Online

Brandriss, Owen Michael

Mechanical Engineering

2023

M.S.

In recent years, the industry of small-satellite technology has experienced massive growth. In 2020, the value of the global smallsat market was valued at $3.2 billion, and is projected to reach $13.7 billion by 2030, with thousands of successful smallsat launches already completed as of 2022. While these satellites are typically inserted into orbit via rideshare on large rockets, maneuvers such as attitude correction, station-keeping, and deorbiting of these sattelites - which often have masses under 10kg - requires the development of very small propulsion systems, with thrust levels as low as individual micro-Newtons. These propulsion systems often use hypergolic liquid propellants, which reduces storage tank size and and eliminates the need for an ignition source. However, the length-scales of these systems, as well as the use of liquid propellants, lead to a number of new design challenges that do not exist in traditional propulsion systems. One of the greatest challenges in the development of micro- and millimeter-scale propulsion systems is the problem of propellant mixing in low Reynolds Number (Re) flows. Methods of propellant mixing in traditional, large-scale propulsion systems rely heavily on the generation of turbulence, which is difficult - sometimes even impossible - in small-scale wall-bounded flows. The use of liquid propellants compounds this issue due to their high viscosities. The purpose of this study is to examine how key geometric parameters and operating conditions affect the performance of a millimeter-scale liquid-liquid swirl mixing design operating in the laminar-to-turbulent transition regime using computational fluid dynamics (CFD). The CFD approach lends itself well to this problem, as it circumvents the technical and financial challenges associated with prototyping at this length scale. The mixing system under investigation is based on a design currently under development by industry company Benchmark Space Systems, but the goal of this work is to examine the performance of the system from a more general perspective. Thus, emphasis will be placed on how propellant flow parameters, injector geometries, and various important dimensionless parameters contribute to improved mixing and the production of favorable flow structures in the mixing chamber, such as swirl and vorticity. Study outcomes and mixing performance will be characterized in terms of these parameters, so as to broaden the applicability of the results not only to aerospace propulsion systems, but to swirl-based low-Re mixing systems as a whole.