Dual Bell Nozzle Optimization (DBNO) – DBNO

Control of flow regime transition and integrated control – thrust vectoring system via secondary fluidic transverse injection in a dual-bell rocket nozzle
To expand the combusted gas products in order to obtain the ideal propulsive thrust ratio, the exhaust nozzle should be adapted to the external pressure. However, as the ambient external pressure is subject to atmosphere ever changing conditions, from high to low pressures with the altitude, from the physics point of view, an ideal exhaust nozzle would be the one which would constantly change its expansion ratio in order to compensate the external conditions evolution. This is practically unfeasible due to engineering limitations and overall vehicle efficiency. Dual bell nozzle incorporates 2 curved contours, named “base” contour adapted for lower altitude and “extension” contour higher altitude. These two contours have their specific operation envelopes in regard to specific impulse. Theoretically, ideal transition should occur at cross-section of these 2 envelopes. However, this is not the case due to several flow physical effects as aspiration drag, adverse pressure zone etc. The transition occurs substantially earlier then the theoretical point, which results in decreased specific impulse and system stability with potentially hazardous side loads that can eventually jeopardize the integrity of the aeronef.
With our expertise of fluidic thrust vectoring via transverse injection in divergent section of a rocket nozzle, we are proposing an integrated fluidic injection system in dual-bell nozzle that is capable of controlling – delaying the early transition (flow reattachment to extension nozzle) and also diverging the jet for the purpose of thrust vectoring. We believe that such a system would allow the full industrial use of the dual bell nozzle addressing the transition issue. For civil application, it would also additionally affect the space launcher market by eliminating the complex and robust actuators used for conventional thrust vectoring systems and thus allowing the development of the efficient and low cost space delivery system especially in the view of the emerging reusable rocket vehicle market. For military applications, increase effectiveness of rocket propulsion can induce an increase of the range or the useful mass for missile or drone. The fluidic thrust vectoring can allows an increase of the flight area by increasing maneuverability and the reaction time. This benefit could allow a strategic advantage.
The project proposed is organized in two parts. The first one deal with the transition regimes control via secondary fluidic transvers injection in dual bell nozzle. The second one deals with the fluidic thrust vectoring in dual bell nozzle.