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National Advisory Committee for Aeronautics, Technical Notes - Preliminary Tests on the Vaporization of Fuel Sprays

High-speed motiOn pictures were taken. of fuel sprays
indec_ted into the combustion. chamber of t_he N. A. C. A. 'com—
bustion appar . Three fuel'sprethyl alcohol, gasoline,
and fuel 911g’wggég' d'1ffered conside'rab1y 1n volatility
were tested. Ex‘Egintgining the en51ne temperature below
that required for gni ion the spray could be studied from
soon after .the start of injection until 130 crank degrees
later. The results show that the sprays vaporize appre—
ciably so that it is possible for the ignition in high—
speed comprIe ssion-igniti on engines to take pl ace from the
vapor phase.

Preliminary results obtained with the H.A.C.A. com—
bustion apparatus (reference 1) indicated that there Was
marked vaporization of the fuel during and following its
injection into highly heated andI dense air. As this pho—
nomenOn should have an appreciable ef_fect on the cOmbus~
tion ofI the fuel, particularly under the conIditions which
cause combustion shock a series of tests was Ioutlined to
investigate fully the vaporization of the fuel sp.ray. _ The
purpose of this note is to. present the first results ob—
tained in these tests. The note is to be fo1IOWed by a '
report which will discuss the vaporization and its_ef -oct
‘on combustion in more detail.

The N. A. C. A. combustion apparatus was used in the in—
vestigation.I The apparatus c'Onsrsts of a single—cylinder
test engine and an injection sys'tem tOgether with a hi_gh—
speed motion picture apparatus. The compression ratio 0.
the engine is 15.8:1. -fhe sides of the'combustion cham—
ber of the engine are formed by glass windows through
which the photographs are taken. In the operation of the
apparatus theJengine is driven at the desired speed by an “
electric motor. By means of a suitable clutch a single
charge of-fuel is injected into the combustion chamber of-
the engine during the compression stroke or the first part
of the expansion stroke. At the same time that the in—
Jection is taking place high~speed_motion pictures are.tak—
on of the fuel Spray. In the present series of tests 13
pictures were taken'at the rate of 1,000 per second. The
-photographs were timod'relatiVe to the'position of the
crankshaft of the engine by means of an electric spark.