INTRODUCTION The quest for an engine which having the same or more power with higher fuel efficiency than the existing ones has started before man y 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 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 pr ov ides id es the th e to rq ue to mo ve th e ve hi cl e. Bu t in a six si x stro st ro ke en gi ne th er e ar e six si x st ro k es 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 internal combustion combustion engines, operating operating on different cycles h av e one common feature, combustion occurring in the cylinder after 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 sixstroke 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 in ternal 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 extracti extracting ng po we r, th e ad di tion ti on al stro st ro ke co ol s th e en gi ne an d re move mo ve s the th e ne ed for fo r a co o li n g s ys te m making the engine lighter and giving 40% increased efficiency over the Otto Cycle. The pist pi ston on s in a six si x stro st ro ke en gine gi ne go up an d do wn six si x time ti me s for fo r ea ch i nj e c ti o n o f fu e l. Th e si x stroke engine has 2 power strokes, one fuel, one steam or air. The combustio combustion n 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 result from 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-str oke 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 c onsumptio n. 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 fro m 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 pi st on mo vem en ts per cyc le . It doe s no t us e any ad di ti ona l wo rk in g fl uid . In the six stroke engine developed by the students of College of Engineering, Trivandrum, India, the first four strokes are th e same as a four stroke intern al 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. Th e valve overlaps have be en remove d and the additional two strokes have been pr ov id ed fo r be tt er sc av en gi ng , us in g ai r in je ctio n. The engine sh ows 40% reduction in fuel consumptio n a nd d ramatic 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 po llut io n when co mp ared with th e fo ur st ro ke en gi ne fr om wh ic h it wa s dev el ope d.
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TYPES
The term six stroke eng ine 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 conventional engine. The currently notable six stroke engine Designs in this class include two designs developed independently: the Beare Head
engine, invented by Australian farmer Malcolm Beare, and the German Charge pump, invented by Helmut Kottmann.
First Category Griffin six stroke engine
Bajulaz six stroke engine
Crower six stroke engine
Beare head engine
German charge pu
Velozeta Six stroke engine
First category GRIFFIN SIX STROKE ENGINE Griffin engine was the first six stroke engine developed in the world. It is developed by the engineer Samuel Griffin in 1883. The key principle of the "Griffin Simplex" was a heated exhaust j a c k e t e d ex ternal vaporiz er, into which the fuel was sprayed. The temperature was held around 550 °F (288 °C), sufficient to ph ysically vaporize 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 vaporizer. In 1886 Scottish steam locomotive makers found a future in Griffin's engine and
Figure 1 : Griffin Simplex
They licensed the Griffin patents also marketed 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 built 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 b y the Bajulaz S A Company, based in Geneva, Switzerland. The Bajulaz six stroke engine is si milar 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 cyl ind er. The hig h pres sur e 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 Figure 2: Actual then used to power an additional stroke of the piston. The pro totype of Baj ulaz advantages of the engine include reduction in fuel engine consumption by 40%, multi-fuel usage capability, and a dramatic reduction in pollution. CROWER SIX STROKE ENGINE This engine is invented by Bruce crower of California in USA in the year 2004. Bruce Crower is actually a race car mechanic with his own workshop. In his six-stroke engine, p o we r is o b t ai n e d i n th e th i rd a n d sixth strokes. First four strokes of this engine are similar to a normal four stroke engine and power is delivered in the third stroke. Just p r i o r t o t h e fi ft h s t r o k e , w a t e r i s injected directly into the heated cylinder via the converted diesel engine's fuel injector pump. The
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Figure 3: Crower six stroke engine
Injected water absorbs the heat produced in the cylinder and converts into 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 ph ase change from liquid to steam removes the excess heat of the engine As a substantial po rtio n of en gi ne hea t no w le ave s th e cylin de r in th e fo rm of st ea m, no coolin g s yst em 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 exhau st stroke, w h i c h e x p a n d s b y h e a t a n d t h e r e f o r e f o r ce s t h e p i s t o n d o w n f o r a n a d d i t i o n a l 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 injection Provide for better gas scavenging. The engine Figure 4: Velozeta six stroke engine Seems 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 Co llege 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
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 Fi g u re 5 : German charge loss of air 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 is claimed to be suited to altern ative fuels s ince there is no corrosi on o r deposits left on valves. The six strokes are 1. Aspiration 2. Pre-compression Figure 6: German charge pump engine parts 3. Gas transfer
4. Compression 5. Ignition and 6. 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 six stroke engine at the age of 47. Actually the name six stroke engines was introduced by Malcolm Beare. Beare created an innovative hybrid engine, combining twostrokes in the top end with a four-stroke above the middle po rtion. So by ad ding th is four pl us two equals six, he de rive d Figure 7: Beare head engine
Six strokes of the engine. M4+2 ENGINE The 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 output of the double-piston engine is transferred by two crankshafts. The characteristic feature of this engi ne is an opportunity of continuous change of cubic capacity and compression rate during engine work by changing the piston's location. The mechanic al and thermo dynami cal models were meant for doub le-piston engines, which enable to draw up new theoretical thermodynamic cycle for internal com bustion d ouble p istons eng ine.
♦ 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. Intake valve 2. Heating chamber valve 3. Combustion chamber valve 4. Exhaust valve 5. C yl inder 6. Combustion chamber 7. Air heating chamber 8. Wall of combustion chamber 9. Fuel injector 10. 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 INCRE ASED 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, 36 0 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° o f which is in closed combustion c ham ber, 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-e ngine, int ake take s place o n the first stroke and ex haust 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 ) L e s s i n e r t i a d u e t o t h e l i g h t n e s s o f t h e m o v i n g p a r t s . 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 co ld 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, theoretica lly 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. R e d u c t i o n i n f u e l c o n s u m p t i o n b y a t l e a s t 4 0 % 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 c ycle 8. Less inertia due to lightness of moving parts 9. L e s s f r i c t i o n - s o , l e s s w e a r a n d t e a r 10 . The six-stroke engine does not require an y 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:
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Lower maintenance costs due to less wearing parts ( cylinder head)
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Longer service intervals possible due to lower operating temperatures recorded
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Increase in thermal efficiency
Comparison in exhaust: Four Stroke Diesel Engine
Six Stroke Diesel Engine
Ni trou s Ox id e [p pm] ( % improve ment)
768
113 (85.3%)
Soot [%]
6.8
28.8
(%impr ovem ent)
Indicated specific heat consumption bi ' [M J/ KW-h]
(- 323.5%)
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 it s use. Furtherm ore, the use of fuels other than gasoline wo ul d 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 an d 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-strok e 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 itprogress within reasonable time and financial limits. The six-stroke engine fits perfectl y 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 wi thin 4 a n d 5 l i t e r s p e r 1 0 0 k m . a n d 3 t o 4 l i t e r s f o r t h e s m a l l - s i z e d c a r s . A ut om ob il es 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.
