Solid-fuel ramjet regulation by means of an air-division valve

An in-flight regulation technique, which can provide an optimal operation of a solid-fuel ramjet (SFRJ) motor over a wide Eight envelope, has been analyzed. Regulation capability is essential for an efficient use of the SFRJ propulsion for applications involving variable flight and operating conditions. The method is based on a controllable air-division valve, which drives part of the inlet air into the solid-fuel port, while the rest of the airflow is channeled through a bypass to the aft-mixing section of the combustor. The model takes into account parameters influencing the burning rate of the solid fuel (e.g., port-flow rate, port diameter) and formulates a general regulation law in terms of the instantaneous opening state of the division valve for a constant fuel-to-air ratio operation. The control law was checked for certain cases, considering typical trajectories. It has demonstrated a good regulation capability over a broad operational range (between sea level and 15-km altitude).