Fuel Supply System In Diesel Engine(TRACTOR)

                            
                                        
1. FUEL TANK: -                                                                                                                                            The fuel tank is used to store the fuel. It may be higher level (Stationary Engine) or at a lower level. The fuel flow down under gravity if it is placed at a higher level. If it placed at a lower level, then the fuel from the fuel tank is lifted with the help of a fuel feed pump. An air vent is provided above the tank to create pressure.

2. FUEL SUPPLY PIPE:-  
The main function of fuel supply pipe is to supply the fuel from one device to another device in proper way.

3. FUEL FEED PUMP: -                                                                                                                       The purpose of the fuel feed pump is to supply the fuel from the fuel tank to the fuel filter.

WORKING OF FUEL FEED PUMP: -        
                                                                         
It is of spring loaded plunger type fuel feed pump. The plunger is actuated through a push rod from the cam shaft. At the minimum lift position of the cam the spring force on the plunger creates a suction which causes the fuel flow from the main tank into pump.
When the cam is turned to its maximum lift position, the plunger is lifted up words. At the same time the inlet valve is closed and the fuel is forced through the outlet valve.
When the operating pressure get released ,the plunger return spring ceases to function resulting in varying of the pumping stroke under varying engine load according to the quantity of fuel required by the injection pump. This type of fuel feed pump is called plunger type fuel feed pump.
                                                                                          
4. FUEL FILTER: -                                                                                                                                  A filter which cleans the fuel by removing the vapors, dirt particles or air bubbles is known as fuel filter. It has been seen that the holes provided in the fuel nozzle are of very small diameter (0.25 to 1mm) and if any foreign material is carried by the oil, the holes may be closed. Therefore, it is important that the fuel supplied to nozzle must be absolutely clean. For this purpose fuel filter are used in diesel engine. The following types of fuel filter are used in the fuel supply system.


These are:-                                                              
a. Preliminary Fuel Filter     b. Secondary Fuel Filter

a. PRELIMINARY FUEL FILTER: -                                                                                                   This type of fuel filter consist of a bowl, a perforated tube and filter element. This filter is mounted on the suction side of fuel feed pump.   As fuel feed pump sucks the fuel, the fuel from the fuel tank first enters into the filter bowl.
There, it passes through the filter element and a perforated tube before it enters into pump. Most of dust particles are contained at the surface of filter element and the perforated tube. These practical are collected at the bottom of the bowl, from where these may be drained out through a drain plug.

b. SECONDARY FUEL FILTER:-                                                                    
The direction of fuel flow ensures that all the fuel passes through the filter. The secondary fuel filters has a fine grade felt, as the filter element, whereas the preliminary fuel filter has a relatively coarse gauge or cloth as a filter element. The passes through the secondary fuel filter before it is delivered to the fuel injection pump. The filter element is made from a special treated paper. The paper is spirally would in vie form to increase the filtering area of the element. The filter element is placed in the bowl and is pushed downward against the spring force, provided at the base of the boil. One sealing ring and O-ring is mounted in between the filter element and the filter to check any leakage of oil. An air venting is blog is provided at the top of the filter.
              
5. FUEL INJECTION PUMP:-
The purpose of the fuel injection pump is to meter the correct quantity of fuel and deliver at the correct time to the engine cylinder acc. to the varying load and speed requirement. There is different type of fuel injection pumps used in the diesel engine.
 But the following types of fuel injection pumps are preferred in diesel engines:-
a. Distributor type fuel-injection pump                                             
b. Plunger type fuel-injection pump

a. DISTRIBUTOR TYPE FUEL-INJECTION PUMP: -                                                                       The distributor type injection pump is a single unit which pumps the fuel and distributor the required quantity of it to each cylinder at the proper time according to the firing order.
A rotary distributor, which is an integral part of the pump, distributes the fuel. There is a central longitudinal passage in the rotor and also two sets of radial holes located at different heights. One sets is connected to pump inlet through central passage while the second set in connected to the injectors of the various cylinder.
When the plunger move away from each other, the fuel is draw into the central rotor from the inlet port. When the radial deliver in the rotor coincides with the delivery port for any cylinder the fuel is delivered to each cylinder in turn.

Advantages:-
 1. Used for multi-cylinder engine having four or more than four cylinder.
2. Light in weight and small size.

b.PLANGER TYPE FUEL INJECTION PUMP: -                                                                                The plunger is driven by a cam and tappet mechanism at the bottom. The plunger reciprocates in the barrel. There are as many plungers as the number of cylinder in the engine. The plunger has rectangular vertical grooves which extend from the top to another helical groove. The delivery valve is lifted from its seat due to the pressure of the fuel against the spring force. The fuel from the delivery valve goes to injector.
There are two ports in the barrel.
One is the supply port while other is known as spill port. The spill port is also known as by pass port as it returns the excess oil to the full tank. When the plunger is at the bottom of its stroke, the supply port and the spill port are uncovered; the fuel from a low pressure pump after filtration is forced into the barrel.
As the plunger is pushed up by the cam and tappet mechanism, a stage comes when both supply and spill port are covered by the plunger and during further movement of the plunger upward causes the compression of the fuel to a high pressure. Then this compressed fuel lifts the delivery valve and the fuel through it goes to the injector.

6. FUEL INJECTION PIPE:-
The function of fuel injection pipe is to supply the atomized fuel from fuel injection pump to fuel injector to inject into the cylinder properly in the form of fine spray.
                                
7. FUEL INJECTOR:-
A nozzle mounted on combustion chamber, which supplies to the engine cylinder in the form of fine spray, is known as fuel injector or atomizer or fuel valve or nozzle or sprayer. By atomizing the fuel into very fine droplets, it increases the surface area of the fuel droplets resulting in better mixing and subsequent combustion. Atomization is done by forcing the through a small orifice under high pressure. The fuel injector consists of the following components:-
A needle valve
A compression spring
A nozzle
An injector body
Nozzle is that part of an injector through which the liquid fuel is sprayed into the combustion chamber.
The main requirements of the injector nozzle are:-
1. The inject fuel at a sufficiently high pressure so that the fuel enters the cylinder with a high velocity.
2. Penetration should not so as to impinge on cylinder walls; this may result in poor starting.
3. Fuel supply and cut-off should be rapid, there should be no dribbling.
4. There are various type of injection nozzle generally employed in diesel engine. The type of nozzle used is greatly dependent on the types of combustion chamber as pre-combustion chamber.
The usual types of the injection nozzle are discussed below:-
a. Single hole nozzle
b. Pintle nozzle
c. Multi hole nozzle
d. Circumferential orifice nozzle
e. Pintaux nozzle

a. SINGLE HOLE NOZZLE:-
This is the simplest type of nozzle. It consists of a single hole bored centrally through the nozzle and closed by the needle valve. The size of hole usually is 0.2 mm. The spray cone of nozzle varies from 5 to 15 degree and injection pressure is order to 8-10 MPa.
In some case, a cone is given a series of spiral groves in order to import a rotational motion to the fuel for bettering with the air. This is the simple type of nozzle and used in open combustion chambers.
ADVANTAGES:-
Simple in construction.

DISADVANTAGES:-
A very high pressure is required to high velocity of injection.
As the spray angle is narrow, this does not facilitate good mixing unless higher air velocity is provided.

b. PINTLE NOZZLE:-
The steam of nozzle valve is extended to form a pin or pintle which extends through the mouth of the nozzle. The size and shape of the pintle nozzle can be varied according to requirement. The spray cone angle is generally 60 degree and spray injection pressure about 8-10 MPa.
ADVANTAGES:-
It prevents the carbon depositing on the nozzle hole.
It provides weak injection and dribbling.
                           
c. MULTI-HOLE NOZZLE:-
It consists of number of holes bored in the tip of the nozzle. This type of nozzle is found extensive used in automobile engine, having open combustion chamber. The numbers of hole varies from 4 to 18 and hole diameter varies between 0.25 to 0.35 mm. The hole angle may be from 20 degree upwards.
ADVANTAGES:-
Distribute fuel properly even at lower motion.
Give good automation.

DISADVANTAGES:-
Hole are small and liable to clogging.

d. CIRCUMFERENTIAL NOZZLE:-
The injected fuel particles tend to be projected in the form of plane, with wide cone angle. The purpose of this is to be obtained as large as an area of fuel spray as possible to come into contact with the air in the combustion chamber.
                                      
e. PINTAUX NOZZLE:-
When an auxiliary hole is provided at the nose of a pintle injector, then it is called pintaux nozzle. The auxiliary hole supplies fuel in the upstream direction during the idling or the starting of the engine.
This helps in easy starting of the engine. During the normal running of the engine, the fuel is sprayed through the pintle nozzle.
 ADVANTAGES:-
Better cold starting performance.

DISADVANTAGE:-
The tendency of the auxiliary hole to choke.
Injection characteristics are proper than the multihole nozzle.

8. OVER FLOW PIPE:-
The function of over flow pipe is back supply of diesel from fuel injector to fuel tank which is not sprayed by the fuel injector into the cylinder.

WORKING OF FUEL SUPPLY SYSTEM :-
First of all fulfill the fuel tank according to capacity and requirement of fuel. Then the fuel is supply to the fuel feed pump by the help of fuel supply pipe.
After when the fuel is reaches in fuel feed pump firstly the fuel is filtered or cleaned with the help of filter which is mounted in the bottom of fuel feed pump. In this filter the thick dust and dirt particles are come out from the fuel then it is supply to the fuel filter with a high pressure.
After when the fuel is reached in fuel filter it is filtered. There are two filters in the fuel filter first is called primary filter or cloth filter and another filter is called secondary filter or paper filter. Firstly the fuel is go into the primary filter or cloth filter, in which the thick dust and dirt particles are come out from the fuel then, it is go into the secondary or paper filter.
 In secondary or paper filter the thin dust and dirt particles are come out from the fuel and now the fuel is filtered or cleaned. After filtering or cleaning of fuel by fuel filter then it is passes to the fuel injection pump by the help of fuel supply pipe. The fuel injection pump is driven with the help of cam which is mounted and operated with the help of   engine shaft. When the fuel is reached in the fuel injection pump the fuel is atomized or breakup into small particles.
 After this it is supply to the fuel injector with the help of fuel injection pipe. When the fuel is reached in the fuel injector it is finely atomized or breakup into small particles. After atomization of fuel it is sprayed in the engine cylinder in the form of fine spray according to the requirement with the help of nozzle which is mounted in the bottom of fuel injector.
The fuel remaining in the fuel injector after spraying in engine cylinder is passed to the fuel tank with the help of over flow pipe. Now the working of the fuel supply system is complete and the circle is repeated again and again until the engine is in working condition or starting condition. If the engine is stopped or not running or working condition the fuel supply is stop.