Experimental cross-correlation Nitrogen Q-branch CARS Thermometry in a Spark Ignition Engine

Lockett, R. D., Ball, D. & Robertson, G. (2013). Experimental cross-correlation Nitrogen Q-branch CARS Thermometry in a Spark Ignition Engine. Optics and Lasers in Engineering, 51(7), pp. 929-943. doi: 10.1016/j.optlaseng.2013.02.010

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A purely experimental technique was employed to derive temperatures from nitrogen Q-branch Coherent Anti-Stokes Raman Scattering (CARS) spectra, obtained in a high pressure, high temperature environment (spark ignition Otto engine). This was in order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch CARS spectra at high pressure. The spectra obtained in the engine were compared with spectra obtained in a calibrated high pressure, high temperature cell, using direct cross-correlation in place of the minimisation of sums of squares of residuals. The technique is demonstrated through the measurement of air temperature as a function of crankshaft angle inside the cylinder of a motored single-cylinder Ricardo E6 research engine, followed by the measurement of fuel-air mixture temperatures obtained during the compression stroke in a knocking Ricardo E6 engine. A standard CARS program (SANDIA’s CARSFIT) was employed to calibrate the altered non-resonant background contribution to the CARS spectra that was caused by the alteration to the mole fraction of nitrogen in the unburned fuel-air mixture. The compression temperature profiles were extrapolated in order to predict the auto-ignition temperatures.

Item Type: Article
Additional Information: NOTICE: this is the author’s version of a work that was accepted for publication in Optics and Lasers in Engineering. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Optics and Lasers in Engineering, Volume 51, Issue 7, July 2013, Pages 929–943, http:/dx.doi.org/10.1016/j.optlaseng.2013.02.010
Uncontrolled Keywords: CARS; thermometry; auto-ignition; engine, cross-correlation
Subjects: T Technology > TJ Mechanical engineering and machinery
Divisions: School of Engineering & Mathematical Sciences > Engineering
URI: http://openaccess.city.ac.uk/id/eprint/2142

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