Temperature and Hydrogen Concentration Measurements by CARS in an Ethylene‐Air Bunsen Flame

Abstract

Local temperatures and hydrogen concentrations in an ethylene‐air Bunsen flame have been determined from CARS measurements of the Q(0) to Q(4) [υ = 1 ← υ = 0] Raman transitions in hydrogen. A crossed beam, BOXCARS, technique of high spatial resolution including non‐resonant background cancellation is employed. The linewidth correction is taken into account for the limit of Doppler broadening. The results agree well with thermodynamic equilibrium calculations.

Plasma Reactions

“…As a result, the technique can be used even in industrial processes that are not readily accessible and which produce high levels of contamination. The method is already used in industrial combustion systems, such as motors and turbine engines, and is now being adopted for the examination of plasma-chemical processes [78]. In contrast, laser-induced fluorescence spectroscopy (LIF) [77] has limited applicability when collisional quenching of the laser-excited electronic energy levels of molecules leads to invalid signals and when the high background radiation level makes the measuring signal hard to detect.…”

Raman spectroscopy

“…It is of unique value in the area of combustion diagnostics, and work has been reported relating to concentration and temperature measurements of typical combustion gases in cells heated to 1800 K (326) and C2 radicals have been identified in an acetylene welding torch flame (327). A range of important molecules in combustion media has been monitored by observing normal rotational-vibrational as well as pure rotational spectra (328) and temperature and hydrogen concentration measurements have been made of an ethylene-air Bunsen flame (329). Instrumental advances have included a highresolution infrared CARS spectrometer to operate in the 1900-5000-cm"1 range (330), an apparatus for turbulent combustion studies (331), and a picosecond CARS microscope (332).…”