07.10.2023

The principle of operation of a carburetor. How a carburetor works: design and principle of operation Carburetor system

Until the mid-80s, gasoline internal combustion engines in cars and light trucks were widely equipped with carburetors. Such engines operate on the principle of combustion of a fuel-air mixture prepared in advance by an external device in the engine cylinders. The specified working mixture consists of droplets of fuel and air. The carburetor is responsible for the process that involves the formation of a mixture of these components in the right proportion for maximum operating efficiency. The simplest carburetor is a mechanical metering device.

Early developments at the dawn of the engine building era used lighting gas as fuel. At an early stage, such engines simply did not need a carburetor. The illuminating gas entered the cylinders due to the vacuum that was formed during engine operation. The main problem with such fuel was its high cost and a number of difficulties during use.

The second half of the 19th century was the period when inventors, engineers and mechanics all over the world tried to replace expensive lighting gas with a more economical, cheaper and accessible type of fuel for the internal combustion engine. The best solution was to use liquid fuel that is familiar to us today.

It is worth considering that such fuel cannot ignite without the participation of air. To prepare a mixture of air and fuel, an additional device was required. Not only that, but it was also necessary to mix air with fuel in the required proportions.

To solve this problem, the first carburetor was invented. The device was released in 1876. The creator of an early model of the carburetor was the Italian inventor Luigi De Christoforis. In its design and operating principle, the first carburetor had a number of significant differences from more modern analogues. To obtain a high-quality fuel-air mixture, the fuel in the first device was heated, and its vapors were mixed with air. For a number of reasons, this method of forming a working mixture is not widely used.

Developments in this area continued, and a year later, talented engineers Gottlieb Daimler and Wilhelm Maybach created the design of an internal combustion engine that had a carburetor operating on the principle of fuel atomization. This device formed the basis for all subsequent developments.

Modernization

The main direction of further work of engineers was the maximum automation of all mixture formation processes. The best minds of many companies producing cars and related equipment worked to improve the design of the carburetor. For this reason, you can find a great variety of simple and complex carburetor models from numerous global manufacturers.

Further development

Carburetors began to be actively replaced by injection systems only at the end of the 20th century. Until this time, the carburetor design was intensively improved. The latest rounds in the evolution of carburetor injection are electronically controlled carburetors. Such carburetors had several solenoid valves, the operation of which was controlled by a special control device. For example, we can mention the Hitachi carburetor brand. The design included nearly 5 valves, and the dampers were electronically controlled.

The latest generation of structurally complex carburetors is perfectly demonstrated by the already mentioned Hitachi carburetor model. This carburetor was installed on Nissan cars in the late 80s and early 90s. The complexity of this generation of carburetors lies in the large number of auxiliary devices, especially if you compare the Hitachi product with the primitive Solex, which was installed on the VAZ.

Auxiliary devices were responsible for stabilizing the operation of the carburetor in various modes. Such modes and operating features include sudden release of gas, idling during idle time on a car with an automatic transmission, leveling and stabilization of power unit speed after turning on the air conditioning system, as well as many others.

The carburetor of the latest generations, brought to perfection, basically consisted of numerous devices. We will name only a few of them for your reference:

Outdoor air temperature control system;.
Intake manifold heater;
Fuel cut-off valve;
Mixture enrichment device valve;
Bimetallic air damper spring in the throttle opening mechanism;
Fast idle system, etc.;

Such devices belong to the latest “electronic” carburetors. Additional elements in these models were made in the form of separate analog devices. The devices were controlled by simple electronics or operated on the principle of self-regulation (bimetallic spring).

It is noteworthy that simple mechanical carburetors are very versatile devices and can be installed using an adapter on different car models. An excellent example is the same Solex carburetor, well known to domestic motorists.

Carburetor and injector

Further in the history of fuel supply and mixture formation systems, monoinjection (monoinjector) first appeared, and fully electronic injection and high-performance fuel injectors finally replaced obsolete carburetors.

The main advantage of the injector is much more accurate and timely dosing of fuel to obtain the required proportions of the fuel-air mixture. The emergence and introduction of affordable microprocessors into the auto industry ultimately led to the fact that the need for a complex carburetor and additional devices in its design simply disappeared. All the functions of the individual elements of the carburetor were taken over by one single control unit (ECU), and simple design devices were installed in the injector design.

It is a mistake to believe that an injector is a more economical solution compared to a carburetor. A well-tuned carburetor demonstrates similar fuel consumption indicators. The popularity of distributed injection is due to the fact that this particular fuel supply mechanism is capable of meeting all stringent modern standards and requirements for the environmental friendliness of internal combustion engines. The carburetor cannot satisfy such requirements, which is due to its design features and the performance of the jets.

Today, carburetor injection is found only on those engines whose main purpose is the target installation on special equipment. The reason for this decision was the vulnerability of electronic injection systems during harsh operating conditions. Electronic components and injector modules suffer from increased humidity and contamination, and injectors are sensitive to fuel quality. As an example, it is worth saying that it is definitely better to install a mechanical carburetor on a special vehicle when using it in swamps, which will not burn out. Such a carburetor can always be easily maintained, cleaned and dried if necessary.

Types of carburetors

As we have already said, the process of modernizing carburetors has generated a large number of types of this device from different manufacturers. All this variety of carburetors can be divided into three groups:

bubbling;
membrane-needle-shaped;
float;

The first two types of carburetors have practically not been seen for a long time, so we will not dwell on these designs. It is more advisable to consider a float carburetor, which can still be seen in various modifications on civilian cars of the 90s era today.

Float carburetor design

The main job of a carburetor is to mix fuel and air. Different models of carburetors carry out this process according to a similar principle. The float carburetor consists of the following elements:

float chamber;
float;
float lock needle,
jet;
mixing chamber;
spray;
Venturi tube;
throttle valve;

The float carburetor is designed in such a way that a special line is connected to its float chamber. This line supplies fuel from the fuel tank to the carburetor. Regulation of the amount of fuel in the chamber is carried out through two elements that are interconnected. We are talking about a float and a needle. A drop in the fuel level in the float chamber means that the float will drop along with the needle. Thus, it turns out that the lowered needle will open access for the next portion of fuel to enter the chamber. When the chamber is filled with gasoline, the float will rise, and the needle will simultaneously block access to fuel.

At the bottom of the float chamber there is the next element called a jet. The nozzle acts as a calibrator and ensures dosing of the fuel supply. Through the nozzle, fuel enters the atomizer. This is how the required amount of fuel moves from the float chamber to the mixing chamber. The process of preparing the working fuel-air mixture takes place in the mixing chamber.

Structurally, the mixing chamber has a diffuser. This element is designed to increase air flow speed. The diffuser is responsible for creating air vacuum in the immediate vicinity of the sprayer. This helps draw fuel out of the float chamber and also helps to atomize it better in the mixing chamber. This is the basic design of a simple float carburetor.

Throttle: cold start and idle

The amount of working fuel-air mixture that enters the engine cylinders will depend on the position of the throttle valve. The damper has a direct connection with the gas pedal. But that is not all.

Some cars with a carburetor had an additional device to control the throttle valve. This element is well known to fans of the old “classics” from VAZ. Motorists popularly nicknamed this device “suction”, and the device itself was created for cold starting. The element is made in the form of a special lever, which is located at the bottom of the dashboard on the driver's side.

The lever allows you to additionally control the throttle valve. If you pull the “choke” towards you, then the damper closes. This allows you to limit air access and increase the level of vacuum in the carburetor mixing chamber.

At increased vacuum, gasoline from the float chamber is drawn into the mixing chamber much more intensely, and the insufficient amount of incoming air forces the carburetor to prepare a rich working mixture for the engine. It is this mixture that is best suited for confidently starting a cold engine.

It is worth noting that the first in the entire design to undergo further modernization was the cold start, already familiar to us under the name “suction”. The simplest carburetors deservedly include the once widespread and popular Solex carburetor, to which the line of classic VAZ cars owes a lot.

The operation of a carburetor engine in idle mode is as follows:

The carburetor is equipped with special additional air jets. These jets are responsible for supplying a strictly dosed amount of air;
the air passes under the throttle valve and is then mixed with gasoline according to the working algorithm. In this case, the entire process occurs when the gas pedal is not depressed and released;

This is what the basic device and operating principle of a float-type carburetor looks like.

Strengths and weaknesses of the device

The main advantage of the carburetor is its affordable maintainability. To this day, there are special repair kits on the market that allow you to return the carburetor to operation quickly enough. Repairing a carburetor does not require an arsenal of any special equipment, and almost any motorist can repair the device if they have certain skills.

A mechanical carburetor is not so afraid of dirt and water, since their entry cannot completely damage it. This simultaneously conceals both the strength and weakness of the device. The carburetor needs to be adjusted quite often and must be cleaned compared to fuel injection, but it is more durable than electronic solutions when a number of conditions arise that are considered difficult or even extreme operating conditions.

Additional advantages of the carburetor include its less sensitivity to low-quality fuel, and the cleaning process does not seem difficult. Although the carburetor is a relatively complex device, it is definitely easier to diagnose problems and maintain it compared to a clogged or faulty injection system.

The main disadvantages of a carburetor include the need for regular cleaning and adjustment. The carburetor can present surprises during operation, as there is a dependence on external weather conditions. During winter, condensation can accumulate in the carburetor body and then freeze. In hot weather, the carburetor is prone to overheating, which leads to intense evaporation of fuel and a drop in engine power.

The last argument against the carburetor is the increased toxicity of the exhaust, which has led to the abandonment of its use on modern cars around the world. Today, the carburetor is justifiably considered a hopelessly outdated “classic” solution.

History of carburetors

The first carburetor was created in 1895. The founder of the idea, as well as the assembler and tester of the carburetor, is considered to be the German Wilhelm Maybach. It is noteworthy that he did not study anywhere, but is a self-taught technician.

Since then, carburetor engines have undergone significant changes, but the essence of their operation remains the same. The main difference between modern carburetors and the first models is the method of forming the air-fuel mixture - in old models, gasoline simply evaporated, but now fuel is atomized in the air.

In 1925, the German company Bosch was the first in the world to launch mass production of carburetor engines. They are already equipped with a high-pressure fuel pump and a gasoline injection system through the use of injectors. Thanks to the new principle of equipping vehicles, it was possible to stabilize the operation of the machines and make them safer.

The introduction of fuel injection pumps and nozzle injection systems into power units provided the impetus for the development of a new type of engine that could consume diesel fuel. Already in 1935, the first passenger car with a diesel power unit rolled off the assembly line of the Mercedes plant.

After the release of diesel cars, it was possible to develop new types of carburetors that increased the power of gasoline engines. These new models were equipped with an intake manifold. Further developments in the field of adding power characteristics to carburetors made it possible to create an engine with direct fuel injection, which had high torque. Cars with this type of carburetor began to be produced en masse in the mid-1940s.

In 1965, Bosch again conquered the global auto industry by designing new carburetors with a distributed injection system. This system reduced the cost of the entire structure, since instead of a massive and expensive fuel injection pump, a conventional electric pump could be used.

In 1994, another company - Mitsubishi Motors - began to introduce a direct injection system into the production of carburetor cars. New power units significantly reduce the amount of fuel consumed, and with the same volume of combustion chambers, such engines provide maximum torque. Direct injection carburetors produce fewer fumes into the environment.

Today, various manufacturers use carburetors with both direct and distributed injection. However, the development of carburetor power units continues.

What is a carburetor

The carburetor is the most important component among all vehicle systems. It refers to the design of an internal combustion engine and is designed to form a fuel-air mixture. Carburetion (that is, creation) of the mixture is carried out by mixing liquid fuel and air, and the proportionality of the parts is important.

The device is mounted on the intake manifold and connected to a variety of hoses and lines

Today, carburetors are used on a wide variety of engines to ensure the operation of a variety of technical devices. The first types of carburetors (bubble carburetors) are no longer used, as they have been replaced by more efficient membrane-needle and float carburetors.

A needle-membrane carburetor consists of chambers that are separated by special membranes. The membranes are quite rigidly fixed to each other by a rod, one of the ends of which is a needle. During carburetor operation, the needle moves up and down and either opens or closes the fuel supply valve. This is the simplest type of carburetor mechanisms today, which is used on lawn mowers, airplanes and some types of trucks (for example, ZIL-138).

The float carburetor is presented today in several modifications, but they all have a similar operating principle. The main element of such a device is a float and a float chamber. It is the chamber that is responsible for the timely supply of fuel and air; the air-fuel mixture is formed in it and supplied to the combustion chamber. The float carburetor guarantees smooth operation of the engine and provides good dynamics and traction. Therefore, this carburetor type of device has gained particular popularity in the modern automotive industry.

The device contains many components interconnected with each other

Comparison of mono injection and carburetor system

Mono-injection is one of the types of electronic fuel injection systems into the engine. We can say that single-injection systems are a kind of transitional model from a carburetor to an injector.

For the first time, mono-injection was developed and installed for aircraft as a more modern modification of the carburetor unit, which eliminated “failures” in the fuel supply during the performance of figures in the air.

A significant difference between a mono-injection and a carburetor system can be considered the presence in a mono-injection device of a computer unit for controlling the supply and consumption of fuel, as well as a gasoline pump and one injector powered by electricity. The mono-injection type of operation is similar to a carburetor, only using more modern components.

The device has minimal dimensions while maintaining all carburetor functions

The main advantage of the mono-injection system is the uninterrupted operation of the engine, since a minimum pressure of 1 bar is constantly maintained in the unit. That is, vehicles with single injection can operate uninterruptedly during sudden overtaking or braking, when carburetor mechanisms cannot always guarantee engine stability in these modes.

In addition, mono-injection guarantees an increase in the power of the power unit due to the absence of power failures.

However, carburetors are still considered more economical devices to this day, since fuel injection is carried out not at one point, but throughout the entire chamber, which allows the entire incoming volume of fuel to be used. For this reason, engines with carburetors are easier to start in winter.

Thus, carburetor devices have good characteristics in terms of economical fuel consumption and the ability to start in any climatic conditions. Single injection ensures more stable engine operation and high quality vehicle power.

Modern car owners assess the benefits of using certain systems differently:

I am for MONOVPRYSK!!! As they say in the Bible, whoever is called to what rank remains the same, but if you can, use the best. You can’t compare the acceleration dynamics of injection with carb, and we didn’t buy cars to make VAZs out of them. So far I have perfected the mono, I have learned so many new things about technical systems that I don’t regret it now. In principle, the statement is confirmed - electrics is the science of contacts. It was also just insulting: why does it work for “them there”, but not for me here!? One of the previous owners was completely negative: - no dynamics, consumption was tortured, 160 with a tailwind - changed the lambda, changed the sensors, nothing was adjusted, but in the end it turned out: they drove a car whose spark was at TDC!!! there is a mixture that was ignited to catch up with the outgoing piston!!! On such a car, I went to Moscow from Yaroslavl for spare parts, with the DGT instrument not working except for the warning lights, with a consumption of 20 liters, with the Chek Engine on, back and forth - GM Delco mono injection, it worked like clockwork. And now on the 1st or 2nd, he presses it into the back of the seat. And the Kalashnikov shoots because the magazine and cartridge are from STG 43 Sturmgever, and the bolt and bolt carrier M1 Garand, well, + everything was sharpened on broken-down machines , - oh yes, increased gaps, “especially so that dirt does not linger

http://clubfiat.ru/forum/index.php?showtopic=3641&page=2

But in my opinion it all depends on the condition of the car. I just brought it to mind under the hood (the previous owner was a big fan of tinkering), so in my crab temp at -10 outside, after 3 minutes the temperature needle crosses the 50 mark. And after another three minutes - if the heater is full - you can undress in the cabin

http://clubfiat.ru/forum/index.php?showtopic=3641&page =

What is a jet

One of the components of modern carburetors are jets. They are small parts with clearly aligned holes. There are fuel and air jets - respectively for supplying liquid or air. There are also main, compensation, idle jets and other types.

This part has a certain throughput, due to which the motor performance that is installed at the factory is achieved. Calibration of the holes is considered the main criterion for the performance of the part, so cleaning the nozzle from dirt and carbon deposits should be done very carefully so that the procedure does not affect the size of the holes.

Small fuel metering device

The economizer is another element of the carburetor

An economizer is a device that is designed to regulate the fuel supply. Depending on the type (EPHH or EMR), economizers provide the necessary torque while the vehicle is moving or parked with the engine running.

The forced idle speed economizer (EFES) is also an electromagnetic valve in the carburetor device. It is mounted in the upper part of the carburetor body and turns off the supply of gasoline if the crankshaft rotation speed is above 2 thousand revolutions and at the same time there is no pressure on the gas pedal. Thanks to the operation of the EPHH, it is possible to significantly save fuel consumption. In addition, this type of economizer is activated during a long descent, which leads to engine braking and provides additional stability to the vehicle.

EMR (power mode economizer) is located below EPHH. The device is designed to increase the flow of fuel at high engine speeds. The EMR is activated at the moment when the gas pedal is depressed more than 2/3. In this case, the throttle valve opens, and the economizer supplies fuel to the atomizer in the required volume. That is, the air-fuel mixture becomes richer, which increases torque.

An important part of the economizer is the needle

Float - what is it?

The most common type of carburetor is a float carburetor. The most important element of the device is the float chamber, which ensures the required fuel level in all modes of engine operation.

The main element of the chamber is the float, which determines how much fuel is currently in the chamber and how much more is required for full, uninterrupted operation. The design of the floats may vary on different modifications of carburetors; they can be made of plastic or brass.

Products made of brass are large in size (plastic floats are much smaller)

Carburetor gasket

The gasket is a necessary element when installing any carburetor device. It is designed to seal the connection between the carburetor and the intake manifold on a car. In some cases, it is justified to use two or three gaskets at once for a more reliable connection.

The only purpose of carburetor gaskets is to prevent air leaks from the outside.

Today, there are three types of gaskets that can be used for carburetor installation:

thermal insulation - serves to lower the temperature in the carburetor, preventing it from overheating;

reinforced - needed to strengthen the connection between the carburetor flange and its heat-insulating part;

paronite - necessary to isolate high temperatures that come from the intake manifold.

When servicing the carburetor yourself, you can make gaskets yourself. Most often, paronite or a thin sheet of metal is taken as a blank. When replacing gaskets, it is recommended to install an analogue of the one that was installed at the factory.

Depending on the modification of the carburetor, gaskets can have a variety of shapes

What is a diffuser

Most drivers believe that the engine receives its air-fuel mixture directly from the carburetor. However, it is not. Any carburetor is equipped with a diffuser, which looks like a narrowed neck for air.

At the moment when the air flow passes through this narrow neck, a vacuum of pressure occurs in it. At the end of the diffuser there is a small hole through which fuel is supplied. The rarefied pressure affects the gasoline supply and displaces fuel from the float chamber into the diffuser. And only after the diffuser can fuel enter the intake manifold container and then into the engine itself.

On the left is the old one, with carbon deposits and dirt, on the right is the new one

GDS

The GDS (or main metering system) is a unit that ensures the supply of fuel to the engine unit. The GDS is activated when the vehicle is operated at medium engine loads.

The system is a combination of several jets, a distributor and a diffuser. The main fuel jet is located in the space between the float chamber and the nozzle. The atomizer is a small tube with calibrated holes through which air is sucked in. It is in the metering system that the air-fuel mixture is formed.

Thanks to the screws and jets, you can independently set the throughput of the device

Why are dispensers needed in a carburetor?

The dispenser performs a very important function in a car. It automatically measures the specified amount of fuel to supply it to the combustion chamber. Thanks to the dispenser, the engine receives exactly the amount of fuel it needs for full operation.

The device is designed to determine the required amount of fuel

Accelerator pump: what is it for?

No carburetor can fully perform its functions without an accelerator pump. This mechanism injects additional fuel. The pump is activated when the throttle valve is opened sharply to absorb the air-fuel mixture to accelerate the vehicle and prevent engine stalling.

An accelerator pump is necessary when operating a vehicle at high engine speeds, since the diffuser cannot always guarantee the supply of fuel in the required quantity.

The diaphragm is the most sensitive element of the pump and is responsible for the performance of the entire device

Purpose of the solenoid valve

The forced idle economizer includes a solenoid valve. EPCH is often called valvular. This valve ends with a special needle, which, when extended, shuts off the fuel supply. The valve is activated at the moment when the driver does not press the gas pedal, as he is performing a long descent. The operation of the valve significantly saves fuel consumption, as engine braking occurs.

The valve is thus responsible for the stability of the engine in idle mode. If the engine idles intermittently or jerkily, it means that the valve has stopped performing its functions correctly.

Responsible for the stability of the engine in idle mode

What is the swirler used for?

The operation of a carburetor is based on the principle of vortex mixing of flammable liquid and air. This mixing is created through the use of a so-called swirler - a special plate with channels. The swirler is not an internal part of the carburetor, but is mounted underneath it.

The air turbulence that the device creates crushes droplets of gasoline, making them suitable for the formation of an air-fuel mixture. The swirler significantly reduces fuel consumption, so on carburetors that are not equipped with this device from the factory, it is recommended to install such a unit separately.

The speed at which turbulence is created depends on the volume of the body and the number of blades.

What is a fortified mixture?

To understand under what conditions such a mixture can form in a carburetor, you will need to understand the basic operating modes of a car carburetor mechanism:

starting the engine (this mode is demanding on enriching the air-fuel mixture);

idle mode;

low load mode;

medium engine load mode;

maximum use of the engine.

It is important that when starting the power unit, a rich air-fuel mixture is formed in the carburetor; at idle speed and when driving at low speed, the mixture should be lean, and when the speed increases to the maximum, it will again need to be enriched.

An enriched mixture is obtained by increasing the amount of flammable liquid in the float chamber capacity. The GDS supplies an increased flow of fuel so that the engine can cope with increased loads.

But in some cases, a constant formation of an enriched air-fuel mixture is possible (the needle is stuck, the needle valve is clogged, the holes in the nozzles are miscalibrated, the life of the dampers is exhausted, etc.). In this case, the engine will receive an excess amount of fuel, which leads to increased fuel consumption and flooding of the engine.

Thus, each element of the engine carburetor system is responsible for performing a specific task. The operation of a carburetor is based on the interaction of all its parts, since failure or severe wear of any part can mean a breakdown of the carburetor unit itself.

On cars of the late 20th and early 21st centuries, carburetors were replaced by fuel injection systems. These microprocessor-controlled injection systems are capable of providing more accurate fuel dosage in all engine operating modes over hundreds of thousands of kilometers, compared to a carburetor. And also maintain engine exhaust parameters within the framework of current environmental requirements. However, carburetors continue to be used on motorcycles; various auxiliary, stationary, generator, boat engines; on gas-powered tools (chainsaw, lawn mower, etc.) Everything about the design, types, and operating principles of carburetors is in this publication.

The word "carburetor" is of French origin and comes from the word carburation - mixing. This is the purpose of this key unit of the internal combustion engine power supply system - to mix gasoline with air and supply a certain amount of this mixture into the working cavities of the cylinders. A carburetor is a mechanical mixing and metering device for an internal combustion engine. The engine runs on a mixture of tiny droplets of fuel with air, which it forms and injects into the cylinders.

As soon as inventors of the second half of the 19th century began to try to equip equipment with engines running on gasoline and kerosene, they had to take into account that this fuel ignites only with the participation of air. Moreover, for the engine to operate efficiently, it is also necessary to mix air with fuel in a certain proportion.

The first carburetor was invented in 1876 by the Italian Luigi Christoforis. In his device, the fuel was heated, evaporated, and its vapors mixed with air. A year later, Daimler and Maybach found a more rational solution by applying the principle of fuel atomization. This simple and effective principle formed the basis for all subsequent developments.

Gottlieb Daimler in a car with a personal driver.

Before the widespread use of float-type carburetors, two more types of these devices were used: bubbler and membrane-needle carburetors.

Bubbler carburetors were gas tanks, inside of which, at a short distance from the surface of the fuel, there was a blank board and two wide pipes - one supplies from the atmosphere, and the second takes the fuel-air mixture into the engine. The air passes under the board, above the surface of the fuel, is saturated with its vapor, and a combustible mixture is obtained.

This is a primitive but effective design. The throttle valve was located separately on the engine. The operation of an engine with a bubbler carburetor depended on the weather outside: the degree of fuel evaporation varied depending on the ambient temperature. Some of the fuel-air mixture may have condensed. The whole structure was quite explosive and difficult to regulate.

A membrane-needle carburetor is a complete device separate from the gas tank. It consists of several chambers, which are separated by membranes and rigidly connected to each other by a rod. A needle is attached to this rod, which locks the fuel supply valve seat. The chambers are connected by channels to the mixing cavity, on the one hand, and to the fuel channel, on the other.

The characteristics of such a carburetor are determined by calibrated springs on which the membranes rest. This is no longer a primitive, but rather simple design, the advantage of which, in addition to its simplicity, is the ability to operate reliably in any position and in any conditions. Such carburetors were installed in the first half of the twentieth century not only on cars and motorcycles, but also on airplanes with piston internal combustion engines.

The third type of carburetor, which eventually became the main one in the entire global automotive industry, is a float carburetor with jets. The float carburetor, the design of which was regularly improved, eventually gained universal popularity throughout the world. It was a very versatile device and could be installed using an adapter on a wide variety of models of cars and motorcycles. Its device will be discussed in the following sections of this publication.

The latest stages in the evolution of carburetor injection devices were float carburetors with solenoid valves, operating under electronic control. In such devices, several electromagnetic valves operated, the operation of which was controlled by a special control device. For example, Japanese Hitachi carburetors had five solenoid valves, and the dampers were controlled electronically.

These carburetors, the latest generation of these devices, were installed on Nissan cars at the turn of the 80s and 90s. Their complexity lies in the large number of auxiliary devices responsible for stabilizing the operation of the carburetor in various modes (sharp release of gas, idling mode when a car with an automatic transmission is idle, leveling and stabilizing engine speed when starting the air conditioning system, etc.) . Accordingly, such a “brought to perfection” carburetor was supplemented with numerous auxiliary devices: valves, bimetallic springs, heaters, etc.

Injection systems have been invented a long time ago, but at first they were expensive for mass production of automobiles. But the emergence and widespread introduction of affordable microprocessors in the auto industry ultimately led to the fact that the need for a carburetor, even the most complex one, with solenoid valves and additional devices, simply disappeared. All functions of the individual elements of the carburetor began to be performed by a single electronic control unit (ECU), and simple design devices were found in the injector design.

The float carburetor provides the most stable parameters of the fuel-air mixture at the outlet and has the highest performance qualities compared to previous types of these devices. By the way, the statement that an injector is definitely more economical than a carburetor is erroneous. A well-tuned float carburetor provides fuel consumption indicators similar to those of an injector, but, of course, it is not so stable in operation.

A float carburetor consists of the following main elements: float chamber; float; float shut-off needle, jet; mixing chamber; spray; mixing chamber with diffuser - Venturi tube; throttle valve. Fuel is supplied to the float chamber through a special line from the gas tank. The amount of this supplied gasoline is regulated in the chamber using two interconnected elements. This is a float and a needle.

Operating principle of a float carburetor

When the fuel level in the float chamber decreases as it is consumed, the float drops along with the needle. This lowered needle allows access for the next portion of fuel to be supplied to the chamber. When the chamber is filled with gasoline to the required level, the float rises, and the needle simultaneously blocks access to fuel. So this float valve maintains a constant level of gasoline in the working cavity.

There is a special balancing hole in the carburetor float chamber. Thanks to it, atmospheric pressure is maintained in the float chamber. In almost all commercially produced carburetors that work with air filters, the role of this hole is instead played by the balancing channel of the float chamber, which leads not into the atmosphere, but into the cavity of the air filter, or into the upper part of the mixing chamber. With this solution, the throttling effect of the filter is reflected evenly on the entire gas dynamics of the carburetor, which becomes balanced.

The next key element of the carburetor - the jet - is located at the bottom of the float chamber. The jet works as a calibrator, providing a dosed supply of fuel. Through the nozzle, the fuel enters the atomizer. This is how the required amount of fuel moves from the float chamber to the mixing chamber. The process of preparing the working fuel-air mixture takes place in the mixing chamber.

The mixing chamber contains a diffuser - a Venturi tube and an inlet pipeline, which distributes the prepared fuel mixture among the cylinders. The atomizer is located in the narrowest part of the diffuser, where the flow rate reaches a maximum and the pressure decreases to a minimum. Under the influence of a pressure difference, gasoline is ejected from the atomizer, crushed and atomized in a stream of air, and, when mixed with it, forms a flammable fuel-air mixture.

Subsequently, instead of a single diffuser, a double diffuser was used in carburetors. This additional diffuser is small in size and is located concentrically in the main diffuser. Instead of liquid fuel in carburetors of modern design, not homogeneous liquid fuel is supplied to the atomizer, but an emulsion of gasoline and air. With this design, better fuel atomization is achieved.

The amount of fuel-air mixture that enters the engine cylinders for combustion is regulated by the throttle valve. In horizontal carburetors, instead of a rotary valve, a slide valve is used.

One of the most important factors in the effective operation of a carburetor is the fuel level in the float chamber. The correct fuel level determines the stable operation of the engine at idle and at low speeds. Since the adjustment of the idle system actually determines the correct compensation of the GDS composition, operation in all other modes indirectly depends on the stability of the fuel level.

The level of gasoline in the chamber is set in such a way that in case of any deviations of the device from the vertical position, there would be no spontaneous outflow of fuel from the nozzles into the mixing chamber. To further compensate for tidal phenomena, more advanced carburetors were equipped with additional economizers, as well as parallel float chambers located on the sides of the carburetor and connected to each other by a transverse channel or a special communicating cavity. The floats in different carburetors were made by soldering from stamped brass halves, or made of plastic.

The mixing chamber ensures that tiny drops of gasoline, this “fog,” are mixed into the passing air stream. This function is performed by a diffuser - a specially narrowed section of the chamber. Thanks to this diffuser, the air passing through it is significantly accelerated. The movement of air during acceleration in the diffuser ensures the formation of a vacuum in the spray tube. Because of this, gasoline is constantly added and mixed into the passing stream.

The engine operates in various modes during operation. Therefore, fuel-air mixtures require different compositions, including those with a sharp change in the content of gasoline vapor fractions. To prepare a mixture of different concentrations, optimal for different engine operating modes, “advanced” carburetors are equipped with dosing devices. They come into operation or turn off at different times, or work simultaneously, providing the most optimal mixture composition for obtaining the best combination of power and efficiency in all engine modes. These metering systems are based on pneumatic compensation of the fuel-air mixture.

Economizers and econostats are additional parallel systems for supplying fuel to the mixing chamber. They enrich the air-fuel mixture only at high vacuum levels (i.e., close to maximum loads), when an economically generated mixture cannot meet the engine's needs. Economizers are equipped with forced control, pneumatic or mechanical.

Econostats are simply tubes of a certain cross-section, in some cases with emulsion channels, led into the space of the mixing chamber above the diffuser - into the zone where vacuum appears at maximum loads.

Idle system

The idle system, which was equipped with the latest generations of carburetors, is designed to ensure stable engine operation at low speeds when the throttle valve is completely closed. These are separate channels through which air and gasoline are supplied under the throttle valve. In this case, the mixing chamber is not used at all, since the idle system supplies the required amount of the fuel-air mixture to the intake manifold, bypassing it.

Not saturation, but simply the amount of working fuel-air mixture that enters the engine cylinders depends on the throttle position. This damper is directly connected to the gas pedal in the cabin. Connoisseurs of the old VAZ “classics” are also familiar with another device for controlling the throttle valve. This is a “suction” for cold starting the engine - a mechanical “suction” lever for fuel, at the bottom of the dashboard. If you pull the “choke” towards you, the damper closes.

This limits the access of air and increases the level of vacuum in the carburetor mixing chamber. At increased vacuum, gasoline from the float chamber is drawn into the mixing chamber much more intensely, and the insufficient amount of incoming air makes it possible to prepare an enriched working mixture for the engine, which is more suitable for starting a cold engine.

Carburetors are classified:

In the direction of flow of the fuel-air mixture - vertical and horizontal.
According to the method of adjusting the cross section of the nozzle and the formation of vacuum - with constant vacuum(the newest and most advanced carburetors made in Europe and Japan); with constant nozzle cross section– all serial carburetors up to the latest generations of these devices, including all mass-produced in the USSR; with spool throttling - for the most part, horizontal carburetors for motorcycles, in which, instead of a throttle valve, the amount of mixture supplied is controlled by a slide valve.
According to the number of mixing chambers – single-chamber and multi-chamber. It makes sense to use “double” carburetors, for example, on engines where the cylinders are located quite far from each other. Then each half injects the fuel-air mixture only into “its” cylinders. In addition to “paralleled” two- and four-chamber carburetors, there were also serial three-chamber carburetors (for example, “K-156” for the 3102 Volga). The 1st and 3rd mixing chambers were working in parallel here; they supplied the mixture to the 2nd – “pre-chamber”.

The advantages of carburetors include the high homogeneity of the mixture at the outlet; low cost and technological accessibility during production; comparative ease of maintenance and repair, maintainability without the need for special equipment. Unlike an injector, which requires electrical power, the operation of a carburetor occurs solely due to the energy of the air flow sucked in by the engine.

These advantages, of course, apply only to “classic” carburetors. The latest generation devices were already very complex units with electronic elements. Their production required very high precision, and their setup required high technical training and the use of special equipment (pneumo-hydraulic stand).

A carburetor is more durable and more efficient than an injector when it comes to particularly difficult or even extreme operating conditions. It is less sensitive to fuel quality. However, the carburetor is more dependent on weather conditions and, unlike the injector, can present an unpleasant surprise at low temperatures. In cold weather, condensation can accumulate in the carburetor body and freeze. And in extreme heat, it overheats, which leads to intense evaporation of fuel and a drop in engine power.

The main reason for the displacement of the carburetor from the automotive power system was the inability to provide a fuel-air mixture of an individual composition for each of the outbreaks. And the injection system with distributed injection operates in exactly this way, stably ensuring economical and environmentally friendly engine operation.

Design and operation of a simple carburetor

Device

The simplest carburetor consists of two main parts: a mixture-forming device and a float chamber. In the mixture-forming device, a flammable mixture is prepared, and the float chamber is a reservoir from which fuel is supplied to be mixed with air.

The carburetor's mixture-forming device has an air inlet, a diffuser, a mixing chamber, a throttle valve, and an outlet. The outlet pipe usually ends in a flange that secures the carburetor to the engine intake manifold.

A hose for supplying air or an air filter directly is installed on the inlet pipe. The diffuser is a local reduction in the cross-section of the mixture-forming device. Thanks to the diffuser, the conditions for fuel atomization are improved, since when the engine is running, the maximum air flow speed is created in the narrowest section of the diffuser. In this place, a sprayer is installed, which is a tube connected to a diffuser. Fuel flows out and atomizes through the atomizer.

The float chamber contains a float mechanism consisting of a float and a needle valve. The float is hinged to the wall of the float chamber. The shut-off needle of the needle valve rests on the float lever.

When fuel is supplied through the fitting into the float chamber, the float floats up and with its lever raises the shut-off needle, closing the needle valve. As soon as the fuel level in the float chamber reaches a predetermined limit, the needle valve will close completely and the flow of fuel into the chamber will stop. When fuel is consumed from the float chamber, the float lowers and opens the needle valve. Fuel begins to flow into the float chamber again until the specified level is reached. Thus, the float chamber, using a float mechanism, ensures that the specified fuel level is maintained under all engine operating modes.

The main jet is located at the bottom of the float chamber. Its main purpose is to dose fuel to obtain a combustible mixture of the desired composition. The jet is a plug with a central calibrated hole. The diameter of the calibrated nozzle hole is selected depending on the required fuel flow. The length of the calibrated hole of the nozzle, the angles of the inlet and outlet chamfers, and the diameters of the channels in the body of the nozzle are also of great importance for the formation of flammable mixtures. The main jet can be installed at the bottom or top of the sprayer.

Job

When the engine crankshaft rotates during the intake strokes and when the throttle valve is open, air passes through the carburetor's mixing chamber. Inside the diffuser, the air flow speed increases significantly, and a vacuum is created at the sprayer outlet. In this case, due to the presence of the hole, the pressure in the float chamber remains equal to atmospheric pressure. Due to the pressure difference in the float chamber and in the atomizer, fuel begins to flow through the main jet and atomizer in the form of a fountain, ending up in the neck of the diffuser. Here, a stream of incoming air crushes the escaping fuel into small droplets, which mix with air, evaporate and form a combustible mixture.

The formation of a combustible mixture in the mixing chamber of the carburetor does not occur in full. Some of the fuel in the form of droplets does not have time to evaporate and mix with air. Unevaporated fuel droplets move in the air flow and settle on the walls of the mixing chamber and inlet pipeline. Fuel deposited on the walls forms a film that moves at low speed. To evaporate the fuel film, the intake manifold is heated when the engine is running. Most often, liquid heating (from the engine cooling system) or heating with exhaust gas heat is used. Thus, we can assume that the formation of a combustible mixture ends at the end of the engine intake pipe.

A lot of passenger cars run on gasoline. More precisely, on a mixture of gasoline and air. Such engines are commonly called internal combustion engines. However, there are two types of internal combustion engines: engines running on gasoline and engines running on diesel (read the article for more details). Today we will talk specifically about gasoline engines, because it is in the structure of a gasoline engine that there is such equipment as a carburetor. The engine itself does not prepare the fuel mixture (air + gasoline) for use; it burns this mixture, pushing the pistons. But the device we will talk about prepares this mixture.

Carburetor – The engine attachment, which is designed to make the combustible mixture that is injected into the engine cylinders for further ignition, is usually located on top of the engine.

Principle of operation

Gasoline enters the carburetor through the fuel line and enters the mixing chamber, but the fuel is atomized through a system of special carburetor devices called jets, that is, the fuel takes the form of steam. Next, the air undergoes additional purification through a filter system and is supplied to the same chamber, which contains fuel vapor, mixing in the required proportion, this mixture is supplied to the engine cylinders, where this mixture is ignited with the help of engine spark plugs. Enriching the mixture in the carburetor leads to fast engine operation and vice versa, this is the work of the accelerator (gas pedal), the driver presses on the gas, the engine shaft rotates faster, the speed increases, if you release the gas pedal, the engine shaft will rotate more slowly, the speed will drop.

That's all, I think, it has now become clear what it is. Read our AUTO SITE

2109

1 0 0

If you find an error, please select a piece of text and press Ctrl+Enter.