Numerical study on a throttling segregated fuel-oxidizer system using quasi-one-dimensional internal ballistics model

A quasi-one-dimensional numerical model is developed to provide the internal ballistics information of a throttling segregated fuel-oxidizer system (SFOS). The present throttling SFOS is capable of regulating its thrust by adjusting the opening radius of a throttle valve mounted between the head-end fuel-rich chamber and the aft-end oxygen-rich chamber. The numerical model employs a simplified reaction mechanism to describe the chemical non-equilibrium processes and considers mass addition, wall friction, and propellant surface regression in the combustion chambers. With this numerical model, the internal flow parameter distributions and the performance of the throttling SFOS are demonstrated. The steady operation results show that when the throttle valve opening radius is adjusted from 10.5 mm to 1.4 mm, the motor thrust can be increased from 121.82 N to 250.60 N, which is a 206% thrust promotion. It validates the conception of throttling SFOS. The flow parameters also suggest that the function of the throttle valve can only be manifested when the valve opening radius is quite small. The dynamic operation results reveal that the performance histories of the throttling SFOS experience slight anti-regulations at the end of the valve actuation, which deserves extra protective measures. A theoretical prediction of the thrust regulation ability of the throttling SFOS is provided. It suggests that the thrust regulation ability is limited by the fuel-rich chamber pressure and the initial mass flow rate ratio, and a compromise has to be made among multiple parameters to achieve a reasonable thrust regulation ratio. Finally, the grain arrangement is tentatively discussed. It shows that, based on the present modeling conditions, the fuel-oxygen grain arrangement is superior in its thrust regulation ability than the reversed oxygen-fuel grain arrangement.