In this article you will learn about fuel injection systems. The carburetor is the very first mechanism that made it possible to combine gasoline with air in the right proportion to prepare the air-fuel mixture and supply it to the engine's combustion chambers. These devices are actively used to this day - on motorcycles, chainsaws, lawn mowers, and so on. That's just from the automotive industry, they have long been supplanted by injection injection systems, more advanced and perfect.
What is a carburetor?
A carburetor is a device that mixes fuel and air, delivers the resulting mixture to the intake manifold of an internal combustion engine. Early carburetors worked by simply allowing air to pass over the surface of the fuel (in this particular case, gasoline). But most of them later dispensed a measured amount of fuel into the air stream. This air passes through the jets. For a carburetor, the condition of these parts is extremely important.
The carburetor was the main tool for mixing fuel and air in internal combustion engines until the 1980s, whendoubts about its effectiveness. When fuel is burned, a lot of harmful emissions are produced. Although carburetors were used in the United States, Europe, and other developed countries until the mid-1990s, they worked alongside more sophisticated control systems to meet carbon emissions requirements.
Development history
Different types of carburetors were developed by a number of automotive pioneers, including German engineer Karl Benz, Austrian inventor Siegfried Markus, English polymath Frederick W. Lanchester and others. Since so many different methods of mixing air and fuel were used in the early years of the existence and development of cars (and the original stationary gasoline engines also used carburetors), it is quite difficult to determine exactly who invented this complex device.
Types of carburetors
Early designs differed in their basic method of operation. They also differ from the more modern ones that dominated for most of the twentieth century. A modern carburetor for a spray-type chainsaw, similar ones are used on modern cars. The very first, historical, so to speak, constructions can be divided into two main types:
- Surface type carburetors.
- Spray carburetors.
Let's look at them in detail later.
Surface carburettors
All early carburettor designs were superficial, though there was a lot of variety in this category as well. For example, Siegfried Markus introduced something called a "revolving carburetor brush" in 1888. And Frederick Lanchester developed his carburettor type wick in 1897.
The first carbureted float was developed in 1885 by Wilhelm Maybach and Gottlieb Daimler. Karl Benz also patented the float type carburetor around the same time. However, these early designs were surface carburetors that worked by passing air over the surface of the fuel in order to mix them. But why does an engine need a carburetor? And without it, it was impossible to supply the fuel mixture to the combustion chambers (the injector was not yet known in the nineteenth century).
Most surface devices functioned on the basis of simple evaporation. But there were other carburetors, they were known as devices that work due to "bubble" (they are also called filter carburetors). They work by forcing air up through the bottom of the fuel chamber. As a result, a mixture of air and fuel is formed above the main volume of gasoline. And this mixture is subsequently sucked into the intake manifold.
Spray carburetors
Although various surface carburetors were dominant during the first decades of the automobile's existence, spray carburetors began to fill a significant niche at the turn of the 19th and 20th centuries. Instead ofrelying on evaporation, these carburetors actually sprayed a metered amount of fuel into the air that was sucked in by the intake. These carburetors use a float (like the Maybach and earlier Benz designs). But they acted on the basis of the Bernoulli principle, as well as the Venturi effect, like modern devices, such as the K-68 carburetor.
One of the subtypes of aerosol carburetors is the so-called pressure carburetor. It first appeared in the 1940s. Although pressure carburetors only resemble aerosol carburetors in appearance, they were actually the earliest examples of forced fuel injection devices (injectors). Instead of relying on the Venturi effect to suck fuel out of the chamber, pressure carburetors sprayed fuel out of the valves in much the same way as modern injectors. Carburettors became increasingly complex during the 1980s and 1990s.
What does "carburetor" mean?
"Carburetor" is an English word that is derived from the term carbure, translated from French - "carbide". In French, carburer simply means "combine (something) with carbon". Similarly, the English word "carburetor" technically means "increase in carbon content".
The K-68 carburetor works similarly, which was used on scooters of the Tula type (later Ant), Ural and Dnepr motorcycles.
Components
All types of carburetors have different components. But modern appliances share a number of common characteristics, including:
- Airchannel (Venturi tube).
- Throttle valve.
- Idle solenoid valve.
- Accelerator pump.
- Carburetor chambers (primary, float and so on).
- Float mechanism.
- Carburetor fuel transfer diaphragm.
- Adjustment screws.
How does a carburetor work?
All types of carburetors work with different mechanisms. For example, wick-type carburetors work by forcing air over the surface of gas-soaked wicks. This causes the gasoline to evaporate into the air. However, wick-type appliances (and other surface-type appliances) are over a hundred years old.
Most carburetors used in vehicles today use a spray mechanism. They all work in the same way. Modern carburetors use the Venturi effect to draw fuel out of the chamber.
Basic principles of carburetors
Carburettors based on the Bernoulli principle have some special features. Changes in air pressure are predictable and directly related to how fast it is moving. This is important because the air passage through the carburetor contains a narrow, compressed venturi. It is needed to accelerate the air as it passes through it.
The airflow (not mixture flow) through the carburetor is controlled by the accelerator pedal. It is connected to the throttle valve,located in the carburetor, using a cable. This valve closes the venturi when the accelerator pedal is not in use and opens when the accelerator pedal is depressed. This allows air to pass through the venturi. Consequently, more fuel is drawn from the mixing chamber. The operation of the carburetor is based on such principles.
Most carburetors have an additional valve above the venturi (called a throttle that acts as a secondary throttle). The throttle remains partially closed when the engine is cold, which reduces the amount of air that can pass into the carburetor. This results in a richer air/fuel mixture, so the throttle should open (automatically or manually) once the engine has warmed up and no longer needs a rich mixture.
Other components of carburetor systems are also designed to affect the air-fuel mixture during various operating conditions. For example, a power valve or metering rod may increase the amount of fuel at open throttle, or it may be in response to low vacuum system pressure (or actual throttle position). A carburetor is a complex element, and the physical basis of its operation is quite complex.
Problems
Some carburetor problems can be solved by adjusting the choke, mixture or idle, while others require repair or replacement. Often the carburetor membrane wears out, stops pumping gasoline into the chambers.
Whenthe carburetor fails, the engine will run poorly under certain conditions. Some problems of carburetor systems lead to engine breakdown, it cannot normally idle without outside help (for example, pulling the choke or constant gasping). The most common problems occur during the cold season, when the engine is most difficult to work. And a carburetor that performs poorly on a cold engine may function fine when warm (this is due to problems with coking channels).
It is worth noting that the carburetor for a walk-behind tractor is the same as a car carburetor. The difference is in the number of elements and their sizes. In some cases, carburetor problems can be resolved by manually adjusting the mixture or idle speed. To this end, the mixture is usually adjusted by turning one or more screws. They have needle valves. These screws allow the needle valves to be physically repositioned, resulting in the amount of fuel being reduced (lean) or increased (rich) depending on the situation.
Carburetor repair
Many carburetor system problems can be solved by making changes or other fixes without removing the unit from the engine. To adjust the carburetor for a walk-behind tractor, there is no need to remove it. But some problems can only be solved with the removal of the device and its complete orpartial recovery. Rebuilding a carburetor typically involves removing the block, taking it apart and cleaning it with a solvent designed specifically for this purpose.
A number of internal components, seals and other parts must then be replaced before installation. Only after careful processing is it necessary to assemble the carburetor and install it in place. To carry out quality service, you will need a carburetor repair kit. It includes all the most important design elements.
So we found out that a carburetor is literally a device that adds gasoline (fuel) to the air and delivers this mixture to the engine's combustion chambers.
