Real-time 2D concentration and temperature measurement method using CT tunable diode laser absorption spectroscopy

It has been a major challenge to reduce anthropogenic carbon dioxide emissions from combustors. Behind the trend is the fact that increased carbon dioxide in the air causes global warming and adversely affects natural ecosystems. It is thus becoming more important to understand the emission characteristics to minimize environmental disruption and to improve the efficiency of combustors such as engines. In particular, detailed measurement techniques for the parameters such as temperature and species concentration are necessary to elucidate the overall nature of combustion systems. In engines, exhaust gas concentration and temperature distributionsareimportant factors in NOx, THC and PM emissions. They are also the catalytically important parameters in both gasoline and diesel engines.In this study, the theoretical and experimental research has been conducted in order to develop the noncontact and fast response 2D temperature and concentration distribution measurement method. The technique is based on a computed tomography(CT) method usingabsorption spectra of molecules such as H₂O and NH₃. The CT tunable diode laser spectroscopy method using 16-path laser beams was applied to measure 2D temperature and NH₃distributions in burner flames and engine exhausts. 2D temperature and NH₃distributions were successfully reconstructed using a set of 16-path absorption spectra. Considering the space averaged characteristics of the CTmethod, measurement results of temperaturedistributions show good agreement with the thermocouple measurements. Since CT tunable diode laser absorption spectroscopy has a potential of the kHz response time, this method enables the real-time 2D temperature and species concentration measurements to be applicable in various industrial processes including engine applications.