The principle of operation of the carburetor. Carburetor - educational program on the design and operation of the unit

Liquid fuel in gasoline engines cannot ensure the operation of the piston group. To create torque on the crankshaft, a series of cyclic micro-explosions in the cylinders is necessary, while liquid gasoline simply burns. When fuel is mixed with air (which contains large amounts of oxygen), a mixture is created that can create a flare that has high kinetic energy.

Automotive carburetors - history of development

At the dawn of engine building, the use of gas became unprofitable. There was a need to create a device that could, with a high degree of reliability and safety, ensure the formation of a high-quality mixture from gasoline and air. The operating principle of the first series carburetor was based on the evaporation of fuel vapor. The chamber was heated from an external heat source, gasoline vapors mixed with air due to convection.

The characteristics of such a carburetor did not allow developing more power, so this design did not take root in engine building. For the first examples of cars, it was enough that they just drove; later, the needs of customers grew, and motorsport began to develop. There was a need to create a carburetor that had no restrictions on engine power.

The next generation, invented by German engineers Daimler and Maybach, worked on the principle of fuel atomization. The size of the unit decreased (there was no need to build in a volumetric evaporation chamber with a heating tank), and productivity, on the contrary, increased significantly. In fact, a vacuum carburetor was created, the design of which is used in modern models. The main technical breakthrough - the transition of fuel into a gaseous state was forced, which gave scope for experiments with performance. Of course, the design of the Daimler-Maybach carburetor was not similar to modern designs of high-performance vacuum models with a special receiver and control of air discharge.

However, the principle of operation was the same as on any modern model.

Carburetor design (typical description for all modifications)

The diagram shows the relative position of the main components:

1. Gasoline supply pipe from the fuel pump;
2. A float with a needle valve that shuts off the fuel line;
3. Jet for receiving fuel from the float chamber;
4. Liquid fuel spray nozzle;
5. Mixer chamber in which the fuel mixture is formed;
6. An air damper that regulates the volume of incoming clean air flow from the filter;
7. Diffuser that shapes the direction of air flow;
8. A throttle valve that regulates the flow of mixture into the engine intake tract.

How does a carburetor work?

Let's consider the operation of each node.

1. Gasoline under low pressure (not to be confused with high-performance nozzles of injection systems) enters the float chamber. It is important to maintain a fuel level in the carburetor that does not exceed the location of the jet. Otherwise, aerosol spraying will not occur in the mixing chamber. For each model, an upper limit for filling the chamber is set, which is mechanically “monitored” by a float with a needle valve. This design was chosen because with a small amount of force the pressure in the incoming fuel line can be maintained. When the limit is reached, the valve closes the inlet; when the level drops, it fills the chamber with gasoline;
2. The disadvantage of the design (unfortunately, there is no alternative) is its high dependence on pollution. The needle valve may become stuck closed and the motor will stop running;
3. Next, gasoline enters the nozzle. The diameter of this element is strictly regulated; deviations of even hundredths of a millimeter are not allowed. Otherwise, aerosol spraying will not occur at the entrance to the mixing chamber, and the air-fuel mixture will not be formed, and, as already mentioned, the internal combustion engine does not work on liquid gasoline;
4. An aerosol of tiny droplets of gasoline emerges from the diffuser, ready to be mixed with air;
5. The mixer chamber (actually the carburetor body) is designed to form a gaseous mixture consisting of gasoline vapor and oxygen contained in the air. Gasoline, like air, does not enter the chamber under pressure, but, on the contrary, due to vacuum. When the cylinder moves down, a difference in pressure arises, a kind of vacuum. Due to the specially designed body shape, fuel and air flows are mixed evenly, forming a high-quality mixture;
6. The dampers (throttle and air), controlled by the gas pedal, measure the intensity of the air flow and the speed of fuel suction from the nozzle. The engine works more intensely, the crankshaft rotation speed changes along with power and torque.

All carburetor systems must work harmoniously: if one of the channels (nozzles) is clogged, or the position of the dampers is incorrectly adjusted, the formation of the mixture will be disrupted. Gasoline consumption will increase, power will be lost, the power unit will operate unstably, so all components must be clean, their size must correspond to factory calculations, and adjustment parameters must be adjusted. There are a number of adjustment screws on the carburetor; the correct specifications are set with their help. The illustration shows an example of an Ozone carburetor.

A well-tuned carburetor “squeezes” maximum performance out of the engine at the lowest fuel costs. Different carburetor models may have their own adjustment methods, but the general principle is the same.

Each carburetor has instructions for setting parameters. Adjustment can be done independently, or at a specialized service. When operating conditions change (the amount of oxygen in the air, regular load on the car, turning on the air conditioner in the summer, etc.), the settings should be re-adjusted.

What is the difference between a classic carburetor and an electronically controlled device?

The principles of operation of a mechanical carburetor were described above. All settings are set using screws and cannot be changed dynamically during operation. The carburetor circuit is constantly being improved, and new models (some of which are still in production today) have quite a lot of electronics. For example, almost all mechanical models are equipped with a solenoid valve.

Let's take a closer look at this device:

The fact is that when the gas pedal is fully released, the throttle valve is closed, and the engine should, in theory, stall. To operate the internal combustion engine without load (just so as not to start it every time after stopping), an idle system has been introduced. With its help, even with the dampers closed, a minimum volume of gasoline and air enters the housing. The formed fuel mixture is sufficient to maintain the operation of the power unit without load on the crankshaft.

This parameter requires precise adjustment: if the idle speed is too high, gasoline consumption will increase, and if it is too low, the engine will stall when stopping. When operating conditions change (temperature, the presence of an air conditioner with air conditioning, additional equipment that puts a load on the generator), the idle speed changes, so an idle speed valve (electric) was installed, which controls the process linearly, depending on the load.

There is no control program; only the power wire goes into the valve. Depending on certain operating conditions, the position of the valve changes.

These are not all electronic systems that can be introduced into the mechanics of the process. For example, all adjustments are made to a control unit, such as an ECU for injection engines. Such a microcomputer constantly monitors the load parameters on the power unit and can change carburetor settings in real time. Asking yourself the question: “which carburetor is better to install?”, You can consider introducing a modern design into the car. Unlike traditional carburetors, electronic systems do not require periodic adjustments, but are more expensive and more difficult to maintain and repair. To provide the electronics with initial data, various sensors are installed on the engine that monitor the motor parameters. Based on the information received, the carburetor actuators are activated.

Types of carburetors by manufacturer - which one to choose?

Everyone has heard the difference of the so-called. Chinese products, and carburetors of famous brands (the list of which includes DAAZ, Solex, and Ozon...). In fact, this is nothing more than prejudice. A product produced at the factory, in compliance with the technology, and with a quality certificate, will work well regardless of the geography of production. Only the so-called “no-name” products, collected by peasants from the Middle Kingdom literally with a file on their knees, are of low quality, so when selecting a new carburetor, first of all, focus on the reputation of the manufacturer and the availability of accompanying documentation. Of course, warranty obligations must also be provided by service centers within accessibility. That is, if you live in Kaliningrad, and the nearest manufacturer’s service center is in Dimitrovgrad, it makes sense to find another copy.

Bottom line

You should not be afraid of this seemingly complex device. The operation scheme is simple and reliable; the key to normal functioning is the cleanliness of all internal elements and correct settings.

If you have any questions, leave them in the comments below the article. We or our visitors will be happy to answer them

The finely atomized fuel and air that occurs outside the cylinders is called carburetion, and the device in which a combustible mixture of a certain composition is prepared depending on the operating mode of the engine is called a carburetor.
The simplest carburetor consists of air pipe, float chamber with float and needle valve, mixing chamber, diffuser, main metering device - atomizer and fuel nozzle, throttle valve.
Float chamber serves to maintain a constant fuel level at the atomizer (1.5-2 mm).
In the mixing chamber fuel vapors mix with air to form an air-fuel mixture.
Spray(thin tube) serves to supply fuel to the center of the mixing chamber.
Jet(calibrated hole) meters the amount of fuel passing to the nozzle.

Carburetor engine intake system

1 - pipeline; 2 — hole in the float chamber; 3 — diffuser; 4 - sprayer; 5 - throttle valve; 6 - mixing chamber; 7 - jet; 8 — float chamber; 9 — float; 10 - needle valve.

A diffuser (a short pipe narrowed inside) increases the speed of air flow in the center of the mixing chamber, thereby increasing the vacuum at the nozzle of the sprayer.

The throttle valve regulates the amount of combustible mixture supplied to the engine cylinders, reducing or increasing the flow area of ​​the mixing chamber.

It works as follows. During the intake stroke, due to the vacuum created by the piston, air enters the diffuser through the air pipe. In the diffuser, the air speed, and therefore the vacuum, increases. Under the influence of the pressure difference between the float chamber and the diffuser, fuel enters the diffuser through the atomizer nozzle, is picked up by the air flow, atomized and evaporated, forming an air-fuel mixture. From the mixing chamber, the combustible mixture enters the engine cylinders through the intake pipeline. As the throttle valve opens, the air flow speed and the vacuum in the diffuser increase, which increases fuel consumption. However, the necessary increase in fuel consumption does not occur; the combustible mixture becomes richer. When the engine operates in various modes, the simplest carburetor cannot provide a combustible mixture of a constant composition.

In advertisements for the sale of a car you can find many offers of not new, but quite decent cars in good condition. As they say, “drive and ride.” But here’s the problem: the selected car has a carburetor. This is a rather old device, which scares off modern car enthusiasts, especially young people, due to its complexity, possible lack of repair parts and possible breakdowns. Whether to buy a car with a carburetor or find a more modern design with a fuel injection system - you can make a decision only after you understand the nuances of the operation and design of this device.

What is a carburetor and what is it for?

In order for an internal combustion engine to operate optimally, it is necessary to mix fuel and air in a certain proportion and feed this mixture into the combustion chamber. The mixture parameters can change depending on the operating mode of the internal combustion engine, fuel consumption too, which means you need a device that will do all this automatically.

A carburetor is a device for mixing air with fuel. As a result of its operation, at the right moment, atomized gasoline mixed with air enters the combustion chamber of the engine, ready for ignition. Despite the fact that there is only one carburetor for several cylinders, the mixture always gets to the right place through the intake manifold thanks to the coordinated operation of all internal combustion engine elements.

Carburetor design

To this day, we have received mainly float models - the latest and most improved. So you can find them on most cars.

A float carburetor consists of many elements.

1. A float chamber, which is responsible for maintaining a certain fuel level.
2. A float with a shut-off needle, designed for automatic dosing of the fuel level in the float chamber.
3. Mixing chamber in which the main mixing of atomized (fine) fuel and air occurs
4. A diffuser is a narrowed area through which the air flow accelerates its movement.
5. A nozzle with a nozzle connecting the float and mixing chambers, through which fuel passes directly to the diffuser.
6. Throttle valve - regulates the flow of mixture entering the cylinders.
7. Air damper - regulates the air flow entering the carburetor. Thanks to it, you can make the mixture “poor”, normal or “rich”. Diagram of the dependence of power on the amount of air in the fuel mixture

   The diagram shows that a normal mixture is when there is about 15 times more air than fuel. Under such conditions, there will be complete combustion of gasoline and maximum power.

8. Idle system - supplies fuel bypassing the mixing chamber when the throttle valve is fully closed. Through special channels, gasoline and air pass into the throttle body.
9. Economizers and econostats are devices for additional fuel supply when the engine is operating at maximum load. In this case, economizers have forced control, and econostats operate from air rarefaction.
10. Fuel suction is a system for forced enrichment of the fuel mixture. By pulling the lever, the driver slightly opened the throttle valve, as a result of which air passed more intensely through the mixing chamber and took in more fuel. The result is a rich mixture, convenient for starting a cold engine.

The principle of operation of the carburetor

After watching the video below, you will clearly see the structure and principle of operation of the carburetor in different operating modes. The video, although old, is still relevant today. Don’t be lazy and watch to the end if you want to fully understand the topic.

Well, let’s summarize below - the operation of all float carburetors is carried out according to a typical scheme.

1. Gasoline is pumped into the float chamber through the fuel line from the tank to the required level, which is regulated and maintained by a float and a shut-off needle.
2. The sprayer, located in the lower part of the float chamber, uses a nozzle to transfer a strictly dosed portion of fuel to the mixing chamber. At the same time, the fuel flow is atomized for better mixing with air and combustion.
3. The fuel from the atomizer is dispersed over a diffuser, which is designed to create a rapid flow of air and better mix it with the already atomized gasoline.
4. The mixture of fuel and air flows to the throttle valve, which is directly connected to the gas pedal. The more fuel the engine needs, the more the throttle is open and the more active the carburetor is.
5. From the carburetor, the fuel-air mixture passes through the intake manifold to the cylinder in which the piston is currently descending with the simultaneous opening of the intake valve.
6. The piston works like a pump, drawing in the mixture already prepared in the carburetor.

Despite the rather simple operating principle, a well-tuned carburetor ensures excellent engine power delivery, good fuel economy and system reliability.

Types of carburetors

The predecessors of the float carburetor already discussed were the membrane-needle and bubbling carburetors. These are already outdated designs that today cannot be found on cars for everyday use (but these rarities still exist on “old cars”).

Membrane-needle The carburetor consists of several chambers separated by membranes. The membranes rest on springs of a given stiffness and are connected to each other by a rod. The membrane chambers have an outlet to the mixing chamber and are also connected to the fuel supply channel. The movement of the rod activated the membranes of the chambers, causing them to pump fuel into the mixing cavity. Yes, the system is somewhat cumbersome and slow to respond to changes in engine operating mode, but at the same time it is reliable to such an extent that it was installed on aircraft engines.

Bubbler The carburetor is the first design and the first attempt to create such a device. It was a blank lid that covered the gas tank at some distance from the fuel. Two pipes were connected to the cover: one inlet for air, the second to the engine. The air, passing under the lid, was saturated with gasoline vapor and in this form was sent to the combustion chamber. This is the first device designed to work with fuel vapors.

The classification of other types of carburetors depends on the design features. Based on the cross-section of the sprayer, devices with constant vacuum(models made in Japan with the highest performance characteristics), with constant spray cross section(carburetors made in the USSR and Russia) and with spool throttling(horizontal carburetors, intended mainly for motorcycles).

Based on the direction of movement of the finished mixture, designs with horizontal And vertical flow (of the latter, the system with a downward flow turned out to be the most effective).

Float carburetors may have one or more mixing chambers. Single-chamber units were in use until the 1960s, when engine developments required increased carburetor capacity.

The creation of multi-chamber carburetors with multiple throttle valves solved this problem. Varieties appeared: carburetors with the simultaneous opening of two throttle valves, each of which fed certain cylinders, and carburetors with the sequential opening of two valves, which were connected to the entire engine and operated in accordance with its mode.

As engine power increased, so did carburetors. Three- and four-chamber types appeared, several carburetors were installed on the car, various options for preparing the fuel mixture were configured (for example, an over-enriched mixture was made in one chamber, and a lean mixture in the other two).

Advantages and disadvantages of carburetors

Only the deaf have never heard of the horrors of constant carburetor repair. But what really? What are the advantages of this device and is there any point in dealing with it at all? Strange as it may sound in our technological age, the carburetor has several serious advantages.

1. Simplicity of design. No, the point is not that this is a very simple mechanism. But compared to the electronic components of today's cars, the carburetor is much easier to repair, maintain, and even operate. Most carburetors do not have any electronics, only mechanical devices, which means that a person with “straight hands” can repair and maintain it himself. The “old guard” – our parents, who are accustomed to delving into their “beloved” Zhiguli and Cossacks – remember this well.
2. Maintainability. Anything that breaks in the carburetor can be repaired without “excess blood.” The necessary spare parts can be purchased (there are manufacturers that still produce repair kits. Why not?).

But there are also disadvantages due to which carburetor cars eventually disappeared from the world automotive arena.

1. Technology required a fuel supply system with flexible adjustments, rather than with constant parameters, in order to minimize fuel consumption (which no one had previously taken into account). Therefore, the carburetor was replaced by an injection system, which is still being developed and improved.
2. The second significant disadvantage is the dependence of the carburetor on weather conditions. During the cold season, condensation collects inside, interfering with operation; in winter, there is a risk of icing of the inside. At the same time, the summer heat also prevents it from working stably due to active evaporation - disruptions in the supply of the mixture begin.
3. Well, the third drawback is that the environmental performance is significantly lower compared to an injector. In the modern struggle for the environment, carburetor cars simply do not stand up to criticism, since their harmful emissions are much higher.

Main malfunctions of carburetors and their causes

Malfunctions in the carburetor are reflected in the operating mode of the engine, and it is by this that one can determine that not everything is normal with the fuel supply system.

1. It is difficult to start an engine that is not warmed up - most likely, there are problems in adjusting the throttle valve. It is necessary to adjust the damper drive so that when the suction is extended, it closes completely, or adjust the starting clearances.
2. An unheated engine starts and immediately stalls when the choke is fully extended - the problem, again, is in the throttle valve drive. Either the gaps are incorrectly adjusted, or the telescopic rod does not work and the damper does not open.
3. A warm engine is difficult to start - the fuel level in the float chamber has not been adjusted, the float mechanism or valve needle has failed, resulting in the fuel level being higher than normal.
4. Unstable engine operation at idle speed - there may be several reasons, and the main one is the adjustment of the idle system. Other reasons - the idle speed ecostat drive does not work or the shut-off valve does not work, the jets are clogged, air is leaking, the float in the float chamber is not working properly
5. When opening the throttle, there is no increase in power - the mixture is too rich or lean due to the accelerator pump nozzle not being sealed.
6. Low acceleration dynamics - lack of fuel due to a lean mixture or shutdown of the secondary chamber.

Conclusion

Despite their somewhat bulky design, carburetors faithfully serve owners of old cars. And, perhaps, the repairs and cleaning that car enthusiasts do on their own are several times cheaper than washing the injectors, which owners of injection-powered cars are forced to resort to.

Should you buy a car if it has a carburetor? Judging by the operating pattern, it is far from the weakest link in the car, and may not be bothered by any breakdowns for a long time. So carburetors, although outdated, are still ready to serve those who value simplicity and reliability.

In order to work, a car engine needs power. Unlike electrical equipment, which is powered from the mains, a machine engine needs fuel, which is why cars have a special power system. It includes the fuel tank, fuel pump, fuel lines, carburetor, air filter, intake and exhaust pipes and muffler. One of the most important parts of the power system is the carburetor. In it, a combustible mixture is formed from fuel.

How does a carburetor work?

The carburetor consists of two chambers - float and mixing. The fuel first enters the float chamber. When it is filled with fuel to the required level, the float floats up and closes the valve through which the fuel flows. As soon as its level drops, the float lowers and fuel begins to flow into the chamber again. Thus, with the help of a float in the carburetor, the required fuel level is constantly maintained.

From the float chamber, the fuel enters the mixing chamber, where the formation of a combustible mixture occurs. Air enters this chamber from above and mixes with fuel. The mixing chamber contains a spray tube with a jet, a diffuser and a throttle. The jet is a plug that limits the flow of fuel from the float chamber. The throttle is a valve that is connected to the pedal. If you press on it with your foot, the throttle opens and the combustible mixture enters the cylinder. At the same time, the speed of the car increases. The spray tube is located in the diffuser, the narrowest point of the mixing chamber.

The principle of operation of the carburetor

When the car engine starts, a vacuum is created in the mixing chamber, causing fuel to spray out of the nozzle. This creates a flow of air, which, mixing with the fuel, carries it into the cylinder.

In addition to the float and mixing chambers, the carburetors of modern cars also have a starting device, an idle system, a metering system, an accelerator pump and an economizer. Carburetors of older car models are not able to ensure good engine operation, because depending on its condition (cold or warm), the composition of the combustible mixture must be different. For example, when starting a cold engine after the car has been standing for a long time, a combustible mixture rich in fuel is needed. But if the engine, on the contrary, is too hot after prolonged operation, a mixture with a small fuel content is needed. If the driver wants to increase speed or is driving a heavily loaded car, then the combustible mixture is necessary with a high fuel content, and the same is required at idle (at low speeds). Of course, a simple carburetor cannot cope with this operating mode.

An accelerator pump is also necessary to enrich the combustible mixture with fuel. When the driver sharply presses the pedal, a flow of air breaks out along with the fuel, the speed of which, as is well known, breaks through. Therefore, for some time there is not enough fuel in the combustible mixture. The accelerator pump helps solve this problem, and the engine starts running faster and more powerful.

The idle system is necessary so that the engine can operate at low speeds. In this mode, the engine runs on a rich mixture, but the metering system alone cannot prepare it, since the throttle is not fully open at idle. But the idle system of modern carburetors is designed in such a way that a combustible mixture forms near the throttle, because in this place, even when it is not fully opened, the vacuum necessary for the combustible mixture is created.

To start the engine, you need a mixture well enriched with fuel. For this purpose, a special damper with a valve for air passage is installed in the mixing chamber. There is a special knob on the dashboard with which this valve can be controlled. If the driver pulls the handle, the valve will open slightly and the amount of air entering the mixing chamber will decrease. This increases the fuel content in the combustible mixture. Therefore, even the very first portions of the combustible mixture are saturated with fuel and the engine starts, as they say, with half a turn. With a starter, the engine will run even at very low temperatures.

The dosing system, which is equipped with the carburetors of all modern cars, allows you to prepare a combustible mixture for various engine operating modes. This system allows you to automatically adjust the composition of the combustible mixture when the engine is running at low or medium load. When the engine operates in this mode, fuel for preparing the combustible mixture enters through the metering system, but even with the throttle fully open, the fuel supply is sometimes not enough. Therefore, when the throttle is almost fully open, the lever associated with it acts on the economizer drive rod, which opens an additional passage for fuel from the float chamber. As a result, the engine can operate with more power.

As you can see, the carburetor is very important for starting the engine. The slightest malfunction can not only damage the engine, but also prevent it from starting at all. But the carburetor is not the whole power system. Fuel is supplied to it from the fuel tank, which in a passenger car is most often located in the rear under the trunk floor or in the front. The hole into which you pour gasoline is located outside and is closed with a plug. Only hardly anyone has studied the cork itself seriously, but in vain! Because the nutrition system begins with her. There are steam and air valves on the fuel tank filler cap. The first is necessary so that in the heat, when the fuel evaporates, increased pressure is not created in the tank. And the air valve is needed so that a vacuum does not appear in the tank, otherwise the fuel supply will be disrupted.

Vehicle power system design

The fuel itself will not get from the tank into the carburetor, so a fuel pump is needed. Its design is such that the fuel, passing through it, is cleaned in the filter and only after that it passes further into the carburetor. If the engine is not running and fuel needs to be pumped into the carburetor, use the manual pumping lever.

Dust that comes from the air falling on them, as well as metal particles formed as a result of friction of the parts, constantly settles on the engine parts. If cars did not have a well-thought-out device for cleaning the engine from dust, then all the parts would wear out very quickly. Car engines have a kind of self-protection from dust, i.e. an air filter that cleans the air. Only purified air flows should flow to the carburetor, otherwise the engine will quickly fail. The air filter must be cleaned periodically. To do this, it is disassembled, the body is washed with kerosene and fresh oil is poured into the filter, which will absorb all the automobile “impurities”.

Let's follow the fuel path further. The carburetor leaves the fuel mixture already required for the engine, which passes into the cylinder through the intake manifold. Exhaust fuel gases exit through the exhaust pipelines. Another thin-walled pipe is attached to the exhaust pipe, which carries gases to the muffler. Its name speaks for itself. After all, if there were no muffler, the exhaust gases would come out with great noise. The action of the muffler is based on the fact that gases, moving from one pipe to another, gradually expand and lose speed. They come out of the muffler in a smooth stream and do not cause noise. It also extinguishes sparks that are formed when fuel particles burn out. Failures and malfunctions can also occur in the power system. For example, the process of forming a combustible mixture of the composition necessary for engine operation is often disrupted. Sometimes fuel leaks, the fuel gauge fails, or the carburetor device stops functioning. All these faults must be eliminated in a timely manner so that minor breakdowns do not lead to serious consequences.

Based on a number of signs, the driver himself will be able to find the reason for poor engine performance and fix the problem. For example, the engine does not start well if the mixture in the cylinder contains few fuel particles. This means you need to check the serviceability of the fuel pump. The filter or nozzle may be clogged, or the tightness of the parts may be broken. When removing and installing a carburetor, you must use special car keys, and you can read what similar tools are needed in a car.

It is very harmful for the engine to run on a fuel-lean mixture. Because of this, it quickly overheats, and popping noises are heard in the air filter. If the mixture is oversaturated with fuel, then most likely the air dampers are not completely closed and fuel enters along with the air flow. The jets may be worn out or the fuel level in the carburetor float chamber may be too high. In short, there can be many reasons for the engine to suddenly malfunction. The main thing is to fix problems in a timely manner and not lead to major repairs.

A very clear and useful video on the structure and operating principle of a carburetor is a video filmed in the USSR, but still relevant in our time.

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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 required proportion to prepare an air-fuel mixture and supply it to the combustion chambers of the engine. These devices are actively used to this day - on motorcycles, chainsaws, lawn mowers, and so on. It’s just that they were long ago supplanted from the automotive industry by injection injection systems, which are more advanced and perfect.

What is a carburetor?

A carburetor is a device that mixes fuel and air and 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 distributed measured amounts 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 device for mixing fuel and air in internal combustion engines until the 1980s, when doubts arose about its efficiency. When fuel burns, a lot of harmful emissions are generated. Although carburetors were used in the United States, Europe and other developed countries until the mid-1990s, they worked alongside more complex control systems to meet carbon dioxide emissions requirements.

History of development

Various types of carburetors were developed by a number of automotive pioneers, including German engineer Karl Benz, Austrian inventor Siegfried Marcus, English polymath Frederick W. Lanchester, and others. Since so many different methods of mixing air and fuel were used in the early years of automobiles (and the original stationary gasoline engines also used carburetors), it is difficult to pinpoint exactly who invented this complex device.

Types of carburetors

Early designs differed from each other in their basic method of operation. They also differ from the more modern ones that dominated much 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, structures can be divided into two main types:

1. Surface type carburetors.
2. Spray carburetors.

Surface carburetors

All early carburetor designs were surface carburetors, although there was a wide variety in this category. For example, Siegfried Marcus introduced something called a "rotating brush carburetor" in 1888. And Frederick Lanchester developed his carburetor-type wick in 1897.

The first float carburetor was developed in 1885 and the float type carburetor was also patented around the same time. However, these early designs were surface carburetors that worked by passing air over the surface of the fuel to mix them. But why does an engine need a carburetor? And without it there was no way to supply the fuel mixture to the combustion chambers (the injector was not yet known in the nineteenth century).

Most surface devices operated on the basis of simple evaporation. But there were other carburetors, they were known as devices that work due to “bubbling” (they are also called filter carburetors). They work by forcing air upward 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 throughout the early decades of the automobile, 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 operated on the basis of Bernoulli's principle, as well as the Venturi effect, just 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 resemble aerosol carburetors only in appearance, they were actually the earliest examples of forced fuel injection devices (injectors). Instead of relying on the Venturi effect to suck fuel from the chamber, pressure carburetors sprayed fuel from valves in much the same way as modern injectors. Carburetors became increasingly sophisticated during the 1980s and 1990s.

What does "carburetor" mean?

"Carburetor" is an English word that is derived from the term carbure, translated from French as "carbide". In French, carburer simply means “to combine (something) with carbon.” Likewise, the English word "carburetor" technically means "increase in carbon content".

The K-68 carburetor works similarly, which was used on “Tula” (later “Ant”) type scooters, “Ural” and “Dnepr” motorcycles.

Components

All types of carburetors have different components. But modern devices have a number of common characteristics, including:

How does a carburetor work?

All types of carburetors operate using different mechanisms. For example, wick-type carburetors work by forcing air across the surface of gas-saturated wicks. This causes gasoline to evaporate into the air. However, wick-type devices (and other surface ones) became obsolete more than a hundred years ago.

Most carburetors used in vehicles today use a spray mechanism. They all work in a similar way. Modern carburetors operate by using the Venturi effect to draw fuel out of the chamber.

Basic principles of carburetor operation

Carburetors, the operation of which is 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 necessary to accelerate the air as 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 used, and it opens when the accelerator pedal is depressed. This allows air to flow through the venturi. Consequently, more fuel is drawn from the mixing chamber. The operation of a carburetor is based on these principles.

Most carburetors have an additional valve above the venturi (called a throttle body) that acts as a secondary throttle valve. The throttle remains partially closed when the engine is cold, reducing the amount of air that can pass into the carburetor. This results in more air/fuel, so the throttle should open (automatically or manually) once the engine warms 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 under open throttle, or in response to low pressure in the vacuum system (or actual throttle position). A carburetor is a complex element, and the physical basis of its functioning is quite complex.

Problems

Some carburetor problems can be solved by adjusting the choke, mixture or idle speed, while others require repair or replacement. Often the carburetor membrane wears out and stops pumping gasoline into the chambers.

When a carburetor fails, the engine will perform poorly under certain conditions. Some problems with carburetor systems cause the engine to break down; it cannot idle normally without outside help (for example, pulling the choke or constantly revving up the engine). The most common problems occur during the cold season, when the engine is most difficult to operate. And a carburetor that does not work well when the engine is cold may 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 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. For this purpose, the mixture is usually adjusted by turning one or more screws. Needle valves are attached 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 or increased (the mixture is enriched) depending on the specific situation.

Carburetor repair

Many carburetor system problems can be solved by making changes or performing other corrections 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 by removing the device and restoring it completely or partially. Carburetor rebuilding typically involves removing the block, disassembling it into pieces, 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 maintenance, 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 combustion chambers of the engine.