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National Advisory Committee for Aeronautics, Technical Notes - Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions

The amount of water in cloud droplet form ingested by a full-scale
supersonic nose inlet with conical centerbody was measured in the NADA
Lewis icing tunnel. Local and total water impingement rates on the cowl
and centerbody surfaces were also obtained. All measurements were made
with a dye-tracer technique. The range of operating and meteorological
conditions studied was: angles of attack of Oo and 4.20, volume-median
droplet diameters from about 11 to 20 microns, and ratios of inlet to
free-stream velocity from about 0.4 to 1.8. Although the inlet was de-
signed for supersonic (mach 2.0) Operation of the aircraft, the tunnel
measurements were confined to a free-stream velocity of 156 knots (Mach
0.257). The data are extendable to other subsonic speeds and droplet
sizes by dimensionless impingement parameters.

Impingement and ingestion efficiencies are functions of the ratio
of inlet to free-stream velocity as well as drOplet size. For the model
and range of conditions studied, progressively increasing the inlet ve-
locity ratio from less than to greater than 1.0 increased the centerbody
impingement efficiency and shifted the cowl impingement region from the
inner- to outer-cowl surfaces, respectively. The ratio of water ingested
by the inlet plane to that contained in a free-stream tube of cross sec—
tion equal to that at the inlet plane also increased with increasing
inlet velocity ratio. Theoretically calculated values of inlet water
(or droplet) ingestion are in good agreement with experiment for annular
inlet configurations.

The NASA has made numerous theoretical and experimental studies of
the trajectories and impingement of cloud droplets on various bodies as
well as on the ingestion of doplets by ducts and engine inlets (refs.
1 to 24). These data and those reported herein provide instantaneous
values of droplet impingement and ingestion but do not consider the run-
back of impinged droplets