Introduction to Dual Fuel Engine

Introduction to Dual Fuel Engine

In our country diesel is primarily used for transportation, agriculture and e lectrical power generation. Diesel is becoming scare and costlier and hence there is a nee d to preserve diesel for only locomotive and agriculture uses. For power ge neration, 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. What is DUAL FUEL ENGINE?

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 li quid fuels. The two fuels can be taken widely varying proportion to run engine; such as engine is usually called Duel fuel engine. • Why Dual fuel engine required? • The shortage of liquid fuel and the realization that gaseous fuels are far cheaper than l iquid 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 dual-fuel 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 injecte d 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 g aseous 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 mo re 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.