what is a Carburetor: How to Fuel and Air Mix-techplaneye

What is a carburetor?

A carburetor is a device, who used in internal combustion engines that mix air and fuel in the correct ratio for the combustion chamber. air passing through a narrow tube (like a venturi), and mixing it with fuel from a small jet. After that, the mixture then enters the engine’s cylinders for combustion and produces power.

what is the function of a carburetor

The carburetor prepares the correct ratio mixture at different engine loads and speeds. For example:

(a) Lean Mixture: Due to defects in the carburetor circuit, the mixture contains relatively more air and less fuel. This mixture is called a lean mixture. For example, lean mixtures have air-to-fuel ratios ranging from 16:1 to 20:1, respectively.

(b) Economic Mixture: When the motor vehicle is running at 30 to 60 km/hr., the engine demands an air-fuel mixture in the ratio of 12:1 to 15:1, depending on the good condition of the carburetor and road conditions. This mixture is called the optimal or economical mixture.

(c) Rich Mixture: The engine demands more fuel when starting the vehicle, increasing speed, or driving in hilly areas, etc. At this time, the ratio of air and fuel in the engine ranges from 5:1 to 4:1. This mixture is called a fertile mixture.

Parts of Carburetor

The construction of the carburetor used in petrol or SI engines is as follows:

Venturi tube
Air intake door
Exhaust jet
Mixing chamber
Throttle
Floating ball
Needle Valve
Leap (Leap)
Needle seat
Lever pin
Lever
Floating chamber
Idle Nozzle
Carburetor consists of metering jet, etc.

How does carburetor works

Explore detailed carburetor circuit diagrams to help you understand engine performance and how to work Carburetor Fuel and Air Mixture circuits. This is perfect for mechanics and enthusiasts alike..

1.Float Circuit:

A circuit as shown consists of a float chamber, float ball, indicator or needle valve, needle, seat, lever pin, lever, etc. Fuel from the reservoir is first pumped into the float chamber, then the chamber valve opens. The floating ball slowly floats upwards. As a result, the indicator valve attached to it sits on its seat. In this condition, the flow of fuel is partially or completely stopped.

Again, when the amount of fuel in the float chamber decreases, the buoyancy ball starts to down. As a result, the indicator valve opens. Pressurized fuel from the reservoir continues to flow into the float chamber through the inlet. If there is more fuel in the float or floating reservoir, more fuel is ejected through the metering jets, splashing out of the jet mouth and falling into the venturi tube. At that time, the throttle valve is partially open, and the rich mixture flows into the combustion chamber of the engine.

Again, if the amount of fuel in the floating cell is less, the opposite effect occurs. The engine gets a lean mixture, as the amount of fuel is relatively less. The fuel level in the float chamber must be at least 1/16 inch (inch) above the metering jet.

Otherwise, no fuel will flow to the metering jet through the floating circuit.

2. Idle or Low-Speed Circuit

This circuit of the carburetor works during engine start or acceleration to provide extra power by supplying a rich mixture to the engine. The idle or low-speed circuit works in combination with the idle path, air intake port, idle exhaust port, throttle, etc., as shown.

When the throttle valve is partially or fully closed, more vacuum is created in the intake manifold. As a result, under the pull of this vacuum, the lighter air with the heavier fuel enters the intake manifold of the engine through the idle door. A small amount of air is mixed with the fuel through the idle tube to form a rich mixture. At this time, the mixture can become vaporized as the air and fuel mix with each other in the annular space to form a smooth mixture.
At this time, the vacuum in the venturi can operate at a lower rate. Then, the fuel injection by the metering jet is stopped. This circuit has an adjusting screw to make the ideal mixture rich and lean. At this time, the throttle valve in the carburetor tube is fully closed or partially open, and the choke valve is fully open.

3. High-Speed Part Load Carrying Circuit

This circuit of the carburetor, as per the diagram, works through the metering rod, metering jet, primary venturi, secondary venturi, main venturi, main nozzle, etc. This circuit operates during engine acceleration. This circuit starts working when the circuit used at idle and low speed is finished. This circuit works when the motor vehicle reaches a speed of more than 20 to 35 km per hour.

This circuit has three venturis to facilitate fuel emission and mixing, and fuel emission and spraying are done through the main pipe. Further, the fuel flows from the floating reservoir to the main pipe through metering jets. In this circuit, the choke valve is fully open and the throttle valve is half open. Because of this, the venturi has a low vacuum level, resulting in a lean mixture being supplied to the engine at high speeds. Excess air in this circuit reduces the amount of fuel coming through the main tube as it arrives through the three venturi areas.

Again, the metering rod works to directly control the amount of fuel. The metering rod is attached to the throttle shaft. As a result, when the throttle valve opens, it moves upwards, and when the throttle valve closes, the main nozzle moves less fuel when the metering area is low, and more fuel flows to the nozzle when the metering area is high. Thus, the partial load-carrying circuit works at higher speeds of the carburetor.

4. High-Speed Full Power

High-speed carburetor circuits are used in automobiles. As per the figure, the high-speed full power circuit consists of the main jet, throttle linkage (connected to the accelerating pedal), metering rod, choke, throttle valve, etc. This circuit of the carburetor is the most powerful. When this circuit works, the throttle valve is fully open and the choke valve is partially open. As a result, the Venturi action at this time reaches its final stage, and through the main jet, petrol fuel enters the engine cylinder mixed with relatively less air.

The throttle valve is connected to the accelerating device, and to this connection, the accelerating pump circuit is connected. So even if the motor vehicle is running at high speed, the rich mixture is moving in the engine. While driving the vehicle in all circuits other than idling and low speed, the throttle valve should be opened more or less depending on the speed by keeping pressure on the accelerating pedal. This is how this circuit works.

5. Accelerating Pump Circuit

This circuit works in a special condition of the motor vehicle. The accelerating linkage of this circuit is controlled by the driver’s right foot. According to the diagram, the accelerating pump circuit consists of throttle linkage (connected to the accelerating device), choke, throttle valve, adjusting screw of the pump circuit, main jet, pump chamber, piston, connecting rod, etc.
The purpose of this circuit is to warm up the engine quickly, provide speed, or provide high power. The accelerating pump circuit works when the accelerating device is pressed suddenly and repeatedly in small strokes; otherwise, this circuit is off.

6. Choke Circuit

The choke circuit consists of the choke or choke valve, exhaust manifold, thermostatic spring, etc., as shown in the figure. The function of this circuit is to supply charge to the intake manifold of the engine by combining more or less air. The choke valve is controlled in two ways; hence it is named in two ways:

(a) Mechanical choke
(b) Automatic choke.

The mechanical choke valve and intake manifold are controlled by vacuum, exhaust gas, or electrical connection by the motorist. Automatic chokes are used in modern automobiles. This circuit supplies more or less air according to the engine’s demand.

Conclusion:
The fundamental principle of a carburetor is to efficiently mix fuel and air in the correct proportions to ensure optimal engine performance. Understanding this mixture is essential for maintaining engine efficiency and functionality.