赤外レーザおよび超音波によるメタンガス濃度の測定

This paper describes the ultrasonic attenuations in gas mixtures of CO2 and air to investigate the possibility of a CO2 gas concentration monitor using with the ultrasonic attenuations. Three kinds of ultrasonic transducers (40, 215 and 500kHz) were used for the measurements. Measurements of the attenuation per unit distance of each ultrasonic wave were carried out by varying the length of a test cell of 26 mm in diameter from 30 mm to 150 mm. From these fundamental results, the practical gas detection cells were designed and the detection method in order to monitor the CO2 gas concentration was developed. Two 215 kHz ultrasonic transducers were installed on the both sides of the gas detection cell of 4 mm in diameter and 70 mm or 40 mm long. The attenuation of 215 kHz ultrasonic is the largest of the three ultrasonics. The ultrasonic waves are sent intermittently from the transducer and were The problem regarding CH4 detection has come to occupy an important position in various aspects of safety engineering. The present research purpuses CH4 detection from from two different physical characteristics which are 3.39μm infra-red ray absorption and 215kHz ultrasonic velocity and attenation. The basic measurement data on the absorptions of 3.39μm infra-red ray generated by a laser and the attenation of a comparable high frequency ultrasonic wave for the wide CH4 concentrations (0 to 100%) of air+CH4 mixing gas are insufficient.
1n this paper, we furnished the more fundamental measurement data about the two physical characteristics and proposed an new CH4 detection method with both of infra-red ray and ultrasonic wave.