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Friday, 2 December 2011

SIX STROKE ENGINE:

SIX STROKE ENGINE

The six-stroke engine is a type of internal combustion engine 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 1990.


TYPES OF SIX STROKE ENGINE:
1) Velozeta Six-stroke engine
2) German Charge pump



1) VELOZETA SIX STROKE ENGINE:
In the first approach, the engine captures the waste heat 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. As well as extracting power, the additional stroke cools the engine and removes the need for a cooling system, making the engine lighter and giving an estimated efficiency of 40%.[1] 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 engine,
2) GERMAN CHARGE PUMP:
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.
OTHER TYPES OF SIX STROKE ENGINE:
1) Crower six stroke engine
2) Griffin six stroke engine
3) Velozeta six-stroke engine
4) Bajulaz six stroke engine
1) 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 steam, 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%.
2) GRIFFIN SIX STROKE ENGINE:
The key principle of the "Griffin Simplex" was an 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.
3) VELOZITA SIX STROKE ENGI NE:
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.
4) 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 the thermal 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.
PRINCIPL OF SIX STROKE ENGINE:
A six stroke engine describes a number of different approaches in the internal combustion engine to capture the waste heat from the four stroke Otto cycle and use it to power an additional power and exhaust stroke of the piston. Designs either use steam or air as the working fluid for the additional power stroke. As well as extracting power, the additional stroke cools the engine and removes the need for a cooling system making the engine lighter and giving 40% [1] increased efficiency over the Otto Cycle. The pistons in a six stroke engine go up and down six times for each injection of fuel.The six stroke engine has 2 power strokes, one fuel, one steam or air. The currently notable six stroke engine designs include Crower's six stroke engine, the Bajulaz engine and the Six-stroke engine The Beare Head engine is called a six stroke by its designer but stands apart from the others. It uses a second opposed piston in each cylinder which moves at half the cyclical rate of the main piston, thus giving six piston movements per cycle. It does not use any additional working fluid. "Six-stroke engine (Trivandrum)"In the six-stroke engine developed by the students of College of Engineering, Trivandrum, India, the first four strokes are the same as a four stroke internal combustion engine. After the exhaust stroke, instead of air/fuel mixture (as in case of petrol engines), fresh air is sucked into the cylinder from the air filter, and is removed during the sixth stroke. The valve overlaps have been removed and the additional two strokes have been provided for better scavenging, using air injection. The engine shows 40% reduction in fuel consumption and dramatic reduction in pollution. Its specific power is not less than that of a four-stroke petrol engine. The engine can run on a variety of fuels, ranging from petrol and diesel to LPG. An altered engine shows a 65% reduction in CO pollution when compared with the four stroke engine from which it was developed.
MAIN ADVANTAGES OF SIX STROKE ENGINE:
1) Reduction in fuel consumption by at least 40%:
2) Two expansions (work) in six strokes
3) Dramatic reduction in pollution:
4) Liquefied Petroleum Gas
5) Cost comparable to those of a four-stroke engine
CONCLUSION:
Billions of explosion engines are running worldwide at this time, and this era is not about to end. It is commercially obvious that the big market if for automobile, heavy goods, construction-site and farm vehicles. This is a priority for the six-stroke engine.Drastically reducing fuel consumption and pollution without radically affecting performances would allow the current concept of the automobile to be reassessed.
There is, at this day, no wonder solution for the replacement of the internal combustion engine. Only improvements of the current technology can help it progress within reasonable time and financial limits. The six-stroke engine fits perfectly into this view. It’s adoption by the automobile industry would have a tremendous impact on the environment and world economy, assuming up to 40% reduction in fuel consumption and 60% to 90% in polluting emissions, depending on the type of fuel being used. Fuel consumption for mid-sized cars should be within 4 and 5 liters per 100km. and 3 to 4 liters for the small-sized cars. Automobiles equipped with the six-stroke engine could appear in the market within 3 to 5 years
USES OF SIX STROKE ENGINE:
1) Motorboats might offer a big outlet for this type of engine. Their characteristics are perfectly suited to its use. Furthermore, the use of fuels other than gasoline would greatly reduce the risks of explosion.
2) Using non-fossil fuels of vegetable origin, natural gases and others, in simple, robust engine, operating with a minimum of adjustments and non-pollutant.
3) Many more applications may also be envisaged.
IMPORTANT WARNING:
The following descriptions, charts and diagrams refer to the patented version of the Bajulaz cycle's principle. They are used to explain the six-stroke engine's functioning but they must not be taken as a final result. The development of the engine's prototype showed many improvements to be taken in consideration. For example, the piston-balanced valves depicted further were not used for the prototype, being replaced by a much more effective valve system, for which new patents are deposited.
FACTORS CONTRIBUTING TO INCREASED THERMAL EFFICIENCY, REDUCED FUEL CONSUMPTION AND POLLUTANT EMISSIONS.
1)The heat that is evacuated during the cooling of a conventional engine’s cylinder head is recovered in the six-stroke engine by the air-heating chamber surrounding the combustion chamber.
2) After intake, air is compressed in the heating chamber and heated through 720 degrees of crankshaft angle, 360 degrees of which in closed chamber (external combustion).
3) The transfer of heat from the very thin walls of the combustion chamber to the air heating chambers lowers the temperature and pressure of the gases on expansion and exhaust (internal combustion).
4) Better combustion and expansion of gases that take place over 540 degrees of crankshaft rotation, 360° of which is in closed combustion chamber, and 180° for expansion.
5) The glowing combustion chamber allows the optimal burning of any fuel and calcinate the residues.
6) Distribution of the work: two expansions (power strokes) over six strokes, or a third more than the in a four-stroke engine.
7) Better filling of the cylinder on the intake due to the lower temperature of the cylinder walls and the piston head.
8) Elimination of the exhaust gases crossing with fresh air on intake. In the six stroke-engine, intake takes place on the first stroke and exhaust on the fourth stroke.
9) Large reduction in cooling power. The water pump and fan outputs are reduced. Possibility to suppress the water cooler.
10) Less inertia due to the lightness of the moving parts.
Lower oil temperature. With combustion taking place in a closed chamber, the high temperatures less stress the oil and the risk of dilution is reduced, even in cold starts. Since the six-stroke engine has a third less intake and exhaust than a four stroke engine, the depression on the piston during intake and the back
Pressure during exhaust is reduced by a third. The gain in efficiency balances out the losses due to the passage of air through the combustion chamber and heating chamber valves, during compression of fresh and superheated air. Friction losses, theoretically higher in the six-stroke engine, are balanced by a better distribution of pressure on the moving parts due to the work being spread over two strokes and the elimination of the direct combustion.
DESIGN AND FUNCTION:
With the six-stroke cycle, the two supplementary chambers allow parallel function from which results a full eight-event cycle: two four-event-each cycles, an external combustion cycle and an internal combustion cycle. The diagram shows the interconnection of the eight events in the six-stroke cycle. Event three and event six occur within closed chambers and have no direct action on the crankshaft. They are called static events compared to the six other dynamic events.
The first cycle of four events is of external combustion
It includes 1. Event 1: pure air intake in the cylinder (dynamic event). 2. Event 2: pure air compression in the heating chamber (dynamic event). 3. Event 3: keeping pure air pressure in closed chamber where a maximum heat exchange occurs with the combustion chambers walls, without direct action on the crankshaft (static event). 4. Event 4: expansion of the super heated air in the cylinder, work (dynamic event). During this four event's cycle, the pure air never comes in direct contact with the heating source.
The second cycle of four events is of internal combustion
It includes 1. Event 5: re-compressions of pure heated air in the combustion chamber (dynamic event). 2. Events 6: fuel injection and combustion in closed combustion chamber, without direct action on the crankshaft (static event). 3. Events 7: combustion gases expanding in the cylinder, work (dynamic event). 4. Event 8: combustion gases exhaust (dynamic event). During this four event, the air comes in direct contact with the heating source.
The sketch shows the cylinder head equipped with both chambers and four valves of which two are conventional (intake and exhaust). The two others are made of heavy-duty heat-resisting material. During the combustion and the air heating processes, the valves could open under the pressure within the chambers. To avoid this, a piston is installed on both valve shafts, which compensate this pressure. Being a six-stroke cycle, the camshaft speed is one third of the crankshaft speed. The combustion chambers walls are glowing when the engine is running. Their small thickness allows heat exchange with the air-heating chamber, which is surrounding the combustion chamber. The air-heating chamber is isolated from the cylinder head to reduce thermal loss. Through heat transfer from the combustion chamber to the heating chamber, the work is distributed over two strokes, which results in less pressure on the piston and greater smoothness of operation. In addition, since the combustion chamber is isolated from the cylinder by it's valves, the moving parts, especially the piston, are not subject to any excessive stress from the very high temperatures and pressures. They are also protected from explosive combustion or auto-ignition, which are observed on ignition of the air-fuel mixture in conventional gas or diesel engines. The combustion and air-heating chambers have different compression ratio. The compression ratio is high for the heating chamber, which operates on an external cycle and is supplied solely with pure air. On the other hand, the compression ratio is low for the combustion chamber, which operates on an internal combustion cycle.
The combustion of all injected fuel is insured, first, by the supply of preheated pure air in the combustion chamber, then, by the glowing walls of the chamber, which act as multiple spark plugs. In order to facilitate cold starts, the combustion chamber is fitted with a heater plug (glow plug).
In contrast to a diesel engine, which requires a heavy construction, this multi-fuel engine, which can also use diesel fuel, may be built in a much lighter fashion than that of a gas engine, especially in the case of all moving parts.
Injection and combustion take place in the closed combustion chamber, therefore at a constant volume, over 360 degrees of crankshaft angle. This Feature gives plenty of time for the fuel to burn ideally, and release every potential calorie (first contribution to pollution reduction). The injection may be split up, with dual fuel using the SNDF system (Single Nozzle, Dual Fuel).
The glowing walls of the combustion chamber will calcine the residues, which are deposited there during fuel combustion (second contribution to pollution reduction).As well as regulating the intake and exhaust strokes, the valves of the heating and the combustion chambers allow significant additional adjustments for improving efficiency and reducing noise. Since new patents are being applied for, design details do not appear in the present description.
CHARACTERSTICKS CURVE FOR SIX STROKE ENGINE:
1) PISTON CRANKSHAFT DYNAMICS:




3) INSTANTANEOUS TORQUE



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