Research and Development of Fiber L2F
Grant-in-Aid for Developmental Scientific Research (B).
|Research Institution||Kyushu University|
HAYAMI Hiroshi Kyushu University, Institute of Advanced Material Study, Professor., 機械物質科学研究所, 教授 (10038606)
|Project Fiscal Year
1990 – 1991
Completed(Fiscal Year 1991)
|Budget Amount *help
¥4,600,000 (Direct Cost : ¥4,600,000)
Fiscal Year 1991 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1990 : ¥2,800,000 (Direct Cost : ¥2,800,000)
|Keywords||Flow Measurement / Laser / Laser Velocimeter / L2F / Diode Laser / Optical Fiber / 流体計測 / レ-ザ / レ-ザ流速計 / 半導体レ-ザ / 光ファイバ|
A new type laser-2-focus velocimeter (L2F) was developed to materialize a small size, a low price and an easier operation. An optical system and a signal processing system based on an optical fiber or based on a diode laser were designed and were built up. The design specifications of new systems were tested applying to a flow measurement in a wind tunnel or in a rotating impeller.
At the first step, a fiber L2F with an optical fiber of 8 m in length used between the laser source and the optical head was developed. The size of the fiber L2F was reduced to a half in weight and a third in volume compared with the original L2F. The optical S/N ratio of the fiber L2F was not deteriorated for application to a flow measurement in a rotating impeller, when the optical shutter was installed ahead of the optical fiber according to the behavior of polarized light in an optical fiber.
At the second step, a diode L2F with a transmitter optics of 48 mm in diameter and of 120 mm of measuring distance
was developed, the size of which is 324 mm in length, 98 mm in width and 140 mm in height, and the weight is 5kg. A diode laser of 840 mm in wave length was used as a light source, and the scattered light from a particles was detected using an avalanche photodiode. An electric amplifier was designed with high sensitivity against the diode laser. The measuring volume of the diode L2F was measured using a fine wier of 5 mum in diameter with a mechanical traversing system.
It was possible to make a flow measurement at I mm close to the bottom wall even when the laser beam was inserted into a small-sized wind tunnel normal to the wall, and this confirmed a high S/N ratio of the diode L2F system. In the case of low turbulence flow, the maximum sampling rate was 2kHz and the probability of a particle traveling through the two foci was beyond 80 percent so that a measuring time was reduced significantly by narrowing the distance between the two foci to 0.1 mm. Velocity distribution in a two-dimensional wake behind a circular cylinder was measured. The diode L2F was applicable to a flow measurement even in a high turbulence flow with 20 % in transverse turbulence intensity.
Research Output (4results)