Effects of Chemical Reactions on Fluidic Thrust Vectoring Performance in Dual-Bell Nozzles

Abstract

Fluidic thrust vectoring (FTV) has emerged as an effective technique for controlling exhaust flow in propulsion systems, with shock vector control (SVC) representing one of its most efficient implementations. Dual-bell nozzles (DBNs), known for their altitude-compensating capability, provide a promising configuration for integrating such control strategies. However, previous studies of SVC in DBNs have been largely restricted to cold-flow simulations using air, which do not accurately represent the high-temperature, chemically reacting environments encountered in rocket propulsion. To address this limitation, the present study investigates the influence of chemical reactions on SVC performance using the ANSYS Fluent computational fluid dynamics (CFD) solver. A kinetic reaction mechanism for LH₂/LO₂ is employed to account for high-temperature dissociation and recombination processes. The analysis is conducted on a novel subscale DBN geometry designed using an in-house method of characteristics (MoC) code, with the resulting contour validated through CFD simulations. Calculated species molar fractions from CFD are further validated against those obtained using NASA’s chemical equilibrium with applications (CEA) code, showing good agreement. Comparative analyses between cold-flow (air) and reacting-flow (LH₂/LO₂) conditions reveal significant differences in SVC performance, highlighting the critical role of thermodynamic and thermochemical effects on vectoring efficiency. These findings demonstrate that cold-flow assumptions may lead to inaccurate predictions, emphasizing the necessity of incorporating reacting-flow models for realistic assessment and design of SVC systems in DBNs.