In this article, you will learn about fuel injection systems. The carburetor is the very first mechanism that allows you to combine gasoline with air in the right proportion to prepare the air-fuel mixture and supply it to the combustion chambers of the engine. These devices are actively used to this day - on motorcycles, chainsaws, scythes and so on. That's just from the automotive industry they have long been superseded by injection systems of injection, more advanced and advanced.
What is a carburetor?
A carburetor is a device that mixes fuel and air, feeds the mixture to the intake manifold of an internal combustion engine. Early carburetors worked by simply letting air pass over the surface of the fuel (in a particular case, gasoline). But most of them later distributed a measured amount of fuel into the air stream. This air passes through the jets. For the carburetor, the condition of these parts is extremely important.
The carburetor was the main device for mixing fuel and air in internal combustion engines until the 1980s, when doubts arose about the effectiveness of its use. The combustion of fuel produces a lot of harmful emissions. Although carburetors were used in the United States, Europe, and other developed countries until the mid-1990s, they worked along with more sophisticated control systems to meet carbon footprint requirements.
History of development
Various types of carburetors were developed by a number of pioneers in the automotive industry, including German engineer Karl Benz, Austrian inventor Siegfried Marcus, English scholar 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 automobiles (and initially stationary gasoline engines also used carburetors), it is quite difficult to determine exactly who is the inventor of this complex device.
Types of carburetors
Early designs differed among themselves in the basic method of work. 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 to those used on modern cars. The very first, historical, so to speak, constructions can be divided into two main types:
- Surface type carburetors.
- Spray carburetors.
We consider them in more detail below.
Surface carburetors
All early carburetor designs were superficial, although there was a wide variety in this category. For example, Siegfried Marcus introduced something called the "rotating carburetor brush" in 1888. And Frederick Lanchester developed his carburetor type wick in 1897.
The first carburetor float was developed in 1885 by Wilhelm Maybach and Gottlieb Daimler. Karl Benz also patented a float-type carburetor at about the same time. However, these early designs were surface carburetors that worked by passing air above the surface of the fuel in order to mix them. But why do we need a carburetor engine? And without it, it was impossible to feed the fuel mixture into the combustion chambers (the injector was not yet known in the nineteenth century).
Most surface devices operated by simple evaporation. But there were other carburetors, they were known as devices that work due to "bubbling" (they are also called filtering carburetors). They work by making air move up through the bottom of the fuel chamber. As a result, a mixture of air and fuel is formed over 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 car, spray carburetors began to occupy a significant niche at the turn of the 19th and 20th centuries. Instead of relying on evaporation, these carburetors actually sprayed a measured amount of fuel into the air, which was sucked in by the air intake. These carburetors use a float (like 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. He first appeared in the 1940s. Although pressure carburetors resemble aerosols only in appearance, they were in fact the earliest examples of fuel injection devices (injectors). Instead of relying on the Venturi effect to suck fuel from the chamber, pressure carburetors sprayed fuel from the valves in much the same way as modern injectors. Carburetors became increasingly complex during the 1980s and 1990s.
What does a 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 carbon content.”
The K-68 carburetor works similarly, which was used on Tula motor scooters (later Ant), Ural and Dnipro motorcycles.
Components
All types of carburetors have different components. But modern appliances have a number of common characteristics, including:
- Air duct (venturi).
- Throttle valve.
- Solenoid valve idle.
- Accelerator pump.
- Carburetor cameras (primary, float, and so on).
- Float mechanism.
- Carburetor membrane for pumping fuel.
- Adjusting screws.
How does a carburetor work?
All types of carburetors operate using various mechanisms. For example, wick-type carburetors work by causing air to pass over the surface of gas-soaked wicks. This causes gasoline to evaporate into the air. Nevertheless, wick type devices (and other surface ones) are out of date more than a hundred years ago.
Most carburetors that are used by vehicles today use a spray mechanism. They all work in a similar way. Modern carburetors function through the venturi effect to draw fuel from the chamber.
Basic principles of carburetors
Carburetors, whose work is based on the Bernoulli principle, have some features. Changes in air pressure are predictable and directly depend on how fast it moves. This is important because the air passage through the carburetor contains a narrow, compressed venturi. It is necessary to accelerate the air when it passes through it.
The air flow (not the 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 it opens when this pedal is depressed. This allows air to pass through the venturi. Consequently, more fuel is drawn in from the mixing chamber. The carburetor operation is based on these principles.
Most carburetors have an extra valve above the venturi (called a throttle, which acts as a secondary throttle). The throttle remains partially closed when the engine is cold, which reduces the amount of air that can enter the carburetor. This leads to a richer air / fuel mixture , so the throttle should open (automatically or manually) as soon as the engine warms up and will no longer need a rich mixture.
Other components of carburetor systems are also designed to act on the air-fuel mixture during various operating conditions. For example, a power valve or metering rod can increase the amount of fuel under an open throttle, or this happens in response to low pressure in the vacuum system (or the actual throttle position). A carburetor is a difficult element, and the physical basis of its functioning is quite complex.
Problems
Some carburetor problems can be resolved 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.
When the carburetor fails, the engine will work poorly under certain conditions. Some problems of carburetor systems lead to engine breakdown; it cannot normally idle without assistance (for example, pulling a suction or constant gas supply). The most common problems occur in the cold season, when the engine is most difficult to operate. A carburetor that does not work well on a cold engine can function normally when it is warm (this is due to problems with coking of the channels).
It is worth noting that the carburetor for a walk-behind tractor is the same in composition as a car. The difference in the number of elements and their sizes. In some cases, problems with the carburetor can be solved by manually adjusting the mixture or idle speed. To this end, the mixture is usually controlled by turning one or more screws. Needle valves are fixed to them. These screws allow you to physically change the position of the needle valves, and this leads to the fact that the amount of fuel can be reduced (lean mixture) or increased (enrichment of the mixture occurs) depending on the specific situation.
Carburetor repair
Many problems of carburetor systems can be solved by making changes or performing other corrections without removing the device from the engine. To adjust the carburetor for a walk-behind tractor, there is no need to remove it. But some problems can be solved only with the removal of the device and its full or partial recovery. The carburetor recovery operation, as a rule, involves removing the block, disassembling it into parts and cleaning with a solvent specially developed for this purpose.
A number of internal components, seals and other parts must then be replaced before installation. Only after thorough processing is it necessary to assemble the carburetor and replace it. To conduct quality service, you need a carburetor repair kit. It includes all the most important structural 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 combustion chambers of the engine.