N14A-T005 TITLE: Design Optimization and Analysis of Advanced Exhaust Systems

TECHNOLOGY AREAS: Air Platform

OBJECTIVE: Develop methodologies to resolve and optimize the multi-physics environment of high-performance engines’ exhausts.

DESCRIPTION: It is recognized that new exhaust systems may include features such as compact, sinuous ducts featuring complex 3-D non-axisymmetric shapes, fixed exit areas, thrust vectoring etc., constructed with a minimum number of moving parts. The current capability in the aerospace industry is to conduct the aerodynamic and structural analyses in an uncoupled fashion, which is a cumbersome, time consuming, and therefore expensive, practice. For that reason it typically results in less than optimal final exhaust configurations under tight time and budget constraints.

Significant recent advances in Computational Fluid Dynamics (CFD), particularly employing the Large Eddy Simulation (LES) method, have revealed the underlying physics of non-ideally expanded hot, transient supersonic exhaust plumes in never before seen detail. The exhaust plumes from non-axisymmetric serpentine exhausts are currently not well understood. However, it is possible that employing LES to analyze the exhaust system interior aerodynamics, together with the plume, will improve the state-of-the-art.

This solicitation seeks the development of an analysis tool that predicts both the steady and unsteady stresses in propulsion system exhaust components and also employs optimization methodologies to minimize component weight and maximize system performance. In addition, these structural analyses should be coupled to advanced aerodynamics analyses of the interior of the gas turbine engine exhaust duct and nozzle and the exterior of the air vehicle aft-deck and engine plume.

PHASE I: Determine feasibility of proposed methodology for the design or optimization of round engine exhausts transitioning to non-axisymmetric exhausts including aircraft aft-decks and Single-Expansion Ramp Nozzle (SERN) type non-axisymmetric nozzles employing state-of-the-art numerical methodologies. The methodology should be capable of accurately resolving the multi-physics environment of high-performance engines exhaust systems, including steady state and acoustic wall pressures, unsteady heat transfer coefficients and exhaust plumes.

PHASE II: Develop prototype software analysis tools and perform an aerodynamic and structural evaluation of a conceptual exhaust system or available nozzle design and verify it against experimental test data. Demonstrate proposed methodology for the design or optimization of advanced exhaust ducts with advanced exhaust nozzles, thrust vectoring and aft decks employing state-of-the-art experimental or numerical methodologies capable of accurately resolving the multi-physics environment of high-performance engines’ exhausts. Validate the obtained analytical results with experimental data.

PHASE III: Transition the developed jet shear layer pressure measurement technology to NAVAIR Propulsion & Power and possibly to original equipment manufacturers (OEMs) responsible for propulsion systems, to analyze the design and implementation of "second generation" nozzles hardware for current/future aircraft programs.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Civil applications of the developed tools/methodologies would benefit from the design of commercial aircraft nozzles employing coupled multi-physics (structural-aerodynamic) and design optimization capabilities, currently not available to industry.

REFERENCES:
1. Thayer, E. B.; Gamble, E. J.; Guthrie, A. R., Kehret, D. F., Barber, T. J., Hendricks, G. J., Nagaraja, K. S., & Minardi, J. E. (2004). Generation 1.5 High Speed Civil Transport (HSCT) Exhaust Nozzle Program. NASA/CR-2004-213131. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040191406_2004198244.pdf.

2. Engblom, W. A. (2003, July 20-23). Numerical Prediction of SERN Performance using WIND code. AIAA 2003-4410. doi:10.2514/6.2003-4410.

3. Deere, K. A., & Asbury, S. C. (1996, July 1-3). Experimental and Computational Investigation of a Translating-Throat Single-Expansion-Ramp Nozzle. AIAA 96-2540.

4. Capone, F. J. (1981). Aeropropulsive characteristics of twin non-axisymmetric vectoring nozzles installed with forward-swept and aft-swept wings. National Aeronautics and Space Administration. Scientific and Technical Information Branch.