Miniature rainbow schlieren deflectometry system for quantitative measurements in microjets and flames

Area of Science:

• Fluid dynamics
• Optical diagnostics
• Microscale phenomena

Background:

• Small-scale flow devices require high-resolution measurement tools.
• Existing methods may lack the necessary spatial resolution for microscale flows.
• Nonintrusive techniques are preferred for accurate scalar property determination.

Purpose of the Study:

• To develop and demonstrate a miniature rainbow schlieren deflectometry system.
• To achieve high spatial resolution for quantitative flow property measurements.
• To validate the system's capability in microscale jets and flames.

Main Methods:

• Utilized a miniature rainbow schlieren deflectometry system with achromatic lenses and a CCD array.
• Achieved high spatial resolution (down to 4 microm) using camera lenses and extension tubes.
• Performed quantitative concentration and temperature measurements in microjets and diffusion flames.

Main Results:

• Successfully obtained quantitative species concentration data in a helium microjet.
• Measured temperature and concentration in a hydrogen jet diffusion flame from a microinjector.
• Visualized underexpanded nitrogen jets, revealing shock structures.

Conclusions:

• The miniature rainbow schlieren deflectometry system is effective for nonintrusive, whole-field measurements in microscale flows.
• The system provides high spatial resolution for detailed analysis of complex flow phenomena.
• Demonstrated applicability in micro-combustion and jet flows, paving the way for advanced microfluidic research.