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Technical Seminar topic onTechnical Seminar topic on
SIX STROKE ENGINESIX STROKE ENGINE
Presented By:-
BHOJARAJA.B.G
Dept of mechanical engg.GMIT
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CONTENTS
Introduction
How six stroke engine works
Working principles
Specification of six stroke engine
Comparison of six stroke engine with four strokeengine
Graphs
Gallery
Thermodynamic advantages Conclusion
References
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Introduction
Malcolm beare built an innovative hybrid design ofthe I C engine , by combining a two stroke with afour stroke engine.
The Beare Head is a new type of four stroke
engine head design known as the Beare Head
The Beare Head uses a piston and ports verymuch like a two stroke engine to replace the overhead valve system that is found in four strokeengines today. The four stroke block, pistons andcrankshaft remain unaltered. This combination oftwo stroke and four stroke technology has giventhe engine its name the six stroke engine (2 + 4= 6).
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Key attributes of the Beare Head
are:
Increased power,
Increased torque,
Fewer, lighter reciprocating parts,
Simpler manufacture.
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HOW SIX STROKE ENGINE
WORKS
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Below the cylinder head gasket, everything is
conventional, so one advantage is that the Beare
concept can be transplanted on to existing engineswithout any need for redesigning or retooling the
bottom end. But the cylinder head and its poppet
valves get thrown away. To replace the camshaft and
valves, Beare has retained the cam drive belt andfitted an ultra short-stroke upper crankshaft complete
with piston, which the belt drives at half engine speed
just as it previously drove the cam. This piston drives
up and down in a sleeve, past inlet exhaust ports setinto the cylinder wall, very much like on a two-
stroke: these are all exposed during both inlet and
exhaust strokes.
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Working Principle
Fuel ignites with
piston at the top
dead center.
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Rotary valve
opens, allowing
exhaust to
escape
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Exhaust
stroke begins
when the
piston is atbottom dead
center
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Exhaust stroke
ends, intake
begins. rotary
valve cutsexhaust .intake of
charge into
cylinder due to
pressuredifference.
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The intake strokehappens when thepiston is on itsdownward path withthe intake valveopen. This actioncreates suction,drawing atomized
fuel in this casegasoline mixed withair, into thecombustion
chamber.
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Top piston nearly
closes completeinlet port and The
compression
begins.
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Combustion
chambercompletely sealed
and ready for the
combustion.
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The power strokebegins at a criticalmoment, just as the air-fuel mixture is at its mostcompressed. Asupercharged voltage isdelivered to the sparkplugs from the ignitioncoil, at that point it ignitesthe fuel mixture. Thevalves in the engine arestill closed during thisperiod. Thus the
explosion forces thepiston down to turn theengine's crankshaft,delivering the power viathe gearbox and clutch to
the driving wheels.
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SPECIFICATION OF SIX STROKEENGINE
PROTOTYPE 5 - DUCATI BASED
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Comparison OfSix Stroke Engine
With Four Stroke Engine
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1. In a six stroke engine the energy absorption is less because
of slower acceleration of reciprocating parts.
2. It reduces the weight and complexity of the engines head by
as much as 50%. Instead of using energy to drive the head.
3.Torque is increased by 35% and efficiency increased by
the same.
4.Increased torque and power output.
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Gallery
UPPER CRANK WITH PISTON
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DISC VALVEThe piston is half way up on the exhaust stroke. When the piston
reaches TDC with the ports fully open, the disk will begin to
cut off the exhaust. The valve runs clockwise
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CYLINDER HEAD
FROM BELOW
CYLINDER
HEADUPPER VIEW
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Thermodynamic Advantages
The intake begins at 0 degrees on the X-axis.
The effect of the additional volume changes that
the upper piston has on the volume of the engine is
all positive from a thermodynamic point of view. If
the engine were a normal 4 stroke the cylindercapacity would be 340cc. Of note - maximum
volume at the end of the intake stroke occurs at
173 degrees instead of 180 degrees- the change in
volume is 308cc which is less than a 4 stroke(340cc)- yet the total volume at the end of the
intake stroke is 415cc as opposed to 375cc for a
conventional stroke.
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Thermodynamic advantages
The change in volume during the compression
stroke is slightly greater than a 4 stroke after the
ports are closed.
The expansion stroke is much greater than a 4stroke, both from T.D.C. to B.D.C. and from T.D.C.
till the exhaust port is open.
It is possible to leave the opening of the exhaustport later than in a 4 stroke because maximum
volume is not reached until after B.D.C.-548 deg.
Instead of 540 deg .
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Thermodynamic advantages
Hence the 6 stroke system is better from athermodynamic point of view because more energy
is extracted from the expansion process.
During the critical combustion period the rate of
change in volume in the 6 stroke is less than a 4
stroke. Minimum volume is not reached until after
T.D.C., at 361 deg. This is because of the phasing
of the upper piston. It is retarded in reaching its
T.D.C. until 20 deg. after T. D.C. (380). This is
much better from a thermodynamic view in thatcombustion occurs at a more constant volume;
hence ignition timing is not as critical as in a 4
stroke. There is room in the combustion chamber
for up to 4 spark plugs and two direct injectors if
needed.
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Conclusion
In a six stroke engine the energy absorption is lessbecause of slower acceleration of reciprocating
parts The piston speed of the upper piston is about
a quarter of the main piston; therefore its service
life should be at least twice that of the main piston.
In the Beare design, per single cylinder, thenumber of parts is 15 compared to a four stroke of
approx 40 to 50 parts. Also, to reduce
manufacturing costs the head and block can be
machined in o-ne piece.
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The bottom piston is a standard design and theBeare Head bolts directly o-nto the engine block,replacing the overhead valves and standard head.
It reduces the weight and complexity of the engineshead by as much as 50%. Instead of using energyto drive the head, the head actually developsenergy for conversion to power back through thetiming chains of an engine.
Torque is increased by 35% and efficiencyincreased by the same. This can be achieved bysimply unbolting an existing head of a four-strokeengine and then bolting on a Beare Head.
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Increased torque and power output,
Better fuel economy and cleaner burning longer
service intervals and considerably reduced toolingcosts when compared with a conventional four-
stroke design.
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REFFERENCES
1. www.autocarindia.com
2. www.sixstroke.com
3. www.dynobike.com
4. www.delphi.com
5. www.engineersedge.com
6. www.howstuffworks.com
7. Applied Thermodynamics by Rajput
8. Automobile Engineering by Dr. Kripal singh
9. Automobile engineering by G.Nagula
10. Mechanical Engineering science byK.R.Gopalakrishna
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THANK YOU