Fabrication and Output Power Characteristics of a Pulley-type SMA Heat-engine with the Cooling Mechanism Contained in Pulley

抄録

The pulley-type heat-engine using a shape memory alloy (SMA), which is consisted of pulleys and a coil or a liner shaped SMA element, is one of the representative SMA heat-engines for recovering low-temperature exhaust heat energy. However, the output-power of pulley-type SMA engines tends to reduce due to the cooling insufficiency of the SMA element because the main cooling method of this engine is air cooling. Furthermore, the reduction in size of the mechanism of this engine is incompatible with augmentation of the power output. For improvement of the cooling efficiency and output power, we propose the use of a tape-shaped SMA element and invented a new cooling system contained in the pulley. By using this system, the mechanism of pulley-type SMA heat-engine can be made compact and temperature stability of the SMA elements during operation is achieved. Results of the experiment show the peak output power to be approximately equal regardless of the presence/absence of operation of the cooling system. However, the output power of the engine without cooling decreases to less than half of the maximum power due to overheating during operating. On the other hand, the decrement of engine output during operation is suppressed by approximately 10 %, by the operation of cooling system. Furthermore, the optimal inter-shaft distance of pulleys is shortened by the cooling system. This tendency is caused by the transformation ability improvement of the SMA element due to the improvement in cooling efficiency.