The Fabrication and Output Power Characteristics of a Heat-Engine using a Shape Memory Alloy Spiral Spring Actuator

Cho, H.; Senju, Masato; Takeda, Yoichi; Yamamoto, Takaei; Sakuma, Toshio

doi:10.14723/tmrsj.38.423

Cited by 7 publications

(5 citation statements)

References 9 publications

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“…We propose a new actuator using a SMA spiral spring as shown in Fig. 4 (Cho et al 2013). This actuator consists of the SMA element in the form of a spiral spring, an outside container in the form of a cylindrical tube, and rotary axis which can turn at the center of the container.…”

Section: Spiral Spring Sma Actuatormentioning

confidence: 99%

Fabrication and Output Power Characteristics of Heat-Engines Using Tape-Shaped SMA Element

Cho

Takeda²,

Sakuma

2017

Advances in Shape Memory Materials

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Heat-engines using shape memory alloy (SMA) were expected to be employed as heat-engines driven by low-temperature thermal energy. However, since the product-life cycle of conventional heat-engines using SMA is too short, SMA heat-engines have not been put into practical use. For the purpose of the product life improvement of the SMA engine, we devised and fabricated some SMA heat-engines using the tape-shaped SMA element. This paper reports the description of fabricated SMA heat-engines and output characteristics of these engines.

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Section: Spiral Spring Sma Actuatormentioning

confidence: 99%

Fabrication and Output Power Characteristics of Heat-Engines Using Tape-Shaped SMA Element

Cho

Takeda²,

Sakuma

2017

Advances in Shape Memory Materials

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“…To help solve the various problems of SMA heat-engines, we devised a spiral spring type SMA heat-engine using a tape-shaped SMA element [8,9] . In terms of cooling efficiency, the tape-shaped SMA element is more advantageous than a wire-shape because the specific surface area of tape-shape is larger than that of a wire-shape.…”

Section: Sma Wire or Coilmentioning

confidence: 99%

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

Fujiki

Nakagawa

Takeda³

et al. 2016

Trans. Mat. Res. Soc. Japan

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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.Key words: shape memory alloy, pulley-type heat-engine using shape memory alloy, cooling system INTRODUCTIONThe recovery method of low-temperature exhaust heat energy (less than 373 K) is not well-established because the energy conversion efficiency of the low-temperature exhaust is less than 10 %.Ti-Ni based shape memory alloys (SMA) are well known as functional materials which show shape recovery and superelastic characteristics [1][2][3][4] . Since Ti-Ni based SMA work by heating from heat sources less than 373 K and show a large recovery force (approximately 10 6 J/m 3 ) [5] , SMA are capable of being applied as the driving element for a heat-engine for energy recovery from low-temperature thermal energy.In previous research, several SMA heat-engines have been produced and researched. One of the representative SMA heat-engine is a pulley-type SMA engine [6,7] as shown in Fig.1. The SMA element of this engine is wire rods memorized to straight liner or coil shape, and made into a hoop by welding. When the SMA is put in hot water, the SMA element recovers to linear shape and produces a recovery force. The tangential component of the recovery force rotates pulleys (generates torque) by the friction with the pulley, and the SMA element moves to the opposite pulley. Here the SMA element is cooled in the air and deformed again by the generating power of other part (heated part) of SMA element. Since these actuations are performed consecutively, this mechanism

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“…The pulley-type SMA heat-engine, which is one of the SMA heat-engines, is driven by heating and cooling of the liner or coil shape SMA element [6][7] . We fabricated tape-shaped SMA element for the purpose of improving the product's life span [8][9][10] . However, shape memory and mechanical characteristics of tape-shaped SMA deteriorates with the increasing number of heating/cooling cycles.…”

Section: Introductionmentioning

confidence: 99%

Effects of Heating and Cooling Cycle on the Shape Memory and Mechanical Characteristics of Tape-shaped Shape Memory Alloy Element

Nakagawa

Cho

2018

Trans. Mat. Res. Soc. Japan

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A pulley-type SMA heat-engine using Ti-Ni shape memory alloy (SMA) driven by lowtemperature waste heat energy was investigated. We have proposed and fabricated a pulley-type heat-engine using tape-shaped SMA element for the purpose of improving of the life span of pulley-type SMA heat-engine. However, shape memory and mechanical characteristics of SMA deteriorate with increasing number of thermal cycles. Therefore, effects of thermal cycling on the shape memory and mechanical characteristics of the tape-shaped SMA element are investigated in this study. The chemical composition of the specimen is Ti-45.0Ni-5.0Cu (at%), heat treatment condition is 673K for 3.6ks and the specimen is memorized horizontal shape. The number of thermal cycling (N) is varied from 0 to 10 5 . Transformation temperatures are almost constant as the N increases to 1×10 3 . However, each difference of transformation temperature (Ms-Mf and As-Af) decrease when the N is within a range of 5×10 3 to 1×10 4 , above which it increases. Mechanical properties improve with increase of N when the N is up to 1×10 4 , above which it deteriorates. Furthermore, 2-stage martensitic transformation appears when N is above 5×10 4 . These tendencies are caused by the variation of dislocation density and residual martensitic phase with the increasing of N.

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The Fabrication and Output Power Characteristics of a Heat-Engine using a Shape Memory Alloy Spiral Spring Actuator

Cited by 7 publications

References 9 publications

Fabrication and Output Power Characteristics of Heat-Engines Using Tape-Shaped SMA Element

Fabrication and Output Power Characteristics of Heat-Engines Using Tape-Shaped SMA Element

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

Effects of Heating and Cooling Cycle on the Shape Memory and Mechanical Characteristics of Tape-shaped Shape Memory Alloy Element

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