Laser and Probe Diagnostics in Fundamental Combustion Research

Abstract

Combustion diagnostics using lasers has matured considerably during the last decade. By now, lasers are routinely relied upon in many practical applications where direct inspection of the combustion process is necessary. Quantitative information, however, may still be a major challenge. In this article, some essential features of laser techniques for fundamental combustion research are discussed in view of their potential and limitations. Laser methods are complemented by molecular beam mass spectrometry. Applications include diagnostics in laminar and turbulent diffusion flames, in fuel-rich and sooting flames, and in combustion chemical vapor deposition (CVD) of thin diamond films. Avenues for further research will be discussed. 30 pm 30 pm Fig. 9. Scanning electron microscopy (SEM) images of two diamond films deposited on molybdenum substrates in an atmospheric pressure acetylene/oxygen torch with and without N,O added (acetylene flow 1.5 slm, oxygen flow 1.75 slm, acetone/acetylene ratio 0.02, deposition time: 45 min). (a) without N,O; (b) upon addition of 58 ppm NZO to the fresh gas flow. Note the increase in crystal size, typically by a factor of 3, with N,O added. Israel Journal of Chemistry 39 I999

Nonaligned Carbon Nanotubes Anchored on Porous Alumina: Formation, Process Modeling, Gas‐Phase Analysis, and Field‐Emission Properties

“…In SEM images on large‐pore samples, mostly short (<0.5 μm) and only a few longer CNTs (>2 μm) are visible, while on smaller pore samples less but more uniform CNTs are observed 28. 41, 46 Beside the strong processing effects, the emitters on both samples show an inverse β ( E on ) correlation, as expected from FN theory.…”

“…To study the gas‐phase chemistry during CVD‐based nanotube synthesis, we employed in situ molecular‐beam‐coupled quadrupole mass spectroscopy (MB‐QMS) (Figure 19),39 which is a powerful analytical tool to detect stable and radical gas‐phase species in combustion46–50 or CVD processes 51. 52 Previously we successfully applied MB‐QMS to diamond CVD53 and MOCVD of GaN54, 55 and InN.…”

Contributions to the investigation of reaction pathways in fuel-rich flames

“…In particular, the combination of laser spectroscopy and mass spectrometry has proven highly useful in these investigations. 20,21 On the one hand, non-invasive laser methods enable additional calibration for some species notoriously difficult to measure, including H atoms, 22 H 2 and H 2 O, 15 and on the other hand, they may assist in the quantification of sampling effects in MBMS. 23 However, some questions remain.…”

Measurement of temperature and concentration in oxy-fuel flames by Raman/Rayleigh spectroscopy

“…The production of soot precursors and soot particles in the reaction zone of carbonic oxy-fuel diffusion flames is enhanced compared with air as oxidizer. Therefore Raman measurements in these flames become even more cumbersome than in CH 4 /air flames [9]. A reasonable interpretation of data from these flames is only possible when polarization techniques for the reduction of background and a sampling of spectra over some 1000 shots are used [9].…”

“…Therefore Raman measurements in these flames become even more cumbersome than in CH 4 /air flames [9]. A reasonable interpretation of data from these flames is only possible when polarization techniques for the reduction of background and a sampling of spectra over some 1000 shots are used [9]. This paper concentrates on H 2 /O 2 flames, but results are applicable to carbonic oxy-fuel flames and in general to all flows, where concentrations of some species are not measurable by Raman or LIF techniques.…”