Combustion of Han-Based Liquid Propellant Sprays at 28 to 38 MPA

ABSTRACT

Experiments were conducted to elucidate the jet breakup, atomization, and combustion of liquid gun propellant (LGP) sprays through the use of imaging techniques. Hydroxylammonium nitrate (HAN)-based monopropellants were injected al velocities ranging from 100 to 240 m/s through circular orifices into 33 MPa. 500°C nitrogen. 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 various nitrate salts to enhance flame luminosity. The sprays were observed to ignite in the far field, and flame advanced upstream, sustained by extensive turbulent gas recirculation in the closed chamber. The experiments revealed the significance of intense, random burning in vortices. The formation and combustion of large liquid droplets in the vortices were also observed. In addition to the LGP sprays, experiments were conducted with liquids whose thermodynamic c point could be exceeded. These results suggest that the LG P spray combustion was subcritical at the ambient conditions achieved in this study. The applicability of single phase incompressible turbulent jet theory and aerodynamic theory for characterizing the dynamics of these sprays is discussed.

Key Words:

• Spray combustion
• liquid monopropellant