Study of UV Rayleigh scattering thermometry for flame temperature field measurement

Abstract

This paper explores Rayleigh scattering thermometry via a wavelength of 355 nm through a unique measurement scheme. In this context, the p-polarization and s-polarization Rayleigh scattering of flame and air (as the temperature calibration reference) are measured. Subtraction of p-polarization Rayleigh scattering intensity from that of s-polarization is proposed to eliminate the background noise and fluorescence interference influence to reduce the temperature measurement uncertainties. To validate this method, the temperature field of CH4/N2/O2 premixed flame at ϕ=0.78 on a McKenna burner is detected by this Rayleigh scattering thermometry, and the axial temperature profile is validated with the literature data. Within the region of interest domain (−5mm to 5 mm in the radial direction), an overall temperature measurement system precision of ±46.5K is reported. The influence of both p-polarization Rayleigh scattering and laser sheet inhomogeneity on the temperature measurement is further quantitatively studied. The measurement uncertainties relevant to laser energy variation and flame Rayleigh scattering cross-section variation due to temperature increase are specified as 1.4% and 2%–8%, respectively. Eventually, temperature measurements of single-shot images are attempted, and the large signal dynamic range (100–1000 [a.u.]) indicates a promising potential for temperature field interpretation of turbulence combustion.