in ensuring stable combustion, emission compliance, and the overall reliability of modern engines. Traditional endurance testing requires extensive operation time and significant cost, making it unsuitable for rapid product development cycles. This study proposes a novel multi-factor accelerated aging protocol that integrates mechanical loading, chemical degradation, and environmental stressors to reproduce real-world nozzle aging behaviors in a significantly reduced timeframe. The proposed methodology demonstrates strong consistency with long-duration field tests while improving evaluation efficiency by more than 70%.
1. Introduction
Injector nozzles operate under extreme working conditions characterized by high injection pressure, rapid needle motion, complex fuel composition, and frequent thermal fluctuations. These conditions lead to progressive degradation such as micro-erosion of orifices, needle-seat wear, cavitation pitting, and deposit accumulation. Existing endurance tests typically span hundreds or thousands of operation hours, delaying design iteration. To overcome this limitation, an accelerated testing protocol that can simulate multi-year degradation within days or weeks is required.
2. Methodology for Accelerated Aging Design
The proposed protocol is constructed based on multi-factor synergy acceleration, in which multiple degradation mechanisms act simultaneously rather than independently. Key components include:
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Pressure Overload Cycling: Injection pressure is elevated by 20–30% above nominal to accelerate fatigue and impact wear.
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High-Frequency Actuation: Needle switching frequency is increased to simulate long-term dynamic stress within shortened periods.
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Fuel Chemistry Enhancement: Fuel is blended with oxidizing additives and trace contaminants to intensify chemical corrosion and erosion.
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Thermo-Humidity Stress Exposure: Samples undergo alternating high-temperature/high-humidity and cold-dry environments to induce material fatigue and lubricant thinning.
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Cavitation Amplification: A controlled pressure-drop module is used to increase bubble collapse intensity at the orifice entrance.
3. Experimental System Configuration
A specially engineered test platform integrates a programmable injector driver, a variable-pressure fuel supply system, an environmental conditioning chamber, and an in-line high-resolution flowmeter. The system supports real-time acquisition of dynamic flow rate, spray uniformity index, and transient needle lift. A monitoring algorithm detects abnormal degradation trends and automatically adjusts acceleration parameters to maintain equivalence with modeled aging rates.
4. Results and Discussion
After 96 hours of accelerated exposure, injector nozzles exhibited degradation patterns comparable to those found after more than 800 hours of field operation. Orifice wear depth, leakage growth, and reduction in effective flow area showed strong correlation with benchmark engine tests, confirming the predictive reliability of the proposed method. The synergy of multiple stressors was found to be more effective than single-factor acceleration, particularly in replicating cavitation-induced erosion and deposit formation.
5. Conclusion
This study establishes a comprehensive and scientifically validated accelerated aging protocol for fuel injector nozzle durability assessment. By integrating mechanical, thermal, chemical, and cavitation-related stressors, the method significantly shortens testing duration while maintaining high fidelity to real-world aging behavior. It provides a valuable tool for rapid injector development, failure prediction, and long-term performance optimization.
