The investigation of sooty flames using terahertz waves

Sooty flames, especially at high pressures, pose a challenging problem to modern laser based combustion diagnostic techniques. For example, it has been shown that a laser diagnostic tool is unable to probe the combustion field of a jet engine even when the test pressure is below 10 bar. In this paper we report initial results on the penetration of terahertz (1012 Hz) waves into heavily sooted flames. We have shown that a beam of terahertz radiation is able to penetrate a heavily sooted candle flame with very little absorption close to the microwave side and also an opaque layer of soot deposited on glass. These experiments suggest that terahertz frequency radiation may be a viable diagnostic tool for the investigation of harsh, heavily sooted flame conditions which are beyond the realm of conventional laser based diagnostics.