Terahertz transmission spectroscopy of high-pressure flames

Laser spectroscopy in the visible and NIR is widely used to study flame behaviour in internal combustion engines and turbines, but is inapplicable at high pressures because high soot concentration renders flames opaque; however they remain transparent to THz radiation. We use THz time-domain transmission spectroscopy to characterise gaseous species in flames. A specially designed high-pressure burner vessel has been built which allows spectroscopy to be carried out at pressures above 5 bar.