Optical particle sizing for in situ measurements Part 1

Area of Science:

• Fluid dynamics and particle analysis
• Optical measurement techniques
• Combustion diagnostics

Background:

• Accurate in situ particle sizing is crucial for understanding two-phase flows.
• Existing methods often lack the capability for real-time, high-temperature measurements.
• Challenges include particle trajectory dependence and signal interpretation.

Purpose of the Study:

• To develop and validate a particle sizing counter for in situ measurements in two-phase flows.
• To enable accurate particle size distribution determination under harsh conditions.
• To address limitations of existing particle sizing techniques.

Main Methods:

• Utilizes near forward-scatter from a He-Ne laser beam and pulse-height analysis.
• Employs a novel numerical inversion scheme to correct for particle trajectory.
• Features a 50 cm working distance for optical elements and on-line computer processing.
• Calibrated using monodisperse aerosols of known size.

Main Results:

• Demonstrated capability for size distributions from 1-30 micrometers at concentrations up to 10^5 cm^-3.
• Successfully measured particle sizes in flows up to 1600 K.
• Results show good agreement with Mie scattering theory predictions.

Conclusions:

• The developed particle sizing counter provides accurate in situ measurements in challenging environments.
• The technique is adaptable for absorbing and irregular particles.
• Anticipated extensions include a wider size range (0.5-50 micrometers) and higher concentrations (10^6 cm^-3).