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2243the amount of the imbibed cornpitions and increased the intrinsic reactivity. However, the reactivity decreased abruptly in a high concentration of NaCl salts due to the limitation of the rate of ion exchange and the decrease of the degree of hydration of the active catalyst site.An experimental study of fuel fouling using optical measurement methods was performed. These measurements included absorption from 350 to 750 nm, scattering at 514.5 nm, and fluorescence using a probe wavelength of 514.5 nm. Measurements were performed using a constant-temperature heating system which exited into an optical cell. Each of the measurements proved useful in monitoring changes in the test fuel, JP-4, at test temperatures up to 775 K and pressures of 400 psig. Absorption measurements demonstrated both molecular changes in the fuel composition and a marked increase in the particulate present in the flow as a result of thermal stress. Scattering measurements indicated room temperature fuel to contain particulate with average diameters greater than 0.1 pm while thermally stressed fuel contained much larger concentrations of particulate with sizes below 0.06 pm. This work clearly illustrates the possibilities of using optical methods for monitoring the fuel fouling process.

Mixing and combusting high-enthalpy flows, similar to those encountered in supersonic combusting ramjet engines, were investigated using a shock tunnel to produce the flow in conjunction with nonintrusive optical diagnostics that monitored the performance of two injector configurations. The shock tunnel was configured to produce Mach 3 flow and stagnation enthalpies corresponding to flight equivalent Mach numbers between 7-11. A pulsed hydrogen injection capability and interchangeable injector blocks provided a means of examining high-speed, high-enthalpy reacting flows. Planar laser induced fluorescence of OH radicals in the near-injector region produced images that show the combusting and mixing zones for the reacting flow. Line-of-sight exit plane measurements of water concentration and temperature were used to provide a unique method of monitoring exit plane products. Near-injector mixing dynamics and exit plane compositions were compared for wall jet and axial injection systems. In addition, exit plane measurements indicated that a quasi-steady-state condition was achieved during the 1-to 2-ms test times.