In an extension of the concept reported in the preceding article, catalytic flow-through chemical reactors of a proposed type would contain catalyst-coated microtubes, possibly in combination with catalyst-coated wires. In addition to the advantages afforded by the catalyst-coated wires described in the preceding article, the microtubes would offer a capability to damp sudden increases in pressure.

Catalyst-Coated Microtubes would be placed in tubular reactors, possibly along with wires. The sizes, shapes, and materials of the reactor components would be chosen to obtain the desired combination of fluid-dynamic, thermal, and chemical characteristics.

In the original rocket-thruster application, such a pressure excursion can occur upon ignition of a propellant fluid in a catalytic reactor; the pressure excursion can cause blow-back and/or pooling of propellant fluid in the propellant-supply system and/or in the reactor; this causes a departure from the desired mode of operation. Therefore, it is desirable to damp the pressure excursion.

In designing such a reactor according to the proposal, one would provide that the microvoids in the microtubes contain sufficient volume to accommodate the rapid expansion that occurs upon ignition of the propellant. The basic concept of catalyzed-microtube reactors admits of numerous variations, including variations like those described in the preceding article for catalyzed-wire reactors. In addition, a reactor could contain one or more microtube(s), possibly with one or more wire(s). Diameters of tubes and/or wires could be varied to allow cross flow in addition to the main flow along the reactor. Some wires and/or tubes could be catalyzed and some uncatalyzed. Some could be thermally conductive, some thermally insulating. These and other variations could be effected in an effort to optimize the fluid-dynamic, thermal, and chemical aspects of operation over the anticipated range of flow variables.

This work was done by Gerald Voecks, J. Morgan Parker, John Blandino, and David Bame of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp  under the Materials category.

NPO-20508

NASA Tech Briefs Magazine

This article first appeared in the March, 2001 issue of NASA Tech Briefs Magazine.

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