Structure and mixing properties of combusting monopropellant sprays

The spray combustion properties of the HAN-based monopropellant LGP 1845 were studied both theoretically and experimentally. Drop size, liquid mass flow rate, and liquid mass flux distributions were measured for pressure-atomized sprays in the atomization breakup regime, burning within a combustion gas environment at pressures of 4.5-5.0 MP_a. Two separated flow models were evaluated using the new measurements: a deterministic separated flow model where drop/turbulence interactions were ignored, and a stochastic separa;ed flow model where drop/turbulence interactions were considered using random-walk computations for drop motion. When based on burning rates found from earlier single drop experiments, both models were in reasonably good agreement with the measurements. Separated flow effects are quite important for these sprays, with the length of the liquid-containing region being relatively independent of injector diameter and extending roughly 300 mm from the injector exit for injector diameters of 0.3 and 0.6 mm.