Design and analysis of hydrogen powered actuator integrating metal hydride storage system

摘要

The multi-fold purposes of this dissertation consists of construction, simulation and validation of a model describing hydrogen sorption kinetics in metal hydride. The project involves a comprehensive review of engineering applications involving metal hydrides and furthermore, design and investigation of a thermo-kinetically driven actuation system integrating metal hydrides for compact and soft robotic actuation. This will also shed some light on the feasibility of designing a damping system integrating metal hydride. Firstly, a mathematical model along with comprehensive simulation strategy of hydrogen absorption and desorption processes in porous metal hydride compacts was developed. A two dimensional axisymmetric model was built in COMSOL to simulate the sorption behavior of a typical metal hydride during hydrogen absorption and desorption processes. The model was formulated by considering mass conservation of hydrogen-absorbed metal alloy, Darcy flow in the porous medium, and heat generation and absorption by exothermic and endothermic reaction for hydrogen absorption and desorption, respectively. Experiments to identify sorption characteristics during hydrogen uptake and desorption were carefully carried out for model validation purpose. The experimental data were used to validate the model describing fundamental physiochemical processes involved. Secondly, to test the plausibility of thermally driven actuator, a conventional piston type actuation system was built and integrated with LaNi5 based hydrogen storage reactor. Copper encapsulation followed by compaction of particles into pellets, were adapted to improve thermal conductivity of the storage material, which minimizes thermal energy input that drives the system. The performance of the actuator was thoroughly investigated for arrays of operating temperature ranges to demonstrate smooth and noiseless actuation over the operating ranges. Consistent and smooth actuation was observed for repeated cycles of operation. Detailed performance analysis was performed along with application of Monte Carlo experiment to evaluate system efficiency and uncertainty associated with the results. The system showed actuation behavior that can be tuned to mimic a wide range of actuators including pneumatic and hydraulic actuators, artificial and biological muscles. Finally, preliminary investigation was carried out to study the feasibility of integration of hydrides in a damping system. Overall, the simulation results are in good agreement with the experimental observation for the hydrogen sorption model and the actuator showed consistent performance and very good level of efficiency within the temperature ranges of low grade waste heat.