NUMERICAL ANALYSIS OF THE INFLUENCE OF DIESEL NOZZLE DESIGN ON INTERNAL FLOW CHARACTERISTICS FOR 2-VALVE DIESEL ENGINE APPLICATION

The current paper studies the potential effect of using tilted injectors on internal nozzle flow characteristics. This kind of injector has been commonly chosen for 2-valve diesel engines. In order to achieve similar spray targeting in a 4-valve configuration, the injector design needs to be modified, inducing a different angle on each of the nozzle holes with respect to the injector axis. To study the implications of this kind of nozzle design, a vertical and a tilted injector have been analyzed for two kinds of hole shape: tapered, which suppresses cavitation; and cylindrical, which is more prone to cavitating flow. A two-component surrogate model has been used to emulate the physical properties of a typical commercial diesel fuel. Full three-dimensional flow simulations have been performed, using a flash boiling model to capture the phase transition induced by cavitation. The simulations have been conducted at the frill needle lift condition. The results show that there is a significant influence of hole angle on the mass flow distribution through the nozzle, as well as on the flow pattern and the outlet velocity profile, leading to an asymmetric spray distribution inside the combustion chamber. It is also demonstrated that cavitation formation is affected by the hole angle.