HIGH TEMPERATURE LDV SEED PARTICLE DEVELOPMENT

TO PERFORM LASER DOPPLER VELOCIMETRY IN THE GAS FLOWS OF AEROSPACE PROPULSION SYSTEMS, LIGHT SCATTERING PARTICLES ABLE TO WITHSTAND THE HARSH AMBIENT ENVIRONMENT ARE NEEDED. A RESEARCH PROGRAM IS PROPOSED WHICH WILL STUDY THE FEASIBILITY OF MANUFACTURING MONODISPERSE, HEAT-RESISTANT PARTICLES HAVING DIAMETERS OF 0.05 TO 0.5 UM WHICH CAN BE SEEDED INTO THE FLOW. THE TECHNIQUE WILL EMPLOY A PULSED CO2 LASER TO DECOMPOSE GASES FLOWING IN A SUPERSONIC NOZZLE,RESULTING IN VAPOR PRODUCTS WHICH CONDENSE, POLYMERIZE, OR REACT TO FORM CARBONACEOUS OR SILICON PARTICULATES WHICH AREPREVENTED FROM AGGLOMERATING. A NOZZLE WHICH IS COMPATIBLE WITH AN EXISTING GAS FLOW CONTROL APPARATUS WILL BE DESIGNEDAND ASSEMBLED. SODIUM CHLORIDE WINDOWS IN THE NOZZLE WALL WILL PERMIT LASER HEATING OF THE FLOWING GAS. THE PARTICLESGENERATED WILL BE COLLECTED AND SUBJECTED TO ELECTRON MICROSCOPY TO EVALUATE THEIR SIZES AND SHAPES, AND TO CHECK FOR AGGLOMERATION. EFFORTS WILL BE MADE TO CONTROL THE PARTICLE DIAMETERS THROUGH ADJUSTMENTS IN BOTH THE POSITION WITHIN THE NOZZLE WHERE THE GAS IS HEATED AND LASERFLUENCE WITH WHICH IT IS IRRADIATED.