[PSUBS-MAILIST] Bulkheads for cylindrical Vessels

["Jay K. Jeffries" <bottomgun@mindspring.com>]

Looks like this didn’t go through with the attached PFD file so including article here.  The image for the article can be viewed at: http://www.frappr.com/?a=viewphoto&id=260879&pid=4279057&myphotos=1

 

Interesting article in the February issue of NASA Tech Briefs concerning usable space and draining upright cylindrical pressure vessels.  While this orientation is rarely used for PSUBs, Carsten’s vertical trim tanks would have been a fitting application for this method.

R/Jay

 

Respectfully,

Jay K. Jeffries

Andros Is., Bahamas

 

It is the mark of an educated mind to be able to entertain a thought without accepting it.
  - Aristotle

 

 

 

 

Asymmetric Bulkheads for Cylindrical Pressure Vessels

These bulkheads would offer advantages over prior concave, convex, and flat bulkheads.
Marshall Space Flight Center, Alabama

 

 

Asymmetric bulkheads are proposed for the ends of vertically oriented cylindri­cal pressure vessels. These bulkheads, which would feature both convex and concave contours, would offer advantages over purely convex, purely concave, and flat bulkheads (see figure). Intended orig­inally to be applied to large tanks that hold propellant liquids for launching spacecraft, the asymmetric-bulkhead con­cept may also be attractive for terrestrial pressure vessels for which there are requirements to maximize volumetric and mass efficiencies.

 

A description of the relative advantages and disadvantages of prior symmetric bulkhead configurations is prerequisite to understanding the advantages of the pro­posed asymmetric configuration:

 

·  In order to obtain adequate strength, flat bulkheads must be made thicker, relative to concave and convex bulk­heads; the difference in thickness is such that, other things being equal, pressure vessels with flat bulkheads must be made heavier than ones with concave or convex bulkheads.

 

·  Convex bulkhead designs increase overall tank lengths, thereby necessi­tating additional supporting structure for keeping tanks vertical. .

 

·  Concave bulkhead configurations increase tank lengths and detract from volumetric efficiency, even though they do not necessitate additional sup­porting structure.

·  The shape of a bulkhead affects the proportion of residual fluid in a tank - that is, the portion of fluid that unavoidably remains in the tank during outflow and hence cannot be used. In this regard, a flat bulkhead is disadvantageous in two respects: (l) It lacks a single low point for optimum placement of an outlet and (2) a vortex that forms at the outlet during outflow prevents a relatively large amount of fluid from leaving the tank.

· A concave bulkhead also lacks a single low point for optimum placement of an outlet.

Like purely concave and purely convex bulkhead configura­tions, the proposed asymmetric bulkhead configurations would be more mass-efficient than is the flat bulkhead configuration. In comparison with both purely convex and purely concave configu­rations, the proposed asymmetric configurations would offer greater volumetric efficiency. Relative to a purely convex bulkhead configuration, the corresponding asymmetric configuration would result in a shorter tank, thus demanding less supporting structure. An asymmetric configuration provides a low point for optimum location of a drain, and the convex shape at the drain location minimizes the amount of residual fluid.

This work was done by Donald B. Ford of Marshall Space Flight Center.

This is the invention of a NASA employee, and a patent application has been filed. Inquiries concerning license for its commercial develop­ment may be addressed to the inventor:

Donald B. Ford

Phone No.: (256) 544-2454

E-mail: Donald.B.Ford@nasa.gov Refer to MFS-31626-1.

 

Graphic: http://www.frappr.com/?a=viewphoto&id=260879&pid=4279057&myphotos=1

Caption:  These Pressure-Vessel Configurations have the same radius (R) and volume (4πR³/3). The different shapes are shown here to illustrate the advantages and disadvantages of each. This is a representative but not exhaustive set of configurations, and is limited to single, non-nested pressure vessels for the sake of simplicity.

 

 

NASA TECH BRIEFS

FEB 07, pg. 50-51