SIX STROKE ENGINE

Guided by :- Prof. Gajanan Thokal Presented by :- Chetan Pawar (PIIT,NEW PANVEL)

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HistoryIntroductionClassificationModifications Suggested For Engine PartsWorking PrinciplesComparison Of Six Stroke Engine With Four Stroke EngineGraphsThermodynamic AdvantagesLimitationsConclusion

TOPICS TO DISCUSS

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HISTORY

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.

Designs either use steam or air as the working fluid for the additional power stroke.

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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. 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 normal Otto or Diesel Cycle.

The pistons in this six stroke engine go up and down six times for each injection of fuel. These six stroke engines have 2 power strokes: one by fuel, one by steam or air.

INTRODUCTION

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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 and also it increases the compression ratio. 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

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CLASSIFICATION

Single piston designs - Griffin six stroke engine Bajulaz six stroke engine Crower six stroke engine Velozeta six stroke engine

Opposed piston design - Beare head M4+2 Piston charger engine

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MODIFICATIONS SUGGESTED FOR ENGINE PARTS

Cam shaft / Crank shaft Sprockets

Cam lobes

Valve Timing

Secondary Air Induction System

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WORKING PRINCIPLE 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.

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First stroke :- During the first stroke the inlet valve opens and air-fuel mixture from carburetor is sucked into the cylinder through the inlet manifold .

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Second stroke :-

 During the second stroke, piston moves from BDC to TDC, both the inlet valve and exhaust valve are closed and the air-fuel mixture is compressed.

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Third stroke :- During the third stroke, power is obtained from the engine by igniting the Compressed air- fuel mixture using a spark plug. Both valves remain closed. Piston moves from TDC to BDC.

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Fourth stroke :-

During the fourth stroke, exhaust the valve and the reed valve opens to remove the burned gases from the engine cylinder. Piston moves from BDC to TDC.

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Fifth stroke: -

During the fifth stroke, the exhaust valve remains open and the reed valve closes. Fresh air from the air filter enters the cylinder through the secondary air induction line provided at the exhaust manifold . The reed valve opens.

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Sixth stroke:-

During the sixth stroke, the exhaust valve remains open. The air sucked into the cylinder during the fifth stroke is removed to the atmosphere through the exhaust manifold. The reed valve opens and the reed valve closes.

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1. In a six stroke engine the energy absorption is less because of slower acceleration of reciprocating parts.

2. It reduces the weight and complexity of the engines head by as much as 50%. Instead of using energy to drive the head.

3. Torque is increased by 35% and efficiency increased by the same.

4. Increased torque and power output.

COMPARISON OF SIX STROKE ENGINE WITH FOUR STROKE ENGINE

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GRAPHS

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THERMODYNAMIC ADVANTAGES

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.

The change in volume during the compression stroke is slightly greater than a 4 stroke after the ports are closed.

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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.

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During the critical combustion period the rate of change in volume in the 6 stroke is less than a 4 stroke. Minimum volume is not reached until after T.D.C., at 361 deg. This is because of the phasing of the upper piston. It is retarded in reaching its T.D.C. until 20 deg. after T. D.C. (380). This is much better from a thermodynamic view in that combustion occurs at a more constant volume; hence ignition timing is not as critical as in a 4 stroke. There is room in the combustion chamber for up to 4 spark plugs and two direct injectors if needed.

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LIMITATIONS

Injecting relatively cold water onto a hot metal piston can damage it over time from thermal expansion and contraction.

Separate water tank would have significant weight and space penalties.

A steam-free cool down reduces the temperature inside the combustion chamber.

Cold climate anti-freezing measures would be needed in the water reservoir.

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CONCLUSION In a six stroke engine the energy absorption is less because of slower acceleration of reciprocating parts The piston speed of the upper piston is about a quarter of the main piston; therefore its service life should be at least twice that of the main piston.

In the Beare design, per single cylinder, the number of parts is 15 compared to a four stroke of approx 40 to 50 parts. Also, to reduce manufacturing costs the head and block can be machined in o ne piece.

The bottom piston is a standard design and the Beare Head bolts directly o nto the engine block, replacing the overhead valves and standard head.

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It reduces the weight and complexity of the engines head by as much as 50%. Instead of using energy to drive the head, the head actually develops energy for conversion to power back through the timing chains of an engine.

Torque is increased by 35% and efficiency increased by the same. This can be achieved by simply unbolting an existing head of a four-stroke engine and then bolting on a Beare Head.Increased torque and power output.

Better fuel economy and cleaner burning longer service intervals and considerably reduced tooling costs when compared with a conventional four-stroke design.

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QUERIES

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