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National Advisory Committee for Aeronautics, Technical Notes - Performance of Conical Jet Nozzles in Terms of Flow and Velocity Coefficients

Perfonnsnce characteristics of conical Jet nozzles were detest-mined
in an investigation covering a range of pressure ratios from 1.0 to
2.8, cone half-angles from 5° to 90°, and outlet-inlet diameter ratios
from 0.50 to 0.91. All nozzles investigated had an inlet diameter of
5.00 inches.

Ellie flow coefficients of the conical nozzles investigated were
dependent on the cone half-angle, outlet-inlet diameter ratio, and
pressure ratio. flhe velocity coefficients were essentially constant
at pressure ratios below the critical. For increasing pressures above
critical pressure ratio, there was a small decrease in velocity coef-
ficient that was dependent on pressure ratio and independent of cone
half-angle and outlet-inlet diameter ratio. Therefore the variation
in performance (air flow and thrust) of several nozzles, selected for
the same performnce at a particular design condition,was proportional
to the ratio of their flow coefficients.

A correctly designed Jet nozzle as a device for converting pres-
sure energr to kinetic energy is an essential part of an efficient Jet-
propulsion power plant. Current Jet power plants utilize, with but
few exceptions, the conical subsonic Jet nozzle because it is simple
and inexpensive to fabricate and the configuration is inherently strong
and rigid.

In the design of Jet nozzles, approximate velocity and discharge
coefficients have had to be used. Elhis necessity, coupled with the
effects of other engine-design uncertainties, often requires that
changes he made in the design of the Jet nozzle during prototype-
power-plant tests. Enact nozzle-performance data would enable a more
rational process of selecting a nozzle to perform a specific task
and would also enable the designer to predict more accwately power-
plant performance over the couplets operating range.

Performance characteristics of 15 conical nozzles were experi-
mentally determined at the MBA Lewis laboratory and are presented.
The noZZle configurations investigated have mtleta-inlet diameter
ratios renging from 0.50 to 0.91 and cone halfaén‘gles ranging from
5° to 90°. All the nozzles have inlet diameters of 5.00 inches.