Application of MEMS Thermal Film Sensor in Vortex Flowmeter on Pipe Flow Experiment

• Main Authors: Chen-Chiang Chen, 陳振強
• Other Authors: Jiun-Jih Miau
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/19526798701029870960

碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 92 === 　　In this research, an array of membrane thermal film sensors array was manufactured by a MEMS fabrication process. The design was featured with using platinum as sensing material, and Aurum as the conducting wires to connect the platinum sensing material and the circuit, Both platinum and aurum are deposited on silicon nitride substrate. Finally, by wet etching the silicon nitride substrate, the membrane thermal film sensors array was finished. Each of the sensors shows the linear temperature-dependence characteristic, with the coefficient of resistance (TCR) of 0.238% /℃ measured. By imposing a stepwise change of surrounding temperature to a sensor, the constant-current circuit output showed a dynamic response up to 3.4KHz. 　　The membrane thermal film sensors array was applied to a vortex flowmeter for flow measurement. The sensors were packaged in the T-shape vortex flowmeter, for the flow velocity ranging between Re=10100-41300 in low-speed wind tunnel. Thus, the vortex shedding frequencies measured fall between 14.65-58.59Hz. That the non-dimensional frequencies are about St=0.093. From the experiments, the optimal position of the thermal film sensor in vortex flowmeter was found about x/d=1.76. 　　Furthermore, a T-shaped vortex shedder was assembled in a 50mm pipe flow. Hot-wire anemometer was employed to obtain the vortex shedding signal as well. The characteristics of the signals obtained from the vortex flowmeter and the hot-wire probe appeared alike. Further, by placing the flowmeter downstream of two elbows out of plane, with and without T-shaped cylinder upstream of inlet of the elbows, the signal quality corresponding to those two case were compared. Both cases showed that the best signal quality (SNR) can be obtained in X’=15D-20D downstream of the exit of the elbows. The results suggest that a vortex flowmeter be located at this location for flow measurement.