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The knowledge of air temperature has always been an.
essential part of any flight test records for aircraft and
engine performance calculations, and therefore the outside air
thermometer is of vital importance.
The majority of engine performance characteristics are
presented as a function of the non-dimensional r.p.m. parameter and as, with the development of more advanced types of
engines, the slopes of the characteristic curves are increasing,
the accurate knowledge of both N and T4 is becoming steadily
more important.
This report is confined to the measurement of temperature,
and Part I is devoted to sore theoretical considerations of the
recovery factor on a flat plate and a cylinder with its axis
parallel to the airstream. The effect of radiation has been
taken into account and heat transfer expressions have been
derived for laminar and turbulent boundary layers. The
equilibrium temperature of a flat plate has also been evaluated
over a range of airspeeds and altitudes assuming various amounts
of radiation, and graphs have been included to show the deviation
of the recovery factor with the variation of these two parameters.
Part II contains an account of the preliminary testing
of one of the temperature probes in the wind tunnel, and these
tests were carried out with two main objects in view. The first
was to ascertain the suitability of using thermistors as
temperature sensing elements in outside air thermometers, and in
particular to investigate their sensitivity and stability over
a period of time. The second and prime object was to determine
what effect a change of incidence would have on the recovery
factor of a ventilated pitot thermometer probe... [cont.]. |
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