Spatial averaging and multiplex coherent anti-Stokes Raman scattering temperature-measurement error

Area of Science:

• Physical Chemistry
• Spectroscopy
• Fluid Dynamics

Background:

• Multiplex coherent anti-Stokes Raman scattering (CARS) is a powerful technique for temperature measurements in reactive environments.
• Accurate temperature measurements are crucial for understanding combustion processes and flame dynamics.
• Spatial averaging effects within the probe volume can influence measurement accuracy.

Purpose of the Study:

• To investigate the impact of spatial averaging on multiplex CARS temperature measurements.
• To quantify potential measurement errors in environments with significant temperature gradients.
• To provide insights for improving the accuracy of CARS thermometry.

Main Methods:

• Numerical simulations were employed to model the spatial averaging effect.
• Experimental verification was conducted using a laminar flame burner.
• Multiplex coherent anti-Stokes Raman scattering (CARS) was utilized for temperature measurements.

Main Results:

• Spatial averaging introduces significant errors in temperature measurements, particularly in media with large temperature gradients.
• The observed errors exhibit a bias favoring colder gas temperatures.
• The magnitude of the error increases proportionally with the temperature difference across the probe volume.

Conclusions:

• Spatial averaging is a critical factor to consider for accurate multiplex CARS thermometry in flames.
• Measurement biases towards colder temperatures can occur due to probe volume averaging.
• Careful consideration of probe volume characteristics is necessary for reliable temperature determination in reactive flows.