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The FairDiesel Limited range of engine designs is based on the "Barrel Engine" concept. Such designs date from the 1910's and consist of a series of parallel cylinders wrapped around a drive-shaft, with the pistons coupled to it through a
swash-plate ---
or a cam,------
or a wobble-plate.,------
As the pistons are driven back and forth the swash-plate, cam or wobble-plate is driven round and is coupled via the drive shaft to
the load.
One such engine, the Statax, is believed to have powered an aircraft in 1914, whilst another, the seven-cylinder Redrup Fury, known to
have flown in
1929, is shown below with part of the casing cut away to show the swash-plate linkage.
The Fury was one of a whole series of engines designed by Charles Redrup whose story is told in Diesel Publishing book, "The Knife and Fork Man". He always claimed that most of his prototypes were made in his home workshop with little more than a knife and fork!
There are many configurations of Barrel Engines;
A modern engine, based on the cam principle, is the Dyna-Cam, a double-ended spark-ignition barrel engine with twelve cylinders arranged on either side of one cam:-
Opposed Piston Engines
The Jumo engine.
The two sets of opposed pistons drove two crankshafts, linked together by a train of gears to the drive shaft. The engine was a two-stroke diesel, and used ports at each end of the cylinder liner for inlet and exhaust. Such engines were produced under licence by Napier during the 1930's.
A modern two-cylinder version of this engine is manufactured by Diesel Air Limited.
The Diesel Air DAIR 100
The FairDiesel Opposed Piston Barrel Engine
FairDiesel Limited has put together the concepts of barrel and opposed piston engines and applied them to produce an exceptionally well-balanced lightweight diesel engine for a wide range of
The engine is shown diagrammatically, with opposed pistons acting on shaped cams.
Its operation is seen in the animation below.
The use of shaped drive cams enables the motion of each piston to be determined independently, unlike a crank-driven engine,
and so the combustion cycle can be optimised.
With the pistons at Top Dead Centre, fuel is injected into the compressed air.
Ignition takes place spontaneously and the pistons are driven in opposite directions, turning the cams as they do so.
During this power stroke, the cams have identical profiles and so all the thrust is balanced and taken by the drive shaft.
The casing experiences no axial thrust at all. Side thrusts from the pistons onto the liner walls are equal,
and produce the driving torque.
At the end of the power stroke, the exhaust port opens and the spent gases exhaust to atmosphere via the turbo-charger.
The cams are so shaped that the inlet port then opens and pressurised air from the turbo-charger enters and scavenges
away the remaining exhaust gases.
The exhaust port then closes, and air continues to charge the cylinder under the action of the turbo-charger.
The cams then drive the pistons together to compress the air in readiness for the next power stroke.
This compression stroke again uses symmetrical cam profiles to maintain balanced forces on the drive shaft.
Because the cam has four lobes, The complete cycle occurs twice for each revolution of the drive shaft.
Thermal Efficiency
FairDiesel Limited has used the ability to design cam profiles flexibly, to optimise the Thermal Efficiency Performance of the two-stroke diesel engine.
With a conventional crank-driven diesel engine the injection of fuel continues during the power stroke.
Thus full combustion pressure is not generated at Top Dead Centre.
With the FairDiesel Limited engine, the cams are profiled so as to retain the pistons at Top Dead Centre until fuel injection is complete, so that full combustion pressure and temperature are available to drive the pistons along the cylinders, thus maximising thermal efficiency, as in a Spark-ignition engine.
Four, six and more cylinder versions of the engine are also planned, with up to 32 cylinders feasible for power generation.
© FairDiesel Limited 2006
