Fuel Injection Nozzle Function and operation.

Fuel injection nozzles are devices used in fuel injection systems to deliver fuel into an internal combustion engine. These nozzles are designed to precisely meter and deliver fuel to the engine’s combustion chamber at the right time and quantity, which is crucial for efficient and effective engine operation.
Fuel injector nozzle function.
Fuel injector nozzle function.


I will discuss the fuel injection nozzle and its function in this article. 



Table of Contents

Fuel injection nozzle- 

Fuel injection nozzles are a critical component in the fuel delivery system of modern engines. They are designed to deliver fuel into the combustion chamber of an internal combustion engine at the right time, in the right amount, and in a precise spray pattern, which is essential for efficient and effective engine operation.

Fuel injection nozzles are commonly used in gasoline and diesel engines and alternative fuel engines, such as those that run on ethanol, biodiesel, or compressed natural gas. The design of the nozzle can vary depending on the fuel being used and the engine’s specific requirements.

The basic function of a fuel injection nozzle is to atomize the fuel into a fine mist, which can then mix more effectively with the air in the combustion chamber, resulting in a more complete combustion process. The fuel is typically injected at high pressure through a small orifice or hole in the nozzle, which helps to create a fine spray pattern.


Fuel injection nozzle function- 

The performance of a modern high-speed fuel engine depends largely upon the functioning of its fuel injection system. For maximum efficiency in operation, the engine must be not only provided with the fuel in quantities exactly timed and proportional to the amount of work it is required to do but also it should receive each charge of fuel in a condition such that it can be completely consumed, without causing smoke in the exhaust. This is the function of the nozzle, which is held in position in the cylinder head by the nozzle holder. 
As the nozzle may have to deal with many hundreds of fuel charges per minute, with widely varying conditions of pressure and temperature, the unerring precision necessary in the production of these parts will be appreciated. 


Nozzle body and valve.
Nozzle body and valve.


The injector(Nozzle holder and Nozzle) is a spring-loaded valve. The nozzle valve and seat are manufactured to close limits and are selectively fitted in the factory. The nozzle uses a cone seat. The angle on the valve is slightly greater than the angle formed in the body near the top of the valve cone. The valve is opened by oil pressure by spring force. 
The injection process is as follows. – 
  1. The spill cut-off is reached by the injection pump plunger. 
  2. The pressure of the fuel oil in the delivery pipe rises rapidly. 
  3. The nozzle valve opens quickly. 
  4. Fuel is injected into the engine combustion chamber in a finely divided form. 
  5. The spill port open position is reached by the injection pump plunger, 
  6. The pressure of the fuel in the delivery pipe falls rapidly. 
  7. The nozzle valve opens quickly. 
The injection process takes only a few milliseconds. Precise control is necessary for clear exhaust gas. For good combustion and a long nozzle life, the valve must open quickly and when closed, should not allow fuel to pass its seat. All internally opening nozzle valves have leak-off connections. Oil, which lubricates the nozzle valve, flows from the leak-off pipe and is then piped back to the fuel tank. The amount of il following is a small an-occasional drop only. 


complete nozzle consists of two parts, the nozzle valve, and the nozzle body, shown separately in Fig. The nozzle valve takes the form of the plunger, accurately lapped into the nozzle body to the closest possible fit within which it will work freely. The inner end of the nozzle valve is reduced in diameter to produce a stern upon which a valve face is formed, while the outer end is provided with a stalk. Fuel is fed to the mouth of the nozzle through small holes drilled vertically in the nozzle body, which terminate in an annual gallery (or reservoir) just above the valve seating. The nozzle valve is raised from its seat in the nozzle body by the pressure of fuel from the injection pump. Thus, the fuel in the gallery is forced by the upward movement of the plunger in the pump, through the hole or holes in the nozzle, to form a spray in the engine combustion chamber.
The type of nozzle to be used depends upon the particular requirements of the engine combustion chamber, and as the nozzles vary considerably with respect to the diameter and length of the hole, spray angle, valve lift, etc., only the correct type of nozzle must be used.


Overall, fuel injection nozzles are a critical component in the fuel delivery system of modern engines. They play a key role in improving fuel efficiency, power, and performance, and their design is constantly evolving to meet the needs of the latest engine technologies.
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