Performance enhancement of an annular expansion-deflection nozzle to enhance rocket thrust

As rockets consume a lot of fuel, the rocket nozzle design is critical. This paper explores performance optimization for expansion-deflection nozzles (EDNs) by incorporating a new design modification that includes an additional divergent section. Traditional EDNs experience a marked decline in thrust efficiency at specific nozzle pressure ratios (NPRs) due to the deflection of the supersonic flow near the nozzle exit plane, leading to flow separation and velocity reduction. To address this, we propose a strategic enhancement that integrates an additional divergent section designed to delay the onset of flow separation and improve overall efficiency. This design exploits expansion fan dynamics to re-expand and re-attach the flow to the nozzle wall, thereby mitigating efficiency losses. Computational fluid dynamics (CFD) simulations were conducted to evaluate the modified EDN at NPRs of 70, 160, and 200, representing open wake, transition, and delayed closed wake modes, respectively. The results indicate a substantial improvement in thrust efficiency, with the modified design effectively delaying the mode transition and maintaining higher efficiency across a broader range of operating conditions.