Experimental Behavior of Pentaborane-Air Combustion Products During Expansion in a Convergent Divergent Nozzle

Branstetter, J. R.; Setze, P. C.

In order to evaluate the post combustion behavior of boric oxide, pentaborane-air mixtures, burned to completion at a combustor pressure of 3 atmospheres, were expanded through a 7.1-inch-long convergent-divergent nozzle having a 4-inch-diameter throat and an exit-to-throat area ratio of 1.68. The experimentally determined thrust performance was in good agreement with the ideal equilibrium performance at stagnation temperatures of 3300 deg R and lower. The boric oxide vapor at the combustor exit required about 400 F deg supercooling before any condensed phase was observed. For a given thrust, fuel consumption was as much as 20 percent greater than predicted from vapor-pressure data for combustor outlet temperatures i n the vicinity of 3600 deg R. A similar result could be expected in full-scale engines, since the test combustor provided an unusually long dwell time and a highly turbulent environment. During the expansion process, the vapor (when present) did not condense to the extent predicted for an equilibrium expansion process. Moreover, condensation was observed only i n the form of small, abrupt phase changes i n the subsonic flow near the throat. Friction, due to liquid boric oxide films on the nozzle surfaces, was negligible when the surface temperature was above 800 F.

Document ID

19670022401

Acquisition Source

Headquarters

Document Type

Other - NACA Research Memorandum

Authors

Date Acquired

September 2, 2013

Publication Date

February 18, 1958

Subject Category

Report/Patent Number

Accession Number

67N31730

Distribution Limits

Public

Work of the US Gov. Public Use Permitted.

Keywords

Available Downloads

Name

Type

19670022401.pdf

STI

No Preview Available

NTRS

NTRS - NASA Technical Reports Server

Available Downloads

Related Records