MODIFICATIONS IN DIESEL ENGINE TO USE CNG€¦ · PPT file · Web view · 2012-09-16launching the world's first volume-produced car with a stratified-charge engine:-The . Civic

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STRATIFIED CHARGED ENGINE

NAME:- DEEPAK GUPTA ROLL NO :-TMEA 11114 GUIDE TEACHER:-PROF.(Mrs.) S. V. DRAVID

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The stratified charged engine is an internal combustion engine in which air-fuel ratio isn't equal throughout the cylinder. The fuel charge consisting of two layers i.e. layering of fuel/air mixture. A rich mixture is provided close to the spark plug by a small auxiliary inlet valve and combustion promotes ignition of a lean mixture in the remainder of the cylinder through the main inlet valve. Stratified charge is a process for petrol engine. It is similar in some ways to the Diesel cycle, but running on normal gasoline.

DEFINITION

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HISTORYIn October 1972 Mr. Soichiro Honda President of Honda Motor Company, introduced the CVCC "stratified-charge" engine. Honda was fulfilling the promise in 1976 by launching the world's first volume-produced car with a stratified-charge engine:-

The Civic CVCC. Today, however, several stratified charge engines are appearing on the market. Mazda, Mitsubishi, Audi, Volvo, Jaguar Cars using this concept. They run at a leaner setting and use, about, 15 to 20% less fuel than non-stratified designs.

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OBJECTIVE The objective was to feed a rich

mixture, through a separate pipe, past the inlet valve and to generate a swirl in the cylinder. This caused the weak mixture to enter the cylinder in the normal way and at the same time a vortex comprising alternate layers of rich and weak mixtures was formed in the cylinder. Since the rich portion of the mixture was directed initially over the sparking plug points, it could be ignited and on burning, also ignite the weak mixture throughout cylinder body.

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CONSTRUCTION

The combustion chamber is dividing so as to create a pre-combustion chamber where the spark plug is located so that rich mixture is produced close to the spark plug. The head of the piston is also modified . It contains a toroidal (donut-shaped) cavity that imparts a swirling movement to the air contained by the cylinder during compression. Also It have a thin fan-shaped fuel spray.

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WORKING

A stratified charge engine only pull air through the transfer system. The fuel required for combustion is forced into the cylinder through an injector place in the top of the cylinder (head).

The injector spray a fuel mixture in the form of a fuel cloud into the cylinder. Surrounding this cloud is air supplied by the transfer system. As the cloud is ignited and burns, the surrounding air provides almost complete combustion before the exhaust port opens.

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In a stratified charge engine, the fuel is injected into the cylinder just before ignition. This allows for higher compression ratios without "knock," and leaner air/fuel mixtures than in conventional internal combustion engines.

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WORKING ANIMATION

FEATURES A stratified charge engine concentrates a

rich mixture near the spark plug (air-fuel ratio is less than 14:1) and lean mixture (at air-fuel ratios of 50:1 or greater) throughout into the cylinder.

It uses a direct-injection system like the Diesel, with its ability to be run at high compressions.

However, like Otto it on relies gasoline’s ability to mix quickly and burn cleanly in order to avoid the poor combustion found in the Diesel.

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ADVANTAGE As very rich mixture near spark plug that

ignites easily and burns smoothly. As the combustion proceeds, it meets a very lean area (often only air) where it cools rapidly and the harmful NOx never has a chance to form. The additional oxygen in the lean charge also combines with any CO to form CO2, which is less harmful. Hence allows for the elimination of the catalytic converter.

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LIMITATION’SThe following physical limit ranges result:-

They have significantly higher HC at medium load and NOx emissions at very high load.

With increasing load, the injected volume of fuel must increase. The area around the spark plug with mixture becomes larger.

It tried to increase the velocity and swirl of the intake charge in keeping the rich and lean mixtures separated.

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SOLUTION This is currently addressed with the use

of a catalytic converter in the exhaust system, which break the NOx back into N2 and O2 .

By using CVCC engine we able to keep the charges adequately separated by combustion chamber shape.

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WHY TO GO FOR STRATIFICATION

Reasons are:-

Ultra-lean air-fuel mixtures. Overall higher fuel economy. Gain in thermal efficiency. Increased compression ratio. Lower the temperature at which the fuel is

sprayed , this leads to a reduction in fuel consumption.

Decreases heat losses. Decreasing the overall emissions.

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Normal engine Stratified engine0%10%20%30%40%50%60%70%80%90%

100%

FUEL CONSUMPTION

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FURTHER WORK In order to improve the thermal

efficiency of SI engines, stratified charge combustion by using fuel DI (Direct Injection) system has been developed.

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THANK YOU!

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QUIERIES