FUEL INJECTOR SYSTEM
FUEL INJECTION SYSTEM (MECHANICAL)
CLASSIFICATION OF INJECTION SYSTEMS
In a constant-pressure cycle or diesel engine, only air is compressed in the cylinder and then fuel is injected INTO THE cylinder by means of a fuel-injection system. For producing the required pressure for atomizing the fuel ether air or mechanical means is used. According the injection system can be classified as:
• Air injection system
In this system, fuel is forced into the cylinder by means of compressed air. This system is little used nowadays because,
3. Reduces the brake power output.
SOLID INJECTION SYSTEM
In this system the liquid fuel is injected directly into the combustion air. Hence it is also called airless mechanical injection system or solid injection system. Solid injection system can be classified as:
6. Fuel filters to prevent dust and abrasive particles from entering the pump and injectors thereby minimizing the wear and tear of the components.
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new topic is FI system (mechanical) The fuel injection system is the most vital component in the working of CI engines. The engine performance viz. Power output economy etc. Is gently depends on the effectiveness of fuel injection system. The injection system has to perform the important duty of initiating and controlling the combustion process.
In a fuel injection system the amount of fuel delivered into the air stream going to the engine is controlled by a pump which forces the fuel under pressure.
When the fuel is injected into the combustion chamber towards the end of compression stroke, it is atomized into very fine droplets. These droplets vaporize due to heat transfer from the compressed air and form a fuel air mixture. Due to the continued heat transfer from hot air to the fuel the temperature reaches a value higher then its self ignition temperature. This causes the fuel to ignite spontaneously initiating the combustion process.
FUNCTIONAL REQUIREMENT OF AN INJECTION SYSTEM
1. Accurate metering of fuel injected per cycle. This is very critical due to the fact that very small quantities of fuel being handled.
2. Timing digestion of the fuel correctly in the cycle so that maximum power is obtained ensuring economy and clean burning.
3. Proper control5 of rate of injection so that the desired heat release pattern achieved during combustion.
4. Proper atomization of fuel into very fine droplets.
5. Proper spray pattern to ensure rapid mixing of fuel and air.
6. Ensure that no lagging during the injection.
CLASSIFICATION OF INJECTION SYSTEMS
In a constant-pressure cycle or diesel engine, only air is compressed in the cylinder and then fuel is injected INTO THE cylinder by means of a fuel-injection system. For producing the required pressure for atomizing the fuel ether air or mechanical means is used. According the injection system can be classified as:
• Air injection system
• Solid injection system
AIR INJECTION SYSTEM
In this system, fuel is forced into the cylinder by means of compressed air. This system is little used nowadays because,
1. Its requires a bulky multi-stage air compressor.
2. Increase in engine weight.
3. Reduces the brake power output.
Advantages
• Better mixing of air and fuel.
• Ability to utilize fuels of high viscosity.
• Less expansive than those engine with solid injection system.
SOLID INJECTION SYSTEM
In this system the liquid fuel is injected directly into the combustion air. Hence it is also called airless mechanical injection system or solid injection system. Solid injection system can be classified as:
• Individual pump and nozzle system
• Unit injector system
• Common rail system
• Distributer system
All above the above systems comprise mainly of the following component.
1. Fuel tank.
2. Fuel feed pump to supply fuel from main tank to the injection system,
3. Injection pump to meter and pressurize the fuel for injection,
4. Governor to ensure that the amount of fuel injected is in accordance with variation in load,
5. Injector to take fuel from the pump and distribute it in the combustion chamber by atomization it into fine droplets,
A typical arrangement of various components for the solid injection system used in a CI engine as shown in fig. fuel from the tank first enters the coarse filter from which is drawn into the plunger feed where the pressure is raised very slightly. Then the fuel enters the fine filter where all the dust and dirt particles are removed. From the fine filter the fuel enters the fuel pump where it is pressurized to about 200 bar and injected in to the engine cylinder by means of the injector. Any spill over in the injector is returned to the fine filter. A pressure relief valve is also provided for the safety of the system.
DIFFERENCE B/W AI SYSTEM AND SI SYSTEM
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