Ultrasonic Techniques for Methanol Concentration Sensor
Date Issued
2007
Date
2007
Author(s)
Tseng, Yu-Lun
DOI
zh-TW
Abstract
Recently, fuel cell technology which has owned an important position in the emerging energy grows rapidly, especially the Direct Methanol Fuel Cell (DMFC). Due to the advantage of high energy density, DMFC is expected to be the major portable energy for the next generation. Since the performance of the DMFC is directly relevant to the density of methanol solution, in order to optimize the efficiency of DMFC, concentration changes must be monitored and controlled. This thesis uses ultrasound sensing to monitor methanol concentration. At the operating concentration range of 0 to 10wt% for DMFC, the resolution of 0.5wt% was expected for the ultrasound sensing module.
Although the theoretical sound speed prediction model had been proposed by other researchers, it can’t be used as a sound speed-concentration conversion formula. Because the forces between the molecules vary a lot for polar liquid such as water which results in a large deviation between these prediction models and actual sound speed.
In this research we intended to measure the actual sound speed of methanol solution under various concentrations, and establish the empirical conversion model through these experiment data. Besides, we estimate how propagation distance and sampling time affect on sound speed measuring by uncertainty analysis. Finally, we investigate the blind spot on ultrasound sensing because of the decreasing sensitivity. New parameters such as peak frequency shift and attenuation will be employed for the concentration sensing in the blind temperature range.
Subjects
甲醇
超音波
聲速
濃度
靈敏度
methanol
ultrasound
sound speed
concentration
sensitivity
Type
thesis
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