Government Engg.Collage-Surat

OverviewOverview of Presentation of Presentation

• Introduction

• Working Principle..

• Dual-Fuel Operation

• Factors Affecting Performance in Dual-Fuel Engine.

• Performance of Dual-Fuel Engine

• Advantages of Dual-Fuel Engine

Introduction to Dual Fuel EngineIntroduction to Dual Fuel Engine

In our country diesel is primarily used for transportation, agriculture and electrical power generation. Diesel is becoming scare and costlier and hence there is a need to preserve diesel for only locomotive and agriculture uses. For power generation, alternate fuels should be used wherever possible so that diesel is conserved and made available for it primary uses. This will also save sizable for an exchange, as we import considerable amount of crude oil to meet our needs of diesel and petroleum products.

Internal combustion engines operating on gaseous fuel have for long been known. Many large stationary engines use two fuels. Normally of these two fuels, one is gaseous and other is a liquid fuels. The two fuels can be taken widely varying proportion to run engine; such as engine is usually called Duel fuel engine.

What is DUAL FUEL ENGINE?

Why Dual fuel engine required ?

• The shortage of liquid fuel and the realization that gaseous fuels are far cheaper than liquid fuels have led to attention on dual-fuel engine.

• natural gas available to most of part of the world at rates cheaper than liquid fuels

THE WORKING PRINCIPLE

The dual-fuel engine works on diesel cycle. The gaseous fuel (the primary fuel) is added to the air inducted by the engine or supplied by the supercharger at a pressure slightly above the atmospheric pressure. This mixture of air and gaseous fuel is compressed in the cylinder just like air in normal diesel operation. At some point in the compression stroke, near top dead center, a small charge of liquid fuel called pilot fuel (or the secondary fuel) is injected through a conventional diesel fuel system. This pilot acts as a source of ignition the gas-air mixture in the vicinity of the injected spray ignites at a number of flame-fronts. Thus combustion stars smoothly and rapidly.

Dual-Fuel Operation

Dual-fuel operation is achieved by the burning of both a gaseous fuel and diesel at the same time in a CI engine

Injection of small amount of diesel fuel can be used as an ignition source

FACTORS AFFECTING COMBUSTION IN A DUAL-FUEL ENGINE

1. Pilot fuel quantity 2. Injection Timing. 3. Cetane Number of Pilot Fuel.4. Inlet Temperature.5. Gaseous Fuels.6. Effect of Throttling.7. Mixture Strength

PERFORMACE OF DUAL-FUEL ENGINE

Dual-fuel engines are capable of producing as much power when running with a gaseous fuel as a primary fuel as when operating on liquid fuels only The efficiency of the dual-fuel engine at part load is poor because of increased delay periods at low mixture strength. This can be increased by increasing the excess air or injecting more pilot fuel at part loads

KNOCK AND ITS CONTROL IN DUAL-

FUEL ENGINE NATURE OF KNOCK: - The phenomenon of knock in a

dual-fuel engine is of the nature of auto ignition of gaseous mixture in the neighborhood of injected spray.

KNOCK IN DUAL-FUEL ENGINE CONTROLLED BY ANY OF THE FOOLOWING METHODS:-

• Excess supply of air.• Use of cold combustion air.• Increased cooling of piston.• Reducing the pressure of the gaseous fuel.

Dual-Fuel Engine Advantages

1) Similar power but with greatly reduced emissions than the equivalent horsepower dedicated diesel engines

2) Lower initial cost and lower operating costs than a dedicated natural gas engine3) Better fuel economy than a dedicated natural gas engine4) Lower maintenance costs than a dedicated natural gas engine5) Diesel substitution rates ranging from 80% to over 90% using less

expensive natural gas6) Extended engine life7) Requires fewer natural gas tanks than a dedicated natural gas engine8) Can be converted back to dedicated diesel enhancing its resale value9) Excellent long term reliability record 10) Similar heat rejection as diesel engine

CONCLUSION

The ignition delay in gas-fueled diesel engines of the dual-fuel type depends strongly on both the quantity and quality of the pilot fuel used.

Dual-fuel engine performance is improved with the employment of high cetane number pilots.

For stationary application, diesel substitution of 70% is possible by using dual fuel engine which is quite considerable and also economical