SIX STROKE ENGINE
The six-stroke engine is a type of internal combustion engine based on the four-stroke engine, but with additional
complexity intended to make it more efficient and reduce emissions. Two types
of six-stroke engine have been developed since the 1990s:
In the first approach, the
engine captures the heat lost from the four-stroke Otto cycle or Diesel cycle and uses it to power an additional
power and exhaust stroke of the piston in the same cylinder. Designs use either
steam or air as the working fluid for the additional power stroke.[1] The pistons in this type of six-stroke
engine go up and down three times for each injection of fuel. There are two
power strokes: one with fuel, the other with steam or air. The currently
notable designs in this class are the Crower six-stroke engine,
invented by Bruce Crower of the U.S. ; the Bajulaz engine by the Bajulaz S.A. company of
Switzerland; and the Velozeta
Six-stroke engine built
by the College of Engineering, at Trivandrum in India.
The second approach to the
six-stroke engine uses a second opposed piston in each cylinder that moves at half
the cyclical rate of the main piston, thus giving six piston movements per
cycle. Functionally, the second piston replaces the valve mechanism of a
conventional engine but also increases the compression ratio.
The currently notable designs in this class include two designs developed
independently: the Beare Head engine, invented by Australian Malcolm
Beare, and the German Charge pump,
invented by Helmut Kottmann.
Engine types
Griffin six-stroke engine
In 1883, the Bath-based
engineer Samuel Griffin was an established maker of steam and gas engines. He
wished to produce an internal combustion engine, but without paying the
licensing costs of the Otto patents. His solution was to develop a
'Patent slide valve' and a single-acting six-stroke engine using it.
By 1886, Scottish steam
locomotive maker Dick, Kerr &
Co. saw a future in
large oil engines and licensed the Griffin patents. These were double acting,
tandem engines and sold under the name "Kilmarnock".[2] A major market for the Griffin engine
was in electricity generation, where they developed a reputation for happily
running light for long periods, then suddenly being able to take up a large
demand for power. Their large heavy construction didn't suit them to mobile
use, but they were capable of burning heavier and cheaper grades of oil.
The key principle of the
"Griffin Simplex" was a heated exhaust-jacketed external vapouriser,
into which the fuel was sprayed. The temperature was held around 550 °F (288 °C), sufficient to
physically vapourise the oil but not to break it down chemically. This
fractional distillation supported the use of heavy oil fuels, the unusable tars
and asphalts separating out in the vapouriser.
Hot bulb
ignition was used,
which Griffin termed the 'Catathermic
Igniter' , a small isolated
cavity connected to the combustion chamber. The spray injector had an
adjustable inner nozzle for the air supply, surrounded by an annular casing for
the oil, both oil and air entering at 20 lbs sq in. pressure, and being
regulated by a governor.[3][4]
Griffin went out of
business in 1923.
Only two known examples of
a Griffin six-stroke engine survive. One is in the Anson engine museum. The other was built in
1885 and for some years was in the Birmingham Museum of Science and
Technology, but in 2007 it returned to Bath and the Museum of Bath at Work.[5]
Bajulaz six-stroke engine
The Bajulaz six-stroke
engine is similar to a regular combustion engine in design. There are however
modifications to the cylinder head, with two supplementary fixed capacity
chambers: a combustion chamber and an air preheating chamber above
each cylinder. The combustion chamber receives a charge of heated air from the
cylinder; the injection of fuel begins an isochoric burn which increases thethermal efficiency compared to a burn in the cylinder.
The high pressure achieved is then released into the cylinder to work the power
or expansion stroke. Meanwhile a second chamber which blankets the combustion
chamber, has its air content heated to a high degree by heat passing through the
cylinder wall. This heated and pressurized air is then used to power an
additional stroke of the piston.
The claimed advantages of
the engine include reduction in fuel consumption by at least 40%, two expansion
strokes in six strokes, multi-fuel usage capability, and a dramatic reduction
in pollution.[6]
The Bajulaz Six-Stroke
Engine was invented in 1989 by the Bajulaz S A company, based in Geneva, Switzerland;
it has U.S. Patent 4,809,511 and U.S. Patent 4,513,568.
The Bajulaz six-stroke
engine features:
§
Reduction in fuel consumption by at
least 40%
§
Two expansion (work) strokes in six
strokes
§
Multifuel, including liquefied
petroleum gas
§
Dramatic reduction in air pollution
§
Costs comparable to those of a
four-stroke engine
Velozeta six-stroke engine
In a Velozeta engine,
during the exhaust stroke, fresh air is injected into the cylinder, which
expands by heat and therefore forces the piston down for an additional stroke.
The valve overlaps have been removed and the two additional strokes using air
injection provide for better gas scavenging.
The engine seems to show 40% reduction in fuel consumption and dramatic
reduction in air pollution.[7] Itsspecific power is not much less than that of a
four-stroke Gasoline engine.[7] The engine can run on a variety of
fuels, ranging fromGasoline and diesel to LPG. An altered engine shows a 65%
reduction in carbon monoxide pollution when compared with the four stroke
engine from which it was developed.[7]
The engine was developed in
2005 by a team of mechanical engineering students Aaron Joseph George, Arun K
Nair, Boby Sebastian, Krishnaraj U of the College of Engineering, Trivandrum.
NIYKADO Six Stroke Engine
This Engine was designed,
developed and patented by Chanayil Cleetus Anil owner of NIYKADO Motors, Kochi during the year 2012. He holds the
Indian patent number IN252642 which was granted to him by IPIndia on 25th May
2012. The engine has already undergone a preliminary round of full-throttle
tests at the Automotive Research Association of India (ARAI), Pune.
This is the only engine
that is categorized under fully working prototype.[citation needed]The first prototype
was developed in 2004 which used only two valves. The second prototype was
improved design from the first prototype which used four valves in 2007.
Crower six-stroke engine
In a six-stroke engine
prototyped in the U.S. by Bruce Crower, water is
injected into the cylinder after the exhaust stroke, and is instantly turned to steam, which expands and
forces the piston down for an additional power stroke. Thus, waste heat that
most engines require an air or water cooling system to discharge is captured
and put to use driving the piston.[8] Crower estimated that his design would
reduce fuel consumption by 40% by generating the same power output at a lower
RPM. The weight associated with a cooling system could be eliminated, but that
would be balanced by a need for a water tank in addition to the normal fuel
tank.
The Crower six-stroke engine
was an experimental design that attracted media attention in 2006 because of an
interview given by 75 year old American inventor has applied for a patent on his
design. ([1])
That patent application was subsequently abandoned.[9]Leonard Dyer invented the first six-stroke internal
combustion water injection engine in 1915, which is very similar to Crower's
design. A dozen more similar patents have been issued since.
Dyer's six-stroke engine
features:
§
No cooling system required
§
Improves a typical engine’s fuel
consumption
§
Requires a supply of pure water to act
as the medium for the second power stroke.
§
Extracts the additional power from the
expansion of steam.
Beare Head
The term "Six
Stroke" was coined by the inventor of the Beare Head,
Malcolm Beare. The technology combines a four stroke engine bottom end with an
opposed piston in the cylinder head working at half the cyclical rate of the
bottom piston. Functionally, the second piston replaces the valve mechanism of
a conventional engine. first use of
"sixstroke" 1994
M4+2
The
M4+2 engine working cycle animation
The M4+2 engines have much
in common with the Beare Head engines, combining two opposed pistons
in the same cylinder. One piston working at half the cyclical rate of the
other. But while the main function of the second piston in a Beare Head engine
is to replace the valve mechanism of a conventional four stroke engine, the
M4+2 take the principle one step further.The double pistons combustion engine's
work is based on the co-operation of both modules. The air load change takes
place in two-stroke engine. The piston of four-stroke engine is exchange aiding
system which improves air load change. It works as a system of valves. The
cylinder is filled with air or with air-fuel mixture. Filling process takes
place at overpressure by the slide inlet system. The exhaust gases are removed
as in the classical two-stroke engine (by exhaust's windows in cylinder). The
fuel is supplied into the cylinder by fuel injection system. The ignition is
realized by two spark plugs. The effective power output of the double pistons
engine is transferred by two crankshafts. The characteristic feature of this
engine is an opportunity of continuous change of cubic capacity and compression
rate during engine work by changing the piston's location. The mathematical
models (mechanical and thermodynamical) were meant for double pistons engines
which enable to draw up new theoretical thermodynamic cycle for internal
combustion double pistons engine.
The working principle of
the engine is explained in the Two- and four-stroke engines article.
]Piston charger engine
In this engine, similar in
design to the Beare head, a "piston charger" replaces the valve
system. The piston charger charges the main cylinder and simultaneously regulates
the inlet and the outlet aperture leading to no loss of air and fuel in the
exhaust.[10] In the main cylinder, combustion takes
place every turn as in a two-stroke engine and lubrication as in a four-stroke engine. Fuel injection can take place
in the piston charger, in the gas transfer channel or in the combustion
chamber. It is also possible to charge two working cylinders with one piston
charger. The combination of compact design for the combustion chamber together
with no loss of air and fuel is claimed to give the engine more torque, more
power and better fuel consumption. The benefit of fewer moving parts and design
is claimed to lead to lower manufacturing costs. Good for hybrid technology and
stationary engines. The engine is claimed to be suited to alternative fuels since
there is no corrosion or deposits left on valves. The six strokes are:
aspiration, precompression, gas transfer, compression, ignition and ejection.
This is an invention of Helmut Kottmann from Germany, working 25 years at MAHLE
GmbH piston and cylinder construction.
Related U.S. patents
§
1217788 Internal combustion and steam engine
Feb 27, 1917. Hugo F. Liedtke seems to be one of the first to contemplate
alternating between internal combustion and steam injection into the combustion
chamber.
§
1339176 Internal combustion engine May 4,
1920. Leonard H. Dyer invented the first 6-stroke internal
combustion/water-injection engine in 1915.
§
3964263 Six cycle combustion and fluid
vaporization engine Jun 22, 1976
§
4143518 Internal combustion and steam engine
Mar 13, 1979
§
4301655 Combination internal combustion and
steam engine Nov 24, 1981
§
4433548 Combination internal combustion and
steam engine Feb 28, 1984
§
4489558 Compound internal combustion engine
and method for its use Dec 25, 1984
§
4489560 Compound internal combustion engine
and method for its use Dec 25, 1984
§
4736715 Engine with a six-stroke cycle,
variable compression ratio, and constant stroke Apr 12, 1988
§
4917054 Six-stroke internal combustion engine
Apr 17, 1990
§
4924823 Six-stroke internal combustion engine
May 15, 1990
§
6253745 Multiple stroke engine having fuel and
vapor charges Jul 3, 2001
§
6311651 Computer-controlled six-stroke internal
combustion engine and its method of operation Nov 6, 2001
§
6571749 Computer-controlled six-stroke cycle
internal combustion engine and its method of operation Jun 3, 2003
§
7021272 Computer controlled multi-stroke cycle
power generating assembly and method of operation Apr 4, 2006
Related Indian Patents
§
IN patent|252642|252642 Six Stroke
Engine May 25, 2012
.
[References
§
Bajulaz Six-Stroke Engine Accessed June 2007
§
Bajulaz
Animation Accessed
June 2007
§
Lyons,
Pete (February 23, 2006). "Inside
Bruce Crower’s Six-Stroke Engine". AutoWeek. Retrieved 2007-06-22.sixstroke.com
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