Flow and thrust characteristics of an expansion–deflection dual-bell nozzle

Expansion–deflection nozzle (EDN) and dual-bell nozzle (DBN) are the designs of altitude compensation nozzles that are currently widely studied. The cold flow subscale experiments and two-dimensional axisymmetric Reynolds-averaged numerical simulations were performed to explore the flow characteristics and the altitude compensation performance of an expansion–deflection dual-bell nozzle (EDDBN), which combines an EDN and DBN. The experimental results, supported by numerical simulation results, showed that the EDDBN is in the sea level closed mode under the experimental nozzle pressure ratios. The transition characteristics of the EDDBN and the DBN were simulated by continuously changing the nozzle inlet total pressure. In wider ranges of nozzle pressure ratios, owing to the lower wall pressure of the extension nozzle, the EDDBN has a higher mode transition pressure ratio than the DBN. Compared with the DBN with the same design pressure ratio, the EDDBN can further improve the thrust performance of the exhaust system during the mode transition, confirming the application value of the proposed nozzle design.