Key points of the working principle of carburetors in aviation piston engines

The key points of the working principle of the carburetor in an aviation piston engine are as follows:

First, basic functions

The carburetor is a key component in the fuel supply system of an aviation piston engine. Its main function is to atomize gasoline and mix it with air in a certain proportion to form a combustible mixture, which is then sent into the engine's cylinders for combustion, providing power for the engine.

Second, working principle

Air entry

Outside air passes through the air filter and then enters the carburetor. The function of an air filter is to remove impurities from the air and protect the engine from wear and tear.

Airflow acceleration and pressure drop

After the air enters the carburetor, it flows through a narrow throat (Venturi tube). According to Bernoulli's principle, when the flow rate of a gas increases, its pressure will decrease accordingly. Therefore, at the throat, the air flow rate increases and the pressure drops, forming a low-pressure area.

Fuel intake and atomization

In low-pressure areas, due to the effect of pressure differences, fuel is drawn in through the fuel injector (or fuel injection pipe) and mixes with air. The carburetor usually has a float chamber inside, which is used to store fuel and control the height of the fuel liquid level through the float to ensure a stable fuel supply.

After the fuel is mixed with air, it is atomized into tiny particles by the impact and shearing effect of high-speed airflow at the throat, forming a combustible mixture.

Mixed gas distribution

The atomized mixture is diverted into each cylinder through the intake manifold. A throttle valve (throttle lever) is usually installed inside the intake manifold to regulate the amount of mixed air entering the cylinder, thereby controlling the output power of the engine.

Third, working characteristics

Automatic proportioning

The carburetor can automatically adjust the ratio of fuel to air according to the working state of the engine (such as speed, load, etc.), keeping the concentration of the mixture in the optimal state to ensure the stable operation and efficient combustion of the engine.

Adapt to height changes

As the aircraft's flight altitude increases, the air density decreases. The carburetor needs to adjust the mixing ratio control lever to reduce the amount of fuel entering the throat in order to maintain an appropriate air-fuel ratio.

Fourth, Structure and Composition

Float chamber

Store the fuel and control the liquid level height of the fuel through the float to ensure a stable fuel supply.

Throat tube (Venturi tube)

It accelerates the air flow rate, reduces the pressure, forms a low-pressure area, and promotes the inhalation and atomization of fuel.

Fuel injector (fuel injection pipe)

Draw the fuel from the float chamber into the throat and mix it with the air.

Intake manifold

The atomized mixture is then diverted into each cylinder.

Throttle valve (throttle lever)

Adjust the volume of the mixture entering the cylinder to control the output power of the engine.

Fifth, maintenance and adjustment

Regular inspection

Regularly inspect the float chamber, throat, fuel injector and other components of the carburetor to ensure they are free from blockage and wear.

Adjust the mixing ratio

Adjust the mix ratio control lever in a timely manner according to the working condition of the engine and changes in flight altitude to maintain an appropriate air-fuel ratio.

Cleaning and maintenance

Regularly clean the carbon deposits and oil stains inside the carburetor to keep it unobstructed.

In summary, the carburetor of an aviation piston engine utilizes the low-pressure area generated when air flows through the throat to draw in fuel and mix it with air for atomization, forming a combustible mixture, which is then sent into the engine's cylinders for combustion. Its working principle is simple and reliable, but it also requires timely maintenance and adjustment according to the working condition of the engine and changes in flight altitude.