Reacting Liquid Monopropellant Sprays-Experiments with High Velocity Full ConeSprays in 33 MPa, 500 Degrees C Nitrogen

摘要

Experiments were conducted to elucidate the jet breakup, atomization, andcombustion of liquid monopropellant sprays through the use of imaging and spectroscopic techniques. Hydroxylammonium nitrate (HAN) based monopropellants LGPI845 and LGPI898 were injected at velocities ranging from 100 to 240 m/s through circular orifices into 33-MPa 500 deg C nitrogen. Experiments with nitromethane, ethanol, and aqueous HAN and TEAN solutions were also conducted. Spray dynamics were recorded via high-speed cinematography. Breakthroughs in the imaging of combusting sprays were achieved by side illumination of the sprays with pulsed laser light sheets, and by seeding the propellants with nitrate salts of sodium or lithium to enhance flame luminosity. Emission spectroscopy was used to identify combustion intermediates and their relative contribution to color content in the cinematic images. Temperature measurements at the center of the sprays provided additional information regarding spray structures and reactivities. In the experiments reported here, sprays ignite in the far field and flame advances ups sustained by extensive turbulent gas recirculation in the closed chamber. The experiments reveal the presence of large liquid drops as well as intense, random burning in vortices. The experiments with nitromethane and ethanol indicate that the dynamic behavior of sprays change when the ambient temperature and pressure exceed critical values. The experimental results are discussed in the context of understanding and modeling spray combustion phenomena in regenerative liquid propellant guns.... Injectors, Liquid atomization, Spray combustion, Supercritical combustion, Color image analysis, Emission spectroscopy, Regenerative liquid propellant guns, Liquid gun propellants.