Particle segregation and forces on internal pipes in model particle-liquid-gas multiphase reactors

As the Navy continues to develop unmanned undersea vehicle (UUV) technologies and a suite of corresponding long-endurance missions,, a persistent need exists for an energy-dense, safe power source. Aluminum has received attention from ONR as an attractive potentia,l solution. When pelletized, activated aluminum is reacted with water, the reaction produces a solid byproduct, heat and hydrogen; t,he latter can then be used in a fuel cell to power a vehicle. The complex multiphase physics within the reactor affect the efficienc,y of the reaction, as well as forces that are exerted on any internal structures. For example, the relative motion of aluminum pelle,ts, byproduct particulate and liquid water affects the aluminum surface area that contacts water, and thus the efficiency of the rea,ction. The physics of such processes are poorly understood, and motivate this basic research proposal, which aims to strengthen our, understanding of the underlying multiphase flow aspects of the problem. --In this basic research effort, we propose to investigate, fundamental physical phenomena in model particle-liquid-gas reactor systems. In particular, our objectives are to characterize par,ticle segregation rates, flow patterns, and forces on internal structures under varying conditions regarding liquid injection, exter,nal vibration and gas flow. To accomplish this, we will build experimental laboratory systems with two-dimensional (2D) and three-d,imensional (3D) geometries. The 2D systems will facilitate measurement of canonical features of the system via high speed imaging an,d image processing, and will allow for complementary modeling that can be validated against findings. The 3D experiments will provi,de a geometry more representative of possible future applications, while still providing a test bed for fundamental phenomena. Furth,ermore, by probing the 3D system with novel magnetic resonance imaging (MRI), we will advance the development of such measurement te,chniques that could be used on a variety of specific reactors. Our objectives, however, are structured to advance fundamental unders,tanding of the underlying physics of the processes that affect many of these reactors.