New Polarized-Depolarized Measurement Capability Extends Use of Raman/Rayleigh Methods to More Flame Types

Blog, Combustion Chemistry, Diagnostics, Engine Combustion

By Robert Barlow Allowing single-shot measurements of all major species in nonsooting flames of simple fuels, such as H2 and CH4, spontaneous Raman scattering has been a key CRF laser diagnostic technique for fundamental turbulent-combustion studies. However, laser-induced fluorescence from soot precursors tends to interfere significantly with Raman scattering signals—limiting this method’s utility. Such fluorescence…

Novel Spectroscopic Method Reveals Intermediates over a Broad Spectrum

Blog, Combustion Chemistry, Diagnostics

CRF researcher Leonid Sheps has developed a new spectroscopic method, Time-Resolved Broadband Cavity-Enhanced Absorption Spectroscopy (TR-BB-CEAS). The new technique is capable of following the time evolution of transient intermediates as they are produced and consumed in a gas-phase chemical reaction by monitoring their absorption of near-UV to visible light (300–700 nm). Existing absorption techniques can…

A New Concept for Time-Resolved Fourier-Transform Spectroscopy

Blog, Combustion Chemistry, Diagnostics

In developing the dual etalon frequency comb (DEFCOM) spectrometer, CRF researchers Haifeng Huang and David Chandler are refining a new concept for time-resolved Fourier-transform (FT) spectroscopy based on the interference between two transient frequency combs. By opening the door to many potential uses—including time-resolved, high-resolution, broad-band spectroscopy with a microsecond time-scale—DEFCOM may prove instrumental in…