• Version
• 179 Downloads
• 638.44 KB File Size
• 1 File Count
• November 25, 2016 Create Date
• November 25, 2016 Last Updated

National Advisory Committee for Aeronautics, Technical Notes - Influence of Several Factors on Ignition Lag in a Compression Ignition Engine

This investigation was made to determine the influ—
ence of fuel quantity, injection advance angle, injection
valve-opening pressure, inlet-air pressure, compression
ratio, and engine speed on the time'lag of auto—ignition
of a Diesel fuel oil in a single—cylinder compression-
ignition engine as obtained from an analysis of indicator
diagrams. Three cam—operated fuel—injection pumps, two
pump cams, and an automatic injection valve with two dif—
ferent nozzles were used. Ignition lag was considered to
be the interval between the start of injection of the fuel
as determined with a Stroborama and the start of effective
combustion as determined from the indicator diagram, the
latter being the point where 4.0 X 10‘6 pound of fuel
had been effectively burned .

For this particular engine and fuel it was found that:
(l) for a constant start and the same rate of fuel in njec—
tion up to the point of cut— off, a variation in fuel quan—
tity from.l.2 X 10~4 to 4.1 X 10 4'pound per cycle has no
appreciable effect on the ignition lag; (2) injection ad—
vance angle increases or decreases the lag according to
whether density, temperature, or turbulence has the con-
trolling influence; (3) increase in valve—opening pres—
sure slightly increases the lag; and (4) increase of inlet— .
air pressure, compression ratio, and engine speed reduces
the lag.

Considerable attention has been given during the past
ten years to the delay period, usually termed "ignition
lag," occurring in conersssion~ignition engines between
injection and bnrning of the fuele This lag is found to
occur when fuel is burned in bombs, on heated .surfaces,
and in internal—combustion engines. “This lag is of con-
.siderable importance in regard-to"_engine performance. If
the delay is too long, a: large quantity of fu-el will be
ignited simultaneously with the consequent liability of
breakage of engine par’ts'.,53urning_of the fuel immed.iately
upon injection would permit combustion to be controlled
and the desired form ef-eycle to-be obtained.by controlling
the rate of injection. Engine performance would be conse~
quently improved and the life 'of the engine parts length—
ened.