chamber causing a reduction in the force exerted on the control plunger will open the needle. The fuel is then injected as the pressure difference between ambient and fuel line pressure.
The Diesel fuel injection system has the most dominant effect on flow processes in the combustion of compression ignition engines; because it controls the process of fuel atomisation, and the subsequent fuel/air mixing, mixture ignition, combustion and pollutant formation (Figure 2.1.2).
The characteristics of Diesel spray usually include spray tip penetration, spray angle, droplet velocities, droplet sizes and distributions, and global spray structure. These characteristics in time and space form are used to describe the performance of the fuel injection system. A good understanding of these characteristics is essential for raising the combustion efficiency and reducing environmental pollution. For instance, size distribution of droplets in a spray has a fundamental effect on compression-ignition engines. Smaller fuel droplets vaporise much more quickly than large ones, but their penetration is shorter and therefore the size distribution must be optimised. Factors that may influence the droplet size distribution include the injection and cylinder pressures, geometry of the injector nozzle and speed operation of the needle. To study the droplet formation from an injector effectively, very finely resolved time measurements are essential.
The different studies previously reported attempt to explore the results of such strategies upon droplet distributions and behaviour with the emphasis on data from the core of the spray. Understanding the droplet behaviour will help explain the benefits of these injection strategies and aid in improving the mixture formation process in Diesel engines.