| Objective: ||Develop and demonstrate innovative airframe-propulsion integration technologies which free the mobility aircraft design space of the constraints of traditional air-breathing propulsion systems.
|| Description: ||Inlet and nozzle design focuses on providing maximum aerodynamic efficiencies for their respective functions to enable maximal propulsion system performance while minimizing the impact of those functions on the airframe. For a mobility aircraft, this functionality has traditionally been met by the use of podded nacelles hung on the wing. For the nacelle inlet, the flow field is isolated from the aerodynamic influences of the airframe; for the exhaust nozzle, this isolation simplifies design and material selection of other airframe elements. Although these designs have proven successful, and there are notable exceptions to this traditional approach, the more highly integrated designs of future and potential air vehicles will require a more radical departure from this norm.
For both advanced military and civil aviation applications, the embedding of the propulsion system – a system which is wholly or partially contained within the airframe outer mold line – has proven attractive as it enables a substantial decrease in total air vehicle drag. In addition to the decrease in wetted and frontal area, some blended wing-body designs incorporate boundary-layer-ingestion inlets for further drag reduction, while military vehicles benefit in ways related to survivability. However, these benefits come with a price. Of foremost concern is the maintaining of aeropropulsive efficiency due to less than ideal inlet and nozzle placement and/or aerodynamic flow paths. Inlets for embedded propulsion systems often incorporate turns which may lead to flow separation, thereby increasing distortion and decreasing pressure recovery. Despite the drag benefits, boundary-layer-ingestion inlets suffer from the same detriment by definition. The exhaust nozzle may be similarly less than ideal from an aerodynamic performance perspective, and depending on placement, exhaust gases may wash over large areas of the airframe structure. Although flow control technologies have mitigated some of these aerodynamic pitfalls, further engineering difficulty may include increased structural weight, decreased volumetric efficiency and more complex thermal management requirements.
To enable new capabilities in air vehicles, innovative airframe-propulsion integration technologies are sought. These advancements should not be constrained by conventional propulsion flow path (i.e., inlet and nozzle) design but are not to regress in the overall capability of the vehicle or are to enable heretofore unseen air vehicle capabilities or concepts. These technologies may be at the integrated propulsion system or at the subsystem level. Examples of the former are (but are not limited to) distributed propulsion, distributed inlet or nozzle apertures, and integration of advanced or unconventional propulsion cycles (e.g., pulse detonation engines or hybrid propulsion). Examples of the later are (but are not limited to) advanced flow control or other aerodynamic technologies for aerodynamic performance improvement, morphing structures for flight condition adaptability, or advanced control concepts or applications which enhance system performance through real-time knowledge and control of system performance parameters. This topic is airframe-propulsion integration technologies as enabling to new air vehicle configurations and is not intended to develop and demonstrate new air breathing engine technologies per se (e.g., new engine cycles or engine component technologies); therefore, the propulsion cycle to be integrated should be beyond the conceptual stage.
|| ||PHASE I: Provide an advanced propulsion system definition and proof-of-concept demonstration through small-scale experiments and/or high-fidelity simulation. Estimated performance and technology benefits assessment for candidate air vehicle application is highly desired but not required.
|| || ||PHASE II: Validate the proposed technology through prototype hardware demonstrations. This includes an integrated propulsion system or subsystem performance demonstration at conditions and scale relevant to the targeted application air vehicle system, off-design performance determination through experiment or high-fidelity simulation, and air vehicle performance estimates and technology benefits assessment.
|| ||DUAL USE COMMERCIALIZATION: Military application: Military application of technologies may enhance the efficiency of current air vehicles, enable new vehicles to fulfill current missions, or provide new means of accomplishing military objectives. Commercial application: Civilian application of technologies may enhance the fuel efficiency of current air vehicles, enable new vehicles to fulfill transportation needs, or provide all new transportation systems.
|| References: ||1. Florea, R., Haas, M., Hardin, L.W., Lents, C.E.,and Stucky, M.B., "Optimization of a Bleed-Flow-Control for an Aggressive Serpentine Duct," Proceedings of the 43rd AIAA Aerspace Sciences Meeting, Reno, NV, AIAA-2005-1205, January 2005.
2. Campbell, R., Carter, M., Pendergraft, O., Friedman, D., and Serrano, L., "Design and Testing of a Blended Wing Body with Boundary Layer Ingestion Nacelles at High Reynolds Numbers," 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, AIAA-2005-459, January 2005.
|Keywords: ||mobility, inlets, nozzles, airframe-propulsion integration|