Introduction 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.
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 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 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 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.
Ø Dual-fuel operation is achieved by the burning of both a gaseous fuel and diesel at the same time in a CI engine
Ø 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 Full Seminar Report and PPT
Dual-Fuel engines operate on both natural gas and diesel fuel simultaneously, majority of fuel burned being natural gas. Diesel fuel acts essentially as a ‘spark plug’ as it auto ignites under compression and then ignites the gas. The use of diesel fuel allows the retention of the diesel compression ratio and its efficiency while the natural gas contributes to economy and is responsible for lowering emissions.
The Fumigation Principle
Natural Gas can be introduced to the combustion chamber by either mixing it with the airflow or injecting it into the manifold/chamber. In the Fumigation process, the gas is blended with air and both enter the inlet together in correct proportion whereas in direct injection the gas is introduced into the engine just prior to burning. The latter is an expensive and complex process whereas the fumigation method is not. More importantly, gas is not the primary fuel in a dual fuel engine and therefore the fumigation process works perfectly well, even for very large engines.
GAS to DIESEL Ratio
The EXCLAIM kit has operated at a replacement ratio of 92%. However, the average substitution of diesel by gas ranges between 50% to 80%.
The EXCLAIM kit will not derate an engine if used with standard Natural gas or LPG. The kit ensures that full power remains available by adjusting ratios and providing necessary BTU energy to the engine. In gases such as LPG where the BTU content is higher than normal, dual fuel operation provides superior energy efficiencies whereas when the gas being used has a low heat value (coal gas, biogas or other gases having BTU content of less than 800) there is a proportional de-rating of the engine.
Unlike dedicated natural gas engines, dual fuel engines do not run hotter. Indeed, in some cases engines may actually run a few degrees cooler.
Changeover between fuels
The EXCLAIM kit is designed to switch seamlessly between full diesel and dual fuel operation without any surge or loss of power, frequency or speed.
Because gas is a better, cleaner fuel, the engine oil life is extended. Oil and filter change intervals are normally extended to generate additional savings.
DUAL-FUEL TECHNOLOGY BENEFITS
Attractive operating economics; replaces expensive diesel with low cost gas.
Greatly reduced emissions
Retains torque and power characteristics of the original diesel engine
Emergency diesel fallback for safety
Excellent long term reliability record
Same heat rejection as diesel