EXPERIMENTAL CHARACTERIZATION OF SHEAR COAXIAL INJECTORS USING LIQUIDGASEOUS NITROGEN/

The spray characteristics of a shear coaxial injector at elevated pres sures, using liquid and gaseous nitrogen to simulate liquid oxygen (LO X) and gaseous hydrogen, were examined under noncombusting conditions. Two injectors were evaluated with different LOX post designs, straigh t and tapered. Flow visualization tests have revealed a contraction of the spray with increasing chamber pressures below the critical pressu re. At pressures above the critical point, stroboscope images revealed art elongation of the liquid breakup length. No differences in the sp ray morphology were evident for the two LOX post shapes. Droplet size and velocity measurements were made with a phase Doppler interferometr ic device for three oxidizer-to-fuel mixture ratios and a range of cha mber pressures. The results indicated improved atomization at lower mi xture ratios, but increased droplet sampling difficulty.