IGNITION AND COMBUSTION STUDIES OF HETEROGENEOUS UDMH-RFNA GEL PROPELLANTS

摘要

Advanced gel propulsion systems are being designed and developed for use in volume-limited space vehicles and advanced missile interceptors where safety, energy management, high performance, and efficient packing are the main concerns. Gelled propellants utilized in such a propulsion device are very delicately balanced systems and exhibit a complex ignition, combustion, and Theological behavior. The ignition and combustion characteristics of such heterogeneous systems have to be precisely understood to design a suitable injector and combustion chamber of the rocket motor to achieve a desired level of performance and combustion efficiency. An experimental investigation on ignition and combustion characteristics of UDMH gelled with high-substitution methyl cellulose as fuel and RFNA as oxidant has been carried out with and without metal additives, using a conventional ignition-delay tester and a customized twin-jet combustor. The ignition and combustion behavior of the gelled systems injected through a single-element injector has also been investigated. Preignition, ignition, and postignition temperature profiles close to the impingement point of the respective jets in a specially designed twin-jet combustor have been recorded using a suitable thermocouple and precision recording system. It has been observed that gels show lower ignition delay than the parent hypergolic system, however, a marginal increase is recorded in the case of metalized systems. The rhe-ological characterization of the fuel gel has been conducted in a wide range of shear rate (10~(-2)-10~6 s~(-1)) and it has been found to be thixotropic in nature with viscosity values drastically falling with shear rate.