• Version
• 216 Downloads
• 1.20 MB File Size
• 1 File Count
• August 25, 2016 Create Date
• August 25, 2016 Last Updated

National Advisory Committee for Aeronautics, Report - Jet Propulsion for Airplanes

This work was undertaken at the Bureau of Standards on the request of the Engineering
Division, Air Ser,vice United States Army, and was submitted, with their approval, to the
National Advisory Committee for Aeronautics, which authorized its publication as a technical
report on recommendation of the Subcommittee on Power Plants for Aircraft.

Air is compressed and mixed with fuel in a combustion chamber, where the mixture burns
at constant pressure. The combustion products issue through a nozzle, and the reaction of
the jet constitutes the thrust.

Data are available for an approximate comparison of the performance of such a device
with that of the motor—driven air screw. The computations are outlined and the results given
by tables and curves.

The relative fuel consumption and weight of machinery for the jet, decrease as the flying
speed increases; but at 250 miles per hour z:‘t-he jet would still take about four times as much
fuel per thrust horsepower-hour as the air screw, and the power plant would be heavier and
much more complicated.

In the usual method of driving airplanes, air entering the propeller circle from ahead is
projected backward in a continuous stream or race, and the reaction of the race against the
air screw constitutes the forward driving thrust. This may evidently be regarded as pro-
pulsion by means of a jet; but the term “jet propulsion,” as commonly understood, implies
the use of a smaller and more intense jet, maintained by some other means than an air screw.
This is the sense in which the term is employed here.

It is a familiar fact in naval and aeronautical engineering that, other things being equal,
it is more economical of power to get a given thrust from a large low-speed race than from
a smaller one of higher speed. But when we make a radical change in the method of pro-
ducing the race, other things are not equal, and the final effect on fuel consumption and
weight of machinery can not be predicted without a somewhat detailed analysis of the par-
ticular process in question.