Six Stroke(Soft Copy)

CONTENTS:CONTENTS:

Introduction to IC EngineIntroduction to IC Engine Classification of IC Engine as per Classification of IC Engine as per

strokes.strokes. Definition of 6 Stroke engine.Definition of 6 Stroke engine. Currently notable 6 Stroke Engine.Currently notable 6 Stroke Engine. Comparison between 6 Stroke & 4 Comparison between 6 Stroke & 4

Stroke Engine.Stroke Engine. Thermodynamic Advantages of 6 Stroke Thermodynamic Advantages of 6 Stroke

Engine with graphical representationEngine with graphical representation

IC EngineIC EngineThe internal combustion engine is an engine in which the combustion, or rapid oxidation, of gas and air occurs in a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer creates gases of high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause pressure, further causing movement of the piston inside the cylinder, for example by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.This contrasts with external combustion engines, such as steam engines and Stirling engines, which use an external combustion chamber to heat a separate working fluid, which then in turn does work, for example by moving a piston.The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as jet engines, most rockets and many gas turbines are also internal combustion engines

Two Stroke Engine:

Four-stroke engineFour-stroke engineThe four strokes refer to intake, compression, combustion and exhaust strokes that occur during two crankshaft rotations per working cycle of Otto Cycle and Diesel engines. The cycle begins at top dead center (TDC), when the piston is furthest away from the crankshaft. On the first stroke (intake/induction) of the piston, as the piston descends it reduces the pressure in the cylinder, a mixture of fuel and air is forced, by at least atmospheric pressure, into the cylinder through the intake (inlet) port. The intake (inlet) valve (or valves) then close(s) and the following stroke (compression) compresses the fuel-air mixture.The air-fuel mixture is then ignited, usually by a spark plug for a gasoline or Otto cycle engine or by the heat and pressure of compression for a Diesel cycle or compression ignition engine, at approximately the top of the compression stroke. The resulting expansion of burning gases pushes the piston downward for the third stroke (power) and in the fourth stroke (exhaust) the piston pushes the products of combustion from the cylinder through an exhaust valve or valves.

6 STROKE ENGINE6 STROKE ENGINE

Six-stroke IC Engine:Six-stroke IC Engine:

The six stroke engine captures the wasted heat from the 4 stroke Otto cycle and creates steam which simultaneously cools the engine while providing a free power stroke. This removes the need for a cooling system making the engine lighter plus giving 40% increased efficiency over the Otto Cycle.Head Technology combines a four stroke engine bottom end with a ported cylinder which closely resembles that of a two stroke, thus 4+2= Six Stroke. It has an opposing piston which acts in unison with auxiliary low pressure reed and rotary valves, allowing variable compression and a range of tuning options

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% increased efficiency over the Otto Cycle. The pistons in a six stroke engine go up and down six times for each injection of fuel.

Advantages of 6 Stroke Engine:

1.Reduction in fuel consumption 2.Dramatic reduction in pollution 3.Better scavenging and more extraction of work per cycle 4.Lower engine temperature - so , easy to maintain the optimum engine 5.temperature level for better performance 6.Less friction – so , less wear and tear 7.The six-stroke engine does not require any basic modification to the existing engines. All technological experience and production methods remain unaltered.

The currently notable six stroke engine designs include Crower's six stroke engine, the Bajulaz engine and the Six-stroke engine (Trivandrum).

CURRENTLY NOTABLE 6 STROKE ENGINE’S

11) ) Bajulaz six stroke engineBajulaz six stroke engineThe 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 and the injection of fuel begins an isochoric burn which has increased thermal efficiency compared to a burn in the cylinder. The high pressure achieved is then released into the cylinder to work the power stroke. Meanwhile a second chamber which blankets the combustion chamber has had its air contents heated to a high degree by heat passing through the walls from the burn. This heated and pressurized air is then used to power another stroke of the piston in the cylinder. The advantages of the engine include reduction in fuel consumption by at least 40%, two expansion strokes (work) in six strokes, multi-fuel usage capability, and a dramatic reduction in pollution.

Bajulaz Six Stroke Engine was invented in 1989 by the Bajulaz S A ,company of Geneva, Switzerland and has U.S. Patent 4,809,511  and U.S. Patent 4,513,568 . The Bajulaz six stroke engine features are:

1.Reduction in fuel consumption by at least 40% 2.Two expansions (work) in six strokes 3.Multifuel 4.Dramatic reduction in pollution 5.Liquefied Petroleum Gas 6.Costs comparable to those of a four-stroke engine

2) Six-stroke engine by (Trivandrum student’s)

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

Its features are:-1.Reduction in fuel consumption 2.Dramatic reduction in pollution 3.Better scavenging and more extraction of work per cycle 4.Lower working temperature makes it easy to maintain optimum engine temperature level for better performance 5.Less friction, so less wear and tear 6.The six-stroke engine does not require any basic modification to the existing engines. All technological experience and production methods remain unaltered

3)Beare Head 6-Stroke Engine

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 a ported cylinder closely resembling that of a two stroke, thus 4+2= Six Stroke. It has an opposing piston that acts in unison with auxiliary low pressure reed and rotary valves, allowing variable compression and a range of tuning options. The engine demonstrably increases both torque and power output, achieves better fuel economy and cleaner burning with reduced emissions, and has longer service intervals and considerably reduced tooling costs when compared with a conventional OHC four-stroke design.The design with 4 intake ports fed by 2 reed blocks per cylinder allows the use of several different intake manifold types:

(1) 4 separate manifolds fed by 4 carburettors or injector bodies, of various length and diameters or all equal length and diameter.  (2) 2 separate manifolds bifurcated to each cylinder so that each has its own carburettor or injector body, with various lengths and diameters. (3) 2 separate manifolds bifurcated to each cylinder in turn, so that each cylinder is fed by 2 carburettors in turn even though the system has a total of 2 carburettors or injectors, with various length and diameter runners..  (4) 3 intake manifolds, with 3 carburettors or injector bodies, 1 bifurcated to each cylinder with long small diameter runners, the other 2 with short large diameter runners. 

4) "Crower's six stroke engine

The Crower six-stroke engine or Crower Cycle is a concept under development by Bruce Crower. Two extra strokes are added to the customary internal combustion engine four stroke Otto cycle. A fifth down-stroke is a "steam stroke" and the sixth is to exhaust the expanded steam while venting heat from the engine.

The engine cold starts on the Otto cycle, coasting through the fifth and sixth strokes for a short period. After the combustion chamber temperature reaches approximately 400 degrees Fahrenheit ( 204oC ), a mechanical operation phases in the fifth and sixth cycles. Just prior to the fifth-cycle, water is injected directly into the heated combustion chamber via the converted diesel engine's fuel injector pump, creating steam and another power stroke. The phase change from liquid to steam removes the excess heat of the combustion stroke forcing the piston down (a second power stroke). As a substantial portion of engine heat now leaves the cylinder in the form of steam, no cooling system radiator is required. Energy that is dissipated in conventional arrangements by the radiation cooling system has been converted into additional power strokes.

Crower has indicated that the volume of water used by the initial prototype configuration is at approximately the same rate as the amount of gasoline consumed. The water is a "total loss" and is not recaptured from the exhaust. Thus the water storage tank should be the same size as the fuel tank and should be refilled at the same time as the fuel, although the engine would still function without water. (This is evidenced by its ability to run without steam during its "warm-up" phase. However, it would overheat quickly running this way.) He has also indicated that water of a high level of purity is required

SPECIAL FEATURES OF CROWER’S 6STROKE ENGINESPECIAL FEATURES OF CROWER’S 6STROKE ENGINE

1.No cooling system required 2.Improves a typical engine’s fuel consumption 3. Requires a supply of distilled water to act as the

medium for the second power stroke

PROBLEMS OR OBSTACLES OF Crower’s 6 STROKE ENGINE

1.A warm up period of at least several minutes would be required in all automotive applications.

2.Power is reduced during warm up period

3.A steam-free cool down period is required to clear water/steam from the engine.

4.The weight of an oil separator and a water condenser are likely additions.

5.Endurance testing will likely identify components that may need to have upgraded materials designated, such as possibly using stainless steel for the valves, cylinders, and rings.

Working of Crowers’s 6 stroke engine

6-stroke bike by Crower6-stroke bike by Crower

Crower’s 6 Stroke EngineCrower’s 6 Stroke Engine

Thermodynamic Advantages of the Six Stroke

Referring to the graph, 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 cylinder capacity 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. 

This means that the extra volume is best swept by gas velocities and not mechanical movement, and therefore mechanical input energy is less. Also, maximum volume is before bottom dead centre 173 deg. Consequently valve timing, if the same as a 4 stroke, is more radical and is of longer duration in relation to engine volume and hence volumetric efficiency is considerably improved.

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 4 stroke; 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 exhaust port later than in a 4 stroke because maximum volume is not reached until after B.D.C.-548 deg. Instead of 540 deg. Hence the 6 stroke system is better from a thermodynamic point of view because more energy is extracted from the expansion process.

Volume-angle diagram for 4-stroke engine

Volume-angle diagram for 4-stroke engine

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Volume-angle diagram for 6 stroke engine

Volume-angle diagram for 6 stroke engine

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Pressure-Volume Diagram for OTTO Cycle

Pressure-volume diagrams for Otto cycle

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Pressure-Volume diagram for DUAL Cycle

Pressure-volume diagrams for Dual cycle

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Torque Angle Diagram For 4 Stroke Engine:

Torque-angle diagram for 4-stroke engine

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Torque angle diagram for 6-Stroke Engine

Torque-angle diagram for 6-stroke engine

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Comparison ChartComparison Chart

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Mechanical Engineering.