| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 97 === Abstract
Subject: Simultaneous Measurements of Local Equivalence Ratio and Temperature in hydrocarbon Flames Using Chemiluminescence Diagnostic System.
Student: Ya-Yun Cheng
Adviser: Dr. Yei-Chin Chao
Keyword: Optical sensor, Chemiluminescence emission, Equivalence ratio, Flame temperature
The objective of this research is to develop a low cost, non-laser based diagnostic system and to apply this system for simultaneous measurements of local equivalence ratio and temperature in turbulent premixed hydrocarbon flames. In addition, the developed optical system can be applied to monitor combustion process and pollutant formation in industrial furnaces and burner.
The system uses Cassegrain optics to eliminate chromatic aberrations and to improve the spatial resolution for light collection. Its spatial resolution is 40μm in diameter and 600μm in length. In our study, Cassegrain optics is coupled with an optics fiber and connected to the monochromator with a liquid-nitrogen-cooled CCD (LN-CCD) camera. The system is performed to study the flame structure and characteristics of the laminar premixed methane/air jet flame operated over equivalence ratio 0.85 to 1.5.
Although the PMT array provides fast data acquisition rate for chemiluminescence emission measurements, but it gives no information on the broadband CO2* emissions and is difficult to eliminate the signal contamination from CO2 emissions. On the other hand, the LN-CCD camera measures the entire spectral range of OH*, CH*, C2*(1, 0), C2*(0, 0), C2*(0, 1) emissions as well as the broadband CO2* emissions though it gives slow data acquisition rate. We can eliminate the broadband noise by subtracting the curve-fitted values from the emission spectrum. In the experimental results, whenΦ<1.35, C2*/CH*, C2*/OH*, and CH*/OH* intensity ratios are found to be linearly related with the equivalence ratio. In addition, we can use the intensity ratio of C2*(1, 0)/C2*(0, 0) for flame temperature measurements.
Therefore, the linear relationship between the intensity ratio of C2*/CH*, C2*/OH*, and CH*/OH* and the equivalence ratio as well as the calibrated instrument constant C3 are used for simultaneous measurements of the local equivalence ratio and flame temperature in turbulent premixed CH4-air flames. These results further demonstrate the capability of the developed optical system for flame chemiluminescence measurements. The developed inexpensive, non-laser-based chemiluminescence optical system will be applied for real-time monitoring and active control for industrial burners and hazardous waste incinerators.
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