Optimization of a Small Gas Ejector Used in Navy Diving Re-breathers

Optimizing the Small Gas Ejector currently used in a Navy Re-breather would reduce the footprint or increase diving duration while becoming applicable to future diving systems. A modified Quasi-Newton method for multivariable optimization using Computational Fluid Dynamics (CFD) to numerically populate the gradient vector and Hessian matrix was solved to optimize four geometric Parameters (throat diameter, throat length, exit diameter and nozzle position) while keeping the nozzle diameter, ambient pressure, and upstream pressure constant. CFD was then used to predict the optimization of each parameter independently as well as to predict how each optimized parameter may vary with changing boundary conditions. Experiments verified that the Quasi-Newton method used with CFD was able to predict the geometry that were all independently optimized for the given boundary conditions as well as predict the trends for how the optimum geometry changes with changing boundary conditions.