Abstract
The ethylene (C2H4) concentration and temperature are simultaneously measured in high temperature environment using a differential absorption scheme combined with a distributed feedback (DFB) diode laser near 1.620 μm. Based on optimal selection criterions, two wavelength pairs with absorption peaks at 6174.58 cm-1 and 6174.98 cm-1 are selected for the measurement. Temperature are obtained from the ratio of the absorption cross section of the two wavelength pairs, and C2H4 concentration is inferred from the differential absorption of one of the wavelength pairs. Measurements are performed in a high temperature cell (T = 300-900 K, P = 1 atm) to verify the accuracy of the system. The accuracies for the measurement of C2H4 concentration and temperature are 1.135% and 2.215%, respectively. Continuous time series measurements indicated that the system has a good stability and the limit of detection achieved by Allan-Werle variance analysis is 6.6 ppm at the optimal average time of 340 s. All the measurements show the scheme is helpful to improve the practicality of laser absorption spectroscopy in combustion diagnosis.
Highlights
Temperature is one of the scalar quantities on large technical combustion systems which directly reflects the combustion efficiency and affects the diffusivity of combustion products
In order to obtain the differential absorption cross-sections for the selected two wavelength pairs, direct absorption spectra of a set of C2H4/N2 mixture with different concentrations are recorded in the temperature range of 300–900 K at normal atmosphere
According to Equation (3), the absorption crosssection of each wavelength pair can be determined from the linear fit to the measured differential absorbance at various C2H4 concentrations
Summary
Temperature is one of the scalar quantities on large technical combustion systems which directly reflects the combustion efficiency and affects the diffusivity of combustion products. It is necessary to develop an accurate and precise experiment approach to directly measure combustion temperature and provide time-resolved information of temperature distribution. Planar laser-induced fluorescence (PLIF) is a kind of laser spectrum measurement technology for the diagnosis of high-temperature variable flow fields [4, 5]. PLIF technology can accurately measure the distribution of component concentration, temperature change, and other information in the combustion environment, but PLIF equipment is complex, expensive, and difficult to apply in industrial applications. TDLAS technology has been demonstrated previously to provide quantitative measurements for species concentrations and temperatures in various combustion systems [8,9,10,11]. Cai et al demonstrated accurate and fast measurement of carbon dioxide concentration and temperature based on TDLAS at high temperature and high pressure [14]
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