Search Results

The development of a four-stroke engine, spark ignition, with direct injection of fuel into the combustion chamber was an important initiative for the global automotive market. The thermodynamic potential of this type of engine and its significant improvement in fuel economy have meant this technology as focus of a large number of research projects, with the objective to understand, develop and improve the system of direct fuel injection. However, to meet new emission limits set by Euro 5 specification, it was necessary to reevaluate the geometry design of the injector, which resulted in the development of a new component with a larger number of holes and with a diameter reduction (multi-holes injector). This change in the project aims to ensure a better spray, optimizing air / fuel ratio and, consequently, a better process of combustion inside the combustion chamber, satisfying the emission limits established by the applicable norms.

The period between the start of fuel injection into the combustion chamber and the start of combustion it's known as Ignition Delay (ID) or Delay Time. Delay period in the diesel engine exerts a very great influence on both engine design and performance. Functionally, the ID can be divided into two parts: the physical and chemical delay. The physical delay, it is the time between the beginning of injection and the attainment of chemical reaction conditions. During this period, the fuel is atomized, vaporized, mixed with air and raised to self-ignition temperature. Viscosity governs the physical delay of fuel combustion process, for low viscosity fuels, the physical delay tends to be small and vice versa. The chemical delay, during this period reactions start slowly and the accelerate until inflammation or ignitions takes place. Generally, chemical delay is larger than the physical delay.