Injection System | Functional Requirements of an injection system | Functions of Fuel injection system | Types of injection system | Air injection system | Solid or airless injection system | Types of solid injection system |Individual Pump Injection System | Unit Injection System | Common-rail injection system | Distributor Injection System |
-: Injection System :-
An injection system is defined as - In C.I. ( Compression Ignition ) engines , a system used to deliver fuel into the engine cylinder , is known as injection system .
-:Functional Requirements of An Injection System :-
The functional requirements of an injection system are as follows -
1- In an injection system , introduction of fuel into the combustion chamber should take place within a precisely defined period of cycle .
2- In an injection system , the metering of the amount of fuel injection per cycle should done very accurately .
3- In an injection system , the quantities of fuel metered should vary to meet the changing load and speed requirements .
4- In an injection system , the injection rate should be such that it results in the desired heat release pattern .
5- In an injection system , the injected fuel must be broken into very fine droplets .
6- In an injection system , the pattern of spray should be such as to ensure rapid mixing of fuel and air .
7- In an injection system , the beginning and end of the injection should be sharp .
8- In an injection system , the timing of injection , if desired , should be change as per the requirements of load and speed .
9- In an injection system , the distribution of the metered fuel , in case of multi- cylinder engines , should be uniform among various cylinders .
10- Beside above requirements , the weight and the size of the fuel injection system must be minimum .
Functions of An Fuel Injection system :- The main functions of a fuel injection system are -
1- Filter the fuel
2- Metre or measure the correct quantity of fuel to be injected.
3- Time the fuel injection .
4- Control the rate of fuel injection .
5- Automise or break up the fuel to fine ( Very small fuel drops ) particles .
6- Properly distribute the fuel in the combustion chamber .
Types of Fuel injection system :- In compression ignition ( C.I.) engines two types (methods) of fuel injection system are used which are given as -
1- Air Injection system
2- Solid / Airless injection system
1- Air Injection System :- An fuel injection system in which air is compressed in the compression to a very high pressure ( greater than pressure of compression stroke ) and then injected through the fuel nozzle into the engine cylinder is known as air injection system .
In air injection system , the rate of fuel admission can be controlled by varying the pressure of injection air .
Advantages of Air Injection System :- The advantages of air injection system are given as -
1- Air injection system provides better automisation and distribution of fuel .
2- As the combustion is more complete , the B.M.E.P.( Brake Mean Effective Pressure ) is higher than with other types of injection systems .
3- Inferior fuels can be used in air injection system .
Disadvantages of Air Injection System :- Air injection system is not used now-a-days due to the following reasons / disadvantages -
1- Air injection system requires a high pressure multi-stage compression .The large number of parts , the intercooler etc make the system complicated and expansive .
2- In air injection system a separate mechanical linkage is required to time the operation of fuel valve .
3- Due to the compression and the linkage the bulk of the engine increases .
4- In air injection system , the fuel in combustion chamber burns very near to injection nozzle which many times leads to overheating and burning of valve and its seat .
5- In air injection system , in case of sticking of fuel valve the system becomes quite dangerous due to the presence of high pressure air .
2- Solid or Airless Injection System :- Solid injection system is defined as - Injection of fuel directly into the combustion chamber without primary automisation is termed as solid injection . It is also known as mechanical injection .
Types of modern fuel injection system :- There are following four types of solid or modern fuel injection system-
(i)- Individual Pump Injection System
(ii)- Unit Injection System
(iii)- Common-rail injection system
(iv)- Distributor System
(i)- Individual Pump Injection System :- An injection system in which each cylinder is provided with one pump and one injector and also a separate metering and compression pump is provided for each cylinder , is known as individual pump injection system .
The design of this type of pump must be very accurate and precise as the volume of fuel injected per cycle is 1/20000 of the engine displacement at full load and 1/100000 of the engine displacement during idling .
(ii)-Unit Injection System :- An injection system in which pump and injector are combined in one housing is known as unit injection system .
In unit injection system each cylinder has one such unit injector and fuel is brought upto the injector by a low pressure pump . The amount of fuel injected is regulated by effective stroke of the plunger .
(iii)-Common Rail Injection System :- An injection system in which a high pressure pump supplies fuel under high pressure to a fuel header , is known as common rail injection system .
In common rail injection system , high pressure to a fuel header forces the fuel to each of the nozzle located in the cylinder . At proper time , a mechanically operated valve allows the fuel to enter the proper cylinder through the nozzle and the amount of fuel entering the cylinder is regulated by varying the length of the push rod stroke .
Advantages of Common Rail Injection System :- The advantages of common rail injection system are as follows -
1- The system arrangement is simple and less maintenance cost .
2- Only one pump is sufficient for multi-cylinder engine .
3- It follows the requirements of either the constant load with variable speed or constant speed with variable load .
4- Variation in pump supply pressure will affect with variable load .
Disadvantages of Common Rail Injection System :- The disadvantages of common rail injection system are as follows -
1- There is a tendency to develop leaks in the injection valve .
2- In common rail injection system , very accurate design and workmanship are required .
(iv)- Distributor Injection System :- An injection system in which a pump pressurizes the fuel and also meters the fuel and time of injection is known as distributor injection system .
In distributor injection system , the fuel pump after the metering of the required amount of fuel , supply it to rotating distributor at the correct time for supply to each cylinder . Since there is one metering element in each pump , a uniform distribution is automatically ensured .
-: Injection System :-
An injection system is defined as - In C.I. ( Compression Ignition ) engines , a system used to deliver fuel into the engine cylinder , is known as injection system .
-:Functional Requirements of An Injection System :-
The functional requirements of an injection system are as follows -
1- In an injection system , introduction of fuel into the combustion chamber should take place within a precisely defined period of cycle .
2- In an injection system , the metering of the amount of fuel injection per cycle should done very accurately .
3- In an injection system , the quantities of fuel metered should vary to meet the changing load and speed requirements .
4- In an injection system , the injection rate should be such that it results in the desired heat release pattern .
5- In an injection system , the injected fuel must be broken into very fine droplets .
6- In an injection system , the pattern of spray should be such as to ensure rapid mixing of fuel and air .
7- In an injection system , the beginning and end of the injection should be sharp .
8- In an injection system , the timing of injection , if desired , should be change as per the requirements of load and speed .
9- In an injection system , the distribution of the metered fuel , in case of multi- cylinder engines , should be uniform among various cylinders .
10- Beside above requirements , the weight and the size of the fuel injection system must be minimum .
Functions of An Fuel Injection system :- The main functions of a fuel injection system are -
1- Filter the fuel
2- Metre or measure the correct quantity of fuel to be injected.
3- Time the fuel injection .
4- Control the rate of fuel injection .
5- Automise or break up the fuel to fine ( Very small fuel drops ) particles .
6- Properly distribute the fuel in the combustion chamber .
Types of Fuel injection system :- In compression ignition ( C.I.) engines two types (methods) of fuel injection system are used which are given as -
1- Air Injection system
2- Solid / Airless injection system
1- Air Injection System :- An fuel injection system in which air is compressed in the compression to a very high pressure ( greater than pressure of compression stroke ) and then injected through the fuel nozzle into the engine cylinder is known as air injection system .
In air injection system , the rate of fuel admission can be controlled by varying the pressure of injection air .
Advantages of Air Injection System :- The advantages of air injection system are given as -
1- Air injection system provides better automisation and distribution of fuel .
2- As the combustion is more complete , the B.M.E.P.( Brake Mean Effective Pressure ) is higher than with other types of injection systems .
3- Inferior fuels can be used in air injection system .
Disadvantages of Air Injection System :- Air injection system is not used now-a-days due to the following reasons / disadvantages -
1- Air injection system requires a high pressure multi-stage compression .The large number of parts , the intercooler etc make the system complicated and expansive .
2- In air injection system a separate mechanical linkage is required to time the operation of fuel valve .
3- Due to the compression and the linkage the bulk of the engine increases .
4- In air injection system , the fuel in combustion chamber burns very near to injection nozzle which many times leads to overheating and burning of valve and its seat .
5- In air injection system , in case of sticking of fuel valve the system becomes quite dangerous due to the presence of high pressure air .
2- Solid or Airless Injection System :- Solid injection system is defined as - Injection of fuel directly into the combustion chamber without primary automisation is termed as solid injection . It is also known as mechanical injection .
Types of modern fuel injection system :- There are following four types of solid or modern fuel injection system-
(i)- Individual Pump Injection System
(ii)- Unit Injection System
(iii)- Common-rail injection system
(iv)- Distributor System
(i)- Individual Pump Injection System :- An injection system in which each cylinder is provided with one pump and one injector and also a separate metering and compression pump is provided for each cylinder , is known as individual pump injection system .
The design of this type of pump must be very accurate and precise as the volume of fuel injected per cycle is 1/20000 of the engine displacement at full load and 1/100000 of the engine displacement during idling .
(ii)-Unit Injection System :- An injection system in which pump and injector are combined in one housing is known as unit injection system .
In unit injection system each cylinder has one such unit injector and fuel is brought upto the injector by a low pressure pump . The amount of fuel injected is regulated by effective stroke of the plunger .
(iii)-Common Rail Injection System :- An injection system in which a high pressure pump supplies fuel under high pressure to a fuel header , is known as common rail injection system .
In common rail injection system , high pressure to a fuel header forces the fuel to each of the nozzle located in the cylinder . At proper time , a mechanically operated valve allows the fuel to enter the proper cylinder through the nozzle and the amount of fuel entering the cylinder is regulated by varying the length of the push rod stroke .
Advantages of Common Rail Injection System :- The advantages of common rail injection system are as follows -
1- The system arrangement is simple and less maintenance cost .
2- Only one pump is sufficient for multi-cylinder engine .
3- It follows the requirements of either the constant load with variable speed or constant speed with variable load .
4- Variation in pump supply pressure will affect with variable load .
Disadvantages of Common Rail Injection System :- The disadvantages of common rail injection system are as follows -
1- There is a tendency to develop leaks in the injection valve .
2- In common rail injection system , very accurate design and workmanship are required .
(iv)- Distributor Injection System :- An injection system in which a pump pressurizes the fuel and also meters the fuel and time of injection is known as distributor injection system .
In distributor injection system , the fuel pump after the metering of the required amount of fuel , supply it to rotating distributor at the correct time for supply to each cylinder . Since there is one metering element in each pump , a uniform distribution is automatically ensured .
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