Fluid structure interactions within a common rail diesel injector.

Abstract

The internal flow of a high-pressure diesel injector is simulated numerically to investigate the complex transient flow structures and the unsteady forces imparted to the injector needle that result from the asymmetric flow fields developed during operation. The gas-liquid two phase flow is simulated using a mixture model with the cavitation numerically modeled using the Zwart-Gerber-Belamri model. Both the k-ε model and the detached eddy simulation (DES) model are used, and the numerical results are compared. This dissertation looks at the internal flow of a generic injector at different lifts and characterizes the flow parameters at high lift and low lifts. This paper shows that the DES model captures the important unsteady flow features missed by the k-ε model. A DES simulation of a dual gain orifice injector is performed and the impact of a unique vortical structure that is generated by the gain orifices on the flow characteristics is discussed. The fluid-structure interactions of an injector at hover are simulated and the behavior of this injector and the impact of the resulting lateral bending motion of the needle is discussed. This paper identifies the geometric feature that creates the asymmetrical flow that leads to the bending motion. In the final portion of this dissertation the fluid-structure interactions are simulated over the entire injection cycle. This dissertation discusses how the bending motion of the needle is initiated and develops over the injection cycle and discusses the impact of this motion on the fuel quantity injected and the vapor formed during operation by comparing the FSI simulation to a simulation where the lateral motion is artificially limited.