Question

What is the principle behind the carburetor of an automobile?

Answer 1

Hint: Carburetor is a device used in automobiles to facilitate proper ratio of air-fuel mixture for combustion in the engine. It works according to Bernoulli’s principle, which talks about the variation of pressure and velocity during fluid flow.

Complete answer:
A carburetor is a device used in automobiles to provide a proper ratio of mixture of air and fuel for easy combustion in the engine. The working principle of a carburetor is based on Bernoulli’s principle. Bernoulli’s principle of fluid flow states that pressure decreases with increasing velocity of the fluid.

To understand the working of a carburetor, let us go through the different parts of a carburetor, as shown in the figure given above. The main part of a carburetor is called a venturi, which is nothing but a cylindrical tube of large radius. The area of the middle portion of this venturi or cylindrical tube is reduced using the throat. This venturi has three openings – one to the engine (C), one to the float chamber (A) and the other to the surroundings (B), to suck air from the surroundings. The opening connected to the float chamber is connected using a thin duct or a thin tube, which facilitates the motion of fuel from the float chamber to the venturi. This opening is made at the centre of the throat, which is the middle portion of the venturi, with a lesser area of cross-section, as shown in the figure. As already mentioned, one opening is pretty large and opens the venturi to the surroundings, to suck the air from outside. Near this opening, there is an air purifier attached so that air from the surroundings is purified before mixing it with the fuel. The last opening of the venturi opens it to the engine, where combustion of air-fuel mixture takes place. All these openings are controlled using valves. The valve in the float chamber is called a float valve. The valve in the opening through which air is sucked is called a choke. The valve near the opening to the engine is called a throttle valve.
As already mentioned, a carburetor works according to Bernoulli’s principle. When the automobile is switched on, air is sucked from the surroundings through the opening meant for it, by adjusting the choke valve. At the same time, fuel from the thin duct is sucked near the throat area of the venturi, to provide the proper ratio of air-fuel mixture. To put it clear, air sucked from the surroundings passes through the opening of the venturi meant for it, to the throat, at the middle of the venturi. When air reaches the throat, the velocity of air increases. This is due to the principle of continuity, which suggests that area of cross-section and velocity of fluid flow are inversely proportional to each other. Since the throat at the middle of the venturi has less area, velocity of air is more here. According to Bernoulli’s principle, when velocity of fluid flow increases, pressure decreases. Therefore, at the throat section of the venturi, low pressure is created. This low pressure, in turn, sucks fuel from the thin duct, connected to the float chamber and placed at the throat. Thus, fuel particles and air get mixed up in the right proportion and serves the engine for proper combustion through the opening meant for it.
Thus, a carburetor works according to Bernoulli’s principle of fluid flow.

Note:
The explanation regarding the working of the carburetor given in the above solution is a basic idea of the same. Nowadays, different types of carburetors are available according to their usage and purpose. Many developments and improvements in their working have facilitated them to be used in the aviation industry too. But the working principle behind all these types of carburetors still remains the same.