Development of a gas/liquid phase change actuator for high temperatures
Matsuoka et al. Robomech J
Development of a gas/liquid phase change actuator for high temperatures
Hiroki Matsuoka 0
Koichi Suzumori
Takefumi Kanda 0
0 Okayama University , 3-1-1, Tsushima-naka, Kita-ku, Okayama 700-8530 , Japan
Gas/liquid phase changes produce large volume changes in working fluids. These volume changes are used as the driving power sources in actuators such as micro-pumps and valves. Most of these actuators are utilized in ordinary temperature environments. However, the temperature range in which the phase change actuator can operate depends on the characteristics of the working fluid. We hypothesized that proper selection of the working fluid and the structure of the actuator can enable such actuators to be applied not only in ordinary environments but also in high temperature environments. Consequently, in this paper, we discuss the design and fabrication of a new gas/ liquid phase change actuator for use in high temperature environments. Our proposed actuator consists of a bellow body, spring, heater, and working fluid. We used the Inconel super alloy, which is highly heat and corrosion resistant, for the bellow and moving parts of the actuator. For the working fluid, we prepared triethylene glycol, which has a boiling point of 287.3 °C and very low vapor pressure at ordinary temperature. As a result, our proposed actuator can be utilized in high temperature environments up to 300.0 °C. The results of several experiments conducted confirm that our proposed actuator generates 1.67 mm maximum displacement in a 300.0 °C atmospheric environment. In addition, we confirmed that the operation of the actuator is stable in that environment. Our results confirm that a gas/liquid phase change actuator can be used in high temperature environments.
Actuator; Gas/liquid phase change; High temperature; Triethylene glycol; Bellow
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Background
Phase changes in materials, resulting from
temperature changes, produce huge volume changes, especially
in liquid/gas phase changes. This attribute is utilized to
provide a power source for micro-pumps and valves in
combination with MEMS (micro-electromechanical
system) heaters, micro-channels, diaphragms, and
membranes [1–10]. Kato et al. used this phenomenon to
provide a power source for actuators and robots. They
made a metal bellow actuator to control cutting
equipment and a pipe inspection robot [11, 12]. Phase change
is used not only in actuators but also in some kinds of
pressure sources. For example, Kitagawa et al. used the
triple point of carbon dioxide as a mobile pressure source
[13], and Shibuya et al. developed a buoyancy control
device for underwater robots using paraffin oil [14].
The actuators described above were developed for use
in ordinary environments. In contrast, our aim is to utilize
these phase change actuators in special environments. In
particular, driving actuators in high temperature
environments is a typical example of the special environments
being considered. For example, in the hydrothermal
synthesis method, which is one of the methods used to
fabricate piezoelectric devices, the water solution inside
the high temperature chamber needs to be agitated [15].
In one instance where this process was used, the water
solution was agitated using an autoclave—an
end-overend shaker with heat. Fabrication of the (Pb, La)(Zr, Ti)
O3 (PLZT) film took 24 h. Not only the rotation
condition but also the attitude of the sample will affect the
quality of the fabrication. The actuators, which produce the
inclination of the shaker, are predictably effective devices.
Another example is the fabrication process for the ferric
oxide crystal via the floating-zone melting method [16].
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In this process, the partially melted sample is turned and
pulled inside the chamber for growth. Both the processes
require 8–24 h and a single directional drive in order to
fabricate the tiny sample. We believe that an actuator that
can realize linear motion in high temperature
environments can rectify these quality problems.
In previous work, we targeted these environments for
utilization of actuators and proposed gas/liquid phase
change actuators. We subsequently fabricated an
actuator driven by the gas/liquid phase change of water. This
actuator consisted of a cylinder as a vessel and actuation
device, an external heater to excite the phase change,
and a spring that controlled the speed of motion. Our
proposed actuator was driven in a 180 °C environment.
Thus, we realized directional motion with gas/liquid
phase changes in a high temperature envi (...truncated)