Single- and dual-band collection toluene PLIF thermometry in supersonic flows

Toluene PLIF has been applied to image temperature in supersonic flowfields containing shock waves. Single- and dual-camera imaging schemes with a single excitation wavelength (266 nm) are presented, and the dual-camera scheme is optimized for imaging temperature from 300 to 900 K. The single-camera technique is implemented to verify the diagnostic and image temperature in uniform pressure, uniformly seeded flowfields; calibration is done using the signal ratio measured across an oblique shock wave of known Mach number. The dual-camera technique utilizes the redshift of toluene fluorescence with increasing temperature for temperature imaging in non-uniform pressure and temperature flowfields. Both single- and dual-camera techniques are verified and demonstrated by imaging the flow behind normal shock waves and oblique shock waves, and the dual-camera technique is further extended to image temperature in the non-uniform pressure and temperature field behind a bow shock. Good agreement is observed between the measured and expected temperature distributions calculated from ideal shock relations or CFD solutions. The accuracy of each technique is also evaluated; for dual-camera thermometry, SNR in temperature ranging from 25 at 300 K to 15 at 900 K is observed in single-shot temperature images.