Although Woolson designed the ingenious weight-saving features, Dorner
was responsible for the engine's diesel cycle which employed the "solid"
type of fuel injection. In order to understand Dorner's contribution, a
brief description of the type of diesel injection pioneered by Dr.
Rudolf Diesel is necessary. His system injected the fuel into the
cylinder head with a blast of air supplied by a special air reservoir at
a pressure of 1000 psi or more. Known as the "air blast" type of
injection it produced good turbulence, with the fuel and air thoroughly
mixed before being ignited. Such mixing increases engine efficiency, but
it involves the provision of bulky and costly air-compressing apparatus
which can absorb more than 5 percent of the engine's power. Naturally
the compressor also adds considerably to the engine's weight.
In contrast to this, a "solid" type of fuel injection may be employed to
eliminate the complications of the "air blast" system. It consists of
injecting only fuel at a pressure of 1000 psi or more. Air is admitted
by intake stroke, as with a gasoline engine. Turbulence is induced by
designing the combustion chamber and piston so as to give a whirling
motion to the air during the intake stroke. The following quotation from
Dorner now becomes readily understandable. "Since 1922 my invention
consisted in eliminating the highly complicated compressor and in
injecting directly such a highly diffused fuel spray so that a quick
first ignition could be depended upon. By means of rotating the air
column around the cylinder axis, fresh air was constantly led along the
fuel spray to achieve completely sootless burning-up.... In 1930 I sold
my U.S.A. patents to Packard."[14]
Valve Ports: The inlet port (which was also the exhaust port) was
arranged tangentially to the cylinder. This design imparted a very rapid
whirling motion to the incoming air, thereby aiding the combustion
process. Engine efficiency and rpm were both increased.
Fuel Injector Pumps: A combination fuel pump and nozzle was provided for
each cylinder in contrast to the usual system of having a multiple pump
unit remotely placed with regard to the nozzles. The former system was
adopted after frequent fuel-line failures were experienced due to the
engine's vibration. Woolson stated that his system prevented pressure
waves, which interfered with the correct timing of the fuel injection,
from forming in the tubing. Leigh M. Griffith, vice president of Emsco
Aero, writing in the September 1930, _S.A.E. Journal_ stated: "Regarding
the superiority claim for the simple combination of fuel pump and
injection valve into one unit, without connecting piping, the author
entirely overlooks the fact that the elasticity of a pipe and its
contained fuel can be important aids in securing that extremely abrupt
beginning and ending of injection which is so desirable."
[Illustration: Figure 29.--Fuel-injector disassembly. U.S. Navy test,
1931. (Smithsonian photo A48323C.)]
A major advantage obtained from combining the fuel pump and injection
valve is the ability of an engine so equipped to burn a wide variety of
fuels. The elimination of the above-mentioned type of high-pressure
tubing reduces the possibility of a vapor lock occurring, thereby
permitting more volatile fuels to be burned. This increases the range of
hydrocarbon fuels the engine can utilize. It could run on any type of
hydrocarbon from gasoline to melted butter.[15]
Another reason for combining the fuel pump and injection valve is given
by P. E. Biggar in _Diesel Engines_ (published in 1936 by the Macmillan
Company of Canada Ltd., Toronto): "In the Dorner pump, for example, the
stroke of the plunger is changed by using a lever-type lifter and moving
the push-rod along the lever to vary its movement. Unfortunately, in all
arrangements of this sort, the plunger comes to a reluctant and weary
stop, as the roller of the lifter rounds the nose of the cam. When the
movement does finally end, the injection does not necessarily stop, as
the compressed fuel in the injection pipe is still left to dribble
miserably into the combustion chamber. To minimize this defect, the
designer has placed the pump and injector together in a single unit."
[Illustration: Figure 30.--Mechanism for retarding valve and
fuel-injection timing during starting (see also fig. 26). U.S. Navy
test, 1931. (Smithsonian photo A48324E.)]
[Illustration: Figure 31.--Upper--valve and fuel injector cam;
lower--fuel-injector cam used for starting. U.S. Navy test, 1931.
(Smithsonian photo A48325.)]
Starting System: On November 1, 1961, C. H. Wiegman, vice president of
engineering of the Lycoming Division of Avco Corporation wrote to the
Museum in part as follows:
Early in the development it became quite evident that cold starting
was a problem. This was finally worked out by Packard through the
use of glow plugs and speeding up the injectors during the cranking
period. It had been felt that during the slow cranking process we
were not vaporizing the fuel through the nozzles and that if we
could speed up the injection pumps during this period of cranking a
better vaporization could be obtained. Our tests showed that we
were right, and that the engine could be started quite easily at
minus 10 deg. F through the use of glow plugs. The method used for
speeding up the injection pumps was accomplished by utilizing a
crankshaft cam during the cranking period. The starter would shift
the running cam out of position allowing the crankshaft cam to take
over. After the engine fired, the starter was disengaged and the
running injector pump cam would assume its original position. The
starting cam would be run at engine speed during cranking, and the
running cam at 1/8 reverse engine speed during engine operation.
The shifting was accomplished by a pin-in-slot and spring
arrangement to change the indexing of the cams to starting position
and return.
An Eclipse electric starter with an oversized flywheel was used....
This was powered by a double-sized battery.