Simulation of flow and CFD predictions of cavitation inside prototype Diesel fuel nozzles

Abstract

This thesis discusses the prediction and the analysis of cavitation inside prototype diesel fuel nozzles. Several prototype nozzles were constructed based on a standard model and later on, a CFD model for each nozzle was created, with the aid of commercial software. Standard CFD models and equations were used, provided by the used software. The model selection focused on achieving good accuracy by using the less possible computer power. In addition, the main focus was given in the mesh construction, as it was considered to be the most vital part for accurate CFD prediction. Although, there is a noticeable difference between the initial simulations compared to the latest ones in mesh quality, the mesh is considered good enough to achieve acceptable results even at the initial cases.

The main goal of each nozzle was to eliminate cavitation that occurred on the first model. The main model developed cavitation due to its geometry, as the fluid had to follow a steep change at its direction. Thus, several bypass tubes were introduced, between the area of cavitation and a higher pressure area, to eliminate cavitation inception. However, none of the used alternative geometries were able to eliminate cavitation inception at the point of interest. Also, in one of the final cases, it was found, that a chocked flow was developed which is the main reason that all of the cases failed to achieve its goal.