Estimation of High-Speed Liquid-Jet Velocity Using a Pyro Jet Injector

Area of Science:

• Fluid Dynamics
• High-Speed Jetting
• Injector Technology

Background:

• High-speed liquid jet velocity is crucial in various applications.
• Injector performance depends on piston motion, liquid properties, and container shape.
• Accurate velocity estimation is vital for optimizing injector design and function.

Purpose of the Study:

• To investigate the liquid ejection mechanism in a pyro jet injector (PJI).
• To develop and validate a technique for estimating high-speed liquid jet ejection velocity.
• To propose a simplified fluid dynamic model (FDM) for velocity prediction.

Main Methods:

• Utilized a two-dimensional numerical simulation with axisymmetric approximation (ANSYS/FLUENT).
• Captured piston motion using a high-speed CMOS camera and motion tracking software.
• Employed boundary-fitted coordinates and a moving boundary method to reproduce piston motion.
• Developed a fluid dynamic model (FDM) considering liquid density but neglecting viscosity.

Main Results:

• The FDM-estimated ejection velocity closely matched ANSYS/FLUENT predictions across various ignition-powder weights.
• Demonstrated that the FDM effectively estimates ejection velocity by accounting for liquid density variations.
• Observed rapid piston displacement (<0.1 ms), piston vibration with large powder charges, and a short pulse jet flow (0.1 ms).

Conclusions:

• The proposed FDM provides a reliable method for estimating high-speed liquid jet ejection velocity.
• The FDM's accuracy is confirmed when liquid density variation is considered and viscosity is neglected.
• The study characterizes key operational aspects of the pyro jet injector (PJI).