Fuel supply system. Injection systems, description and principle of operation

The fuel supply system is necessary for the fuel to flow from the fuel tank, its further filtration, and also the formation of an oxygen-fuel mixture with its transfer to the cylinders of the engine. Currently, there are several types of fuel systems. The most common in the 20th century was the carburettor, but today the injection system is increasingly popular. There was also a third one - a mono-shot, which was good only in that it allowed to cut fuel consumption somewhat. Let's consider in more detail the injector system and understand its principle of operation.

General Provisions

Most modern engine power systems are similar in fuel. The difference can only be in the stage of the mixture formation. The structure of the fuel system includes the following nodes:

1. The fuel tank is a compact product with a pump and a filter for cleaning from mechanical particles. The main purpose - storage of fuel.
2. The fuel lines form a complex of hose and tubes for the transfer of fuel from the tank to the system of mixture formation.
3. Mixing device. In our case there will be a question about the injector. This unit is designed to produce an emulsion (air-fuel mixture) and feed it into the cylinders in the stroke of the motor.
4. Block control of the system of mixture formation. It is installed only on the injector engines, which is due to the need to monitor the sensors, injectors and valves.
5. Fuel pump. In most cases, a submersible option is used. It is a small electric motor that connects to a liquid pump. Lubrication is realized by fuel, and long-term use of the vehicle with less than 5 liters of fuel can lead to an electric motor failure.

In short, the injector is a point feed of fuel through the nozzle. The electronic signal comes from the control unit. Despite the fact that the injector has a number of significant advantages over the carburetor, it has not been used for a long time. This was due to the technical complexity of the product, as well as low maintainability of parts that failed. Currently, point injection systems have almost replaced the carburetor. Let's take a closer look at what is so good about the injector and what its features are.

Features of fuel equipment

The car has always been the object of attention of environmentalists. The exhaust gases are released directly into the atmosphere, which is fraught with its pollution. Diagnosis of the fuel system has shown that the amount of emissions with incorrect mixture formation increases many times. For this simple reason, it was decided to install a catalytic converter. However, this device showed good results only with a high-quality emulsion, and in the event of any deviations, its efficiency dropped significantly. It was decided to replace the carburetor with a more precise injection system, which was the injector. The first variants included a large number of mechanical components and, according to studies, such a system became worse as the vehicle was used. This was quite natural, since important knots and working organs were polluted and went out of order.

In order for the injection system to correct itself, an electronic control unit (ECU) was created. Along with the built-in lambda probe, which is located in front of the catalytic converter, this yielded good results. It's safe to say that fuel prices today are quite high, and the injector is good in that it saves gasoline or diesel. In addition, there are the following advantages:

1. Increase the performance of the motor. In particular, the increased power by 5-10%.
2. Improving the dynamic performance of a vehicle. The injector is more sensitive to load changes and adjusts the composition of the emulsion itself.
3. Optimal fuel-air mixture reduces the amount and toxicity of exhaust gases.
4. The injection system can be easily started regardless of the weather conditions, which is an essential advantage over the carburetor engines.

Injection system of fuel supply and its device

First of all it is worth noting the fact that modern injection engines are equipped with injectors, the number of which is equal to the number of cylinders. Between each other, the injectors are connected by a ramp. There, the fuel is kept under low pressure, and creates its electric appliance - a gasoline pump. The amount of fuel injected directly depends on the duration of the opening of the injector, which is determined by the control unit. To do this, indicators from various sensors that are installed throughout the vehicle are taken. Now we will consider the main of them:

1. The gauge of the charge of air. Serves to determine the fullness of the cylinders with air. In the event of a breakdown, the reading is ignored, and tabular data is taken as the main indicators.
2. The throttle position sensor reflects the load on the engine, which is due to the position of the throttle, cyclic filling with air and engine speed.
3. Temperature sensor of the coolant. With the help of this controller, the control of the electric fan and the correction of the fuel supply as well as the ignition are realized. In the event of a fault, an instant diagnosis of the fuel system is not necessary. The temperature is taken depending on the duration of the ICE.
4. The crankshaft position sensor (crankshaft) is needed to synchronize the system as a whole. The controller calculates not only the engine speed, but also its position at a certain point in time. Since it is a polar sensor, if it fails, further operation of the vehicle is not possible.
5. The oxygen sensor is needed to determine the% oxygen in the gases emitted into the atmosphere. Information from this controller is transmitted to the computer, which, depending on the readings, corrects the emulsion.

It is worth paying attention to the fact that not all vehicles with injectors are equipped with an oxygen sensor. They have only those cars that are equipped with a catalytic converter with the norms of toxicity "Euro-2" and "Euro-3".

Types of injection systems: single-point injection

Currently, all systems are actively used. They are classified according to the number of nozzles and the place of fuel supply. There are three injection systems:

• Single-point (mono-shot);
• Multipoint (distributive);
• direct.

First, let's look at one-shot injection systems. They were created immediately after the carburetor and were considered more advanced, but now they are gradually losing their popularity due to many reasons. There are several undeniable advantages of such systems. The main ones are substantial fuel economy. Considering that the fuel prices today are rather big, such an injector is actual. Interestingly, this system contains somewhat less electronics, so it is more reliable and stable. When information from the sensors is transmitted to the control element, the injection parameters change immediately. It is very interesting that almost any carburetor engine can be converted to single-point injection without significant structural changes. The main disadvantage of such systems lies in the low acceleration of the internal combustion engines, as well as in the settling of a significant amount of fuel on the walls of the reservoir, although this problem was inherent in carburetor models.

Since the nozzle in this case is only one, it is located on the intake manifold in place of the carburetor. Since the nozzle stood in a good place and was constantly under the flow of cold air, its reliability was at the highest level, and the design was extremely simple. Flushing the fuel system with a single-point injection did not take much time, as it was enough to blow only one nozzle, but increased environmental requirements led to the fact that they began to develop other, more modern systems.

Multi-point injection systems

Distributed injection is considered more modern, complex and less reliable. In this case, each cylinder is equipped with an insulated nozzle, which is located in the intake manifold in the immediate vicinity of the intake valve. Consequently, the emulsion is dispensed separately. As noted above, with this injection, the engine power can be increased to 5-10%, which will be noticeable when driving on the road. Another interesting point: this injector fuel delivery system is good in that the injector is located very close to the intake valve. This minimizes the subsidence of fuel on the walls of the collector, so that you can achieve significant fuel savings.

There are several types of multipoint injection:

1. Simultaneous - the opening of all injectors occurs at one time.
2. Parallel-parallel - opening nozzles in pairs. One injector opens into the intake stroke, and the second in front of the exhaust stroke. At present, such a system is used only at the moment of emergency start of the internal combustion engine in the event of a phase failure (crankshaft position sensor).
3. Phased - each injector is controlled separately, and opens before the intake stroke.

In this case, the system is quite complex and relies entirely on the accuracy of the electronics. For example, flushing the fuel system will require much more time, as it is necessary to flush each nozzle. And now let's go further and consider another popular type of injection.

Direct Injection

Injection cars with such systems can be considered the most environmentally friendly. The main purpose of introducing this method of injection is to improve the quality of the fuel mixture and to slightly increase the efficiency of the vehicle engine. The main advantages of this solution are as follows:

• Careful spraying of the emulsion;
• Formation of a high-quality mixture;
• Effective use of the emulsion at various stages of the ICE.

Based on these advantages, we can say that such systems save fuel. This is especially noticeable with quiet driving in urban conditions. If we compare two cars with the same engine volume, but different injection systems, for example, direct and multipoint, then the immediate system will have much better dynamic characteristics. The exhaust gases are less toxic, and the taken liter capacity will be somewhat higher due to air cooling and the fact that the pressure in the fuel system is somewhat increased.

But it is worth paying attention to the sensitivity of direct injection systems to the quality of fuel. If you take into account the standards of Russia and Ukraine, the sulfur content should not be more than 500 mg per 1 liter of fuel. At the same time, European standards mean the content of this element is 150, 50 and even 10 mg per liter of gasoline or diesel.

If we briefly consider this system, it looks like this: the nozzles are located in the head of the cylinder blocks. On this basis, the injection is carried out directly into the cylinders. It is worth noting that this injector system is suitable for many gasoline engines. As noted above, a high pressure is used in the fuel system, under which an emulsion is fed directly into the combustion chamber, bypassing the intake manifold.

Fuel Injection System: Lean

A little bit earlier we discussed direct injection, which was first used on Mitsubishi cars, which had the abbreviation GDI. Let's briefly consider one of the main modes - work on a lean mixture. Its essence lies in the fact that the vehicle in this case operates under small loads and moderate speeds of up to 120 kilometers per hour. Fuel injection is carried out by the torch in the final stage of compression. Reflecting from the piston, the fuel mixes with the air and falls into the zone of the spark plug. It turns out that the mixture is significantly depleted in the chamber, nevertheless its charge near the spark plug can be considered optimal. This is enough to ignite it, after that the remaining emulsion also lights up. In fact, such a fuel injection system ensures the normal operation of the internal combustion engine even with an air / fuel ratio of 40: 1.

This is a very effective approach, which makes it possible to significantly save fuel. But we should pay attention to the fact that the issue of neutralization of exhaust gases was sharply raised. The fact is that the catalyst is inefficient, since nitrogen oxide is formed. In this case, the exhaust gas recirculation is used. A special ERG system allows diluting the emulsion with waste gases. This somewhat reduces the combustion temperature and neutralizes the formation of oxides. Nevertheless, this approach will not allow increasing the load on the engine. A storage catalyst is used to partially solve the problem. The latter is extremely sensitive to combustible with a high sulfur content. For this reason, a periodic check of the fuel system is required.

Homogeneous mixture formation and 2-step regime

Powerful mode (homogeneous mixture formation) is an ideal solution for aggressive driving in urban conditions, overtaking, and also driving on highways and highways. In this case, a conical torch is used, it is less economical compared to the previous version. The injection is carried out at the intake stroke, and the emulsion formed usually has a ratio of 14.7: 1, that is, close to the stoichiometric one. In fact, this system of automatic fuel supply is exactly the same as the distribution system.

Two-stage mode involves fuel injection at the compression stroke, as well as the start-up. The main task - a sharp increase in the engine. A vivid example of the effective operation of such a system is the movement at low speed and a sharp depression on the accelerator. In this case, the probability of detonation increases significantly. For this simple reason, instead of one stage, the injection goes into two.

At the first stage, a small amount of fuel is injected at the intake stroke. This allows you to slightly lower the temperature of the air in the cylinder. We can say that in the cylinder there will be a super-poor mixture in a ratio of 60: 1, hence, detonation is impossible as such. At the final stage of the compression stroke, a jet of fuel is injected, which brings the emulsion to the rich in a ratio of approximately 12: 1. Today we can say that such a fuel system of the engine is introduced only for vehicles of the European market. This is due to the fact that Japan does not have high speeds, therefore, there are no high loads on the engine. In Europe, however, a large number of highways and highways, so drivers are accustomed to travel quickly, and this is a big load on the ICE.

Something else interesting

It is worth paying attention to the fact that, unlike carburetor systems, the injector requires that there is a regular check of the fuel system. This is due to the fact that a large number of complex electronics can fail. As a result, this will lead to undesirable consequences. For example, excess air in the fuel system will lead to a violation of the composition of the emulsion and the incorrect mixture ratio. In the future, this affects the engine, unstable work, the controllers fail, etc. In essence, the injector is a complex system that determines when the cylinders need to be supplied with a spark, how to deliver a quality mixture to the cylinder block or intake manifold, When to open the nozzles and what proportion of air and gasoline should be in the emulsion. All these factors affect the synchronized operation of the fuel system. Interestingly, without most controllers, the machine can work properly, without significant deviations, since there are emergency records and tables that will be used.

The economy of the ICE in our case is determined by how correct the data received from the controllers will be. The more precise they are, the less possible the various malfunctions of the fuel system. An important role is played by the speed of the system as a whole. Unlike carburettors, manual adjustment is not required here, and this eliminates errors during calibration work. Therefore, we will get a more complete combustion of the mixture and a better system from the ecological point of view.

Conclusion

In conclusion, it is worthwhile to tell a little about the shortcomings that are inherent in injection systems. The main disadvantage is the high cost of ICE. By and large, the cost of such units will be higher by approximately 15%, which is significant. But there are other disadvantages. For example, a failed fuel system valve in most cases can not be repaired, which is caused by a breach of the tightness, so you just need to change it. This applies to the maintainability of equipment in general. Some parts and parts are much easier to buy new, rather than spend money on their repair. This quality is not inherent in carburetor vehicles, where you can sort out all the important components and restore their performance without much time and effort. Without any doubt, the electronic fuel supply system is being repaired by large forces and means. Complex electronics can hardly be restored to the first SRT that has fallen.

Well, we talked with you about what an injection system is. As you can see, this is a very interesting topic for conversation. You can still talk a lot about what good injectors and the ability to instantly adjust the engine. But we have already mentioned the main points. Remember that the fuel system of the gasoline engine should be regularly inspected for possible defects. For example, due to the low quality of fuel, which is inherent in our country, jets are often jammed. Because of this, the engine starts to work with interruptions, power drops, the mixture becomes too lean or vice versa. All this is very bad for the car as a whole, so you need constant and regular monitoring. In addition, try to refuel only the gasoline, which advises the manufacturer of your vehicle.