Today we will learn about types of nozzle used in IC
engines. Nozzle is that part of an injector through which the liquid fuel is
sprayed into the combustion chamber. It is used in Diesel engine in which fuel
is drawn separately through injector at end of
compression stroke and air is drawn into cylinder in suction stroke. The
nozzle used in IC engine should follow following functions.
- It should automizate fuel. This is a very important function since it is the first phase in obtaining proper mixing of the fuel and air in the combustion chamber.
- Distribute the fuel in require area within the combustion chamber.
- To prevent fuel from impinging directly on the walls of combustion chamber or piston. This is necessary because fuel striking the walls decomposes and produces carbon deposits. This causes smoky exhaust as well as increase in fuel consumption.
- To mix the fuel with air in case of non-turbulent type of combustion chamber.
Types of Nozzle in IC Engine:
The design of nozzle must be such that the liquid fuel
forced through the nozzle will broke up into fine droplets, or atomize, 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. Various types of nozzles
are used in IC engines. These types are as follow.
The Pintle Nozzle:
In this type of nozzle the stem of nozzle valve is extended
to from a pin or Pintle which protrudes through the mouth of the nozzle. The size
and shape of the Pintle can be varied according to the requirement. It provides
a spray operating at low injection pressures of 8-10MPa. The spray cone angle
is generally 60 degree. The main advantage of this nozzle is that it avoids
weak injection and dribbling. It prevents the carbon deposition on the nozzle
hole.
The Single Hole Nozzle:
In this type of nozzle at the center of the body there is a
single hole which is closed by the nozzle valve. The size of the hole is
usually of the order of 0.2 mm. Injection pressure is of order of 8-10MPa and
spray cone angle is about 15 degree. One of the major disadvantages of this
nozzle is that they tends to drible. Besides, their spray angle it too narrow
to facilitate good mixing unless higher velocities are used.
The Multi Hole Nozzle:
This nozzle consists of a number of holes bored in the tip
of the nozzle. The number of holes varies from 4 to 18 and the size from 35 to
200 micro meters. The hole angle may be from 20 degree upwards. These nozzles
operate at 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:
This type of nozzle is a type of Pintle nozzle which has an
auxiliary hole drilled in the nozzle body. It injects a small amount of fuel
through this additional hole which is called pilot injection in upstream
direction slightly before the main injection. The needle valve does not lift
fully at low speeds and most of the fuel is injected through the auxiliary
hole. The main advantage of this nozzle is better cold starting performance. A
major drawback of this nozzle is that its injection characteristics are poorer
than the multihole nozzle.
This is all about types of nozzle used in IC engines. If you
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