Simple carburetor working, diagram and limitations

Simple carburetor construction, working, diagram, imitations | get ppt and pdf

We have already discussed the concept of the carburetor, the use of carburetor and different types of carburetor in our previous articles. In this post, we are going to explain what is simple carburetor? in which we will learn about the definition of the simple carburetor, working of the simple carburetor and its limitations and disadvantages.
We are going to learn the following topics from this article on simple carburetor –

Table of contents

Sr. No
Definition of a simple carburetor
Working of a simple carburetor
What is Nozzle lip ?
Limitations of a simple carburetor
Applications of a simple carburetor
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What is a simple carburetor?

A simple carburetor consists of different parts such as the float chamber, main fuel jet, venturi, jet tube, and throttle valve. Where there is a float in the float chamber. With the help of a fuel pump, fuel is supplied to the float chamber from the fuel tank through the strainer. We can call this full assembly a simple carburetor.
Simple carburetor working, diagram and limitations
Diagram of a simple carburetor [click on it to zoom]

Working of a simple carburetor:

We are going to learn the working of this carburetor stepwise-
  1. As we know, there is a float chamber in a simple carburetor that is open to the atmosphere. It keeps atmospheric pressure in the float chamber.
  2. Fuel from the external fuel tank is supplied to the float chamber with the help of the fuel pump. This fuel from the fuel tank is filtered using the strainer which removes any solid particles from the fuel.
  3. Now fuel from the float chamber is supplied to the main nozzle which is a part of the jet tube. This flow of fuel from the float chamber to the main nozzle is carried out by the main fuel jet.
  4. The engine sucks air from the atmosphere through the choke valve. This air passes through the venturi, it causes a reduction of the area of a cross-section at the throat of venturi.
  5. Due to this, the pressure at the main nozzle decreases and the velocity of air increases.
  6. This difference in pressure-induced at the float chamber and the main nozzle causes the mixture of fuel and incoming atmospheric air.
  7. Increased velocity of air after the venturi partially vapourize the engine fuel which is then totally evaporated by the heat in the intake manifolds of the combustion chamber and cylinder walls.
  8. Carburetors only install in a petrol engine because petrol engines are quantity governed.
  9. When we open the throttle valve present at the bottom of the jet tube, it allows more air flows through the venturi tube and a more quantity of the air-fuel mixture is supplied to the engine, causes, the engine develops more power.
  10. When we close the throttle valve, reverse action takes place and the power of the engine reduces.

What is nozzle lip in the simple carburetor?

To avoid the overflow of the fuel from the nozzle, the end of the main nozzle is slightly kept higher than the level of fuel in the float chamber. This difference of level between the tip of the main nozzle and fuel level in the float chamber is called nozzle lip. You can see the nozzle lip level in the diagram above.

Limitations of a simple carburetor:

  • In this carburetor, the air-fuel mixture totally depends upon the position of the throttle valve.
  • Also, the air-fuel ratio decreases when the speed of the engine increases.
  • The main limitation or disadvantage of a simple carburetor is that when speed is too low, we get a strong mixture which causes trouble in the ignition of the mixture.

Application of simple carburetor:

  • This is only used in small and stationary engines, not any modern engines.

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