High Efficiency SiC/SiC Composite Heat Exchanger Structures

Scramjet propulsion systems for future hypersonic aerospace vehicles will be subjected to heating rates far greater than current materials can manage. In order to sustain high thermal loading while preheating the fuel, regeneratively cooled hot flow path components fabricated from ceramic matrix composites are being considered. The limited availability of high-temperature/environmentally durable materials focuses attention to silicon carbide fiber-reinforced silicon carbide (SiC/SiC) composites. These materials exhibit a unique combination of low density, high thermal conductivity and outstanding strength to near 3000oF. In order to exploit the benefits of SiC/SiC composites, methods are needed for fabricating high density/high conductivity components incorporating impermeable metal tube liners. Additionally, practical methods are needed for uniformly distributing coolant to the array of tubes via manifolding on the backside of the hot flow path surface. The objective of this Phase I program is to demonstrate a promising method for producing a high thermal efficiency SiC/SiC composite heat exchanger with low residual porosity and high interlaminar strength without having to resort to exotic and costly 3D fiber preforms. A functional actively cooled composite panel test article incorporating refractory metal tubes will be designed, fabricated and delivered to NASA for burner rig and/or thermal evaluation.

Similar requirements for high-temperature materials exist for commercial/industrial applications as well. Although less aggressive than the aerospace/defense and nuclear energy-related initiatives, programs are in place for evaluating fiber reinforced ceramics for land-based turbine components, catathermal combustion devices, heat exchangers and radiant burners, which represent opportunities in energy generation and pollution abatement technologies that may mature over the next 10 or so years.

Hot structures fabricated from ceramic composite materials are an attractive design option for specialized components of future aerospace vehicles and propulsion systems to increase performance, reduce weight and increase durability. Current fabric-laminated ceramic composite materials and components suffer from insufficient interlaminar strength and are thus vulnerable to delamination when subjected to high velocity impact damage and exacerbated by severe thru-thickness thermal gradients. The ability to improve the interlaminar properties over current materials without having to resort to the use of costly, exotic multidirectional fiber preforms will better enable the utilization of these materials for certain thermal-structural applications critical to the US military and aerospace industrial complex. Fiber-reinforced ceramic-matrix composites are recognized as an enabling class of materials for a variety of high-temperature applications in chemical rocket engine throat inserts, combustion chambers and nozzles; airbreathing scramjet hot flow path components; aero-engine combustors, turbine blades, vanes, and exhaust nozzles; hypersonic airframe hot structure and thermal protection systems; spacecraft re-entry heatshields; and a variety of industrial power generation radiant burner and heat exchanger tubes.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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