Carborater work on Bernoulli's principle :-
The faster air moves, the lower it's statistics pressure and higher the dynamic pressure is.
Accelerator Pedal :
The vehicle operates at different loads and speeds. The power required for different loads are adjusted by the driver by pressing or depressing the accelerator pedal.
Throttle Valve :
The valve which controls the quantity of air sucked by changing the vacuum inside the carburetor. When the throttle valve is fully closed i.e. no load condition the engine vacuum is not transferred to the carburetor resulting in no air sucked in. When the throttle valve is fully opened under full load condition increased quantity of air and fuel is sucked in resulting increased quantity of mixture prepared.
Float Tank :
The fuel from the fuel tank is received and stored in the float tank. Float tank consists of a float in the fuel. This float is connected with a needle valve. The float is used to maintain the level of the fuel inside the float chamber. When the level of the fuel drops the needle valve opens resulting in supply of additional fuel to regain the original level. When the fuel level is adequate the needle valve is closed resulting no fuel entering the float chamber.
Main jet and Main nozzle :
The line through which the fuel is transferred to the carburetor from the float chamber on account of the vacuum at the venture through nozzle. The nozzle atomises the fuel and sprays the atomized fuel in the air flowing through the carburetor to prepare combustible mixture.
Venturi:
The cross section having minimum throat diameter so as to create pressure difference (depression) between the atmospheric pressure on top of fuel level in float chamber and at the venturi or throat section.
•
This pressure difference results in flow of the fuel from float chamber to Venturi.
•
As the pressure difference increases amount of fuel supplied increases to meet the increased load demand.
Choke :
Under normal conditions choke valve is always open. For cold starting conditions the supplied air-fuel mixture is not sufficient to initiate the combustion.
•
Engine requires rich mixture to initiate the combustion. When the choke lever is pressed the choke valve gets closed which drastically reduces supply of the air to the carburetor resulting in more fuel sucked at the venture hence rich mixture is supplied.
•
Once the engine starts normally choke lever is released resulting normal air fuel mixture getting supplied to the engine.
Idling jet:
The minimum mixture supply under idle conditions when accelerator is zero is controlled by the idle jet which is located between the engine and the throttle valve.
The ratio of fuel air is controlled by adjusting needle valves and this allows you to select the proper mixture for the conditions under which you operate your engine
Too lean a fuel-air mixture may result in hard starting, overheating, pre-ignition & valve burning
Too rich a fuel-air mixture may result in excessive fuel consumption, carbon build up in the cylinder and cause pre-ignition
