A novel semi-flexible coaxial nozzle based on fluid dynamics effects and its self-centering performance study

Area of Science:

• Materials Science
• Mechanical Engineering
• Fluid Dynamics

Background:

• Conventional coaxial nozzles struggle with real-time coaxiality adjustment, leading to uneven fiber wall thickness.
• Poor coaxiality in fiber production results in defects and reduced quality of core-shell structures.
• Existing designs lack dynamic self-centering mechanisms to correct needle misalignment during operation.

Purpose of the Study:

• To develop and validate an innovative semi-flexible coaxial nozzle with a dynamic self-centering function.
• To investigate the influence of fluid dynamics and material properties on nozzle coaxiality.
• To provide a solution for real-time correction of coaxiality errors in fiber production.

Main Methods:

• Established a self-centering model for coaxial nozzles based on fluid dynamics and fluid-structure interaction principles.
• Utilized finite element simulation to analyze the impact of external fluid velocity and inner needle elastic modulus on centering time and coaxiality error.
• Performed online observation of the coaxial extrusion process and measured wall thickness to verify self-centering performance.

Main Results:

• Coaxiality error was found to increase with higher Young's modulus and decrease with increased flow velocity.
• Centering time for inner needle force balance reduced with increased Young's modulus and fluid velocity.
• The nozzle dynamically reduced initial coaxiality error from 380 to 60 μm within 26 seconds, controlling manufacturing errors within 8 μm.

Conclusions:

• The proposed semi-flexible coaxial nozzle with dynamic self-centering effectively addresses real-time coaxiality challenges.
• The design significantly improves the uniformity of fiber wall thickness and overall quality of core-shell fibers.
• This research offers valuable solutions for mitigating coaxiality errors in advanced fiber manufacturing processes.