Spatially resolved Raman scattering for multi-species and temperature analysis in technically applied combustion systems: Spray flame and four-cylinder in-line engine

Broadband 308 nm vibrational Raman spectroscopy of gaseous species using a potassium hydrogen phthalate liquid filter and polarization fluorescence suppression

“…[1][2][3][4][5][6][7][8][9][10][11][12] The widespread use of KrF excimer lasers as an excitation source for VRS in combustion research is similarly noted in the review papers of Hassel and Linow 13 and Rothe and Andresen. A review of the literature suggests that the KrF excimer laser ͑operating at 248 nm͒ has become the de facto standard excitation source for VRS studies in combustion.…”

“…17,18 Where this is not possible, the mostly polarized nature of the light emitted from narrowband, tuneable lasers makes it possible to subtract the polarization insensitive background fluorescence from the polarization sensitive Raman signal. 2 If single shot Raman spectroscopy is not possible, the background fluorescence technique can only be implemented for steady flow applications or when the spectra/fluorescence is being collected from quasistationary objects. This therefore makes Raman spectroscopy with background fluorescence subtraction difficult to implement in unsteady flows unless the spectra are collected simultaneously from a single laser shot.…”

“…17 Hence, at shorter wavelengths, the greater is the necessity for low-pass filters with sharp, precisely placed cutoffs in order to avoid loss of information regarding species with small Raman shifts. 2,6,22 At this point the authors pause to reflect that, aside from the reasons presented above, narrowband excitation is not specifically required in many applications outside of fundamental research in the fields of physics and chemistry. 20,21 The choice of UV laser wavelength for Raman spectroscopy is therefore limited to those for which suitable low-pass filters can be found.…”

Measurement of Fuel Concentration Distribution in a Sooting Flame through Raman Scattering

“…Thus, the Raman spectroscopy has been widely used for the combustion diagnostics of simple laboratory flames such as hydrogen diffusion flames (2) - (4) and premixed flames of various fuels (5), (6) . Furthermore, application of the Raman spectroscopy to diagnostics of practical combustion devices (7), (8) can be found in some recent studies. However, since the measurement of Raman scattering from a luminous flame had been considered very difficult, application of the Raman spectroscopy was almost limited to a non-sooting flame.…”

Challenges to laser-based imaging techniques in gas turbine combustor systems for aerospace applications

“…5 However, the point-wise and alignment-critical nature of CARS places severe limitations upon its application in an environment where there is a high degree of vibration, large temperature fluctuations, and the test cell is inaccessible during operation. Only recently have advances in the development of spatially resolved Raman spectroscopy been applied to combusting flowfields, 6 although it has yet to be demonstrated in an actual aero-combustor. Similarly, degenerate four-wave mixing 7 (DFWM) and transient grating spectroscopy 8 (TGS) have shown great promise as diagnostic tools for high pressure combusting flowfields.…”