Filler-Free Channel Close-Out for High-Performance Heat Exchangers

For better fabrication of fluid-cooled rocket nozzles
The improved channel wall nozzle is manufactured with an outer liner that is fused to the inner liner to contain the coolant, with no filler material in the coolant channels. The off-axis wire freeform laser technology is a large-scale additive manufacturing deposition process. The process starts with a slotted liner that is positioned in a fixture on a rotary table. A robotic and wire-based fused additive welding system creates a freeform shell on the outside of the liner. Building up from the base, the rotating weld head spools a bead of wire around the circumference of the nozzle liner, touching down at each channel land (ledge) and creating a localized bond there, as depicted in the cross-section sketch to the right of this page. During the build, the laser's energy is focused and controlled to enable a quality bond. Most of the laser's focus is applied to the previous layer, and only partial focus is on the channel lands. This prevents overheating and burn-through of the channel lands and enables a robust bond interface at each channel land. With a robotic welder, the process is automated. The process accommodates real-time inspection and process adjustments to be made.
Abstract: 
Large-scale liquid rocket engines with regeneratively cooled nozzles will enable reliable and reduced-cost access to space. The coolant that circulates through the thin internal passages within the nozzle helps contain the fluid under high pressure and maintain adequate wall temperatures to prevent failure. It has been a challenge to affordably manufacture the intricate nozzle channels and close them out. As such, NASA and Keystone Synergistic Enterprises developed a novel, advanced manufacturing technology to close out the coolant channels using a freeform, filler-free technique. The new capability reduces the time to fabricate the nozzle and allows for real-time inspection during the build. It has been demonstrated on a series of different alloys, hot-fire testing is complete, and micrograph examination has verified that the bonds are reliable with little deformation to the coolant channels. The technology provides a reliable and lower-cost option to a traditional tube wall nozzle.
Benefits: 

Filler-free: no filler needed in the cooling channels during fabrication

applications: 

Aerospace: nozzles and combustion chambers for liquid rockets

Oil and Gas production: heat exchangers

Nuclear power: heat exchangers

Reps: 
Patent Number: 
9,835,114
Internal Laboratory Ref #: 
MFS-TOPS-84
Patent Status: 
Patent Issue Date: 
March 24, 2018
Agency
NASA
Region
Southeast
State: 
Alabama
Phone: 
256-544-9151
Email: 
terry.taylor@nasa.gov
Lab Representatives
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