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The second important point - the way to the fuel supply. The gasoline engine working fluid is a mixture of gasoline and air. The mixture is prepared in advance (in the carburetor), or directly at the point of supply to the cylinders (injection systems) - the main thing is that the fuel is supplied together with the air and ignited and burns relatively homogeneous toplivovoz sultry mix.

In a diesel engine fuel and air takes place separately. Initially, air is sucked into the cylinder, then it is compressed, and only then the fuel is injected, so to speak of a homogeneous air-fuel mixture is not necessary. Injection is performed at the end of the compression stroke, fuel and air are not virtually mixed with each other combustion takes place on the front of the compressed air injected into the fuel stream.

Self-ignition of fuel is accompanied by a sharp, abrupt increase in pressure in the cylinder - this explains the typically noisy and hard work of the diesel engine. In low-speed diesel engines with a large cylinder capacity, which are used in trucks, this deficiency is manifested to a lesser extent, and put up with it. The diesel engines of cars trying to get rid of it using the vortex chamber or pre-chamber - a small bay of the combustion chamber into which fuel is injected. There is ignited, partially mixed with air, and then burning the mixture was spread on the main cylinder volume. This method slightly reduces the rigidity of the engine, but it reduces the thermal efficiency and fuel economy. For a smoother ignition of the fuel used by the two-stage fuel injection and sophisticated electronic control circuit.

A characteristic feature of diesel engines is the presence of particulate matter in the exhaust gas. Due to the heterogeneity of the combustion process to poverhnos minute particulate fuel always there is some lack of oxygen, whereby instead of a partial oxidation to form a thermal decomposition of solids - carbon black. For a good diesel fuel combustion takes considerable even excess air.

Also, the degree of compression in the diesel engine 2 times higher than that of a gasoline engine. High, not less than 14 (up to 25), the compression ratio is necessary in order that the temperature in the cylinder has risen to a value sufficient for ignition of fuel. Generally, in diesel engines the compression ratio of 21-22 and is limited only by the strength characteristics of the engine.

Devices for supplying the fuel in diesel engines is much more complicated than gasoline. Their complexity is determined by the first of all the fact that it is necessary to inject very small, just a few milligrams, a quantity of fuel in the high pressure environment. These portions should be very precisely metered - exactly the amount of fuel supplied is controlled by the diesel engine. This requires a high-speed boiling and precise injectors. High compression requires the application of appropriate constituent of the fuel pump - the pressure in the injector nozzle should reach several hundred bars. All this complicates and increases the cost significantly and the fuel supply system, respectively, the diesel engine itself.

Fuel from the fuel tank is taken high pressure fuel pump, and then under high pressure is supplied to the fuel injectors.

To reduce the amount of harmful substances contained in exhaust gases of vehicles with diesel oxidation catalyst installed. Also used admixing exhaust system to the fresh air entering the engine, thereby decreasing the percentage of oxygen in the air to be burnt in the engine cylinders. As a result, it decreases the combustion temperature of the fuel mixture, thereby reducing the amount of nitrogen oxides formed.

There are three ways of injecting diesel fuel into the engine cylinders. Through the pre-chamber through the swirl chamber and direct injection.

When injected through a pre-chamber diesel fuel sprayed by the settling chamber and instantly ignited. In connection with a minor amount of oxygen in the prechamber is burned only a part of the fuel and the remaining fuel displaced from the premix chamber into the cylinder, where it is combusted completely.

When the fuel injection through the vortex chamber of combustion produced in the same manner as with the fuel injection via the prechamber. The difference lies in the shape and size of a channel connecting the vortex chamber with the combustion chamber. By injecting fuel into the swirl chamber is much better mixing of fuel with air, and the combustion process is carried out more smoothly.

Direct fuel injection

With direct injection, fuel is supplied directly into the combustion chamber. The fuel pump supplies fuel at a pressure of about 900 bar and the fuel injection is performed in two stages.

Using a dual fuel injector makes it possible to produce an initial injection of insignificant tion of the fuel, thereby improving combustion of fuel, and the combustion process proceeds more smoothly. The amount of injected fuel is regulated by the electronic engine management system. The amount of fuel injected is regulated by a control system based on information from the following sensors:

- The accelerator pedal sensor transmits the information to the engine control unit of the position of the accelerator pedal at the present time;
- The gauge of turns of the crankshaft of the engine;
- Motion sensor fuel injector needle. Based on information from this sensor is determined by the fuel injection timing and the injection process is adjusted depending on the operating conditions and revolutions of the engine crankshaft;
- Dr. Occupancy pressure of air entering the engine (boost gauge);
- Dr. Occupancy temperature of arriving air to the engine;
- D Occupancy coolant temperature;
- Dr. Occupancy temperature of diesel fuel;
- N otentsiometr spool position. Based on information from this sensor is determined by the actual injection quantity.

The air entering the engine in the intake ducts, spirals, resulting in improved combustion process in the cylinders of the engine. Also in this case easier cold start and preheat the engine must be carried out at temperatures below -10 ?�.

Before entering into the fuel injection pump the fuel passes through a fuel filter, in which it also separates from the water, which must be drained periodically.

Drive a fuel pump is driven by the engine crankshaft via a toothed belt. The internal moving parts are lubricated by the fuel pump diesel.

Do not spill diesel on the cooling hoses. Hoses for which long influenced diesel fuel must be replaced.

The fuel system of the diesel engine is particularly sensitive to pollution, so when working on the fuel system, observe maximum cleanliness. Before disconnecting the fuel thoroughly clean them from dirt.

Do not use compressed air to clean the fuel system components installed on the engine.

When testing the operation of fuel atomizers never substitute hands or any part of the body under the stream of fuel coming out of the nozzle. Fuel exits the injector at high pressure can penetrate into the body through the skin.