Pressure measurement in gas flows using laser-induced grating lifetime.

Area of Science:

• Optical diagnostics
• Laser-induced grating scattering (LIGS)
• Gas-phase property measurement

Background:

• Optical diagnostics for gas-phase pressure are uncommon.
• Existing LIGS pressure measurement methods are slow and complex, requiring signal fitting and specialist knowledge.

Purpose of the Study:

• To develop a novel, rapid, and robust optical method for real-time gas-phase pressure determination.
• To simplify the analysis of LIGS signals for pressure measurement.

Main Methods:

• Directly measuring the decay lifetime of a laser-induced grating scattering (LIGS) signal.
• Utilizing a physics-based model to construct a calibration surface for converting decay lifetime to pressure.
• Applying the method to an optically accessible single-cylinder internal combustion engine.

Main Results:

• Achieved real-time gas-phase pressure measurements using LIGS.
• Demonstrated an accuracy of better than 10% for pressure measurements above atmospheric pressure.
• The new method provides pressure data with a simple analysis, complementing LIGS's temperature measurement capabilities.

Conclusions:

• A novel, rapid, and robust LIGS-based method for real-time gas-phase pressure measurement has been successfully demonstrated.
• This technique simplifies pressure diagnostics by directly measuring signal decay lifetime and using a physics-based calibration.
• The method offers a complementary and straightforward approach to optical thermometry for internal combustion engine analysis.