Spatially resolved gas phase composition measurements in supersonic flows using tunable diode laser absorption...

Area of Science:

• Physical Chemistry
• Fluid Dynamics
• Spectroscopy

Background:

• Condensation processes in supersonic flows are crucial for understanding various natural and industrial phenomena.
• Accurate measurement of vapor concentration and temperature during phase transitions is experimentally challenging.
• Supersonic Laval nozzles are used to achieve high-speed gas flows and study condensation dynamics.

Purpose of the Study:

• To investigate the condensation of heavy water (D2O) in a supersonic Laval nozzle.
• To compare spectroscopic measurements with static pressure measurements during condensation.
• To analyze discrepancies between measurement techniques and their implications for boundary layer behavior.

Main Methods:

• Utilizing a tunable diode laser absorption spectrometer to monitor D2O condensation.
• Measuring vapor concentration and spectroscopic temperature along the nozzle.
• Comparing spectroscopic data with results from static pressure measurements.

Main Results:

• Good quantitative agreement between spectroscopic and pressure measurements upstream and in early condensation stages.
• Downstream, spectroscopic data indicated lower gas phase concentration and higher temperature than pressure measurements.
• Spectroscopic results predicted a higher condensate mass fraction compared to pressure-based inferences.

Conclusions:

• Discrepancies between spectroscopic and pressure measurements increase downstream.
• The observed differences are consistent with boundary layer compression effects induced by condensation.
• Spectroscopic methods provide valuable, detailed insights into condensation dynamics in supersonic flows.