Characteristics of system of injection

Characteristics of usual system of injection

In usual systems of injection of fuel with the switching centre and the pump of direct injection the injection system includes only the main phase of injection – without control and late injection. On the distributive fuel pump with electromagnetic management of action occur to approach to a control phase of injection of fuel. In usual systems of operation of creation of pressure and adjustment of quantity of injected fuel are connected with each other at the expense of interaction of a cam and плунжера the fuel pump. It makes following impact on characteristics of injection of fuel:

– Pressure of injection increases together with increase in speed and quantity of air arriving in the engine;
– During actual process of injection pressure of injection increases and then decreases to final pressure of injection.

As a result of it following consequences take place:

– The smaller quantity of fuel with lower pressure, than quantity of air arriving in the engine is injected;
– Peak pressure makes more than the doubled average value of pressure of injection;
– According to requirements for effective combustion the curve of speed of unloading actually is triangular.

Peak pressure is solving for mechanical loading of elements of the fuel pump and its drive. On usual systems of injection of fuel it is solving for quality of formation of a mix in the combustion chamber.

Characteristics of system of injection Common Rail (storage fuel system)

In comparison with usual systems of injection for reception of the ideal characteristic of injection it is necessary to fulfil following requirements:

– For each operational mode of the engine division of the knot creating pressure, and knot of injection of fuel is necessary;
– During the initial moment of injection the quantity of injected fuel should low be possible how much it (i.e. it should be considered инерционность between the initial moment of injection and the ignition beginning).

These requirements are carried out by injection system Common Rail – storage fuel system – with its control and main phases of injection.

Common Rail represents block system and, as a matter of fact, following knots are responsible for the characteristic of injection of fuel:

– Atomizers with the electromagnetic management, screwed in a head of cylinders;
– The high pressure accumulator (rail);
– The fuel pump of a high pressure.

Also following knots are necessary for system functioning:

– Electronic control device ECU;
– The gauge of frequency of rotation of a cranked shaft;
– The gauge of position of a camshaft (the phase gauge).

In cars for pressure creation the radial piston pump of a high pressure, thus pressure is used created irrespective of process of injection of fuel. Productivity of the pump is directly proportional to frequency of rotation of a cranked shaft of the engine. In comparison with usual systems of injection actual forcing of fuel is homogeneous, i.e. in Common Rail the fuel pump of a high pressure not only has the smaller sizes, but also its drive is to a lesser degree subject to peak loadings.

Fuel atomizers are connected with rack short pipelines and, in essence, include sprays and the solenoidal valve operated ECU. After a pressure stopping delivery on the solenoidal valve fuel injection stops. Assuming constant pressure, quantity of injected fuel in direct ratio to an interval of time during which the solenoidal valve is opened. This process is completely independent of frequency of rotation of a cranked shaft of the engine and frequency of rotation of the pump (injection of fuel depending on time).

High-speed switching of the solenoid is reached at the expense of high voltage and current use. It means that it is necessary to use specially developed solenoidal valve providing a platform at the moment of opening. The injection moment is defined by control system EDC (Electronic Diesel Control – Electronic control by the diesel engine) which uses the gauge of frequency of rotation of a cranked shaft and the gauge of position of a camshaft for phase definition of a running cycle.