Investigation on hot fluid based actuation of SMA spring and their application for the development of heat engine

Abstract

Shape Memory Alloys (SMA) were invented many years ago, though using of SMA in applications related to engineering is only prominent from last few years. Reason behind using SMA is its ability to change its crystalline structure by applying a temperature gradient. Its simultaneous memory effect and elastic behavior makes it suitable for applications involving actuation and control. In this process of finding application of this interesting material, a device for conversion of waste heat into work could be of utmost importance. The proposed engine consists of group of SMA springs, stretched at one end connected with hub and other end connected to an aluminium wheel, due to the change in the position of centre of gravity, synchronized to rotate in a direction. During operation, the engine is positioned between two distinct thermal reservoirs such that half of its springs are heated by heat energy (medium which acts as a source) while the other half are cooled by an normal atmosphere. Springs on the hot side attempt to contract, driving the engine in the direction that relieves the heat-induced stress. In this work, two different hot reservoirs namely hot water and exhaust gas of an automobile engine was used. When this setup is inserted in hot side of around 80°C or more, the ring begins to rotate. Then work is done thus serving purpose of converting waste heat into mechanical work. © 2018 Author(s).