INTRODUCTION

The quest for an engine which having the same or more power with higher fuel efficiency than the existing ones has started before many years. As a result of all these researches a new engine concept is formed, which is a six stroke engine. Lot of research works are conducting on this topic nowadays and already six types of six stroke engines were discovered yet. Of these the recently developed three six stroke engines, i .e. , Beare head, Bruce crowers and Velozeta's are undergoing tremendous research works.

During every cycle in a typical four stroke engine, piston moves up and down twice in the chamber, resulting in four total strokes and one of which is the power stroke that provides the torque to move the vehicle. But in a six stroke engine there are six strokes and out of these there are two power strokes. The automotive industry may soon be revolutionized by a new six-stroke design which adds a second power stroke, resulting in much more efficiency with less amount of pollution.CONCEPT

The majority of the actual internal combustion engines, operating on different cycles have one common fea ture , combus t ion occur r ing in the cy l inder a f te r each compression, resulting in gas expansion that acts directly on the piston (work) and limited to 180 degrees of crankshaft angle. According to its mechanical design, the six-stroke engine with external and internal combustion and double flow is similar to the actual internal reciprocating combustion engine. However, it differentiates itself entirely, due to its thermodynamic cycle and a modified cylinder head with two supplementary chambers: Combustion, does not occur within the cylinder but in the supplementary combustion chamber, does not act immediately on the piston, and it 's duration is independent from the 180 degrees of crankshaft rotation that occurs during the expansion of the combustion gases (work).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% 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 combustion chamber is totally enclosed within the air-heating chamber. By heat exchange through the glowing combustion chamber walls, air pressure in the heating chamber increases and generate power for an a supplementary work stroke. Several advantages resul t f rom this , one very important being the increase in

Thermal efficiency. In the contemporary internal combustion engine, the necessary cooling of the combustion chamber walls generate important calorific losses. In six- stroke engine 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 pis ton charger , in the gas t ransfer channel or in the combust ion 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 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. 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.

• TYPES

The term six stroke engine describes two different approaches in the internal combustion engine, developed since the 1990s, to improve its efficiency and reduce emissions,In the first approach, the engine captures the waste heat from the four stroke Otto cycle or Diesel cycle and uses it to get an additional power and exhaust stroke of the piston in the same cylinder. The currently notable six stroke engine designs in this class are the Crower's six stroke engine, invented by Bruce Crower of the U.S.A; the Bajulaz engine by the Bajulaz S A Company, of Switzerland; and the Velozeta's 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 which 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 convent ional engine . The current ly notable s ix s t roke engine

Designs in this class include two designs developed independently: the Beare Head

First Category

Griffin six stroke engine

Bajulaz six stroke engine

Crower six stroke engine

Velozeta Six stroke engine

Figure 1: Griffin Simplex

engine, invented by Australian farmer Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.

Beare head engine

German charge pu

First category

GRIFFIN SIX STROKE ENGINE Griffin engine was the first six stroke engine developed in the wor ld . I t i s deve loped by the engineer Samuel Griffin in 1883. The key principle of the "Griffin Simplex" was a heated exhaust-j acke ted ex te rna l vapor ize r , into which the fuel was sprayed. T h e t e m p e r a t u r e w a s h e l d a r o u n d 5 5 0 ° F ( 2 8 8 ° C ) , s u f f i c i e n t t o p h y s i c a l l y v a p o r i z e t h e o i l b u t n o t t o break it down chemically. This fractional distillation supported the use of heavy oi l fuels , the u n u s a b l e t a r s a n d a s p h a l t s s e p a r a t i n g o u t i n t h e

v a p o r i z e r . I n 1 8 8 6 S c o t t i s h steam locomotive makers found a future in Griffin's engine and

Figure 2: Actual prototype of Bajulaz

engine

Port wish EvapCrititOr In-,u!ill*r Wilt/ catalyst

Expander

1-Fig15 pre B3411'0 Condens erwales Izni!

Figure 3: Crower six stroke engine

They l i censed the Gr i f f in pa ten ts a l so marke ted the engine under the name `Kilmarnock'. They used this engine mainly for electric power generation. Only two known examples of a Griffin six-stroke engines survive today. One is in the Anson engine museum. The other was bui l t in 1885 and for some years was in the Birmingham Museum of Science and Technology but in 2007 it returned to Bath.

BAJULAZ SIX STROKE ENGINE

The Bajulaz Six Stroke Engine was invented in 1989 by the Bajulaz S A Company, based in Geneva, Switzerland. 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 f ixed capaci ty chambers : a combust ion c h a m b e r a n d a n a i r p r e h e a t i n g c h a m b e r a b o v e e a c h cylinder. The combustion chamber receives a charge of heated air from the cylinder; the injection of fuel begins an i sochor ic burn which increases the thermal e f f ic iency compared to a burn in the cyl inder . The high pressure achieved is then released into the cylinder to work the power or expansion stroke. Meanwhile a second chamber which b lanke t s the combus t ion chamber , has i t s a i r con ten t 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 40%, multi-fuel usage capability, and a dramatic reduction in pollution.

CROWER SIX STROKE ENGINE This eng ine i s inven ted by Bruce crower of California in USA in the year 2004. Bruce Crower is actually a race car mechanic wi th h i s own workshop. In his six-stroke engine, power is obtained in the third and sixth strokes. First four strokes of this engine are similar to a normal f o u r s t r o k e e n g i n e a n d p o w e r i s de l ivered in the th i rd s t roke . Jus t p r io r to the f i f th s t roke , wa te r i s i n j e c t e d d i r e c t l y i n t o t h e h e a t e d cy l inder v ia the conver ted d iese l eng ine ' s f ue l i n j e c to r pump . The

Figure 4: Velozeta six stroke engine

In jec ted wate r absorbs the hea t p roduced in the cy l inder and conver t s in to superheated steam, which causes the water to expand to 1600 times its volume and forces the piston down for an additional stroke i.e. the second power stroke. The phase change from liquid to steam removes the excess heat of the engine 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. In Crower's prototype, the water for the steam cycle is consumed at a rate approximately equal to that of the fuel, but in production models, the steam will be recaptured in a condenser for re-use.

VELOZETA SIX STROKE ENGINE

In a Velozeta engine, fresh air is injected into the cylinder during the exhaust stroke, which expands by hea t and therefore forces the p is ton down for an addi t ional

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%. 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 valve overlaps have been removed and the two additional strokes using air injectionProvide for better gas scavenging. The engineSeems to show 40% reduction in fuel consumption and dramatic reduction in air pollution. Its specific power is slightly less than that of a four-stroke gasoline engine. The engine can run on a variety of fuels, ranging from gasoline and Diesel fuel 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. The engine was developed in 2005 by a team of mechanical engineering students , Mr. U Krishnaraj, Mr. Boby Sebastian, Mr. Arun Nair and Mr. Aaron Joseph of the College of Engineering, Trivandrum.

Second category

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 or piston charger replaces the valve mechanism of a conventional engine but also increases the compression ratio. 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

Figure 6: German charge pump engine parts

Cyl inde r , combus t i on t ake s p l ace eve ry t u rn a s i n a two- s t roke eng ine and lubrication as in a four-stroke engine. Fuel injection can

take place in the pistonCharger, in the gas transfer channel or in the combustionC h a m b e r . I t i s a l s o

Poss ib l e t o cha rge twoWork ing cy l inders wi thOne pis ton charger . TheCombination of compactDesign for the combustionChamber together with no Figure 5:

German charge loss of a i r and fuel is

P u m p c l a i m e d t o g i v e t h e e n g i n e m o r e t o r q u e , m o r e p o w e r a n d b e t t e r f u e l 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 i s c la imed to be su i ted to a l ternat ive fuels s ince there i s no corrosion or deposits left on valves. The six strokes are

1.Aspiration2.Pre-compression3.Gas transfer

4.Compression5.Ignition and6.Ejection.

This is an invention of Helmut Kottmann from Germany, while working 25 years at MAHLE GmbH piston and cylinder construction.

BEARE HEAD ENGINE

Malcolm Beare, an Australian wheat farmer is the inventor of this s ix s t roke engine at the age of 47. Actually the name s i x s t r o k e e n g i n e s w a s introduced by Malcolm Beare. Beare created an innovat ive hybrid engine, combining two-strokes in the top end with a four-stroke above the middle portion. So by adding this four plus two equals six, he derived

Figure 7: Beare head engine

Six strokes of the engine.

M4+2 ENGINEThe M4+2 engine is based on the combined working of a two stroke and a 4 stroke engine simultaneously. The success of this type of six-stroke engine is based on the cooperation of both modules. The air load change takes place in the two-stroke section of the engine. The piston of the four-stroke section is an air load exchange aiding system, working as a system of valves. The cylinder is filled with air or with an air-fuel mixture. The 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 windows in the cylinder. The fuel is supplied into the cylinder by a fuel injection system. Ignition is realized by two spark plugs. The effective power ou tpu t o f the doub le -p i s ton eng ine i s t r ans fe r red by two c rankshaf t s . The characteristic feature of this engine is an opportunity of continuous change of cubic capaci ty and compress ion ra te dur ing engine work by changing the pis ton 's location. The mechanical and thermo dynamical models were meant for double- piston engines, which enable to draw up new theoretical thermodynamic cycle for internal combustion double pistons engine.

♦ DETAILED WORKING PRINCIPLE

Among the different types of six stroke engines described above the ones from the same category have no major fundamental difference in their working principle.

Here the working principle of Bajulaz six stroke engine will be explained as an example.The parts of the engine as numbered in figure 10 are:

1. In take va lve2.Heat ing chamber va lve3.Combust ion chamber va lve4.E x h a u s t v a l v e5.C y l i n d e r6.Combus t i on chambe r7.Air hea t ing chamber8.Wal l o f combus t i on chambe r9.Fue l i n j e c to r10. H e a t e r p l u g

FIRST STROKE

During the first stroke the inlet valve is opened and air or air-fuel mixture is sucked into the cylinder.

SECOND STROKE

During this stroke air or air fuel mixture compressed to the maximum pressure. 

THIRD STROKE

This is first power stroke of the engine. This is given by primary fuel (petrol or diesel or LPG). During this stroke all valves are remains closed.

FOURTH STROKE

During this stroke exhaust valve will be opened and burned gases send out to the atmosphere through the heat recovery system for warm-up the water.

FIFTH STROKE

In this stroke, Water is injected into the hot cylinder through the steam valve. By absorbing the heat from cylinder wall, the steam expands causing the piston to move down.  

SIXTH STROKE 

The expanded steam escapes through the opened exhaust valve and hence the piston moves upward. These exhaust steams also send via heat recovery system for warm-up the water.

♦ 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 iner t ia due to the l ightness 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 va lves , du r ing compress ion o f f r e sh and supe rhea t ed a i r . F r i c t i on lo s ses , 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.

♦ ADVANTAGES & DISADVANTAGES

Advantages

1.Reduct ion in fuel consumption by at least 40 %

2.Two expansions(work/Power stroke) in six strokes

3.Dramatic reduction in pollution ( up to 65 %)

4.Higher overall efficiency

5.Lower engine temperature 85 noise level

6.Due to more air intake, the cooling system is improved

7.Better scavenging and more extraction of work per cycle

8.Less inert ia due to l ightness of moving parts

9.Less fr ic t ion - so , less wear and tear10.The six-stroke engine does not require any basic modification to the

existing engines. All technological experience and production methods remain unaltered

11.Cost comparable to those of a four-stroke engine

Disadvantages

1.Brake power 85 indicated power per cycle per cylinder is comparatively lesser

2.Engine size increases due to many number of cylinders 85 additional components

♦ COMPARISON

Apart from the advantages and dis advantages mentioned earlier there are some more features of six stroke engine that can be said in comparison with two stroke and four stroke engine:

>Lower maintenance costs due to less wearing parts (cylinder head)

>Longer service intervals possible due to lower operat ing temperatures recorded

>Increase in thermal e f f ic iency

Comparison in exhaust:Four Stroke

Diesel EngineSix Stroke Diesel

Engine

Nitrous Oxide [ppm] 768 113( % improvement) (85.3%)

Soot [%] 6.8 28.8(%improvement) (- 323.5%)

Indicated specific heat consumption bi' [MJ/KW-h]

7.51 6.61

(12.0%)

(% improvement)

APPLICATION

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)Motor-pumps, generator sets, stationary engines, etc ....intended for agriculture and

industry.4)Automobiles, heavy goods, construction-site and farm vehicles .5)Many more applications may also be envisaged .

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 is for automobile, heavy goods, construction-site and farm vehicles. This is a priority for the six- stroke engine. Drast ical ly reducing fuel consumption and pollut ion without radically affecting performances would allow the current concept of the automobile to be reassessed.

There i s , a t th i s day , no wonder so lu t ion for the rep lacement o f the in te rna l combust ion engine . Only improvements of the current technology can help i tprogress within reasonable time and financial limits. The six-stroke engine fits perfectly into this view. Its 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 wi th in 4

and 5 l i te rs per 100km. and 3 to 4 l i te rs for the smal l -s ized cars . Automobiles equipped with the six-stroke engine could appear in the market within 3 to 5 years.

♦ REFERENCES

Information: Wikipedia, sechstaktmotor.de , peswiki.com , authorstream.com , sumitshrivastva.blogspot.com , wordpress.com etc.Images: Google images and some other sites.