You do realize that fuel is mixed in internal combustion engines? This mixing occurs in the carburetor. New automobiles now use fuel injection for the same process. Nevertheless, the scientific secret behind most transportation, either by land, sea, or sky, is that fuel is turned into power. This occurs when it burns with air, causing a small explosion, although that may not be our primary goal here—perhaps it could be!
In this reading, we’ll explore what a carburetor is, its function, parts, types, and how it works. We’ll also learn its advantages and disadvantages.
Let’s get started!
What Is A Carburetor?
A carburetor is designed to take in the exact air and fuel needed for proper combustion. The part has been the heart of a vehicle’s engine, making it run smoothly and give better horsepower. The mechanical device known as a carburetor is able to precisely mix air and fueleven when it is cold starting or operating at a high speed.
A carburetor mixes the fuel from the gas tank with air. This mixture then moves to the combustion chamber, where the spark plug ignites it. The air-fuel mixture must be precisely calibrated. An efficiently functioning engine requires precise calibration of the carburetor. The engine “runs lean” when there is insufficient fuel-to-air mixture, which can lead to the engine breaking down or not starting at all.
Functions of Carburetor
The carburetor in a car engine serves quite a lot of functions. Here are the key functions of a carburetor:
- It regulates the air-fuel ratio and also mixes the fuels.
- Controls the engine speed.
- According to engine speed and load changes, carburetors increase or decrease the amount of mixture.
- It vaporises the fuel and mixes the air into a homogeneous air-fuel mixture.
- It also helps to keep a certain amount of fuel in the float chamber all the time.
- It helps the fuel burn smoothly and properly without any problems.
A brief history of the invention of a carburetor is that carburetors have been around since the 19th century. Karl Benz, the creator of Mercedes, was a pioneer in the automobile industry who created it first. This, which has become an unforgettable history, was designed in 1888 and still, and date carburetors are still in application.
Related: What Is An Automobile Engine? Its Diagram, Parts & How it works
Diagram Of A Car Carburetor
Functional Parts of Carburetors
Here are the main parts of a carburetor and their functions:
Throttle Valve
The function of a throttle valve in a carburetor is to control the air/fuel mixture (charge) that enters the engine cylinder. This throttle valve is opened when the accelerating pedal is pressed.
Metering System
This part controls the flow of fuel into the nozzle, making it responsible for the exact mixture of air and fuel. It is made up of a fuel discharge nozzle and a metering orifice.
Idling System
The passage from the float chamber to the venturi tube is called an idling system. It offers a rich mixture during idling and at low speed. It works when the throttle is open below 15% or during idling.
Strainer
A strainer is a device that filters the fuel before entering the float chamber. It is made of a fine wire mesh, which filters the fuel from dust and other suspended particles. Nozzles get blocked if particles are not removed from the surface of the strainer.
Venturi
A venturi is a cross-sectional hollow that gradually decreases to reduce the air pressure in the chamber. From it, fuel comes out of the fuel pipe to mix.
Choke Valve
A choke valve is another part of the carburetor that controls the mixture of air and fuel. Its purpose is to control the quantity of air inside the mixing chamber. It is a valve that normally stays in a semi-open condition, but when a rich mixture is required, the valve is operated.
Float Chamber
Float chambers are storage tanks for fuel that aid in the continuous supply of fuel. It features a floating valve that maintains the level of fuel in the float chamber. When the fuel level increases, the float moves upward, which closes and stops the fuel supply.
Mixing Chamber
The mixing chamber is where the air and fuel mixture takes place, which is then transferred to the engine cylinder.
Idle and Transfer Port
In the carburetor’s venturi, there are two nozzles or ports that help deliver fuel to the engine cylinder. In modern automobile engines, there are some additional parts that feature their carburetors to improve efficiency. These parts include:
Throttle Return Check
The fact that the total throttle on an engine running at a very high speed causes a very high intake manifold vacuum. This will draw exhaust into the engine intake during v/v overlap. The intake chart will be diluted, causing misfiring or stalling.
Automatic Mixture Control
A solenoid and spring control a plunger-shaped valve in a carburetor. It operates the separate jet in the float chamber. The solenoid is turned on, and the v/v is lifted to increase the amount of fuel supplied to the jet.
Anti-Dieseling Solenoid
Because modern emission control engines usually run hotter, this results in some hot spots in the combustion chamber. These hot spots cause pre-ignition in the chamber. Carburetors are designed with an anti-dieseling solenoid in modern engines to prevent pre-ignition.
Types of Carburetors
Carburetors come in different designs, depending on the type of engine they are used in and their specific function. Here are the main types of carburetors:
Up-draft Carburetor
In the up-draft types of carburetor, air enters through the bottom side and leaves through the top. This is to let the direction of its flow upward. The float chamber provides the fuel, and venturi creates the pressure difference between the two chambers. Fuel comes out from the fuel pipe and mixes with the inlet air to make the fuel-air mixture. The fuel passes through the throttle valve, which is directly connected to the accelerator. This mixture then goes into the engine cylinder to perform combustion.
Down-draft Carburetor
The down-draft carburetor is the most common because of its advantages. It supplies air from the top portion of the mixing chamber. Some of its advantages include:
- The gravity assists the flow of the mixture, making the engine pull better at lower speeds under load.
- The position of the carburetor is easily accessible.
- A higher value of volumetric efficiency can be achieved with an engine with such a part.
Though some disadvantages still occur, before that, let me explain why it is considered better than the up-draft type:
To prevent the limitation of down-draft carburetors revealed above, up-draft is the only option. It is placed at a level higher than the inlet manifold, where the air and mixture will generally follow a downward course.
Even though the air velocity is low, the fuel moves into the cylinders by gravity rather than by air friction like the first type. Thus, the design of the mixing tube and throat can be made large, which will increase the engine speed and the possibility of high outputs.
Horizontal Carburetor
The horizontal carburetor is the third type, which is known when a down-draft carburetor is in a horizontal direction. Its working principle is very simple. The carburetor stays in a horizontal position where the air is coming in through one end of it. it mixes the fuel before going into the engine cylinder for combustion.
Related: The Difference Between 2-Stroke And 4-Stroke Engines
How A Carburetor Works
Based on Bernoulli’s principle, the carburetor draws more fuel into the airstream as the speed at which the intake air’s static pressure decreases. The majority of the time, the engine’s fuel supply does not increase instantly when the driver presses the throttle pedal (except from the accelerator pump). The fuel intake mixture is instead enhanced by increasing the airflow through the carburetor.
Carburetors differ greatly in terms of complexity and design. The most basic one is a horizontal fuel pipe connected to a massive vertical air pipe above the engine cylinders. As air speeds through the narrow bend in the middle of the pipe, its pressure decreases. This kinked part is known as a venturi. Through the side fuel pipe, the air is drawn in by the sucking effect of the lowering pressure of the air.
There are two swiveling carburetor valves above and below the venturi. The choke valve at the top is in charge of controlling airflow. The venturi takes in more fuel, and the engine gets a fuel-rich mixture when the choke is closed. That helps when the engine is cold, starting slowly, and running slowly. The throttle valve is under the venturi.
As the throttle is opened wider, more air is forced into the carburetor, causing it to draw fuel in from the side pipe. The engine produces more power and accelerates with more fuel and air. This is the reason a car accelerates when the throttle is opened; it works similarly to blowing on a campfire to increase the oxygen and speed up the burning process. In cars and motorcycles, the throttle is connected to the accelerator pedal or handlebar.
Carburetor Video
Advantages
Carburetors have been used in internal combustion engines for decades, particularly in older vehicles and small engines like motorcycles and lawnmowers. Although modern engines mostly use fuel injection systems, carburetors still offer several advantages:
- Carburetor parts are less expensive when compared to that of the fuel injector.
- The air-fuel mixture is perfectly done with the components.
- It has more power and precision than the air-fuel mixture.
- The engine component is not restricted by the amount of gas pumped fr the fuel tank. This is to say, the cylinders may pull more fuel through the carburetor, leading to greater power and a denser mixture in the chamber.
Disadvantages
While carburetors have certain advantages, they also come with several disadvantages, especially compared to modern fuel injection systems. Here are the main disadvantages of carburetors:
- The mixture supplied at a very low speed is weak, making the engine not perfectly ignite.
- Changes in atmospheric pressure can have an impact on the engine part.
- More fuel is consumed when compared with fuel injectors.
- More air emissions than fuel injectors.
- Higher maintenance than fuel injectors.