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Temperature measurements in a laser-heated gas by quantitative shadowgraphy
Applied Optics
|May 22, 2010
Summary
A novel quantitative shadow imaging technique precisely measures gas temperatures during laser ignition experiments. This method offers high spatial and temporal resolution for detailed analysis of combustion processes.
Area of Science:
- Combustion Science
- Optical Diagnostics
- Laser Physics
Background:
- Laser ignition is crucial for controlled combustion.
- Accurate temperature measurement is vital for understanding ignition dynamics.
- Existing methods may lack sufficient spatial or temporal resolution.
Purpose of the Study:
- To develop and validate a whole-field quantitative shadow method for temperature determination.
- To assess the method's spatial and temporal resolution capabilities.
- To compare shadow temperature measurements with established techniques like Rayleigh scattering.
Main Methods:
- Utilized a CO(2) laser to heat an ethylene-air mixture.
- Employed a collimated laser beam for illuminating the hot gas.
- Recorded and digitally analyzed shadow images.
- Performed computer simulations to evaluate parameter sensitivities.
Main Results:
- Achieved high spatial (15 microm) and temporal (10 ns) resolutions.
- Demonstrated good agreement between shadow measurements and Rayleigh light scattering (1-4% difference).
- Quantified the impact of diffraction and parameter uncertainties on temperature readings.
Conclusions:
- The quantitative shadow method is a viable and accurate technique for temperature measurement in laser ignition.
- The method's high resolution enables detailed studies of transient combustion events.
- This technique offers a simple yet effective optical diagnostic for combustion research.
