Optimal dimensionless design and analysis of jet ejectors as compressors and thrust augmenters

Abstract

A jet ejector may be used as a compressor or to enhance thrust of watercraft or aircraft. Optimization of jet ejectors as compressors and thrust augmenters was conducted using the software GAMBIT (Computer Aided Engineering (CAE) tool for geometry and mesh generation) and FLUENT (Computational Fluid Dynamics (CFD) solver kit). Scripting languages PYTHON and SCHEME were used to automate this process. The CFD model employed 2D axis symmetric, steady-state flow using the ε−k method (including wall functions) to model turbulence. Initially, non-dimensionalization of the jet ejector as a gas compressor was performed with respect to scale, fluid, and operating pressure. Surprisingly, rather than the conventional parameters like Mach or Re number, the results showed a completely new parameter (christenedGM- Gauge Mach) that when kept constant will result in non-dimensionalization. Non-dimensionalization of a jet ejector for watercraft propulsion was conducted using 2D axis symmetric, steady-state flow modeling using the ε−kmethod (including wall functions). It showed consistent results for the same velocity ratio (r) of nozzle velocity to free-stream velocity for different scales, fluids, and ambient pressures.