Fluid Structure Interaction Analysis of Acrylic Optically Transmissive Nozzles

In this paper, a contrast experiment has been carried out for discussing the phenomenon of fuel dripping at the end of injection by using the different nozzles with varied materials. The experiment results show that the nozzle deformation has an important effect on the fuel dripping at the end of injection. The duration of the fuel shut-off process with the steel nozzle which producing smaller deformation is shorter than the polymethyl methacrylate nozzle. The mass of fuel dripping with the steel nozzle is less. For implementing a deep analysis on the experimental phenomenon about the fuel dripping with the polymethyl methacrylate nozzle, a three dimensional numerical simulation research was carried out for analyzing the influence of fuel flow inside nozzle on the solid deformation and stress distribution of the nozzle by using Fluid-Structure-Interaction method. The simulation results show that the deformation and the stress are mainly occurred in the sac and the inlet of the orifice. And the maximum stress has been observed at the entrance of the sac. The maximum stress is over the adhesive force and cause the failure of the optically transmissive nozzle. Then the fluid volume change with the injection pressure and the fluid flow characteristic considering the solid deformation were also researched. The results of this research show that the solid deformation of polymethyl methacrylate nozzle lead to a delay of the injector fuel shut-off time which comparing to the real injector made by steel, and the total fuel mass discharging from the nozzle is slightly increase. The solid deformation also lead to a fact that the fuel is continually discharged from the optically transmissive nozzle over a long time after the closing of injection, similar to that seen in the experimental results.