Which Type of Injector Nozzles Are Best for High Efficiency of the Engine

Types of nozzle:- 

The design of the nozzle must be such that the liquid fuel forced through the nozzle will be broken up into fine droplets, or atomized, as it passes into the combustion chamber. This is the first phase in obtaining proper mixing of the fuel and air in the combustion chamber.

The fuel must then be properly distributed, or dispersed, in the desired areas of the chamber. In this phase, the injection pressure, the density o the air in the cylinder and the physical quantities of the fuel in use, as well as the nozzle design, become The important factor. Higher injection pressure results in better dispersion as well as greater penetration of the fuel into all locations in the chamber where its presence is desired. It is also produced finer droplets which tend to mix more readily with the air. The greater the density of the compressed air in the combustion chamber, the greater the resistance offered to the travel of the fuel droplets across the chamber with resultant better dispersion of the fuel itself, such as viscosity, surface tension, etc. also enter into the dispersion o the fuel.

The nozzle must spray the fuel into the chamber in such a manner as to minimize the quantity of fuel reaching the surrounding walls. Any fuel striking the wall tends to decompose, producing carbon deposits, unpleasant odour and a smoky exhaust, as well as an increase in fuel consumption.

The Design of the nozzle is closely interrelated to the type of combustion chamber used. It is sufficient to state here that the turbulent type of combustion chamber depends upon chamber turbulence to produce the required mixing of the fuel and air.

Various types o nozzles are used in CI engines.

These types are shown below. The most common types are:

1. The pintle nozzle.
2. The single-hole nozzle.
3. The multi-hole nozzle.
4. Pintaux nozzle.

• Pintle Nozzle:- The stem o the nozzle valve is extended to form a pin or pintle which protrudes through the mouth of the nozzle. The size and shape o the pintle can be varied according to the requirement. It provides a spray operating at a low injection pressure of 8-10 MPa. The spray cone angle is generally 60 degrees. The advantage of this nozzle is that it avoids weak injection and dribbling. It prevents carbon deposition on the nozzle hole.

• Single HoleNozzle:- At the centre of the nozzle body there is a single hole that is closed by the nozzle value. The size of the hole is usually of the order of 0.2mm. Injection pressure is o order 8-10 MPa and the sprays cone angle is about 15 degrees. The major disadvantage ith such a nozzle is that they tend to dibble. Besides, their spray angle is too narrow to facilitate good mixing unless higher velocities are used.

• Multi-hole Nozzle:- It consists of several holes bored in the tip of the nozzle. The number of holes varies from 4 to 18 and the size from 35 to 200 micrometre. the hole angle may be from 20 degrees upwards. these nozzles operate at a high injection pressure of the order of  18 MPa. their advantage lies in the ability to distribute the fuel properly even with lower air motion available in open combustion chambers. 

• Pintaux Nozzle:- lt is a type of pintle nozzle that has an auxiliary hole drilled in the nozzle body. lt injects a small amount of fuel through this additional hole (Piolet Injection in an upstream direction slightly before the main injection).