The Class 50's 16CSVT Diesel Set
The 16 Cylinder power plant fitted to the class fifty is
a development of the long line of traction diesel sets manufactured by
the English Electric Company. The ancestors saw use in classes 08, 20,
40, 37 and the development still went on for the Valenta power plant used
in the HST and others used in classes 56 and 58.
How does it work
The heart of any diesel locomotive is its power
plant, this is in principle no different to the engine found in many road
vehicles, only more powerful. A diesel engine is made up of a number of
cylinders, each is a tube bored in to a common piece of metal called the
cylinder block. In each tube is a piston that can slide up and down. To
prevent excessive wear on the block each cylinder has a liner made of a
material better able to withstand the sliding action of the piston and cheaper
to replace than the whole block when worn out. The piston is surrounded by a
number of rings of metal which seal the gap between the piston and the liner
preventing the atmosphere above the piston reaching the area below it.
The movement of the piston up and down inside the
cylinder is called its stroke, one slide from top to bottom and then back up
again (two strokes) will turn the crank shaft through 360 degrees (see
diagrams on the next page). The crank shaft is connected to the piston by the
connecting rod (or con rod) which has a bearing at each end, (big end below,
little end above). By this means the linear motion of the piston is converted
into rotational movement.
The crank shaft connects all the pistons via their
con rods and it is used to transfer the power produced out of the engine. At
the top of the cylinder in the head are valves and the fuel injector, these
are also driven off the crank shaft to keep them in time with the piston.
Most diesel locomotives use what is known as a four
stroke engine (that is the piston has to travel up and down twice to complete
a full power cycle). This is best described by the diagrams below;
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1.
The first downward stroke of the cycle is called Induction, here air is
drawn into the cylinder from the outside world, through the inlet valve.
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2.
The second stroke (upward) is called Compression. At the start of this
stroke the inlet valve is closed and the air is pressurised making it
hot.
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3.
The Third stroke is called Power. At the start of this second downward
movement of the piston fuel is sprayed into the cylinder, where it
instantly ignites on contact with the hot air. The resulting explosion
forces the piston down.
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4. The last stroke is called
Exhaust, here the combustion gasses are vented out through the outlet
valve which is open from the bottom to the top of the stroke.
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To increase the power available from a given size
of engine more fuel needs to be burnt. Increasing the amount of fuel used also
requires more oxygen to ensure complete combustion. A turbo-charger is used to
pump air under pressure into the cylinder and hence increase the amount of
oxygen in the cylinder. In addition cool air has more oxygen in a given volume
than warm air, so it is common to use an inter-cooler to increase the oxygen
density too.
The power developed by the 16CSVT engine
fitted to the class 50, comes from 16 cylinders of 10 inch diameter and 12 inch
stroke, these are arranged in a V formation which allows two banks of cylinders
to drive a common crank shaft. Each set of four cylinders is feed by a separate turbo
charger and inter-cooler.
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