Computational modelling of a smart impeller actuated by shape memory alloys

Abstract

Smart (SMA-Shape Memory Alloy) Technology continues to advance rapidly as engineers move closer to and understand better the industrial and commercial needs for SMA. As a matter of fact, all types of products, which exercise some type of control over their function, are rapidly making their way into the marketplace [36] Nonetheless, nowhere has been evidence in the development of a SMA impeller. Unlike traditional impellers with no control over their function and sometimes fixed angle of attack, this paper demonstrates numerical investigations using analytical algorithms (Matrix laboratory programming and excel spread sheet) and advanced computer simulation package, Engineering Fluid dynamics (EFD) into the feasibility of using a smart impeller to study the performance of a pumping system and the best angle of attack for a Shape Memory Impeller. Primarily, Bench mark data and dimensions are obtained from a standard centrifugal pump run on a FM21 demonstration unit. Using the same standard centrifugal pump, and keeping all other dimensions the same but altering the angle of attack, EFD simulations where made. From analytical algorithm and EFD comparison, it was evident that the best angle of attack is 12 degree at the outlet angle with respect to the inlet angle. From EFD results, it is palpable that, by increasing the angle of attack from 35 degree to 45 degree at the outlet there will be huge increase in flow rate by 63.47% There is also a slight decrease in the impeller Torque from 35 degrees to 42 degrees by 0.72%. It is economically feasible to work at an outlet angle of 42 degrees due to increase in efficiency of 62.1% and a drop in torque of 0.72% by varying the outlet angle from 35 degrees to 42 degree. Understanding how critical actuator design is, it should be suggested that any shape memory impeller should never be used in critical components without a prior history of thermal and mechanical loading. Therefore, a NiTi impeller constitutive model can be designed, with impeller blades made from NiTi plates, trained to remember its best angle of attack (Martensitic phase). NiTi shape memory metal alloy (plates-blades) can exist in a two different temperature-dependent crystal structures (phases) called martensite [9](lower temperature-normal pumping condition) and austenite [9] (higher temperature or parent phase-trained best angle of attack.)