You are here

Affordable Materials and Coatings for Pressure Gain Combustion

Description:

TECHNOLOGY AREA(S): Materials 

OBJECTIVE: Identify, test, and life materials, coatings, and components thereof in an environment representative of pressure gain combustion. Emphasis will be on ground testing of affordable materials for single-use air-breathing applications. 

DESCRIPTION: Pressure Gain Combustion (PGC) has the ability to create greater thermodynamic efficiency and power density than constant pressure combustion cycles used in more conventional propulsion schemes. Rotating Detonation Engines (RDEs) in particular offer very compact hot sections for air-breathing propulsion, but simultaneously push the limits of available materials. Hydrocarbon RDEs for single-use applications require affordable hot-section materials that are chemically stable at heat-soak temperatures at or above 1450oC with sections adjacent to the detonation requiring additional resistance to superimposed localized heat fluxes, higher (flame) temperatures, and high-frequency shock loading (3-12kHz). Refractory Metals with EBC/TBCs, CMCs, monolithic ceramics, ablators, and hybrid structures/assemblies thereof will be considered. Candidate materials must handle thermal shock during heat-up (especially in localized hot-spots), cool-down, and typical mission throttling. Candidate materials must nominally withstand oxidation for a short life (approximately 1 hour) and operate at meaningful pressures for a propulsion system; any glass-forming components or coatings must be able to resist modest shear loading and hot cavitation. Experience has shown that coated refractory systems require significant cooling to maintain environmental stability [1]; cooling schemes will be considered within a mission-capable window of system size-weight-and-power (SWAP) constraints. At the end of this SBIR, it is anticipated that the trade space between material life and affordability will be well understood through coupon testing, component testing, with supporting experimentation and simulation as required [2]. Target component life is 1 hour under conditions that would be comparable to an engine in the 1000 lb thrust class with an appropriate hydrocarbon fuel. However, a successful ground testing campaign for qualification will require 10-20 hours of testing to adequately assess life-limiting mechanisms and improve certainty of short-life material behavior. It is expected that such a ground testing campaign will be conducted, and achieve—or with a short, clear path to— an acceptable ground qualification of hot section components. An assessment of the cost of low production volumes of final component assemblies (1-1000 units) is desired. Teaming with an appropriate propulsion test facility is highly encouraged. 

PHASE I: After assessing the environment with test engineers, identify, optimize, and process coupons for testing in a PGC environment. Testing must achieve thermal equilibrium (at least 3 minutes of continuous operation). An assessment of performance under throttling is desirable, as is materials characterization. Phase I deliverables will include monthly status reports, material coupons, test data, and a final report. 

PHASE II: Hot-section assemblies derived from phase I deliverables and accompanying analysis will be manufactured and ground tested at an appropriate facility with a target of achieving at least 10 hours of test time. At least 1 additional design cycle to address unanticipated material-structure interactions (e.g. erosion, attachment schemes, localized over-temping) is expected. Phase II deliverables will include monthly status reports, tested assemblies, test data, and a final report including an assessment of cost for assembly designs over representative production volumes. 

PHASE III: Continue to refine component performance and cost models with appropriate testing and analysis to complete aspects of ground qualification, minimize assembly cost, and maximize life. Deliver and integrate assemblies for flight testing with an appropriate integrator/test facility. 

REFERENCES: 

1: D. King, et al. "Ceramic Matrix Composites for Air Cooled Rotating Detonation Engines," National Space & Missile Materials Symposium, 2017.

2:  C. Stevens, M. Fotia, J. Hoke, F. Schauer. "Quasi Steady Heat Transfer Measuments in an RDE", 2018 AIAA Aerospace. Sciences Meeting, AIAA SciTech Forum, (AIAA 2018-1884).

KEYWORDS: SiC/SiC, Process Modeling 

CONTACT(S): 

Garth Wilks 

(937) 255-5007 

garth.wilks.1@us.af.mil 

US Flag An Official Website of the United States Government