Operating system of the carburetor
Such a simple carburetor can not meet the requirements of the internal combustion engine under various working conditions. Therefore, the general carburetor for the internal combustion engine, especially the automobile internal combustion engine, also need other systems, including the main fuel system, idle system, thickening system, acceleration system and starting system.
The main fuel system
The main fuel system is the main fuel supply system of the carburetor. There are 3 common main fuel system correction (compensation) methods:
- Compensation with infiltration air;
- Change the area of the main volume hole with an fuelneedle;
- 3.Simultaneously change the area of the throat and main orifice.
The first method is more common application. The air compensation method is to add the main air volume hole and foam pipe between the main volume hole and the nozzle, thus infiltrating into the air to reduce the vacuum at the main volume hole, so as to control the fuel flow, and the required gas mixture composition can be obtained. In order to stabilize the mixture composition, the float chamber has a through hole connected with the atmosphere, and control the fuel needle valve to keep the height of the fuel fuel in the float chamber stable. The liquid level is usually 5 to 6 mm lower than the nozzle to prevent fuel overflow when the internal combustion engine leans.
The shape and size of the throat determine the air flow rate and vacuum, which affects the inflation of the internal combustion engine, the fuel supply of the main fuel system and the fuel atomization. In order to obtain high speed airflow to atomization well and increase the amount of inflation, double or triple throat can be used. The main fuel system can only meet the requirements of the gas mixture under most working conditions. In special working conditions, an auxiliary system is also needed.
When the internal combustion engine itself is running but does not do any work externally, it is called idle operation. At this time, the throttle is close to closing, and the vacuum at the throat can not suck out and atomize the fuel. Therefore, there is an idle nozzle behind the throttle, using the vacuum here to suck out the fuel. The idle fuel volume hole and the idle air volume hole are provided in the idle fuel circuit to control the fuel volume and foam the fuel fuel. The idle speed can be adjusted by the idle screws. In order to ensure the smooth transition from the idle system to the main fuel system, a transition nozzle is also provided on the idle fuel road between the idle nozzle and the throat.
Fuel saver thickening system
In order to meet the economic requirements, the main fuel system provides the relatively thin mixture under most working conditions. But when the throttle is close to full opening, it requires the maximum power, which requires the supply of a thick mixture. Fuel saver is usually used to achieve this goal. There are two kinds of mechanical and vacuum types. The former uses the lever connected with the throttle, while the latter uses the vacuum behind the throttle to open and switch the throttle valve. When the valve is opened, a part of the fuel through the power fuel hole to strengthen the mixture, so as to get the maximum power.
As the internal combustion engine accelerates, the throttle suddenly opens wide up. The fuel quality is larger than the air, so the inertia is also large, it is difficult to increase the fuel supply in time, so the mixture instantly becomes thin, which makes the engine speed increase slowly, and even the intake pipe recharge or stop. Therefore, there is a permanent acceleration pump, which is driven by the throttle through a pull rod and a spring. When acceleration, the acceleration pump injects the fuel into the throat; when the throttle slows, the fuel returns to the float chamber through the intake valve of the acceleration pump to stop the injection.
The engine starting speed is very low, the temperature is also low, and the fuel atomization and gasification are very poor, so a thicker mixture is required to ensure the starting combustion of the internal combustion engine, so a separate starting system is required. The starting system takes many forms, the most common is to install a damper in front of the throat, and close it when starting, creating a high vacuum at the throat, forcing a lot of fuel out, forming a thicker mixture.