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SEMINAR ON
FREE PISTON ENGINEGuided By, By,
wazzim MENISH S
7333
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FREE PISTON ENGINE
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INTRODUCTION
It is a linear , crank less internalcombustion engine.
The piston movement is not controlled bycrankshaft but determined by theinteraction of forces in the combustionchamber gases , a rebound device and aload device.
In 1807, de Rivaz tested an early engine thatoperated a free piston on a chain.
The modern free piston engine wasproposed by R.P. Pescara.
It is in practice restricted to two strokeoperating principle. 3
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INTRODUCTION [CONTD]
The piston is free because its motion is not
restricted by the position of the rotating
crankshaft.
Some of the distinct characteristics areVariable stroke length
The need for active control of piston
motion
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INTERNAL COMBUSTION
ENGINE
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TYPES OF FREE PISTON
ENGINES
Single piston
Double piston
Opposed piston
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SINGLE PISTON
It consists of three parts a combustion
cylinder, a load device and a rebound
device.
High controllability is the main strength ofthe single piston engine.
The rebound device give the opportunity to
accurately control the amount of energy
put in to the compression process.
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DOUBLE PISTON
It eliminates the need for a rebound device.
The working piston provides the work to
drive the compression process in the other
cylinder. Simple and more compact device with high
power to weight ratio.
The control of piston motion in a particular
stroke length and compression ratio isdifficult.
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OPPOSED PISTON
It consists of two single piston units with
common combustion chamber.
Each piston requires a rebound device and
a load device may be coupled to one or bothof the pistons.
Perfectly balanced and vibration free
design.
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OPPOSED PISTON [CONTD]
Reduced heat transfer losses due to the
opposed piston cylinder
It allows uniflow scavenging to be used,
giving high scavenging efficiency. Need of piston synchronization is the
important disadvantage of it.
It is complicated and bulky
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FIRST GENERATION FREE
PISTON ENGINES
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Air compressors
Gas generators
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AIR COMPRESSOR
Air compressor cylinders where coupled to
the moving parts , often in a multi stage
configuration.
Some of the engines utilize the airremaining in the compressor cylinder to
return the piston , thereby eliminating the
need of rebound device.
It had the advantage of high efficiency,
compactness and low noise and vibration.
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GAS GENERATORS
These are free piston engines feeding hot
gas to a power turbine.
The only load for the engine itself is that to
supercharge the intake air, the output workis taken out entirely from the power
turbine.
High compression and pressure ratio.
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MODERN APPLICATIONS
Hydraulic free piston engine.
Free piston engine generators.
Off highway vehicles.
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ADVANTAGES
Optimized combustion through variable
compression ratio.
Higher part load efficiency and possible
multi fuel operation. Reduced frictional losses.
Compact engine with low maintenance cost.
Enhanced fuel air mixing, reduction in the
time available for heat transfer losses andformation of temperature dependent
emissions such as nitrogen oxides.
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DISADVANTAGES
The main challenge for the free piston
engine is the engine control.
Misfiring .
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CONCLUSION
It is a crank less engine having higher part
load efficiency and variable compression
ratio.
More research is required to investigate thepotential advantages over conventional
technology.
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REFERENCES
R. Mikalsen , A.P. Roskilly . A review of
free piston engine history and applications
Wikipedia
M.L.Mathur , R.P.Sharma. a course inInternal combustion engines .
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