## 2 Impact of Fuel Injection Parameters on the Combustion Process in a Compression Ignition Engine
The auto-ignition delay period according to [PERSON] is determined by the following relationship [9],  
\[\tau_{s}=(0.36+0.22\cdot c_{m})\cdot\exp[E_{a}(\frac{1}{RT_{2}}-\frac{1}{17.19 })\cdot(\frac{21.2}{P_{2}-12.4})^{0.63}], \tag{1}\]  
where P\({}_{2}\) is the temperature in the combustion chamber, T\({}_{2}\) is the pressure in the combustion chamber, E\({}_{a}\) is the amount of activation energy, and c\({}_{m}\) is the average piston speed. The activation energy value is calculated from the formula  
\[E_{a}=\frac{618.840}{LC+25}\ [\mathrm{J/mol}], \tag{2}\]  
where LC is the cetane number. Based on relationship (1), it can be stated that increasing the cetane number of fuel extends the delay of auto-ignition. According to theoretical considerations, the quality of fuel atomization in the combustion chamber does not affect the auto-ignition delay period. However, the considerations apply to older design engines operating at low pressures in the injection system, and the old generation fuel injectors. The Common Rail system works at working pressures of 25-200 MPa. Phenomena inside the system are very variable. The occurring turbulent flow of liquid in the fuel atomizer means that the atomization, width, range, and angle of the stream of flowing fuel have different values than in classic systems. Additionally, the changes made to the fuel atomizer can affect the additional turbulence of the liquid and improve its mixing with air. The second stage of the combustion process, called kinetic combustion (rapid combustion), lasts from the moment of the ignition of the combustible mixture until reaching the maximum pressure in the cylinder. During this phase, oxidation of part of the fuel-air mixture prepared during auto-ignition delay occurs, resulting in rapid heat release and pressure build-up. At the end of this stage, the combustion process is limited by the speed of mixing of the fuel with air. The following factors influence the kinetic combustion period. 1. The injection dose introduced during the auto-ignition delay period and during kinetic combustion, and the characteristics of the injected fuel stream. A smaller amount of fuel supplied during the auto-ignition delay causes a smaller value of pressure increase in the combustion chamber in relation to the crankshaft rotation. If the atomization is finer, the faster the first doses of fuel mix with the air, and the more gently the pressure in the cylinder in the second phase increases. 2. The design of the combustion chamber significantly affects the development of the second stage, and in particular, its impact on the auto-ignition delay period and the amount of air-fuel mixture prepared for combustion after it has started. 3. Increasing the charge movement speed to a certain value in the combustion chamber intensifies heat release in the kinetic combustion phase. 4. When the engine speed increases, the atomization improves, the auto-ignition delay decreases, the charge movement speed in the combustion chamber increases, and pressure and temperature increase. These factors accelerate chemical reactions. 5. By reducing the engine load, the duration of the second stage is shortened, resulting in a reduction of the fuel dose and a shorter time for its supply to the cylinder. The third stage of combustion begins when the reaction speed is much higher than the mixing speed of the reactants, then the duration of the combustion process depends on the mixing speed of the reactants. This period is called diffusion combustion. It begins at the moment of the greatest pressure in the cylinder, and continues until the maximum temperature is reached. In modern diesel engines, the temperature reaches a maximum of 20-40 \({}^{\circ}\)C according to GMP. This is due to the fact that intense heat production is caused by the second period of the combustion process. The third stage of combustion of the combustible mixture in a compression ignition engine depends on the following factors. 1. The use of engine boost increases the amount of heat generated.