DUAL FUEL SIX STROKE ENGINE WITH EGR TECHNOLOGY

DUAL FUEL SIX STROKE ENGINE WITH EGR TECHNOLOGY

ABSTRACT

The Present scenario of Fuel Consumption is well known to everyone. Everyday technical people talk about the depleting Fuel sources and Exhaust hazards. Particularly about the Diesel engines find their importance more than the Petrol engines due to their operating cost and Fuel consumption But Diesel engines have their demerits in the area of Exhaust and Power loss. Necessary steps have to be taken in order effectively use the Fuel available. We have brought the UTILIZATION OF SIX STROKE ENGINES which runs on DUAL FUEL to your view. The Six Stroke Engine’s Principle resembles the Double Stage Compressor. By this way effective Compression is done and the need for Turbocharger is completely neglected. We have also considered Cylinder’s position in Six Stroke engine. Also the Pollution (NOx) emitted by the Diesel Engines is also taken into account. We found the solution in the form of Dual fuel and Exhaust Gas Recirculationsystem. The Combusting Temperature is above 2000 F and this is the prime reason for NOx Emission. So an Alternative Fuel which can be combusted below the level of Diesel should be used. Moreover the availability and production cost must be taken into consideration. We found Ethanol as a better alternative for Diesel. The Cold Starting of the Engine is made easier using GLOW PLUG which is used to preheat the Charge coming inside the Combustion Chamber.

INTRODUCTION

In today’s world, the usage of Internal Combustion Engines is inevitable..Oxides of Nitrogen (NOx) are formed when Temperatures in the Combustion Chamber get too hot. At 2500 F, the Nitrogen and Oxygen in the Combustion Chamber can chemically combine to form Nitrous Oxides, which, when combined with Hydrocarbons (HCs) and the presence of Sunlight, produces harmful effects. In order to reduce these effects, a Dual Fuel technique is implemented in which ethanol is used as a Running Fuel which has less NOx emission than the Conventional Diesel Engines.

In order to achieve such a High Compression Ratio , Efficiency. Six Stroke CI engine is found to be more suitable. Starting of CI engines during cold weather becomes severe when compared to the SI engines. The conventional method of circulating hot water is being replaced by GLOW PLUG, thereby diesel consumption during starting period is reduced considerably and quick starting is achieved

Exhaust Gas Recirculation (EGR)

This system also gets added up in the list so as to reduce the NOx effect. A simple recirculation circuit dilutes the incoming charge in the inlet manifold thereby reducing the combustion temperature to some 100 degree which optimally reduces the NOx problem. We also had the idea of implementing Turbo charger, but usage of six stroke engine and EGR eradicated that idea.

SIX STROKE ENGINE

Considering the importance of cleaner, powerful and economical engine we have come up with this new idea for practical implementation of six stroke engine , which will be nearly 40% more fuel efficient than the existing four stroke engines. The engine is also more efficient and powerful than the existing six stroke and four stroke engines. The engine is also having the scope of using heavy fuels and bio-fuels.

The majority of the actual internal combustion engines, operating on different cycles have 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 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 and an Air Heating Chamber, both independent from the cylinder. Combustion does not occur within the cylinder but in the supplementary combustion chamber, does not act immediately on the piston, and its duration is independent from the 180 degrees of crankshaft rotation that occurs during the expansion of the combustion gases (work).

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 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 generates important calorific losses.

The engine has better turbulence due to which the combustion is smooth and effective. The engine has better air pollution control than existing four stroke engines. The engine may be smokier with heavy fuels but the pollution level when compared to the existing heavy fuel engines will be within limit. With the use of conditioned heavy fuels, this sulphur smoke can be dramatically reduced and pollution can be reduced considerably

BASIC ENGINE PARTS

Inlet Valve: when open supplies fresh air into the engine

Exhaust Valve: When open removes the burned gases from the engine

Combustion chamber Valve: The valve connects the cylinder with the combustion chamber. Opens to permit the flow of compressed air from the cylinder to the combustion chamber and also to permit the flow of exhaust gases from the combustion chamber to the cylinder to drive the power stroke.

Heating chamber Valve: The heating chamber has been provided with a valve, to release the pure air into the cylinder. The valve makes scavenging much more effective than what is found in the existing six stroke or four stroke engines.

Fuel Injector: Highly pressurized is injected into the combustion chamber.

Cylinder: Supplies compressed air to the combustion chamber. It also aids in providing better turbulence in the combustion chamber making combustion smooth and effective

Combustion Chamber: The combustion of the compressed fuel occurs with the aid of the fuel pumped into the cylinder.

Piston: moving in the cylinder, gets power from the exhaust of the combustion chamber and the air from the heating chamber

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GLOW PLUG:--PREHEATER

To preheat the cylinder before starting. One such method is the circulation of hot water into the water jacket of the cylinder.Glow plug emerges as a very good alternative. A heating element is placed nearby the fuel injector, which is being supplied with a very high current of 25-35 amperesfor a period of 5 to15 seconds prior to the starting. The heat is transferred by means of combustion from the cylinder surface to the incoming air, thereby reducing time taken to heat the air medium.

WORKING OF A GLOW PLUG

Fuel blend assists in using a heater for a better running condition .High latent heat and low vapour pressure reduces the temperature of cylinder wall which necessitates the use of Glow plug.

THE STROKES:

FIRST STROKE

During the first stroke the inlet valve is opened and air is sucked into the compression

Chamber. The air is compressed in the combustion chamber.

SECOND STROKE

The heating chamber valve is opened and the air sucked in by the cylinder is compressed and send to the heating chamber. Simultaneously the fuel is injected in the combustion chamber. Thus the combustion takes place inside the combustion chamber

THIRD STROKE

The combustion chamber valve opens and the combustion gases is realased into the cylinder. The high pressure with which the exhaust gases are pushed out aids to obtain a power stroke. Simultaneously there is a heat exchange takes place between the combustion chamber and heating chamber which is filled with pure air.

FOURTH STROKE

The exhaust valve is opened, driving out the exhaust gases from the cylinder

FIFTH STROKE

By heat exchange through the glowing combustion chamber walls, air pressure in the heating chamber is increased. When the heating chamber value is opened the high-pressured air formed will enter the cylinder which will result in another power stroke.

SIXTH STROKE

When the combustion chamber valve opens, the expanded air is re-compressed and sends into the combustion chamber.

ADVANTAGES

• 30% reduction in fuel consumption and Two Power Strokes
• More powerful than the existing conventional engines.
• Heavy fuel Usage, Better Scavenging
• Dramatic reduction in pollution

FACTORS CONTRIBUTING TO ADVANTAGE:

1. The heat that is evacuated during the cooling of a conventional engine’s cylinder head isrecovered 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-engines, 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.

DUAL FUEL TECHNOLOGY

Dual fuel engine is one which operates with two different fuels. One is the igniting fuel (diesel) and other is the running fuel. We can find huge variety of running fuels from the present researches. One such fuel is ALCOHOL.

Under Alcohol, many types are found to satisfy the budding problem such as Methanol, ethanol, Butyl alcohol, etc. We Prefer Ethanol as the suitable running fuel because of the following properties listed..

Chemical formula	Chemical weight (kg/mole)	Specific gravity	Boiling point (C)	Latent heat (KJ/kg)	Combustion energy (KJ/kg)	Vapour pressure @100F (psi)	Solubility part in 100 parts H2O
CH3CH2(OH)	20.906	0.79	78	189.463	6296.332	2.2	infinite

Moreover some additional advantages related with ethanol are:

• It is not a fossil fuel (i.e.) combusting it does not cause any Green House Effect.
• It is Biodegradable which does not affect the environment.
• Higher oxygen content ultimately reduces the NOx emission and other harmful pollution
• The fuel is very much economical for long run.
• The compression ratio is high of the order 25-27.

Since the alcohols have very high self ignition temperature, so the design of the engine using ethanol as the primary fuel will be robust and expensive .So a general idea of using ethanol in dual fuel operation is practiced.

PRINCIPLE OF OPERATION

In dual fuel engine the alcohol is generally injected into the combustion chamber. Due to high self ignition temperature of alcohols, there will be no combustion with usual diesel compression ratios of 16-18. So a little before the end of compression stroke, a small quantity of diesel oil is injected into the combustion chamber through normal pumping techniques. The diesel oil readily ignites and this initiates combustion in the alcohol-air mixture also.

METHODS OF INJECTING ETHANOL

Methods used are pneumatic spray nozzle, vapourizer, carburetor and fuel injector.

Another important method that can be implemented is the direct injection of ethanol into the combustion chamber after the diesel fuel injection. By this way, alcohol cooling of the charge is avoided to a degree which will jeopardize the ignition of the diesel fuel.

This system requires two complete and separate fuel systems with their necessary fuel feed systems.

In the dual fuel engines, major portion of the heat release is by the alcohol supplied and this alcohol is ignited by a spray of diesel oil injection.

ENERGY CONSIDERATION

The calorific value of alcohols is lower than the diesel oils and hence a larger quantity of alcohols has to be used for producing the same amount of power output. However the air requirement for combustion is lower and hence the energy content of the mixture is the same. Since the latent heat of vapourisation is very high, the temperature and pressure at the end of compression come down due to their evaporation. Hence if the alcohol

Injection rate exceeds a limit, the injected diesel will not be able to ignite and hence the engine will fail to function.

EXHAUST GAS RECIRCULATION

NEED FOR EGR

During acceleration and normal running condition, the combustion temperature inside the combustion chamber is around 2000 Fahrenheit. This condition is favorable for the NOx formation. The nitrogen and oxygen in the combustion chamber can chemically combine to form nitrous oxides, which, when combined with hydrocarbons (HCs) produces harmful effects.

EVOLUTION OF EGR :-- General Motors in 1970

PRINCIPLE:-

The exhaust from the combustion chamber is being circulated back to intake manifold by a simple piping mechanism. By this way the fuel charge is diluted and temperature is reduced so as to reduce harmful emission.

The amount of exhaust circulated is determined by the Electronic control unit (ECU).Depending upon the engine loading condition, the flow is allowed by the EGR valve which is actuated by ECU.

Conditions when EGR should not respond are:

Higher accelerating conditions.

During idling and cold start conditions.

EGR has to work for a normal loading and running condition. This phenomenon is not really understood by the people early and they started to disconnect the EGR system from the Engine. To overcome the above listed problems, closed loop system was invented in the early 1980s. The working of such EGR system is explained below.

THE DESIGN CHALLENGE

The EGR system of today must precisely control the flow of re-circulated exhaust. Too much flow will retard engine performance and cause a hesitation on acceleration. Too little flow will increase NOx and cause engine ping. A well-designed system will actually increase engine performance and economy. As the combustion chamber temperature is reduced, engine detonation potential is also reduced

It has a diaphragm that pulls open a valve stem, which allows exhaust to enter

the intake manifold when ported vacuum is applied to it. Ported vacuum increases with throttle opening. A thermal vacuum switch prevents vacuum from reaching the EGR during cold engine starts.

Lowering the amount of oxygen in the cylinder and the combustion temperature, NOx emission is reduced therefore at the source of origin. Cooling the recirculate gas enhances the effectiveness of EGR and thus the further reduction in NOx. Intensified EGR cooling serves to reduce NOx and exhaust smoke particularly at peak load.

Increased EGR cooling has practically no effects on NOx and smoke emission at very low loads (1000 rpm, 2 bar), nevertheless this causes increased HC and CO emissions. Therefore, to control these emissions, an EGR cooler by-pass has to be installed. This by-pass serves to conduct partial flow or full flow of the exhaust gas depending on the load and speed. The EGR cooler will also be by-passed for engine cold start and warm-up.

EGR can also be used by using a variable geometry turbocharger (VGT) which uses variable inlet guide vanes to build sufficient back pressure in the exhaust manifold. For EGR to flow a pressure difference is required across the intake and exhaust manifold and this is created by the VGT.

The purpose of the Exhaust Gas Recirculation (EGR) system is to reduce engine exhaust gas emissions in accordance with EPA regulations.

Part of the exhaust gasses from the combustion chamber is routed from the exhaust manifold through the EGR cooler, past control and reed valves, and are mixed with the intake manifold charge air. The addition of cooled exhaust gasses back into the combustion airflow reduces the peak in combustion temperature. Less oxides of nitrogen (NOx) are produced at lower combustion temperatures. The recycled exhaust gasses are cooled before engine consumption in a tube (radiator) and circulated

FLOW DIAGRAM OF EXHAUST GAS IN EGR TECHNOLOGY

COMPONENTS:--

EGR COOLER

The EGR Cooler is equipped with a single-pass cooler. Part of the exhaust gasses from the cylinders are directed through the EGR shutoff valve and through the cooler and reed valves, past the EGR modulated control valve and the mixer and then back to the cylinder.

EGR CONTROL VALVES

The EGR shutoff valve and the EGR modulated control valve are control valves. The EGR shutoff valve is a pneumatically driven butterfly valve, located at the inlet of the EGR cooler. It closes when the exhaust flap or turbo-brake actuates, avoiding exhaust gas flow and excessive pressure in the EGR cooler and reed valves. The EGR modulated control valve is an electronically actuated butterfly valve located after the EGR cooler and reed valves, controlled by the ECU. This valve controls the exhaust gas flow for the intake manifold.

REED VALVES

The reed valves work like a check valve, allowing flow of gas only in one direction, avoiding gas back flow when the intake pressure is higher than exhaust gas pressure. As the average exhaust pressure is lower than the intake pressure, the gas flow through the reed valves is possible due to exhaust gas pressure peaks — peaks slightly higher than the intake air pressure, which occurs as the engine exhaust valves open. During this peak of pressure, the reed valves open and allow gas flow to the EGR modulated valve and mixer.

EGR MIXER

The purpose of the mixer is to ensure good mixing of the cooled EGR gasses with filtered charge air. Once the exhaust gasses are cooled and have completed their cycle through the EGR system, they are released into the EGR mixer. The recycled exhaust gasses are combined with the charged air and directed to the cylinder.

EFFECT ON EMISSIONS AND DRIVEABILITY

Too little EGR flow may cause detonation and emission failure for excessive NOx. Because EGR tends to reduce the volatility of air fuel charge, loss of EGR causes detonation to occur.

Too much EGR flow for driving conditions may cause stumble, flat spot and hesitation. Because EGR dilutes the air fuel charge, too much EGR for a given engine demand can cause a misfire. It is uncommon to see tip in hesitation, stumble and surging when too much EGR is metered.

CONCLUSION

• A good engine needs high efficiency, high performance characteristics, low emission standards. It seems that the above mentioned solution meets all these specified standards.
• For the practical implementation, changes in the design of Compression Ignition engines are not of a greater magnitude. The only change that has to be implemented is that the metering system should be able to meet 9:1 air fuel ratio.
• Further cold starting is performed efficiently using glow plugs. It is very much essential to implement the dual fuel technique ASAP in order to save the ozone layer and to live in a green world.
• Indian economy can be considerably saved because the fuel usage does not involve any foreign exchange.