DEVELOPMENT OF A NEW LASER ANEMOMETER

Research Project

Project/Area Number	59850034
Research Category	Grant-in-Aid for Developmental Scientific Research
Allocation Type	Single-year Grants
Research Field	Fluid engineering
Research Institution	Hokkaido Institute of Technology
Principal Investigator	KOBASHI Yasujiro 北海道工業大学, 工, 教授 (70001758)
Project Period (FY)	1984 – 1985
Project Status	Completed (Fiscal Year 1985)
Budget Amount *help	¥16,300,000 (Direct Cost: ¥16,300,000) Fiscal Year 1985: ¥5,700,000 (Direct Cost: ¥5,700,000) Fiscal Year 1984: ¥10,600,000 (Direct Cost: ¥10,600,000)
Keywords	Flow measurements / Laser Doppler Anemometer / Interference Fringes / Image Sensors / Gate Circuits
Research Abstract	The Multi-Sensor Laser Velocimeter (LMSV) is composed of the usual foward scattering Laser Doppler Anemometer (LDV) and a screen of an arrangement of image-sensors which act as substitutes for the interference fringes of the usual LDV. Each sensor is connected with one of the gate switches which accepts an electric signal only when the preceeding gate is open and closes when the next gate recieves a signal so that the interval of the gate openings gives the exat speed of the particle even if there exist excessive particles within the measuring section at the same time. It enables us to introduce much more particles into the fluid which is necessary to obtain continuous signals but is forbidden for the usual burst mode LDV due to the distortion of the Doppler signals. The signals from the sensors are quite pulse-like and even a coarse high-pass filter is good enough to remove photo noises from the particle signals. The tests in water show that, when the particle sizes are not smaller than 10 microns, we can measure the flow speed from almost zero to 6 m/s very acculately without filter. The newly developed LMSV is quite accurate and easy to handle and its cost is expected to be reduced to less than one half of the LDV anemometer if photo-multipliers of the image sensor are replaced by photo-diodes.