The
six-stroke engine is a type of
internal combustion engineThe internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine the expansion of the high temperature and pressure gases, which are produced by the combustion, directly applies force to a movable...
based on the four-stroke engine, but with additional complexity to make it more efficient and reduce emissions. Two different 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
The Diesel cycle is the thermodynamic cycle which approximates the pressure and volume of the combustion chamber of the Diesel engine, invented by Rudolph Diesel in 1897. It is assumed to have constant pressure during the first part of the "combustion" phase , v2 to v3 in the diagram...
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. The pistons in this type of six-stroke engine go up and down six 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 engineThe Crower six-stroke engine is a high-efficiency variant of an internal combustion engine under development by Bruce Crower.Two extra strokes are added to the customary internal combustion engine four stroke Otto cycle, which makes a 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
An opposed piston engine is one in which the cylinders are double-ended, with a piston at each end and no cylinder head.-Configurations:Some variations of the Opposed Piston or OP designs use a single crankshaft like the Doxford ship engines and the Commer OP truck engines. They should not be...
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 ratioThe compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber; from its largest capacity to its smallest capacity...
. The currently notable designs in this class include two designs developed independently: the Beare HeadThe Beare Head engine internal combustion engine technology combines a four stroke engine bottom end with a ported cylinder head closely resembling that of a two stroke, thus 4+2= six stroke. The head piston is smaller and has half the speed of the opposing piston...
engine, invented by Australian Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.
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.Dick, Kerr and Company was a locomotive manufacturer based in Kilmarnock, Scotland and Preston, England.Having previously been known as W.B.Dick and Company the company had built all kinds of tramway equipment and rolling stock. From 1883 the company joined with John Kerr and under its new name, it...
saw a future in large oil engines and licensed the Griffin patents. These were double acting, tandem engines and sold under the name "Kilmarnock". 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 , 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 ignitionThe hotbulb, or hot bulb engine or heavy oil engine is a type of internal combustion engine. It is an engine in which fuel is ignited by being brought into contact with a red hot metal surface inside a bulb....
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.
Griffin went out of business in 1923.
Only two known examples of a Griffin six-stroke engine survive. One is in the
Anson engine museumThe Anson Engine Museum is situated on the site of the old Anson colliery in Poynton, Cheshire, England. It is the result of years of work by Les Cawley and Geoff Challinor who began collecting and showing stationary engines for a hobby. When the number and size of engines they collected...
. 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 WorkThe Museum of Bath at Work is at Camden Works, Julian Road, in Bath, Somerset, England.This museum was established in 1978 to present the commercial development of Bath over the last 2000 years and includes displays on four floors. The main exhibit is the reconstruction of a engineering and mineral...
.
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-Internal combustion engine:The hot gases produced by the combustion occupy a far greater volume than the original fuel, thus creating an increase in pressure within the limited volume of the chamber. This pressure can be used to do work, for example, to move a piston on a crankshaft or a turbine...
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
isochoricAn isochoric process, also called a constant-volume process, an isovolumetric process, or an isometric process, is a thermodynamic process during which the volume of the closed system undergoing such process remains constant...
burn which increases the
thermal efficiencyIn thermodynamics, the thermal efficiency is a dimensionless performance measure of a thermal device such as an internal combustion engine, a boiler, or a furnace, for example. The input, , to the device is heat, or the heat-content of a fuel that is consumed. The desired output is mechanical...
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 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
pollutionPollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light...
.
The Bajulaz Six Stroke Engine was invented in 1989 by the Bajulaz S A company, based in
GenevaGeneva, is the second-most-populous city in Switzerland and is the most populous city of Romandie...
,
SwitzerlandSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
; it has and .
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. Its
specific powerIn engineering, the term specific power can refer to power either per unit of mass, volume or area, although power per unit of volume is more formally known as power density, and power per unit area as surface power density...
is not much less than that of a four-stroke petrol engine. The engine can run on a variety of fuels, ranging from petrol and diesel to
LPGLPG may stand for:* Liquefied petroleum gas* Laboratoire de Planetologie, Grenoble, France* Landwirtschaftliche Produktionsgenossenschaft * Llanfairpwll railway station, Wales; National Rail station code LPG.* LPG...
. An altered engine shows a 65% reduction in carbon monoxide pollution when compared with the four stroke engine from which it was developed.
The Velozeta engine features are:
- Reduction in fuel consumption
- Dramatic reduction in pollution
- Better scavenging and more extraction of work per cycle
- Lower working temperature makes it easy to maintain optimum engine temperature level for better performance
- The six-stroke engine does not require significant modification to existing engines.
- Better cooling due to additional air strokes, which mostly removes the need for a cooling system
- Lighter engine
This six-stroke engine was developed by and awarded the 'Indian Society for Technical Education - National awarded' for Best B. Tech project of 2006. (ISTE/BBSBEC-B.Tech./Award/2006) The technology is being developed by Velozeta, a Technopark (Trivandrum) supported by the National Institute of Technology based in Calicut. Velozeta has been awarded a Phase-I research grant from the Department of Scientific & Industrial Research (Govt. of India) under the Technopreneur Promotion Programme (TePP).
Crower six stroke engine
In a six-stroke engine developed in the U.S. by Bruce Crower, fresh water is injected into the cylinder after the exhaust stroke, and is quickly turned to superheated
steamSteam is vaporized water. It is a transparent gas . At standard temperature and pressure, pure steam occupies about 1,600 times the volume of an equal mass of liquid water...
, which causes the water to expand to 1600 times its volume and forces the piston down for an additional stroke. This design also claims to reduce fuel consumption by 40%. Maximum efficiency would theoretically be obtained by applying the design to a non-turbocharged diesel engine, where the high compression ratio would allow greater expansion of the steam.
The Crower six stroke engine was invented in 2004 by 75 year old
AmericanThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
inventorAn inventor is a person who creates or discovers a new method, form, device or other useful means. The word inventor comes form the latin verb invenire, invent-, to find...
Bruce Crower who has applied for a patent on a design involving fresh water injection into the cylinders. As of May 2008, no patent has been awarded.
(
http://www.autoweek.com/apps/pbcs.dll/article?AID=/20060227/FREE/302270007/1023/THISWEEKSISSUE)
Leonard DyerLeonard H. Dyer was an inventor, patent attorney, and yachtsman from Washington, DC.-Inventions:The most remarkable of his inventions was a patented six stroke engine using water injected as a 5th stroke for extra power and cooling, to be ejected on the final exhaust stroke...
invented the first six-stroke internal combustion water injection engine in 1915, which is very similar to Crower's design.
Crower's six stroke engine features:
- No cooling system required
- Improves a typical engine’s fuel consumption
- Requires a supply of distilled water to act as the medium for the second power stroke.
Beare Head
The term "Six Stroke" was coined by the inventor of the
Beare HeadThe Beare Head engine internal combustion engine technology combines a four stroke engine bottom end with a ported cylinder head closely resembling that of a two stroke, thus 4+2= six stroke. The head piston is smaller and has half the speed of the opposing piston...
, 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.
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. 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 less 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
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.
Internal combustion engine May 4, 1920. Leonard H. Dyer invented the first 6-stroke internal combustion/water-injection engine in 1915.
Six cycle combustion and fluid vaporization engine Jun 22, 1976
Internal combustion and steam engine Mar 13, 1979
Combination internal combustion and steam engine Nov 24, 1981
Combination internal combustion and steam engine Feb 28, 1984
Compound internal combustion engine and method for its use Dec 25, 1984
Compound internal combustion engine and method for its use Dec 25, 1984
Engine with a six-stroke cycle, variable compression ratio, and constant stroke Apr 12, 1988
Six-stroke internal combustion engine Apr 17, 1990
Six stroke internal combustion engine May 15, 1990
Multiple stroke engine having fuel and vapor charges Jul 3, 2001
Computer controlled six stroke internal combustion engine and its method of operation Nov 6, 2001
Computer controlled six stroke cycle internal combustion engine and its method of operation Jun 3, 2003
Computer controlled multi-stroke cycle power generating assembly and method of operation Apr 4, 2006
External links