The diesel injector is one of the main elements of the diesel engine power supply system. The nozzle (injector) provides direct supply of diesel fuel to the combustion chamber of a diesel engine, as well as dosing of the supplied fuel at a high frequency (more than 2 thousand pulses per minute). The injector provides an effective spray of fuel in the space above. As a result of such a spray, the fuel takes the form of a torch. The injectors of fuel supply systems that are different from each other have design features and differ in the way they are controlled. Injectors are divided into two groups:
- mechanical;
- electromechanical;
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The principle of operation of a mechanical nozzle
The principle of operation of the diesel power supply system with mechanical control of the nozzle is as follows. K is supplied with fuel from . The booster pump is responsible for the supply, which creates the low pressure necessary for pumping diesel fuel through the fuel lines.
Further, the high-pressure fuel pump in the required sequence distributes and pumps fuel under high pressure in the line leading to a mechanical nozzle. Each nozzle of this type opens for the next injection of a portion of diesel fuel into the cylinders under the influence of high fuel pressure. The decrease in pressure causes the diesel fuel injector to close.
A simple mechanical injector has a body, atomizer, needle and one spring. In the device, the locking needle moves freely along the guide channel of the atomizer. The nozzle of the nozzle tightly overlaps at the moment when there is no necessary pressure from the injection pump. At the bottom, the needle rests on the atomizer seal, which has a conical shape. The clamping of the needle is realized by means of a spring fixed on top.
The atomizer is one of the most important components among other elements in the injector nozzle device. Atomizers can have a different number of spray holes, differ in the way the fuel supply is adjusted.
Simple diesel engines that have a split combustion chamber often end up with a single orifice and needle atomizer. Diesel engines, which are based on direct fuel injection, are equipped with nozzles with multiple spray holes. The number of holes in such a sprayer ranges from two to six.
The fuel supply is regulated depending on the design of the atomizer, since there are two main types of such solutions:
- atomizer with the possibility of overlapping channels;
- nebulizer with overlapping volume;
In the first case, the nozzle needle shuts off the fuel supply by closing each hole. The second type of nozzle means that the needle covers a kind of chamber at the bottom of the atomizer.
The pressure of the fuel injected by the injection pump causes the needle to rise due to the presence of a special step on the surface of such a needle. Diesel fuel penetrates into the body under the specified step. At the moment when the fuel pressure is stronger than the force that the pressure spring creates, the needle moves up. This opens the spray channel. Diesel fuel under pressure passes through the atomizer and it is sprayed in the form of a torch. This is how fuel injection works.
Further, a certain amount of fuel, which is supplied by a high-pressure pump, will pass through the atomizer and enter the combustion chamber. After that, the pressure on the step of the needle begins to decrease, as a result of which the needle returns to its original position due to the force of the spring and tightly closes the channel. Then the supply of diesel fuel to the atomizer is completely stopped.
Injector with two springs
The efficiency of fuel supply and subsequent combustion of fuel in diesel cylinders can be influenced by changing various characteristics of the injector, such as the structure and number of atomizer channels, spring force, etc. One of the design solutions was the introduction of a special needle lift sensor into the nozzle device. This rise is taken into account by special electronic control units that interact with the injection pump.
Diesel injectors with two springs have become another round of development. The design of such injectors is more complicated, but the result is greater flexibility in the fuel delivery process. The combustion of the working mixture becomes softer, the diesel engine runs quieter.
A feature of the operation of these injectors is a two-stage lifting of the needle. It turns out that the fuel injected by the high-pressure fuel pump first exceeds the pressure force of the resistance of one spring, and then the other. In idle mode and at low loads on the engine, injection is carried out only through the first stage, supplying a small amount of diesel fuel to the engine. When the engine enters the load mode, the pressure of the injected fuel injection pump increases, the fuel is supplied in two metered portions. The first injection of a small volume (1/5 of the total), and then the main one (about 80% of diesel fuel). The injection pressure difference for opening the first and second stages is not particularly large, which ensures smooth fuel delivery.
This approach made it possible to increase the uniformity, efficiency and usefulness of the combustion of the mixture. The diesel engine began to consume less fuel, the amount of toxic impurities in the exhaust gases decreased. Diesel injectors with two springs were actively used on units with direct fuel injection until the advent of power systems called Common Rail.
Electromechanical diesel injector
Further development of diesel fuel supply systems led to the emergence of injectors in which diesel fuel is supplied to the cylinders by means of electromechanical injectors. In such injectors, the nozzle needle opens and closes access to the atomizer not under the influence of fuel pressure and counteracting the spring force, but with the help of a special controlled solenoid valve. The valve is controlled by the engine, without the corresponding signal of which the fuel will not enter the atomizer.
The control unit is responsible for the start of fuel injection and the duration of fuel supply. It turns out that the ECU doses diesel fuel for a diesel engine by supplying a certain number of pulses to the injector valve. The parameters of the pulses directly depend on the frequency with which the engine rotates, in what mode the diesel engine operates, what the temperature of the internal combustion engine, etc.
In the Common Rail power system, an electromechanical injector can supply fuel in one cycle through several separate pulses (injections). Fuel injection per cycle is carried out up to 7 times. Injection pressure has also increased significantly compared to previous systems.
Due to the dosed high-precision supply of gases to the piston, as a result of the combustion of the mixture, the fuel-air mixture grows smoothly, the fuel-air mixture itself is more evenly distributed over the diesel cylinders, it is better sprayed and fully burns out.
The following video clearly illustrates the principle of operation of an electromechanical injector using a gasoline engine as an example. The main difference is that the fuel pressure in the diesel injector is much higher.
This approach made it possible to finally shift the task of injection control from injectors and high pressure fuel pumps to the electronic unit. Electronic injection works much more accurately, a diesel engine with similar solutions has become even more powerful, economical and environmentally friendly. The developers managed to significantly reduce vibration and noise during the operation of the diesel unit, increase the overall resource of the internal combustion engine.
One of the varieties of diesel power systems are designs in which there is no high-pressure fuel pump. The so-called diesel unit injectors are responsible for creating a high injection pressure. The principle of operation of the system is that the low-pressure pump first delivers diesel fuel directly to the injector, which already has its own plunger pair to create a high injection pressure. The plunger pair of the nozzle works from the direct impact of the cams on it. This system allows you to achieve the best quality of diesel fuel atomization due to the ability to create a very high injection pressure.
The exclusion from the fuel supply system of the high-pressure fuel pump makes it possible to make the placement of the diesel engine under the hood more compact, to get rid of the drive of the fuel pump and the power take-off for its constant rotation. It has also become possible to remove from the power system solutions that distribute fuel from the injection pump to the cylinders. The injectors in the system with unit injectors have an electric valve, which allows fuel to be supplied in two pulses.
The principle is similar to the operation of a mechanical nozzle with two springs. The solution makes it possible to implement an additional injection first, and only then supply the main portion of fuel to the cylinder. Pump-injectors implement the fuel supply at the most precisely specified moment of the start of injection, better dose diesel fuel. A diesel engine with such a system is economical, runs smoothly and quietly, the content of harmful substances in the exhaust gases is minimized.
The main disadvantage of the solution can be considered that the injection pressure of the pump injector directly depends on the engine speed. The list of shortcomings also includes: complexity of execution, high demands on engine oil, cleanliness and quality of fuel. During operation, there are difficulties in the process of repair and maintenance, as well as the overall high cost compared to systems that are equipped with the usual injection pump.
Read also
Diesel injector malfunctions, checking and self-identification of problems. Diesel engine injector nozzle cleaning, injection pressure regulation.
In this article we will try to figure out what it is, what it is for and where the injector is located. Injector is a cognate word with the word injection, and injection is an injection. Although the injector bears little resemblance to a syringe, it also injects fuel into the engine cylinders. Strictly speaking, the injector is a nozzle that sprays fuel in small drops to enter the cylinders with a mixture of air and gasoline vapor. You say it does everything the same. Same, but not quite.
The carburetor jet works almost like spraying gasoline in its chamber. But gasoline is sucked into the carburetor by the engine piston, which takes about 10% of its power. Plus, it’s almost impossible to adjust the carburetor to an ideal state: it either overflows fuel, that the engine “chokes” and smokes, and part does not burn out, then it does not top up, and the engine works with dips and does not pull.
Gasoline is pumped into the injector using a special electric pump, and the mixing of gasoline and air vapors occurs in the cylinder combustion chamber itself. The amount of fuel is clearly portioned, and it depends on the amount required at the moment for optimal traction.
Where is the injector located?
In normal cases, the injector is installed instead of the carburetor, or rather, in general, in its place. As an injector, only one nozzle is used, which “serves” all cylinders, and fuel injection will be into the intake manifold, the so-called mono injection. There is only one advantage over the carburetor scheme here: the engine does not expend power on sucking fuel through the carburetor jet.
The system of multi-point or distributed injection is also made into the intake manifold. Thanks to the distributed injection, the fuel that enters each cylinder is better dosed. But still, only direct injection directly into the combustion chamber of the cylinder gives the best results, just like in.
Reading 3 min. Views 1.4k. Posted on August 19, 2015
Many car enthusiasts, hearing from service station masters about the need to flush or replace injectors, do not understand what it is and where they are located. All modern gasoline and diesel internal combustion engines are equipped with a fuel injection system. The nozzle, like a pump for supplying a powerful but thin jet of fuel, is an integral part of this injection system. In this article we will tell you where the nozzles are located in the car and how they work.
Definition of a nozzle
The nozzle is a solenoid valve that is controlled by a special program in the engine control unit. Thanks to the nozzle, fuel is dosed into the cylinders. When they talk about an injector, they mean a system of controlled nozzles.
There are different types of nozzles for:
— central fuel injection;
— distributed fuel injection;
- direct fuel injection.
The principle of operation of the nozzles
Fuel from the fuel rail is supplied to each nozzle under a certain pressure. The injector solenoid receives electrical impulses from the engine control unit. They actuate a special needle valve that opens and closes the channel in the nozzle. The longer the applied electrical impulse, the longer the needle valve is open, and the more fuel is supplied. The opening time of the needle valve is controlled by the engine control unit. In addition, the types of injectors allow you to create different shapes and directions of the sprayed fuel jet, which significantly affects the mixture formation process.
The location of the injectors in the car engine
The table below shows the location of the injectors in the engine depending on the type of fuel injection.
Washing nozzles
Due to the presence of harmful impurities in the fuel, carbon deposits may accumulate on the injectors. The injector flushing operation involves the process of washing out contaminants from the injector system. You can flush the nozzles with a special liquid (special additive). In this case, the nozzles can not even be removed from the engine. Such an additive is added to the fuel, and the engine is allowed to run on such a mixture for 2-3 thousand kilometers. You can also do faster flushing of the injectors without removing them from the engine. For this, a special installation is used, which is connected to the engine instead of the fuel pump. The nozzles are supplied with a special flushing fuel - solvent. This flush takes about 15 minutes.
You can also clean the nozzles from carbon deposits using an ultrasonic stand. To do this, the nozzles are removed from the engine fuel system.
Designed for metered fuel supply, its atomization in the combustion chamber (intake manifold) and the formation of a fuel-air mixture.
The nozzle is used in injection systems of both gasoline and diesel engines. On modern engines, nozzles with electronic injection control are installed.
Depending on the method of injection, the following types of nozzles are distinguished: electromagnetic, electro-hydraulic and piezoelectric.
Electromagnetic nozzle
The electromagnetic nozzle is installed, as a rule, on gasoline engines, incl. equipped with a direct injection system. The nozzle has a fairly simple device, including a solenoid valve with a needle and a nozzle.
The operation of the electromagnetic nozzle is carried out as follows. In accordance with the inherent algorithm, the electronic control unit provides voltage supply to the valve excitation winding at the right time. This creates an electromagnetic field, which, overcoming the force of the spring, retracts the anchor with the needle and releases the nozzle. Fuel is injected. With the disappearance of voltage, the spring returns the nozzle needle to the seat.
Electro-hydraulic nozzle
The electro-hydraulic nozzle is used on diesel engines, incl. equipped with a common rail injection system. The design of the electro-hydraulic nozzle combines a solenoid valve, a control chamber, an inlet and a drain throttle.
The principle of operation of the electro-hydraulic injector is based on the use of fuel pressure, both during injection and when it is stopped. In the initial position, the solenoid valve is de-energized and closed, the nozzle needle is pressed against the seat by the force of fuel pressure on the piston in the control chamber. Fuel injection does not occur. In this case, the fuel pressure on the needle due to the difference in contact areas is less than the pressure on the piston.
At the command of the electronic control unit, the solenoid valve is activated, opening the drain throttle. Fuel from the control chamber flows through the throttle into the drain line. At the same time, the intake throttle prevents the pressures in the control chamber and the intake manifold from quickly equalizing. The pressure on the piston decreases, and the pressure of the fuel on the needle does not change, under the influence of which the needle rises and fuel is injected.
Piezoelectric nozzle
The most advanced device that provides fuel injection is a piezoelectric injector (piezo injector). The nozzle is installed on diesel engines equipped with a common rail injection system.
The advantages of the piezo injector are quick response ( 4 times faster than solenoid valve), and as a result, the possibility of multiple injection of fuel during one cycle, as well as the exact dosage of injected fuel.
This was made possible through the use piezo effect in the control of the nozzle, based on the change in the length of the piezocrystal under the action of voltage. The design of the piezoelectric nozzle includes a piezoelectric element, a pusher, a switching valve and a needle placed in the housing.
The piezo injector, as well as the electro-hydraulic injector, uses the hydraulic principle. In the initial position, the needle is seated on the seat due to the high fuel pressure. When an electrical signal is applied to the piezoelectric element, its length increases, which transmits force to the pusher piston. The diverter valve opens and fuel enters the return line. The pressure above the needle drops. The needle rises due to the pressure in the lower part and fuel is injected.
The amount of injected fuel is determined by:
- the duration of exposure to the piezoelectric element;
- fuel pressure at the fuel rail.
Injectors for diesel engines- these are the parts of the fuel equipment that are most subject to wear. They are considered the easiest to maintain and carry out diagnostics in the conditions of service centers. The quality of fuel combustion in the engine cylinders, its start, the dynamics of car acceleration, efficiency and the amount of harmful emissions depend on how efficiently the injectors work.
Injectors for diesel engines - what is it?
Depending on the type of atomizers and the fuel system, the maximum pressure of diesel engine injectors in the atomizer at the moment of injection is about 200 MPa, and the time is from 1 to 2 milliseconds. The level of engine noise, the amount of soot, nitrogen oxides and hydrocarbon emissions into the atmosphere depend on the quality of the injection.
Modern models differ in the shape of the body, the size of the atomizers, as well as in the way they are controlled. The difference between different types of nozzles is the use of different injection systems and types of sprayers, which are pin and perforated. Pinned ones are used in engines with a prechamber ignition system, perforated ones are installed on diesel engines with direct fuel injection.
According to the control method, the parts are divided into single-spring, double-spring, with sensors for controlling the position of the needle and controlled by piezoelectric elements. Among other things, the scheme of the diesel engine nozzle depends on how it is mounted in the head: using a flange, clamp or by screwing into the socket.
The principle of operation of the diesel engine nozzle - briefly about the complex
The main purpose of such parts is the dosing and spraying of fuel, as well as hermetic insulation of the combustion chamber. As a result of research, pump-injectors were developed, which are installed in each cylinder separately. The principle of operation of a new type of diesel engine injector is that it functions from the camshaft cam through the pusher. Fuel supply and discharge is carried out through special channels in the block head. Dosing of fuel takes place through the control unit, which sends signals to the shut-off solenoid valves.
The pump-injector works in a pulsed mode, which allows pre-supply of fuel before the main injection. As a result, engine operation is significantly softened and the level of toxic emissions is reduced.
Fuel injectors in most cases need simple maintenance, most often, in order to return them to working condition, it is enough just to clean and rinse them. Regardless of how many nozzles are in the engine, it happens that when you sharply press the gas pedal, jerks and dips are felt or power is noticeably reduced, the engine starts to work unsteadily at low speeds, which means that the nozzle channels are clogged with solid tar deposits. What to do?
Flushing diesel engine nozzles - ways to implement
Contamination of this element leads to a violation of the atomization of the fuel and leads to an incorrect formation of the air-fuel mixture.. Ideally, spraying should be as uniform as possible. The main source of pollution is the resins contained in the fuel. Flushing the injectors of a diesel engine can eliminate all problems in the fuel supply to.
The injector cleaning process involves the removal of various contaminants in the fuel channels. Several methods are currently used:
- cleaning nozzles of diesel engines using ultrasound;
- flushing nozzles with fuel with the addition of special additives;
- flushing with special liquids on stands;
- washing by hand.
For motorists, the last option is the most acceptable, since it allows you to clean the nozzles at home. However, in advanced cases, you have to turn to the services of auto centers, where cleaning is carried out using ultrasound, which is a tougher way. It is recommended to resort to this type of cleaning only if washing with special liquids did not give a positive result.
