The sealing structure design for aluminum fuel nozzles must focus on material properties, structural optimization, process control, and supporting measures. This multi-dimensional synergy ensures long-term stable operation of the fuel system under high pressure, high temperature, and complex operating conditions, preventing safety hazards and performance degradation caused by leakage.
The selection of aluminum materials is fundamental to the sealing structure. Aluminum and aluminum alloys offer low density, corrosion resistance, and ease of processing, but alloying modifications are necessary to optimize the fuel environment. For example, adding elements such as magnesium and silicon to create high-strength aluminum alloys improves creep resistance and reduces plastic deformation under long-term high pressure. Surface treatments such as anodizing or plating create a dense oxide film, which protects the substrate from corrosion by sulfides and acids in the fuel, preventing damage to the sealing surface due to material degradation.
The core design of the sealing structure lies in the creation of a multi-level barrier. Aluminum fuel nozzles typically utilize a combined sealing solution: the first stage is a metal-to-metal hard seal. Through precision machining, the nozzle housing and connector mating surfaces achieve micron-level flatness, leveraging the elastic deformation of the aluminum material to achieve an initial seal. The second stage is a soft seal compensation, adding an oil-resistant rubber ring or fluoroplastic gasket to the hard seal. Its low compression set properties can fill gaps caused by machining errors and thermal expansion and contraction. The third stage is a dynamic seal protection. To combat high-pressure fuel pulses, a spring-loaded sealing ring is designed. The spring preload offsets pressure fluctuations and ensures continuous sealing contact.
Structural optimization requires addressing the high thermal expansion coefficient of aluminum. Aluminum fuel nozzles operate over a wide temperature range, and aluminum's thermal expansion is significantly greater than that of mating components (such as stainless steel valve cores), which can easily lead to variations in the interference fit of the sealing surface. "Thermal matching" structures are often employed in designs: compensating gaps are reserved at key contact points, or alloys with thermal expansion coefficients similar to aluminum are selected as matching materials. Simulation analysis is also used to optimize the length-to-diameter ratio of the sealing surface to control the impact of thermal deformation on the sealing pressure distribution and avoid leakage caused by localized stress concentration.
Precision control in the manufacturing process is crucial for sealing reliability. The sealing surface of aluminum fuel nozzles requires ultra-precision machining techniques, such as single-point diamond turning or grinding and polishing, to ensure a surface roughness below Ra0.2μm, minimizing leakage paths caused by microscopic defects. Assembly utilizes a low-temperature assembly process to minimize the impact of aluminum thermal expansion on the interference fit. The sealing assembly is secured by laser welding or cold riveting to prevent vibration-induced loosening. Furthermore, the internal oil circuit of the nozzle is integrally forged or 3D-printed, reducing the number of welded joints and mitigating leakage risks at the source.
Auxiliary sealing measures can further enhance system safety. For example, a dual-stage filter structure is designed at the nozzle inlet to intercept impurities in the fuel and prevent them from scratching the sealing surface. An integrated pressure monitoring sensor provides real-time feedback on pressure changes in the seal chamber, triggering an alarm or automatically shutting off the fuel supply when the pressure drops abnormally. For high-temperature environments such as aircraft engines, thermal insulation coatings or film cooling technologies are used to reduce the temperature in the sealing area and slow the aging of rubber seals.
Long-term maintenance strategies are equally important. Regularly replace the fuel filter to prevent impurity accumulation and wear on the sealing surface. Select sealing materials with temperature resistance levels that match the operating environment. For example, perfluoroelastomer (PFEE) is used in the aviation industry to withstand extreme temperatures ranging from -55°C to 200°C. Establish sealing performance testing standards, using airtightness tests or fluorescent penetrant testing to promptly identify and repair potential leaks.
