11 March 2018

Parts of carburetor and function

A carburettor consists of the following main parts :
  • Fuel strainer
  • Float chamber
  • Main fuel metering and idling nozzles 
  • Chock and throttle 
Parts that mentioned above are discussed briefly below : 

  • The fuel strainer :
As the petrol has to pass through a narrow nozzle exit there is every possibility that the nozzle may get clogged prolonged operation of the engine. To prevent this possibility of blockage of the nozzle by dust particles, the petrol is filtered by installing a fuel strainer at the inlet of the float chamber. 

The strainer made of a fine wire mesh or another type of filtering device. The fuel strainer is an either cone-shaped or cylindrical shape. 

  • The float chamber :
The float chamber is to supply the fuel to the nozzle at a constant pressure head. This is possible by maintaining a constant level of fuel in the float bowl. The float in a carburettor is provided to control the level of fuel in the float chamber. In order to provide the correct amount of fuel and to prevent the leakage of fuel from the nozzle fuel level must be maintained slightly below the discharge nozzle outlet holes. 

  • The main fuel metering and idling system :
The main fuel metering system of the carburettor controls the fuel feed for cruising and the full-throttle operations. 

It consists of three principles:
  • The fuel metering orifice through which fuel is drawn from the float chamber.
  • The main discharge nozzle.
  • The passage leading to the idling system. 
The main three functions of the main metering system are :
  • To proportion the air-fuel mixture.
  • To decrease the pressure at the discharge nozzle exit.
  • To limit the airflow at full throttle. 

  • Chock and throttle :
When the vehicle is kept stationary for a long period during cold whether it may be overnight too then starting of the vehicle becomes more difficult. 

For low cranking speeds and intake temperatures, a very rich mixture is required to initiate the combustion. The main reason is that a very large fraction of fuel may remain as liquid suspended in the air even in the cylinder. The most popular method of providing such mixture is by the use of chock valve.

Throttle valve controlled the speed and the output of an engine. The more the throttle is closed the greater is the obstruction to the flow of the mixture placed in the passage and the less is the quantity of mixture delivered to the cylinders. 

As the throttle is opened, the output of the engine increases. But this is not always the case as the load on the engine is also a factor.  

As we discuss the throttle is simply a means to regulate the output of the engine by varying the quantity of charge going into the cylinder.