A simple carburetor consists of three parts: the upper part, the middle part and the lower part. The upper part has the air inlet and the float chamber, the middle part has the throat, the measuring hole and the nozzle, and the lower part has the throttle valve, etc. The float chamber is a rectangular container that stores gasoline from the gasoline pump. Inside the container is a float that uses the height of the floating surface (oil level) to control the amount of oil fed. One end of the oil inlet of the nozzle in the middle is connected with the measuring hole of the float chamber, and the other end of the oil outlet is at the throat of the throat.
The larynx is in the shape of a bee waist, the two ends are large and the middle is small, and the cross-sectional area at the middle throat is the smallest. When the engine starts, the piston descends to generate suction, and the inhaled airflow passes through the throat with the highest velocity and the lowest static pressure, so the throat pressure is lower than the atmospheric pressure, that is to say, there is a pressure difference between the throat of the throat and the float chamber, that is With what people often say “vacuum degree”, the greater the pressure difference, the greater the vacuum degree. Gasoline is ejected from the nozzle outlet under the action of vacuum, because the air velocity at the throat of the throat is 25 times that of gasoline, so the oil flow ejected from the nozzle is dispersed by the high-speed air flow, forming a large Different fog-like particles, that is, “atomization”. The preliminarily atomized oil particles are mixed with air to form a “mixture”, which enters the combustion chamber of the cylinder through the throttle valve, intake duct and intake valve. Here, the opening of the throttle valve and the speed of the engine determine the degree of vacuum at the throat, and the change of the opening of the throttle valve directly affects the proportion of the mixture, which are important reasons for affecting the operation of the engine.