Fri, Apr 01, 2005
Diesel Radial Engine Designed For 1 HP Per Pound Of
Weight!
04.01.05 Special Edition: Radical Radial
Engines Incorporated is in the final stages of design of a new 6
cylinder radial engine that is specifically optimized for the light
sport aircraft market. The engine uses several modern technologies
to achieve 1 horsepower per pound of fully equipped ready to run
total engine package weight.
The engine is a 2 stroke, multi-port fuel injection
turbo-normalized diesel with 22:1 compression ratio. High pressure
fuel injection is electronically controlled with injectors located
in the transfer tubes between the lower stepped piston charging
chamber and the combustion chamber. (The two stroke oil injectors
can also be located in the transfer tubes. The engine initially
will use premixed oil in the fuel at a ratio of 190:1.) The
compression ratio is high enough that no glow plugs are needed for
cold starts to -60 degrees Fahrenheit. The engine operates with no
throttle, so there is no restriction in the intake system to reduce
induction efficiency. Power is selected by the pilot through an
electronic signal provided by a potentiometer, but it is controlled
by the electronic fuel injection system. The turbo-normalizing
maintains sea level rated power to 15000 feet.
Due to the three lobed cams that drive the pistons each piston
fires three times for each revolution, for a total of 18 power
pulses per output shaft rotation. The engine incorporates stepped
pistons that directly charge the cylinders via transfer porting to
the adjacent cylinder. The stepped piston charging allows use of a
standard dry sump lubrication system to lubricate the standard
bearings for the drive shafts, and the cam rollers and gearing that
drives the counter rotating 3 lobe cams. A minimal amount of 2
stroke oil (190:1) is still required to lubricate the upper piston
ring, but it is drastically less then that need for standard 2
stroke engines (50:1).
The engine uses one piece cylinder/head units cast
from high silicon content hypereutectic aluminum which has
excellent strength and high temperature characteristics. These
cylinder/heads are cast using lost foam methods to near net shape,
require minimal machining. The 3 block components are CNC machined
from aluminum billet and plate. The hypereutectic aluminum pistons
and the cylinder bores are ceramic coated to minimize heat transfer
and reduce wear. The internal drive cam roller and gear components
are hardened and ground 4140 steal.
The cams allow refined control of piston motion compared to the
fixed sinusoidal motion generated by a crank shaft. This allows for
very quick compression to maximum pressure, long dwell at top dead
center for fast, efficient, clean burning of a very lean mixture
and maximum torque generation with a large moment arm through the
power stroke.
Radical Radial Inc. plans to complete design and manufacturing
of the prototype engine by August 2005. The engines fuel injection
system will then be tuned using dynamometer runs to optimize
performance. Endurance testing will take place on a test stand
prior to placing the engine on a test aircraft mid 2006. The long
term schedule estimates production of engines starting mid
2007.
Specifications
(estimated, all specifications subject to change)
|
|
Engine weight (complete, ready to run) |
112 Pounds (air cooled version) |
Engine weight (complete, ready to run) |
122 Pounds (water cooled version) |
Power, maximum 5 minute limited |
112 HP @ 3000 RPM |
Torque, maximum 5 minute limited |
196 ft-lbs @ 3000 RPM |
Power, maximum continuous |
100 HP @ 2800 RPM |
Torque, maximum continuous |
190 ft-lbs @ 2800 RPM |
BSFC (@Pmc) |
.426 lbs/HP/hour
(Diesel or Jet A) |
Bore |
1.75 inches |
Stroke |
2.02 inches |
Compression Ratio |
22:1 |
Width |
22 inches |
Height |
22 inches |
Length |
12 inches |
Displacement |
11.11 cubic inches (per cylinder) |
Displacement |
200 cubic inches (total per revolution) |
Price |
$9640.00 |
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