KEROSENE CARBURETORS
Experiments have been carried on for quite some time pertaining to the
development of a more successful carburetor which will burn the heavier
fuels. The chief difficulty encountered is to find a more suitable way
to vaporize these low grade fuels.
Kerosene can be used, only with an application of heat to the manifold
to aid in the evaporation of the heavier parts of this fuel. The
exhaust pipes are available for this source of heat, but as there is no
heat from this source until the engine is running, it is necessary to
start the engine on gasoline and switch over to the heavier fuels after
the warming-up process.
[Illustration: Fig. 43. Holley Kerosene Carburetor]
Fig. 43 shows the Holley kerosene carburetor which is adaptable to
any type of engine by making simple changes in the exhaust manifold
to include the heating coil tube. This carburetor will operate
successfully on any hydro-carbon fuel with a boiling point below
600° F. Two float chambers are provided to take care of the starting
and running fuels. The engine is started on the gasoline part of the
carburetor and after a short warming-up period the feed is switched to
the kerosene part of the device.
[Illustration: Fig. 44. Holley Kerosene Carburetor Installment]
The principle upon which this device operates is to provide a primary
mixture by means of a needle valve and a very small aspirating jet
which gives a mixture that is too rich for combustion. This rich
mixture of atomized fuel is carried through a coil tube of very thin
wall thickness, which is exposed to the exhaust gases, directly in the
exhaust manifold.
The temperature in this coil tube reaches as high as 500 degrees F.
The globules of the over rich mixture are broken up here and flow
directly into the mixing chamber, where additional air enters, diluting
the mixture to make it combustible. The opening of the air valve is
controlled by the suction of the engine and by the throttle valve. The
shifter valve for changing the operation from gasoline to kerosene is
conveniently arranged for dash control, when the engine becomes warm. A
primer is arranged in the manifold just above the carburetor and aids
in cold weather starting.
Fig. 44 shows the installation of the Holley kerosene carburetor. In
this case it was necessary to add a compartment on the exhaust manifold
to contain and heat the coil tube. There are some details that must be
taken care of on installation. A small auxiliary tank must be provided
to hold the gasoline for starting, while a larger tank must be provided
to carry the main supply of kerosene.
The adjustments of this type of carburetor is through a needle valve
located in each fuel chamber, and as it is impossible to give any set
adjustment that would apply to the many different types of motors, the
proper adjustment must be worked out. This is done by shifting to the
gasoline and turning the needle valve to the right and left and noting
the point at which the engine runs the smoothest. The needle valve is
then set at this point. The fuel shifter valve is turned to feed the
kerosene, and this adjustment is made in the same manner.