In Spark-Ignition engines uses volatile liquid fuels. we have to use an air-fuel mixture as the working fluid in these engines. A well-mixed fuel mixture will result in the greater performance of the engine. So this can not be done in the inlet manifold itself. So it has to be done outside the engine.
The process of preparation of a combustible air-fuel mixture by mixing the proper amount of fuel with the air before it goes into the cylinder is called Carburetion.
We have to use a special device for this action called Carburetor.
the Carburetion ffecting
- Engine Speed
- Volatility of fuel
- The Temperature of Air coming into the Carburetor
- Design of Carburetor
The modern engines are running at very high speeds. So that the time available for the carbonation is very limited.
Lets take example of an engine running at 3000 RPM, it would take 10 milliseconds for the mixture induction during suction stroke, where as the the engine running at 6000 RPM then the time required for the mixture induction is 5 milliseconds only.
In order to achieve high-quality air-fuel mixture the velocity of the air passing thru the Carburetor has to be increased particularly at the point where the fuel is injected in the Carburetor. This can be done by introducing the venturi tube in the Carburetor.
The fuel will be injected into the venture tube at the minimum cross section. this is called Venturi or Throat.
Volatility of Fuel
The vaporization characteristics of the fuel plays an important role in producing the high quality air-fuel mixture.
As we have already discussed the time taken for the introduction of the mixture into the cylinder is very less so that the fuel needs to evaporate within stipulated time by the time of mixing in the Carburetor. This is depends on the volatility of the fuel.
The Temperature of Air coming into the Carburetor
The temperature and the pressure of the air coming into the Carburetor has a high influence on efficient carburetion. As the temperature is high the vaporization of fuel will increases results in the more homogeneous mixture.
But due to the high temperature, more fuel will vaporize and having less mass flow into the cylinder if the same air-fuel ratio is maintained. this will lead to less volumetric efficiency of the engine.
Design of Carburetor
Proper design of the Carburetor ensures the supply of the desired composition of the mixture under different operating conditions of the engine.
We have discussed the definition of Carburetion and also the different factors affect the quality of the mixture. Let us know your thoughts in the comment section below.