Combustion Characteristics Of Non-Toxic Non-Hypergolic Bi-Propellants

The combustion behavior of PERSOL 1 oxidizer (hydrogen peroxide/ammonium nitrate/water) with a gelled ethylammonium nitrate (EAN)-based fuel containing boron nano-sized particles can produce high-temperature combustion products for propulsion purposes. These two bi-propellant components can be used in non-toxic, nonhypergolic liquid propellant systems for various military missions. There are three major findings of this study including: 1) development of a set of stable gelled bi-propellants having high propulsive performance, 2) measurement of physical and thermal properties, and 3) characterization of combustion behavior including burning rate, temperature sensitivity, and flashback characteristics. In order to determine the optimal chemical ingredient percentages, a series of theoretical performance calculations was performed using the NEWPEP thermochemical code. It was found that a fuel composition containing 23% boron powder satisfied both energy and handling requirements. To verify ignitability and to characterize the burning rate, static tube tests were conducted individually for both the fuel and oxidizer components. For the fuel component, burn rates were measured over a pressure range of 0.79 to 17.2 MPa (100 to 2500 psig) and combustible thin wall tubes were used to contain the propellant in order to reduce confinement and heat loss effects. The measured regression rates varied from approximately 2.3 mm/s (0.09 in/s) at 0.79 MPa to 18.8 mm/s (0.74 in/s) at 17.2 MPa, with a slope break appearing near 3.5 MPa. A feeding test setup with a small orifice to generate high flow velocity and large pressure drop was utilized to simulate injector conditions. Test results suggested that flashback can be avoided for the B-EAN-AN gel. PERSOL 1 was found to self-quench after ignition energy was removed at all conditions tested.