5.2.4. Control injection of fuel
The control injection of fuel can be made in the provision of a bent shaft 90 ° to VMT. If the beginning of injection of fuel occurs less than 40 ° to VMT, fuel can be laid for the surfaces of the piston and walls of the cylinder and to lead to undesirable dissolution it in engine oil. At control injection a small amount of diesel fuel (1 … 4 cm3) moves in the cylinder in "previously conditional" the combustion chamber.
Efficiency of combustion of fuel can be improved and the following effects are reached:
– compression pressure insignificant to start reaction and incomplete combustion of fuel that, in turn, brings to:
- to delay of ignition of the main injection of fuel;
- to reduction of pressure at combustion of fuel and to smoothing of peaks of pressure (softer combustion).
These effects reduce noise from combustion, reduce fuel consumption and in many cases reduce toxicity of the fulfilled gases. In case of unloading speed without control injection of fuel according to compression only insignificant increase in pressure before VMT which reaches a maximum rather sharply in a point of the maximum pressure takes place.
Sharp increase in pressure together with abrupt peak makes the significant contribution to creation of noise at combustion of fuel in the diesel engine. As shown in the curve speed of unloading with control injection, pressure about VMT reaches a little higher value and pressure increases with a smaller speed. As it reduces an ignition delay, the control injection makes an indirect contribution to formation of torque of the engine. Specific fuel consumption can increase or decrease as function of the main injection and time between control and main injection of fuel.