Investigation of Aerodynamic and Icing Characteristics of a Flush Alternate-Inlet Induction-System Air Scoop Page: 6 of 44
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NACA RM E53E07
location of the total-pressure tubes and thermocouples is given in
figure 4. All air-flow measurements were made by means of thin-plate
orifices. Thermocouples were also used to measure the preheat-air and
The carburetor top-deck pressure recovery was determined for both
the ram and alternate inlets for clear air over a range of mass-air-flow
ratios at angles of attack of 00 and 40, Pressures at the alternate
inlet were also obtained in clear air with varying mass flows through
the alternate inlet for angles of attack of 00 and 4. All these tests
were made at airspeeds of approximately 150, 200, and 270 miles per hour,
mass-flow rates of 0 to 3.55 pounds per second, and a tunnel-air total
temperature of 250 F. Flow studies with wool tufts were made over the
forward nacelle area and the alternate-inlet ramp.
Both the ram- and alternate-inlet systems were tested in icing con-
ditions to determine the type of icing on the external surfaces and the
inner ducting, the degree of blockage of the carburetor screen, and the
effects of icing on the pressure recovery. Tests were made at various
combinations of liquid-water content and median-droplet diameter for
airspeeds of 150 to 180 miles per hour, tunnel-air total temperature
of 00 and 250 F, angles of attack of 00 and 40, and mass-air-flow ratios
of 0.35 to 0.8. The combinations of liquid-water content and droplet
size used in the investigation were chosen to give the maximum rate of
impingement. The values chosen are based upon a probability of being
exceeded of less than 1 in 100 as given in the statistical analysis of
icing conditions in reference 4. The droplet diameter hereinafter
referred to is the median diameter; the size distribution of water drop-
lets in the icing tunnel corresponds to approximately a D distribution
as defined in reference 5.
The procedure followed in the icing tests was as follows: After
the system was stabilized at the desired tunnel airspeed and temperature
conditions and the desired flow rate through the model, an initial clear-
air reading including the top-deck pressures was made. The icing cloud
was then turned on, all pertinent data were recorded at various time
intervals, and photographs of the ice on the inlets were taken during
the icing period. Efforts were made to maintain constant mass air flow
through the model within the limit of performance of the exhaust fan by
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Lewis, James P. Investigation of Aerodynamic and Icing Characteristics of a Flush Alternate-Inlet Induction-System Air Scoop, report, July 24, 1953; (https://digital.library.unt.edu/ark:/67531/metadc59807/m1/6/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.