CARS Investigations in Sooting and Turbulent Flames.
Abstract
Coherent anti-Stoke Raman spectroscopy (CARS) investigations in sooting, laminar and turbulent, propane-fueled diffusion flames are reported. For a 5320 A pump wavelength, using a frequency-doubled neodymium laser, interferences can occur at very high soot densities. For N2 CARS, there are both incoherent and coherent components to the interference. The incoherent interference arises primarily from anti-Stokes fluorescence from C2 excited by Stokes laser absorption. The C2 is created by the laser vaporization of soot particulates, shown to occur even on a nanosecond time scale. The coherent interference arises most probably from electronically-resonantly enhanced wave mixing in the C2. Fortunately, neither interference is very large. By proper experimental design, interference-free CARS spectra from flame N2 can be obtained even at high soot densities. CARS signatures from N2 have been employed to map the temperature field with high spatial precision throughout a small, luminous, highly sooting, laminar propane diffusion flame. Single pulse (approx, 10 nanosecond) CARS thermometry has been demonstrated in various regions of a highly swireld, turbuelnt propane diffusion flame. Based upon these investigations, CARS continues to appear very promising for diagnostic applications to practical combustion sources. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1979
- Accession Number
- ADA069169
Entities
People
- Alan C. Eckbreth
Organizations
- Purdue University