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DESCRIPTION JPH02132327

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DESCRIPTION JPH02132327
[0001]
[Object of the Invention] (Industrial field of application) The present invention relates to a
transmitter / receiver of an ultrasonic flowmeter using, for example, ultrasonic waves, and in
particular, the flow measurement around a boiler in thermal power generation or nuclear power
generation, or high speed The present invention relates to a high temperature ultrasonic sensor
suitable for flow rate measurement of liquid Na used as a coolant in a breeding reactor.
(Conventional art) An example of a conventional sensor for a high temperature ultrasonic
flowmeter is shown in FIG. 4 (cited reference Japanese Utility Model Publication No. 55-72160).
In order to efficiently propagate the ultrasonic wave generated by the ultrasonic transducer (1)
to the measurement target side, in this case, the wedge (3), grease etc. are formed on the bonding
surface of the ultrasonic transducer (1) and the wedge (3) Use the liquid substance of However,
when the object to be measured is high temperature, a propagation medium such as grease can
not be used in terms of heat resistance, and as shown in FIG. 3, it propagates high temperature
resistant oil (11) and gold foil (12). There was one used as a medium. (Problems to be Solved by
the Invention) Although oil is used as a propagation medium in the prior art, in the case of oil,
the heat resistance is at most about 250 ░ C., which is required for measuring Na flow rate in a
fast breeder reactor. It was far from 600 ░ C. Therefore, an object of the present invention is to
realize a high-temperature ultrasonic sensor including a highly heat-resistant propagation
medium which can be sufficiently used for Na flow rate measurement, and the object of the
present invention is also there. In the ultrasonic sensor for high temperature according to the
present invention, a minute surface is formed on the bonding surface of the ultrasonic transducer
and the wedge, leaving the periphery of the bonding surface. It is the structure which provided
the space | gap part by the recessed part of the depth, and enclosed the liquid metal in this space
| gap part. (Operation) In the ultrasonic sensor for high temperature according to the present
invention, when NaK (an alloy of Na and K and liquid at normal temperature) is used as the liquid
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metal sealed in the air gap, the propagation medium in the high temperature range up to about
700'C. Function and can efficiently propagate ultrasonic waves. (Example) The invention will be
described in detail on the basis of the exemplary embodiments shown in the drawings. 1 and 2
show a high temperature ultrasonic sensor according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A of FIG. The ultrasonic transducer (1) is joined to a wedge
(3) made of a high temperature resistant material (for example, a metal material such as stainless
steel). The bonding surface of the wedge (3) is provided with a void (6) by a recess of a minute
depth formed leaving the periphery of the bonding surface, and the void (6) is a liquid NaK (a
propagation medium) 2) is enclosed. The ultrasonic transducer (1) generally has an
electrostrictive element (4) such as barium titanate or lead zirconate titanate in a disk shape, and
an electrode (5 And the like.
Propagation media to be enclosed in the cavity (6) include mercury (melting point -38.87 ░ C,
boiling point 356.6 ░ C), sodium (melting point 98 ░ C, boiling point 889 ░ C), potassium
(melting point 63.4) C., boiling point 757.degree. C.) and NaK-based alloy NaK (e.g., K 78%, Na
22%, melting point -11.degree. C., boiling point 784.degree. C.), etc., but liquid at normal
temperature and high boiling point NaK is most suitable, however, each of the above-mentioned
substances causes a chemical reaction when it is exposed to air or water and changes its physical
properties, so it must be kept out of contact with air or water. Therefore, the ultrasonic
transducer (1) and the wedge (3) join the contact portion (7) of the entire peripheral edge thereof
by brazing or the like in order to airtightly isolate the gap portion (6) from the outside. Then,
after drawing the inside of the void portion (6) to a vacuum, NaK (2) is injected into the void
portion (6) so that bubbles and the like do not remain, and the inlet 4 is sealed. The operation of
the high temperature ultrasonic sensor of the embodiment of the present invention configured as
described above will be described below. When a voltage is applied to the electrodes (5) at both
ends of the ultrasonic transducer (1), the electrostrictive element (4) vibrates, and the vibration is
wedged (3) through the enclosed NaK (2) Propagated to FIG. 3 shows an example of an ultrasonic
flowmeter using the high temperature ultrasonic sensor of this embodiment. A high temperature
fluid (9) such as Na flows in the direction of the arrow through the pipe (8). The pipe (8) is
provided with a pair of wedges (3), (3 ') as shown in the figure, and the wedge (3). Ultrasonic
transducers (1) and (1 ') are joined to (3'), respectively. The ultrasonic wave generated by the
ultrasonic transducer (1) is transmitted to the wedge (3) via NaK of the propagation medium, and
is further propagated in the fluid (9) via the pipe (8) outer wall, It is transmitted to the ultrasonic
transducer (1) through the pipe wall, the wedge, and NaK. When the high temperature fluid (9) is
flowing, the propagation time of the ultrasonic wave at this time changes according to the flow
velocity. The flow velocity of the fluid is detected from the change in ultrasonic wave propagation
time due to the flow velocity, and the flow rate is calculated. In the case of the ultrasonic
flowmeter, in order to eliminate the influence of the temperature change of the fluid, the
transmission of the ultrasonic wave is alternately repeated vibrator (1) ? (1 ') and (1') ? (1). The
transmission and reception waves are alternately switched by the same vibrator. That is, the pair
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of ultrasonic transducers (1), (1 ') and the wedges (3), (3') may have the same shape. As described
above, in the high temperature ultrasonic sensor according to the embodiment of the present
invention, liquid NaK (boiling point 784 ░ C.) is hermetically sealed as a propagation medium
between the ultrasonic transducer (1) and the wedge (3). The ultrasonic wave transmission
efficiency is good, and it can be used at high temperatures up to about 700 ░ C. Since NaK is
hermetically sealed, deterioration of NaK does not occur, and it can withstand long-term use.
[Effects of the Invention] As described in detail above, according to the present invention, a high
temperature ultrasonic sensor is realized in which a liquid metal such as NaK is hermetically
sealed as a propagation medium on the bonding surface of the ultrasonic transducer and the
wedge. It is possible to provide a high temperature ultrasonic sensor which has a high ultrasonic
wave propagation efficiency and which can be used at high temperatures up to about 700 ░ C.
and withstands long-term use. In addition, if using the ultrasonic flowmeter using the high
temperature ultrasonic sensor of the present invention to measure the high temperature and
high pressure feedwater flow rate of thermal power generation where an orifice flowmeter is
currently used, the measurement accuracy is around 2% Can be improved to about 1%. In
addition, the ultrasonic flowmeter using the high-temperature ultrasonic sensor of the present
invention can be used for Na flow measurement of fast breeder reactors where electromagnetic
flowmeters are currently used, and significant cost reduction is expected. .
[0002]
Brief description of the drawings
[0003]
1 is a schematic cross-sectional view showing a high temperature ultrasonic sensor according to
an embodiment of the present invention, FIG. 2 is an enlarged view of part A of FIG. 1, and FIG. 3
is a high temperature ultrasonic sensor of FIG. FIG. 4 is a schematic view showing an ultrasonic
flowmeter, and FIG. 4 is a schematic view showing an example of a conventional hightemperature ultrasonic flowmeter sensor.
DESCRIPTION OF SYMBOLS 1 иии Ultrasonic transducer 2 иии Liquid metal 3 enclosed иии Wedge 4 иии
Electrostrictive element 5 иии Electrode 6 иии Gap portion 7 иии Contact section agent Patent attorney
Hu Hu
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