Closeup of HPFS

Cutaway rendering of the High Pressure Flow System (HPFS) test section. A well-developed flow (laminar or turbulent) of carrier gas (N2) enters from the upper right (blue parabaloid). A reagent, in excess ([XS]) is well mixed in the carrier gas. A radical, usually OH, is produced in a sidearm with a titration reaction as shown (Gold discharge cavity). The radical is injected into the center of the flow tube, where it forms a spreading plume (green parabaloid). The radical is measured at 5 separate locations in the center of the flow tube (gold detectors, violet laser beam threading through axes) using laser induced fluorescence (LIF). The different axes correspond to different reaction times through the relation z = t. The velocity is measured with a pitot-static tube (blue gauge, sliver pitot tube). The excess reagent concentration, [XS], is measured with FTIR absorption in a multipass White cell situated between LIF axes 1 and 2 (Red IR beam). Measurements at a number of different [XS] result in the final kinetics measurement

k = - d/dz d/d[XS] ln sig[OH]